2nd CYCLE STUDIES
DIAGNOSIS AND TREATMENT OF
THE LOCOMOTOR SYSTEM:
HINDLIMBS AND AXIAL
SKELETON
SEPTEMBER 26-27, 2014
CASTELLA DE ITAIPAVA
SEPTEMBER 28-29, 2014
HORSE CENTER CLINIC
ITAIPAVA – PETRÓPOLIS
RIO DE JANEIRO – BRAZIL
Course faculty: Natasha Werpy, Bruce Bladon, Roger Smith,
Filip Vandenberghe and Michael Schramme
HOW TO RECOGNISE AND GRADE HINDLIMB LAMENESS SUBJECTIVELY
AND OBJECTIVELY WITH THE USE OF WIRELESS INERTIAL SENSORS
Michael Schramme DrMedVet, CertEO, PhD, DECVS, DACVS, AssocECVDI
Campus Vétérinaire de Lyon, VetAgro Sup
Université de Lyon, France
A careful and logical approach to the examination of a lame horse is required if the
clinician is to arrive at an accurate diagnosis of the cause or causes of the lameness.
The development of such a system depends on an appreciation of the way in which
the individual aids to diagnosis complement each other. This paper outlines a
protocol which maximizes the information obtained from each part of the lameness
examination, in the hope that standardization will lead to more consistency both in
the examination of the lame horse and also in the examination of the horse for
purchase.
Gait evaluation
The aim of this part of the examination is to identify:
1. The presence or absence of a gait abnormality.
2. The limb or limbs involved.
3. The character of any abnormality present.
4. The degree of abnormality.
All horses are worked-up with their shoes on, if this is the way that they are normally
ridden. Horses are always examined “in-hand,” being led by their owner or handler,
although in a few cases they can be ridden as well. Horses should be stripped of all
tack, rugs and blankets and should be held by a loose rope that is fixed to a
headcollar or bridle. Each horse is first walked, and then trotted, on a concrete
surface in a straight line towards and away from the investigator.
This part of the examination involves close scrutiny for any asymmetry of gait and
head carriage which might indicate the presence of lameness, and the leg or the legs
which are affected. Initial evaluation should be performed at the walk to identify
those horses which are markedly lame where trotting may be hazardous. Variations
in foot placement and limb movement, e.g. shortening of one phase of the stride on
one limb, are generally most easily appreciated at the walk when limb movement is
slower. In addition, mechanical and neurological causes of lameness are often more
apparent at the walk.
The trot is the most consistent and easily graded as it is a symmetrical 2-beat gait.
The horse should be observed moving in a straight line and at an even pace from in
front, the side and behind. Hindlimb lameness is best observed while the horse is
trotted away or past and away from the examiner. Observation from the side is easier
if the observer is on the side of the lame limb.
Pelvic movements are key to the recognition of hindlimb lameness. Keegan
determined that a sound horse will move its pelvis up and down twice per stride in a
symmetrical pattern such that frequency analysis of the vertical pelvic movement
signal will yield a single frequency, which will be equivalent to twice the stride rate. In
a horse with unilateral hindlimb lameness, one of three distinct patterns of pelvic
motion may be detected.
1. During the deceleratory phase of stance, which is the cranial one-half (from
impact to midstance), the downward inertia of the pelvis is “damped” by the upper
hindlimb musculature, resulting is less down- ward motion of the pelvis. Thus,
lameness with the most significant pain occurring in the cranial one half of stance
will result in the first pattern of pelvic motion associated with hindlimb lameness.
The pelvis will move down during the stance phase of the lame limb, but the
absolute height will be higher than during the stance phase of the sound limb. The
pelvis moves up after pushoff of the lame limb, but the absolute height is the same
as after pushoff of the sound limb. As an example, a horse with mild distal tarsal
arthritis caused by the shear strain on the distal tarsal joints will be greatest during
the deceleratory (first one-half) phase of stance and will primarily exhibit less
downward movement of the pelvis during stance.
2. During the acceleratory phase of stance, which is the caudal one-half (from
midstance through pushoff), limb “pushoff” force is weak, and the pelvis is driven
upward to a lesser extent than after pushoff of the sound limb. Thus, lameness
with the most significant pain occurring in the caudal one-half of stance will result
in the second pattern of pelvic motion associated with hindlimb lameness. The
pelvis moves down during the stance phase of the lame limb, but the absolute
height is the same as during stance phase of the sound limb. The pelvis moves up
after pushoff of the lame limb, but the absolute height is lower than after pushoff of
the sound hindlimb. As an example, in a horse with patellar ligament desmitis the
pain or dysfunction is most apparent during limb pushoff, resulting is less pelvic
height after the stance phase of the affected limb.
3. Pain in both the deceleratory and acceleratory phases of stance (i.e.,
throughout stance) will result in the third pattern of pelvic motion associated with
hindlimb lameness. The pelvis moves down during the stance phase of the lame
limb, but the absolute height is higher than during the stance phase of the sound
limb. The pelvis moves up after pushoff of the lame limb, but the absolute height is
lower than after pushoff of the sound hindlimb (i.e., a combination of patterns 1
and 2). The more severe the lameness, the more likely that pain will be
significantly present throughout the stride.
Hindlimb lameness can be observed clinically in different ways, according to clinician
preference:
1. By assessing the vertical movement of the entire pelvis throughout the stride
and comparing this vertical movement during both halves of the stride
2. By assessing the vertical amplitude of movement of the tuber coxae of each
hemipelvis throughout the stride and comparing the left and right hemipelvis
movements
3. By assessing the extension angle of the fetlock (fetlock drop) of each hindlimb
during maximum weightbearing and comparing left and right hindlimbs
4. By assessing the position of the head during the weightbearing phase of each
hindlimb and comparing between left and right hindlimbs
5. By assessming various joint angles and stride length and foot flight
characteristics (less useful).
An important principle in the recognition of hindlimb lameness is the concept of the
pelvic hike or hip hike. Since the horse has two “hips” and only one pelvis, the term
pelvic hike is more accurate. Pelvic hike is the vertical elevation of the pelvis when
the lame limb is weight bearing. In other words, the entire pelvis “hikes” upward when
the lame limb hits the ground and moves downward when the sound limb hits the
ground. It is the shifting of weight or load that occurs as the horse tries to reduce
weight bearing (unload) in the lame limb and transfer weight (load) to the sound limb.
This difference is best observed by tracking the movement of the top of the croup
region (both tubera sacralia) throughout the entire stride.
Many horses with hindlimb lameness (certainly not all) drift away from the lame limb
toward the sound limb. Drifting is one of the earliest adaptive responses of a horse
with unilateral hindlimb lameness, allowing the horse to break over more easily or to
reduce load bearing. Drifting may decrease the magnitude of the observed pelvic
hike, but more important, it makes the lame side look lower than the sound side. This
is why it is important to watch the entire pelvis as a unit rather than the individual
sides of the “hips.” Many driven STBs with hindlimb lameness drift away from the
lame limb or are “on the shaft.” Horses with LH lameness have a tendency to be on
the right shaft and vice versa.
In horses with hindlimb lameness the normal symmetrical vertical movements of both
quarters, as observed by focusing on the vertical displacement of the tuber coxae of
each hemipelvis from behind the horse, is disturbed. The quarter on the lame side
will rise and fall through a greater range of motion (increased vertical amplitude of
movement of the tuber coxae) than that of the sound limb. This is usually
characterized by a long downwards drop of the tuber coxae of the lame limb during
the swing-phase of the stride, followed by a fast, sudden, upwards flick, or hike of the
tuber coxae of the lame limb, during the weightbearing phase of the stride. The
degree of lameness is subjectively assessed and recorded on a numerical scale. To
help the investigator, hip markers can be applied to aid the recognition of asymmetry
of hindlimb movement in cases which are only slightly lame (May and Wyn-Jones
1987).
Pain-related lameness will result in a reduction in the extension of the
metatarsophalangeal joint providing there is no disruption of the palmar soft tissue
supporting structures, hence making this sign a useful predictor of the lame limb. This
may be easier to detect by video analysis than in a clinical situation and may be more
recognizable at the walk than at a trot. It is less useful for detecting subtle lameness
and for scoring the severity of lameness.
Head movements are less helpful in the recognition of hindlimb lameness. With
moderate to severe lameness, the horse may attempt to shift its centre of gravity
forward when the lame hindlimb starts to bear weight, which results in downwards
movement on the lame hindlimb. This can give the misleading impression of a
downward head nod during the support phase of the contralateral forelimb, and
hence ipsilateral forelimb ‘referred’ lameness.
Alteration in the relative lengths of phases of the stride may help identify the lame
hindlimb. The cranial phase of the stride is that part which occurs in front of the
footprint of the contralateral limb, while the caudal phase occurs behind it. If the
horse is moving in a straight line, the overall stride length in a pair of contralateral
limbs must be even; therefore a reduced cranial phase must always be accompanied
by an increased caudal phase. Overall reductions in stride length frequently
accompany bilateral orthopaedic conditions leading to a ‘pottery’ or restricted gait.
Alteration in the arc of foot flight may help identify the lame hindlimb. Lowering of the
arc of foot flight may occur as a compensation to reduce impact when the foot lands
or to reduce limb flexion during protraction. If severe, it may lead to dragging of the
toes. Exaggerated elevation of a foot due to hyperflexion of the limb joints is
occasionally seen , e.g. in neurological conditions, such as . in ‘stringhalt’. Variations
in the path of foot flight and in foot placement may occur for similar reasons to those
that cause alterations in the arc of foot flight. The foot may be swung medially or
laterally during protraction of the limb. The foot may land asymmetrically contacting
the ground first at the toe, heel or on one or other side. Landing of the hindfeet on the
lateral wall and toe region is referred to as ‘stabbing’ or “stabby” gait. During
protraction of the lame hindlimb or hindlimbs, the limb travels medially, close to the
opposite hindlimb, and then moves laterally during the later portion of the swing
phase and is placed lateral to the expected foot placement. This motion results in
excessive wear of the lateral or dorsolateral aspects of the shoe. Although this gait
often is seen in horses with distal hock joint pain, it can be seen with many other sites
of pain from the distal tibia to the foot.
In some horses with hindlimb lameness the limb is carried forward in a position lateral
to the expected position (i.e. abducted), which is sometimes referred to as a “wet
nappy trot”. In some horses with this limb flight the limb swings outside the expected
line of limb flight, only to strike the ground near the expected position or by stabbing
laterally. This gait abnormality may be seen in many horses with stifle lameness.
Plaiting means to braid or pleat, or to make something by braiding. The term is used
to describe horses that
walk or trot by placing one foot directly ahead of the other foot. In horses with both
unilateral and bilateral hindlimb lameness, it appears that limb flight actually may be
altered in both hindlimbs, resulting in both hind feet being placed close together or in
some horses, ahead of the opposite foot. Plaiting is observed most commonly in
horses with osteoarthritis of the coxofemoral joint, pelvic fractures, bilateral distal
hock joint pain, suspensory desmitis or sacroiliac disease.
Horses with bilateral hindlimb lameness may have a short, choppy gait that lacks
impulsion, but they may have no pelvic hike. Other methods to exacerbate the
baseline lameness should be performed, such as circling the horse at a trot in hand
or while on a lunge line. Lameness may be accentuated when the lame or lamer limb
is on the inside or outside of the circle
Circles
In the next phase of the examination, the horse is lunged on a hard (concrete)
surface in circles of about 15-20 meters in diameter. Lunging the horse in tight
circles is helpful in demonstrating more clearly lameness that is subtle or inapparent
when the horse is moving in a straight line. The animal is trotted in circles at a steady
medium pace, until the investigator is satisfied that he or she can recognize a
consistent level of lameness, if present, on each circuit. This is again recorded on
the numerical scale outlined below. The process is then repeated for the right rein.
Bilateral hindlimb lameness is often very difficult to recognize when the horse moves
in a straight line. The horse usually shows a stiff, stilted gait with bilaterally shortened
stride length. More pronounced unilateral signs of lameness are usually observed
when the limbs are subjected to uneven stresses (e.g. by lunging in tight circles).
Horses are also lunged on a soft sand surface in circles of about 15 meters. This is
done because some lameness is worsened by certain surfaces – e.g. lameness
caused by proximal suspensory desmitis on soft ground, foot lamenesses on hard
ground. Proximal lameness may be exacerbated with the affected limb on the outside
of a soft circle while distal lameness is usually worse with the affected limb on the
inside of a hard circle. These ‘rules’ are certainly not absolute. For instance, one
must take into account whether the painful locus is located on the medial or lateral
aspect of the limb and certain weight-bearing lamenesses, such as those arising from
the proximal suspensory region, are commonly associated with greater lameness
with the limb on the outside of the circle.
Flexion tests
Flexion tests may be utilized for three basic reasons:
1. To demonstrate occult lameness in a horse that appears ‘sound’ on initial gait
evaluation.
2. To exacerbate a mild lameness.
3. To aid localization of the abnormality causing the lameness.
A flexion test is performed by holding the joint under consideration in a firmly flexed
position for a period (usually 1 minute) and then immediately watching the horse
move, usually at the trot, to detect any change in gait compared to that observed
before performing the test. The response to a flexion test should be interpreted in the
light of other findings, and it is wise to avoid using it as the sole criterion upon which
to base the use of nerve blocks. If the lameness produced by any flexion tests is
consistent on repeating the procedure, the investigator may consider moving on to
nerve blocks in order to localize this revealed lameness. However, great care must
be taken to standardize the flexion test, in terms of duration and force applied, in
order to obtain meaningful results in this situation.
In view of the difficulty in recognizing very slight hindleg lameness, even on the
lunge, particularly in horses in which both hindlegs are affected, separate flexion
tests are performed on each hock and on each hind fetlock and digit. Immediately
after flexing the joint, the horse is trotted away from the observer and the degree of
lameness is assessed over a distance of about 40 meters. Any asymmetry of gait in
the first three strides is ignored.
Subjective and objective scoring of lameness
Visual scoring of lameness, in straight lines and circles, after excitatory tests, and
after diagnostic anesthesia, is an essential part of the lameness examination. In
order to evaluate whether diagnostic analgesia has alleviated the lameness, a visual
lameness grade is given to the lameness on each occasion from which a percentage
improvement can be semi-objectively determined. Different grading systems, varying
from 0-4, 0-5, 0-8, and 0-10, have been described, where 0 is sound and the
maximum grade is non-weight-bearing.
AAEP scale (integration of all gaites):
0 - Lameness not perceptible under any circumstances.
1 - Lameness is difficult to observe and is not consistently apparent, regardless of
circumstances (e.g., under saddle, circling, inclines, hard surface, etc.).
2 - Lameness is difficult to observe at a walk or when trotting in a straight line, but
consistently apparent under certain circumstances (e.g., weight carrying, circling,
inclines, hard surface, etc.)
3 - Lameness is consistently observable at a trot under all circumstances.
4 - Lameness is obvious at a walk.
5 - Lameness produces minimal weight bearing in motion and/or at rest or a
complete inability to move.
0-10 scale (assessed at the trot but applicable to each gait or test):
0 - Sound
1 - The minimal degree of lameness detectable which may be inconsistent
2 - A consistent, but mild, degree of lameness – detectable and consistent subtle
head-nod
3 - Consistent and obvious head nod/pelvic asymmetry
4 - Pronounced head nod/pelvic asymmetry
5 - Marked head nod/pelvic asymmetry
6 - Very marked head nod/pelvic asymmetry
7 - Difficulty trotting; only just able to place heels to the ground
8 - Minimal weight-bearing, heels not placed on the ground
9 - Only able to touch the limb to the ground
10- Unable to put limb to the ground
However, these subjective numerical grading systems have been shown to have
limited inter-observer agreement, to improve with experience (Keegan et al. 1998,
Keegan et al. 2010) and to be significantly influenced by bias (Arkell et al. 2006).
Technological advances in the last decade have improved our objectivity in lameness
exams, from the simplest, using high definition video cameras, to the development of
more practical wireless sensor-based gait analysis systems which can be deployed
within the constraints of a clinical lameness examination (Keegan et al. 2002 and
2004, Pfau et al. 2007 and 2009). With these wireless sensor-based systems
essential lameness parameters (e.g. head nod or hip hike) can be objectively
quantified and assist clinicians, in particular with recognition of mild lameness, with
quantifying improvement after diagnostic anesthesia and with monitoring progress in
lameness grades over a longer time period. In particular the Lameness LocatorTM
from Equinosis has gained clinical recognition and is now routinely used during
lameness examinations in several specialist clinics around the world. It was
specifically designed as an aid to the practicing equine veterinarian for detection and
evaluation of difficult lameness in horses. Lameness Locator™ consists of 3 inertial
sensors, a tablet PC for data analysis, a sensor battery charger, and accessories for
attaching the sensors to the horse’s body. The inertial sensors are attached to the
head, right forelimb pastern and pelvis. Vertical accelerations of the head and pelvis
and angular velocity of the right distal forelimb are measured and wirelessly
transmitted in real time to a hand-held tablet computer. Custom-designed algorithms
are used to detect and quantify forelimb and hindlimb lameness when the horse is
trotting. Lameness is detected and quantified by reporting 1) the ratio of vertical
movement due to lameness to natural vertical movement, and 2) the means and
standard deviations of maximum and minimum height differences of the head
(forelimb lameness) and pelvis (hind limb lameness) position between left and right
strides. Location of lameness to the right or left limb and location of peak lameness
within the stride (impact or push-off lameness) are determined by the association of
head and pelvic movement to angular velocity of the right forelimb. It has been shown
that the wireless, sensor-based systems can be a practical way of assisting clinical
decision-making in all lameness cases by providing objective evidence (Keegan et al.
2013).
Conclusion
The examination of a horse with hindlimb lameness is a time-consuming exercise,
but it is important that it is done carefully and systematically to establish a correct
diagnosis. Only by following a logical system, with regard to clinical examination, the
use of local analgesic techniques, radiography, and other imaging modalities, can the
clinician maximize the information obtained from a case, and gauge accurately the
site and the cause of pain. It is important that a consistent approach is adopted with
regard to the examination of the musculoskeletal system of the horse so that when it
is pronounced lame or not lame all clinicians are conversant with the basis for the
conclusion. Clearly, the person who only examines a lame horse in a straight line
may come to a very different conclusion about the pattern of lameness from someone
who lunges the horse on a soft surface, and this person in turn may come to a
different conclusion about the pattern of the lameness from the person who lunges
the horse on a hard surface. The protocol for lameness investigation outlined here
adds, at each stage, a further piece to the puzzle which is the lame horse. It should
be regarded as a package of complimentary measures aimed at obtaining an
accurate diagnosis. Only an accurate diagnosis can offer hope of formulating a
correct prognosis and initiating appropriate treatment.
References
1. Arkell M, Archer RM, Guitian FJ, May SA. Evidence of bias affecting the
interpretation of the results of local anaesthetic nerve blocks when assessing
lameness in horses. Vet Rec. 2006 Sep 9;159(11):346-9.
2. Church EE, Walker AM, Wilson AM, Pfau T. Evaluation of discriminant analysis
based on dorsoventral symmetry indices to quantify hindlimb lameness during
over ground locomotion in the horse. Equine Vet J. 2009 ;41(3):304-8.
3. Keegan KG, Dent EV, Wilson DA, Janicek J, Kramer J, Lacarrubba A, Walsh DM,
Cassells MW, Esther TM, Schiltz P, Frees KE, Wilhite CL, Clark JM, Pollitt CC,
Shaw R, Norris T. Repeatability of subjective evaluation of lameness in horses.
Equine Vet J. 2010 ;42(2):92-7.
4. Keegan KG, Wilson DA, Kramer J, Reed SK, Yonezawa Y, Maki H, Pai PF,
Lopes MA.Comparison of a body-mounted inertial sensor system-based method
with subjective evaluation for detection of lameness in horses. Am J Vet Res.
2013; 74:17-24.
5. Keegan KG, Wilson DA, Wilson DJ, Smith B, Gaughan EM, Pleasant RS, Lillich
JD, Kramer J, Howard RD, Bacon-Miller C, Davis EG, May KA, Cheramie HS,
Valentino WL, van Harreveld PD. Evaluation of mild lameness in horses trotting
on a treadmill by clinicians and interns or residents and correlation of their
assessments with kinematic gait analysis. Am J Vet Res. 1998 ;59:1370-1377.
6. Keegan KG, Yonezawa Y, Pai PF, Wilson DA, Kramer J. Evaluation of a sensorbased system of motion analysis for detection and quantification of forelimb and
hind limb lameness in horses. Am J Vet Res. 2004 ;65:665-70.
7. Keegan KG, Yonezawa Y, Pai PF, Wilson DA. Accelerometer-based system for
the detection of lameness in horses. Biomed Sci Instrum. 2002 ;38:107-112.
8. May SA and Wynn-Jones G. Identification of hindleg lameness. Equine Vet J.
1987; 19:185-188
9. Parkes RS, Weller R, Groth AM, May S, Pfau T. Evidence of the development of
'domain-restricted' expertise in the recognition of asymmetric motion
characteristics of hindlimb lameness in the horse. Equine Vet J. 2009 ;41:112117.
10. Pfau T, Robilliard JJ, Weller R, Jespers K, Eliashar E, Wilson AM. Assessment of
mild hindlimb lameness during over ground locomotion using linear discriminant
analysis of inertial sensor data. Equine Vet J. 2007 ;39:407-13.
HINDLIMB LAMENESS IN THE RACEHORSE
Bone scan or not?
Bruce Bladon BVM&S, Cert EP, DESTS, Dipl ECVS, MRCVS
Donnington Grove Veterinary Surgery
Newbury, Berkshire, United Kingdom
Hindlimb lameness in the Thoroughbred racehorse is a common presenting
complaint, with a myriad of potential causes. This lecture will only deal with some of
the more frequent conditions, and will not be an exhaustive list of causes of hind limb
lameness. In particular, the lecture will look at stress fractures of the tibia and tarsus,
fractures of the lateral malleolus, and will concentrate on plantar osteochondral
disease of the fetlock.
The approach to hindlimb lameness in the racehorse is surprisingly difficult.
Horses are often presented with fairly obvious lameness, unlike the dressage horse,
and initially the approach would appear obvious. Clinical examination to detect any
obvious signs of pathology, then nerve block from the foot up, followed by imaging
the affected area, much like in a forelimb. However…
The first thing to consider in any racehorse lameness is the likelihood of a fracture.
Experience has taught me that clients are not receptive to fractures which are
exacerbated by investigation at a veterinary clinic. Careful palpation of the fetlock is
thus indicated. Effusion is a common but not invariable finding with a fetlock fracture.
Pain on pressure on the dorsal aspect of P1 is often present with sagittal fractures.
Pain on deep palpation over the caudomedial tibia is an unusual finding with a tibial
stress fracture but is worth a look. Practically I would always advise radiographs of
the fetlock in a racehorse prior to nerve blocking this area.
The other thing to consider with racehorse lameness is the frequency of upper
limb lameness. A racehorse which presents with a moderate acute onset unilateral
hindlimb lameness with no localising signs probably has a stress fracture, and two of
the commonest sites are the pelvis and tibia. A conventional lameness examination
will not localise either of these conditions, and may have subjected the horse to four
or five nerve blocks, often at considerable risk of injury to the clinician.
There is an alternative approach, which is to perform gamma scintigraphy, a bone
scan. This is expensive, and not always available. It does not always yield a
diagnosis either, soft tissue injuries do not show up, typically suspensory desmitis
and injuries of the stifle. The principle drawback with gamma scintigraphy though is
the expense. It is impossible to justify a bone scan on every racehorse with a hind
limb lameness. Of course, the greatest error is to perform a couple of nerve blocks,
take a collection of X-Rays, and then recommend a bone scan, having already
generated a significant bill. This conundrum, of when to stop and recommend a bone
scan, is difficult, and I have not been able to develop a consistent and reliable regime
for the investigation of hindlimb lameness. However, it would be very common that
horses are subjected to radiography of the fetock, hock and stifle, and
ultrasonography of the pelvis, in a “screening” approach early in the investigation.
One final point to consider in the approach to hindlimb lameness is recurrence of
lameness. The lameness associated with most stress fractures will resolve in a day
or so. This will recur when the horse is put back into work after a week or so. It is
unusual, but not unheard of, that a return to exercise immediately results in the
development of a complete and frequently fatal fracture. However, if the further
limited rest followed by exercise is repeated a few times, then a complete fracture is
inevitable. Thus, recurrent lameness is almost invariably a good indication for a bone
scan.
Some of the most common conditions associated with hindlimb lameness in the
racehorse are discussed below. Fractures of the pelvis are common and important,
but are dealt with in a separate lecture.
1) Bone cysts in the medial femoral condyle
Bone cysts in the medial femoral condyle are a common developmental condition
of the horse. They are often detected when the horse is a yearling, but many cases
do not become apparent until the horse starts athletic activity. There is also the
syndrome of the yearling which is treated for a bone cyst, and is then sold when
sound without a full clinical history. The horse can then show lameness during the
two or three year old career.
There are seldom any localising features of medial femoral condylar bone cysts.
Some skilled operators may detect effusion of the medial femorotibial joint. However,
I find this is a subtle finding sufficiently common that it is clinically unhelpful. Nerve
blocks are also unhelpful. Many cases do respond to intra-articular anaesthesia of
the medial femorotibial joint. However, if communication between joint and cyst is
incomplete, then a negative response is commonly observed.
Diagnosis is by radiography. The only comment I have to make about
radiography is that the caudo cranial view is not the best view to diagnose a bone
cyst. Problems with radiography are much less common nowadays with the
extraordinary quality of DR systems. However, the best view to diagnose a bone cyst
is a flexed lateral view. This will bring the medial condyle away from the weight
bearing surface of the tibia. Flexion will naturally angle the leg outwards slightly,
ensuring the medial condyle is positioned slightly lower than the lateral, thus
“skylining” the area of the bone cyst.
Arthroscopic medication of bone cysts with corticosteroids is an effective
treatment1. We find this treatment much more effective than medication with
ultrasound guidance. I believe that this is because arthroscopic medication is usually
into the bone cyst, while ultrasound guided medication is usually done somewhere
random near the stifle. Over the years we have flirted with many different treatment
options for bone cysts. Currently, our favoured option for the few cases which do not
respond to medication is the transcondylar screw2. This is relatively simple and can
be undertaken with routine surgical equipment and does not necessitate complex
laboratory back up.
2) Stress fractures of the tibia
Stress fractures of the tibia are one of the commonest causes of hindlimb
lameness in the racehorse. Horses usually present with a moderate lameness with
no localising clinical signs. Palpation of the caudal distal tibia, using a hand wrapped
around the tibia to apply pressure caudally, may produce a pain reaction, particularly
in the acute phase. Nerve blocks are unhelpful. Radiography is usually indicated
based on clinical suspicion of the possibility of a tibial stress fracture. There are
three predilection sites - proximally, distally, and in the middle. Most fractures involve
the caudal or caudolateral cortex. Fracture planes are very seldom visualised
radiographically. The radiographic signs of a tibial stress fracture include periosteal
new bone. This can be particularly marked with proximal fractures. In the mid
diaphysis care needs to be taken interpreting radiographs as there are multiple
normal ridges of bone on the caudal cortex which can give the appearance of new
bone. Distally periosteal new bone is relatively unusual. If cortical disruption is
evident then it is usually with distal fractures. Exactly the right view is necessary,
usually in the DP plane, viewing the fracture through the tibia. Endosteal new bone
is one of the commonest radiographic findings with tibial stress fractures. This can
be quite obvious with distal fractures, resulting in a change of curvature for the
normal thinning of the caudal cortex.
Radiographs are not helpful with ageing of tibial stress fractures. While
aggressive periosteal new bone can be distinct, endosteal new bone is usually
relatively smooth. This finding can remain for many years after a horse has
recovered from a tibial stress fracture.
The diagnosis is confirmed by gamma scintigraphy. A marked focal increase in
uptake of radioisotope is observed at the site of the fracture. It is common that the
condition is bilateral, even with unilateral lameness. There are two patterns of uptake
which could be mistaken for a tibial stress fracture. The first is marked increase in
uptake in the head of the fibula, or in the tibial fibial articulation. We recognised this
and usually manage it in the same way, but we are unsure of the pathology behind it.
The second is an intense increase in uptake in the tibial tuberosity. This can be
observed with (traumatic) fractures of the tuberosity, and is sometimes observed in
the absence of a radiographically apparent fracture, but with a history of trauma to
the area, presumably a “pre-fracture” bone trauma. Sometimes this uptake is
observed with no relevant history or lameness.
The treatment of tibial stress fractures is rest. Typically, box rest for one month,
followed by two months horse walker exercise. The horse could then be subjected to
repeat scintigraphy, or further radiography. Typically, scintigraphy, though potentially
useful, is considered too expensive, so the horse undergoes repeat radiography,
which is invariably inconclusive. Clinically monitoring the horses progress on return
to exercise is a perfectly reasonable approach.
The prognosis is very good. Our results show 68% of horses with tibial stress
fractures racing again, comparable to the number of uninjured Thoroughbreds which
race again. Complete tibial fractures are mercifully rare. Horses with tibial stress
fractures usually show significantly recurrent lameness that investigation is prompted
prior to a fatal injury.
3) Lateral malleolus fractures
Fractures of the lateral malleolus in the tarsocrural joint are a distinct condition.
There is almost invariably a risk of a fall, and as such the condition is predominantly
diagnosed in the National Hunt racehorse. Diagnosis is straightforward. There is a
history of a fall with firm swelling of the lateral side of the hock and a marked effusion
of the tarsocrural joint. Radiographs confirm the diagnosis. The most useful view is
“just” DMPLO, perhaps 10 - 20º medial to the DP plane. This highlights the lateral
malleolus.
Conservative management has been advocated, as has treatment by arthrotomy.
However, we prefer removal of the fracture fragments by arthroscopy. It is essential
if tackling this arthroscopy, to have a technique to cut the fragments out of their soft
tissue attachments. They cannot be pulled out. We use radiofrequency.
The prognosis is very good. Our results showed 10 / 12 (83%) racehorses
returned to racing a median time of 241 days after surgery3.
4) Slab fractures of the tarsus
Slab fractures of the tarsus are a less usual site of stress fracture in the
Thoroughbred. There are often no localising signs. Occasionally careful palpation of
the lateral aspect of the hock may reveal a pain response, but this is not consistent.
It is also very short lived. A veterinary surgeon presented with the horse the day it
has gone lame may detect the lateral hock pain, but once admitted to a hospital a
few days later this sign has often faded.
The diagnosis is by radiography. A DMPLO view is necessary, and often taken
slightly more dorsoplantar than normal. Do not ignore a shadowy irregularity on the
lateral aspect of the central or third tarsal bone. Multiple oblique views are necessary
to accurately delineate the fracture plane. Once an accurate radiograph is obtained,
a remarkable degree of displacement is often appreciated.
Sadly, despite the displacement, most of these fractures resolve very well with
conservative management. I have buckled under pressure in the past and put a
3.5mm screw across the fracture in lag fashion. No surgeon should resist this
pressure for long, as most of these fractures will get better despite rather than
because of surgery, and the outlook is very good with 3 - 4 months rest4.
5) Sagittal fractures of the fetlock
Sagittal fractures of the fetlock, both “split pastern” and “split cannon” occur with
similar frequency in the hindlimb and the forelimb. In the majority of cases the
diagnosis is self evident, with an acute onset marked lameness and marked effusion
of the fetlock joint. The lameness may be associated with work, and the horse pulling
up. However, it is common for horses to walk back to the stables sound and for
lameness to be discovered several hours later.
Radiography reveals the fracture in the majority of cases. Occasional sagittal
fractures of P1 may be difficult to detect on radiographs. Further radiography in 1 - 3
weeks may subsequently reveal a fracture plane, and may reveal more fracture
planes in cases where the original fracture was apparently evident. Scintigraphy can
be helpful in subtle cases, as can MRI.
The treatment is surgery in the large majority of cases. We now almost invariably
perform surgery in the standing sedated horse5. This controls the expense, with no
need for general anaesthesia or for a cast for anaesthetic recovery. It also reduces
the risk to the horse, avoiding the dangerous phase of anaesthetic recovery. Surgery
is performed under a four point nerve block with a dorsal ring. The secret to standing
surgery is to exploit the advantage of the technique - namely that intra-operative
radiographs are much easier to obtain. If combined with DR technology, allowing
interpretation of radiographs within a few seconds of acquisition, the surgery can be
guided by multiple intra-operative radiographs yet still be quick and efficient. To
place two lag screws across a simple lateral condylar fracture, I would routinely
acquire ten radiographs.
Medial condylar fractures of the hindlimb are a particular concern. These
fractures tend to propagate into the proximal cannon bone and are potentially
unstable. It is quite common that these fractures become complete, displaced and
fatal during the first few weeks after injury. It is recommended practice to cross tie a
horse with a medial condylar fracture of MT3, to reduce the chance of completion of
the fracture during anaesthetic recovery. We have published the results of treatment
of these fractures with a contoured plate6. This surgery does produce a stable
construct, though we have seen fatal propagation. Placement of lag screws under
general anaesthesia almost invariably resulted in fatality. We now favour surgery
under standing sedation to place two or three screws in lag fashion from lateral.
The results of surgery in the standing sedated horse are good, and are much the
best results we have ever produced for fracture repair. We have operated on 63
cases, of which 7 were not racehorses, and 17 have less than 6 months follow up.
27 have raced again, 16 have not, 63% return to racing. This included sagittal
fractures of P1 (split pasterns), 10 have raced again, 6 have not, 63% return to
racing. Lateral condylar, 7 raced again, 5 did not, 58%. Medial condylar fractures, 9
did race again, 5 did not race again, 65%, and this includes no fatalities.
6) Plantar osteochondral disease of the fetlock.
Plantar osteochdondral disease is a common and important condition of the
racing Thoroughbred. It is also diagnosed in performance horses including eventers
and endurance horses. Various terms have been given to describe the disease,
including subchondral bone disease, maladaptive remodelling, sclerosis of the lateral
condyles, and most recently, palmar/plantar osteochondral disease (POD). The
diagnosis is relatively difficult, as advanced imaging is required, either scintigraphy or
magnetic resonance imaging. However, the clinical signs are quite distinctive, with
mild lameness, or often simply “poor action”, and minimal palpable abnormalities.
The action is often improved, or lameness switches to the other limb, following
anaesthesia of the lateral plantar metatarsal nerve, at the level of the distal end of the
splint bones. Radiology is usually disappointing, with no detectable abnormalities.
Specialised views such as flexed plantardorsal (dorsopalmar) oblique and proximal
dorsolateral – distal palmarmedial and proximal dorsomedial - distal palmarlateral
oblique views may highlight some increased radiodensity and sometimes some focal
radiolucencies within the palmar/plantar condyles of the metacarpus/metatarsus.
However, these findings are seldom definitive.
The diagnosis is confirmed by advanced imaging. Scintigraphy typically shows a
bilateral focal increase in uptake of the radioisotope in the lateral metatarsal
condyles, often accompanied by a bilateral uptake in both metacarpal condyles. It is
important to use a plantar view to allow assessment, and the view must be perfectly
aligned. Otherwise the lateral sesamoid will be superimposed over the cannon bone,
while the medial sesamoid is displaced medial to the cannon, giving a false positive.
It is often necessary to acquire two separate views plantar to each hindlimb, as the
horse will normally stand with the hind limbs “toe out”. Uptake in this area is normal
in the performance horse, and diagnosis is made by the degree of uptake. Parker
(2010) reported that affected cases usually had a pixel count of the lateral condyle
relative to the mid metatarsus of >1.5, significantly greater than control horses7.
Magnetic Resonance Imaging is an excellent imaging modality for the fetlock of
the racehorse8. With MRI, everyone wants to know if you can get images of the
proximal suspensory ligament, particularly behind. Yet proximal suspensory desmitis
is as disappointing on MRI as it is on ultrasound, with variable normal anatomy and
unreliable pathological findings. At the same time, it has been almost overlooked that
excellent images can be simply obtained of the fetlock, and the enhanced contrast of
bone rather than soft tissue gives excellent diagnostic accuracy. There are three
principle MRI findings - hypo intensity on T1 sequences, classically termed sclerosis.
Hyperintensity on STIR sequences, bone oedema or bruising, is observed in
relatively acute cases. Finally parasagittal fissures are often observed, but the
significance of these is uncertain. It has been shown that these occur in similar
frequency in apparently uninjured horses9.
The treatment of plantar osteochondral disease is difficult. This condition, more
than any other is plagued by “needle jockeys” visiting racing stables, injecting various
potions into the fetlock joints, and pronouncing the horse better. One of the principal
difficulties with managing POD is that it is an incurable disease causing poor
performance, and thus efficacy is very hard to define. If presented in a positive light,
many treatments can be perceived as effective by trainers and indeed veterinary
surgeons, and there is no gold standard effective treatment to compare. Intraarticular medication of POD was widely discounted at one stage. However, in our
series of cases the majority of horses did response to intra-articular anaesthesia as
well as perineural. Thus there is a rationale behind intra-articular medication. The
most widely used drugs for intra-articular medication are cortisone. If the horse is to
remain in training, rather than undergo prolonged rest, then medication of the fetlock
with cortisone with 5 mg of triamcinolone is usually used in the first instance.
Autologous conditioned serum (irap®) is also widely used in the management of
POD. However, the rationale for this particular agent hinges around the simplicity of
using irap® in a horses in training, where there is no concern about drug withdrawal
times.
Other agents which have been used include platelet rich plasma, including
lyophilised platelet rich fraction.
This is rich in growth factors, particularly
transforming growth factor β1 though a clear mechanism of alteration of bone
remodelling is not apparent. Intra-articular ketorolac has been advocated. This is a
non-steroidal anti-inflammatory drug, used for post-operative analgesia in human
surgery, but is of short duration of action. Thus it is hard to see a specific mechanism
of action which will be beneficial in the long term management of POD.
Intra-articular stanozolol has been shown to have significant benefits in clinical
use. This is an anabolic steroid that is water soluble10. However, the drug
withdrawal implications of using anabolic steroids in horses in training should be
considered carefully. In the UK anabolic steroids are banned in all Thoroughbred
racehorses, with a lifetime ban and zero tolerance.
Agents which act directly on the bone modelling process are potentially of use in
this condition. We use tiludronate (Equidronate®) extensively in the management of
POD. The rationale is that this is a drug which acts on bone and POD is a disease of
bone, therefore we’ll use it. However, electron microscopy of POD does show
significant osteoclastic activity, which potentially would be modulated by treatment
with tiludronate. Generally, we administer one third of the systemic dose by
intravenous regional perfusion to the affected metatarsus/carpus, with the remainder
of the drug being administered by intravenous infusion. We believe that the agent is
effective in the management of this condition. However, the earlier comments about
presenting treatment in a positive way apply. Accurate assessment of efficacy would
at least require a case series and likely a comparison with another treatment, and this
is not available yet.
The cornerstone of the management of lameness in the racehorse is rest. It is
well recognised that rest is of limited benefit in the management of plantar
osteochondral disease. Generally rest periods of 6 weeks or less appear to
exacerbate the condition. Presumably the sudden change in exercise intensity
results in further derangement of the complex remodelling process of metatarsal
condyles. It is often reported that rest is not helpful in the management of POD.
However, rest can be very effective, but must be prolonged11. Generally a period of
6 months out of training will be necessary and anything less than this is unhelpful12.
Though a prolonged period of rest, this is often not as impractical as it at first sounds.
Effectively, following diagnosis, the horse is removed from training until the next
season. Our experience has been that prolonged rest is usually effective in the
management of this condition, for a period of time. However, it is not curative. Thus
following 6 months of rest a horse might be anticipated to perform well for the
following season, but progressive loss of action and poor performance will recur in
later seasons.
References
1. Wallis TW, Goodrich LR, Mcilwraith CW, Frisbie DD, Hendrickson DA, Trotter
GW, et al. Arthroscopic injection of corticosteroids into the fibrous tissue of
subchondral cystic lesions of the medial femoral condyle in horses: a
retrospective study of 52 cases (2001-2006) 2008;40:461–7.
2. Santschi EM, Williams JM, Morgan JW, Johnson CR, Bertone AL, Juzwiak JS.
Preliminary Investigation of the Treatment of Equine Medial Femoral Condylar
Subchondral Cystic Lesions With a Transcondylar Screw 2014:n/a–n/a.
3. O'neill HD, Bladon BM. Arthroscopic removal of fractures of the lateral malleolus
of the tibia in the tarsocrural joint: a retrospective study of 13 cases.
2010;42:558–62.
4. Elce Y, Ross M, Woodford A, Arensberg C. A review of central and third tarsal
bone slab fractures in 57 horses. Proceedings of the American Association of
Equine Practitioners Annual Convention 2001;47:488–90.
5. Compston PC, Payne RJ. Standing fracture repair - a new chapter 2013;25:386–
8.
6. Goodrich LR, Nixon AJ, Conway JD, Morley PS, Bladon BM, Hogan PM.
Dynamic compression plate (DCP) fixation of propagating medial condylar
fractures of the third metacarpal/metatarsal bone in 30 racehorses: Retrospective
analysis (1990-2005). 2013:n/a–n/a.
7. PARKER RA, Bladon BM, PARKIN T. … evaluation of subchondral bone injury of
the plantaro‐lateral condyles of the third metatarsal bone in Thoroughbred horses
identified using nuclear scintigraphy: 48 …. Equine Veterinary … 2010.
8. POWELL SE. Low-field standing magnetic resonance imaging findings of the
metacarpo/metatarsophalangeal joint of racing Thoroughbreds with lameness
localised to the region: A retrospective study of 131 horses 2011:no–no.
9. Tranquille CA, Parkin TDH, Murray RC. Magnetic resonance imaging-detected
adaptation and pathology in the distal condyles of the third metacarpus,
associated with lateral condylar fracture in Thoroughbred racehorses 2012:no–
no.
10. Ramzan P, Sommerville G, Shepherd M, Steven WN, Head MJ, Powell S, et al.
Preliminary clinical impressions on the use of stanozolol as a novel intraarticular
therapy for athletic horses: 60 cases. European Veterinary Conference
Voorjaarsdagen 2012:1–1.
11. Pinchbeck GL, Clegg PD, Boyde A, Barr ED, Riggs CM. Horse, training and racelevel risk factors for palmar/plantar osteochondral disease in the racing
Thoroughbred 2012:n/a–n/a.
12. Tull TM, Bramlage LR. Racing prognosis after cumulative stress-induced injury of
the distal portion of the third metacarpal and third metatarsal bones in
Thoroughbred racehorses: 55 cases (2000–2009). J Am Vet Med Assoc
2011;238:1316–22.
TECHNIQUE AND INTERPRETATION OF LOCAL ANALGESIA IN HINDLIMBS:
RULES AND PITFALLS
Michael Schramme DrMedVet, CertEO, PhD, DECVS, DACVS, AssocECVDI
Campus Vétérinaire de l’Université de Lyon, VetAgro Sup, 69280 Marcy L’Etoile,
France
In contrast with the forelimb, hindlimb foot lameness is rare in the hindlimb. Therefore
diagnostic analgesia of hindlimb lameness without localizing clinical signs of swelling
or pain on flexion, frequently begins with a low 6-point nerve block, in order to rule
out distal limb pain. If lameness is clearly improved following a low 6-point nerve
block, radiography and ultrasonography of the foot, pastern and fetlock is indicated.
More specific distal limb blocks may follow. If lameness is not improved following a
low 6-point nerve block, the clinician may choose to perform a radiographic
examination of the hock and stifle regions to rule out obvious abnormalities of these
joints prior to continuing diagnostic analgesia.
The only anatomical structures that can be desensitized (not always consistently) in
the upper limbs proximal to the sites of tibial and fibular nerve blockade are the large
articulations (stifle and hip) and some bursae. Apart from these synovial structures,
there remains a large volume of muscular, ligamentous, tendinous and osseous
tissue in the upper limbs that cannot be adequately desensitized with regional
analgesic techniques and therefore not be ruled out as a potential source of pain
during the course of a lameness examination.
Plantar digital nerve block
As in the forelimb, to desensitize the plantar aspect of the foot. Due to the presence
of the dorsal and plantar metatarsal nerves and their variable distal continuation into
the dorsal corium of the foot, a plantar digital nerve block does not desensitize the
dorsal aspect of the hoof and possibly the distal interphalangeal joint.
Abaxial sesamoid nerve block
Due to the presence of the dorsal and plantar metatarsal nerves and their variable
distal continuation into the dorsal corium of the foot, anaesthesia of the plantar
nerves at the level of the proximal sesamoid bone alone does not desensitize the
entire foot and pastern region. In order to desensitize the foot and pastern totally,
anesthesia of the dorsal metatarsal nerves and the dorsal continuation of the plantar
metatarsal nerves must also be performed. This is done by subcutaneous injection of
2 x 2 ml of local anesthetic solution on the dorsolateral and dorsomedial surface of
the proximal phalanx and thereby essentially performing a high pastern ring block.
Low 6-point nerve block
To perform a low plantar nerve block (low four-point block), the medial and lateral
plantar nerves and the medial and lateral plantar metatarsal nerves are anesthetized
at the level of the distal end of the second and fourth metatarsal bones. Because the
plantar pouches of the metatarsophalangeal joint (fetlock) can be entered
inadvertently when anesthetizing the plantar nerves at this level, some clinicians
prefer to anesthetize the plantar nerves more proximally. However, if a 25 gauge, 5/8
inch needle is carefully placed in a subcutaneous position parallel with the skin, the
risk of inadvertent fetlock joint injection can be minimized. Bulging of the skin during
injection suggests that local anesthetic solution remains in a superficial location. The
lateral and medial plantar nerves lie between the suspensory ligament and the deep
digital flexor tendon. To anesthetize them, deposit 2 mL local anesthetic solution
subcutaneously adjacent to the dorsal surface of the deep digital flexor tendon. The
medial and lateral plantar metatarsal nerves lie between the palmar surface of the
third metatarsal bone and the axial surface of either the second or fourth metatarsal
bone. To anesthetize them, use a ⅝-inch (1.6-cm), 25-gauge needle to deposit local
anesthetic solution, usually 1 mL, next to the periosteum beneath the distal end of
each small metatarsal bone where the nerve emerges.
By anesthetizing these four nerves, the fetlock and structures distal to it are
desensitized. The superficial and deep digital flexor tendons below this region are
desensitized as well as the distal aspect of the branches of the suspensory
apparatus. Proximal diffusion of local anesthetic solution to the extent that pain in
the proximal metatarsal region would be abolished is possible but according to one
report unlikely. Inadvertent and unrecognized injection of the digital sheath can also
occasionally occur when performing this block.
Due to the presence of dorsal metatarsal nerves, anesthesia of skin over the dorsal
aspect of the proximal phalanx and the fetlock can only be obtained by injecting 2 x 2
mL of local anesthetic solution on the dorsolateral dorsomedial surface of the third
metatarsal bone on either side of the long digital extensor tendon, at the same level
as the plantar metatarsal nerve blocks. Some clinicians believe this dorsal part of the
low 6-point nerve block to be unnecessary as they consider the sensory innervation
of the dorsal metatarsal nerves to be cutaneous only.
Subtarsal analgesia
Techniques include the high 6-point nerve block, the tibial nerve block, direct
infiltration of local anesthetic solution around the origin of the suspensory ligament
and anesthesia of the deep branch of the lateral plantar nerve.
With the high 6-point block, anesthesia of the medial and lateral plantar nerves, the
medial and lateral plantar metatarsal nerves, and the dorsal metatarsal nerves just
distal to the tarsometatarsal joint provides complete analgesia to structures in the
metatarsal region and below. To anesthetize the plantar metatarsal nerves in this
region, insert a 1.5-inch (3.8-cm), 20- to 22-gauge needle about 2 cm distal to the
tarsometatarsal joint and axial to the second or fourth metatarsal bone until its point
contacts the third metatarsal bone. Withdraw the needle slightly (2-3 mm) and
deposit 2 to 3 mL of local anesthetic solution at this location. The plantar metatarsal
nerves are usually anesthetized in this location with the horse bearing weight on the
limb. Anesthetizing both plantar metatarsal nerves alone at this level desensitizes the
second and fourth metatarsal bones and their interosseous ligaments as well as the
proximal portion of the suspensory ligament. Although not likely, local anesthetic
solution could
be inadvertently placed in the tarsometatarsal joint with this block. Inadvertent
administration of local anesthetic solution into the tarsal sheath is more likely when
blocking the plantar metatarsal nerves.
To anesthetize the medial and lateral plantar nerves in this location, deposit 2 to 3
mL of local anesthetic solution through a ⅝-inch, 25-gauge needle inserted through
the heavy fascia of the plantar tarsal flexor retinaculum to where each plantar nerve
lies adjacent to the dorsal surface of the deep digital flexor tendon. The plantar
nerves are usually anesthetized in this location with the horse bearing weight on the
limb.
All but the proximodorsal aspect of the limb distal to the tarsometatarsal joint is
desensitized by anesthetizing the medial and lateral plantar nerves and the plantar
metatarsal nerves. Subcutaneous deposition of 2 mL of local anesthetic solution at
the dorsomedial and the dorsolateral aspect of the metatarsus (either side of the long
digital extensor tendon) at this level though a ⅝-inch (1.6-cm), 25-gauge needle
anesthetizes the dorsal metatarsal nerves and completes the high 6-point nerve
block. Some clinicians believe this dorsal part of the high 6-point nerve block to be
unnecessary as they consider the sensory innervation of the dorsal metatarsal
nerves to be cutaneous only.
Anesthesia of the deep branch of the lateral plantar nerve has a better chance of
improving the specificity of diagnostic analgesia compared to the other techniques.
The horse is restrained with a twitch, the affected hindlimb lifted and the fetlock
supported on the clinician’s knee with the hock flexed at 90 degrees and the third
metatarsal bone positioned vertically. The superficial digital flexor tendon is deflected
medially and a 25 mm, 23 G needle inserted perpendicular to the skin surface, 15mm
distal to the head of the fourth metatarsal bone, on the plantarolateral surface of the
metatarsal region. The needle is advanced in a slightly dorsomedial direction
between the fourth metatarsal bone and the lateral border of the SDFT up to the hub
and 3 ml of mepivacaine is injected without resistance. Occasionally blood is seen to
flow freely from the needle indicating puncture of the venous portion of the (proximal)
deep plantar arch, in which case the needle should be re-directed slightly more
dorsolaterally to avoid intravascular injection. The lateral placement of the needle in
this technique reduces the risk of inadvertent penetration of the tarsometatarsal joint
and the tarsal sheath, when compared to other methods of subtarsal anesthesia.
However, in up to 20% of horses in which 2.5 ml of mepivacaine was injected at this
site, the lateral plantar nerve also appeared to have been desensitized. Therefore it
is always advisable to assess the effect of anesthesia of the distal limb with a low 6point nerve block first, prior to performing diagnostic anesthesia of the deep branch of
the lateral plantar nerve. Furthermore, recent studies have shown that significant
diffusion of local anesthetic solution up to 107 mm proximal to the injection site is
possible. In addition, penetration of the tarsometatarsal joint or the tarsal sheath
occurred in up to 25% to 38% of horses.
It is important to compare the degree of improvement following anesthesia of the
deep branch of the lateral plantar nerve with that seen after intra-articular analgesia
of the distal tarsal joints. Subtarsal analgesia may improve tarsometatarsal joint pain
and vice-versa, but most improvement in suspensory pain is usually seen following
anesthesia of the deep branch of the lateral plantar nerve. It has been suggested that
pain is less successfully alleviated by anesthesia of the deep branch if enthesopathy
of the proximal plantar portion of the metatarsal cortex is present. In these cases,
direct deeper infiltration of 2-4 mL of mepivacaine at the bone surface may be more
effective in abolishing lameness. Anesthesia of the tibial nerve alone eliminates
suspensory ligament pain without completely removing sensation from the distal
tarsal joints.
Intrasynovial analgesia of the tarsus
It is often claimed that injection technique can be rendered more simple by injecting
the tarsometatarsal (TMT) joint alone, thereby relying on communication between the
TMT joint and the distal intertarsal (DIT) joint for therapeutic benefits in both joints.
This would be especially practical when the DIT joint is partially collapsed or
ankylosed on the medial side, making injection difficult or impossible. In truth
however, reports of communication vary between 8 and 38%, and in spite of
anecdotal evidence that a tarsometatarsal joint block alone is often sufficient to
cause a significant improvement in horses with bone spavin, the practical conclusion
is that each of the two distal joints must be injected separately to ensure therapeutic
concentration of the drug in both joints.
Tarsometatarsal joint
A square inch of skin is clipped over the plantarolateral aspect of the hock, just
proximal to the head of the lateral splint bone. A preliminary surgical scrub is
performed and surgical spirit is applied. Using a 23-gauge needle, 2 ml of
mepivacaine can be injected subcutaneously, approximately 1 cm proximal to the
most prominent part of the head of the lateral splint bone. This procedure is often
facilitated by holding the limb in flexion in one’s lap. A second thorough surgical scrub
is performed and surgical spirit applied
The ipsilateral forelimb can be lifted and a twitch applied. Although sometimes
unnecessary, this precaution may stop some horses from trying to move off the limb
when injection pressure in the joint mounts.
With a pair of sterile gloves and a 23-gauge, 1-inch needle is inserted through the
skin and the plantar tarsal ligament into the plantar synovial outpouching of the
tarsometatarsal joint. The needle is inserted through the site of the skin bleb, 1 cm
proximal to the most prominent part of the head of the lateral splint bone and
advanced in a slightly proximodistal direction, angled approximately 30O lateral to the
sagittal plane of the limb. The tip of the needle should come to rest in the angle
between the fourth tarsal bone and the proximal articular surface of the lateral splint
bone. Five ml of mepivacaine hydrochloride is injected, the syringe and needle
withdrawn, and finger pressure maintained for 30 seconds on the skin to prevent
back flow of the anaesthetic solution. If the examiner is planning to inject the TMT
joint only, a volume of 10 ml may be injected into the joint under pressure as this is
believed to force a communication between the TMT and DIT joints. However, recent
evidence suggests that this is untrue and that local anesthetic diffuses distally to the
injection site with increasing volume. After injecting approximately 3 to 4 ml, the
horse will resent the increase in intra-articular pressure and attempt to move off the
limb. Further injection is easier if an assistant already has the ipsilateral forelimb
raised, or the procedure is performed with the limb lifted off the ground.
Distal intertarsal joint
Careful palpation of the medial surface of the tarsus allows identification of the
interosseous space between the combined first and second tarsal bone and the third
tarsal bone. This space can be felt as a small vertical depression along the medial
surface of the distal row of tarsal bone. It is approximately in line with the
interosseous space between the medial splint bone and the metatarsus, and can be
detected by continuing palpation of this space proximally. The vertical interosseous
space between the first/second tarsal bone and the third tarsal bone forms a T with
the horizontal line of the distal intertarsal joint space. The site for injection is at the
most proximal extent of the vertical component of the T-shaped interosseous space.
This site is prepared by clipping, scrubbing and possibly placing a subcutaneous skin
bleb of local anaesthetic solution. Wearing sterile gloves, a 23-gauge, 1-inch needle
is introduced through the skin bleb, searching for the interosseous foramen at the top
of the ‘T-shaped space’. This may require repeated attempts at redirecting the needle
in a slightly dorsomedial to plantarolateral direction. When the needle enters the
foramen, it can usually be advanced for approximately 1/2 to 3/4 inch. Sometimes the
space is too tight for a 23-gauge, 1-inch needle, in which case a 25-gauge, 5/8-inch
needle should be used. Fiveml of local anaestheticsolution is injected, the needle
withdrawn and finger pressure maintained for 30 seconds. Injection of collapsed DIT
joints can be difficult and a lot of pressure on the plunger of the syringe may be
required. If there is no joint space to be injected, high pressure injection results in
obvious subcutaneous accumulation of mepivacaine.
If the joints have been medicated, a small dressing consisting of a pad of gamgee
and a roll of elastic adhesive bandage can be applied to cover the injection site for a
few hours.
Tibiotarsal Joint
The tibiotarsal joint communicates with proximal intertarsal joint and the talocalcaneal
joint in all horses. With a 20 gauge, 1 inch needle positioned in the dorsomedial
pouch of the joint, between extensor tendons and the saphenous vein or just behind
the saphenous vein and approximately halfway between the medial malleolus and
the medial epicondyle of the talus, 10-15 mL mépivacaïne is injected into the joint.
Tarsal sheath
Synoviocentesis is performed on the medial aspect of the tarsus, just proximal or
distal to the chestnut. The landmark for needle position is the deep digital flexor
tendon, since the sheath follows it closely. The proximal needle entry site lies
between the tuber calcis and the sustentaculum tali, the distal entry just distal and
plantar to the most proximal extent of the medial splint bone. The proximal pouch of
the tarsal sheath lies caudoproximal to the plantaromedial pouch of the tibiotarsal
joint. It is difficult to inject if there is no synovial distension.
If there is no synovial effusion of the tarsal sheath, the best way of maximising
success of injection, is to perform the injection with the help of ultrasonographic
guidance. Ultrasonography is used to visualize the DDFT running across the plantar
surface of the sustentaculum tali. Pockets of synovial fluid can usually be visualized
dorsal to the DDFT at the proximal and distal margins of the sustentaculum tali in a
superficial position close to the skin surface. These pockets frequently offer the best
opportunity for insertion of a 20 gauge, 1 inch needle in the tarsal sheath. Analgesia
of the sheath is performed by injecting 10-15 mL mepivacaïne.
Tibial and Fibular nerve blocks
Anesthetizing the tibial and deep and superficial fibular (peroneal) nerves proximal to
the point of the hock desensitizes the entire distal portion of the limb. The tibial nerve
is anesthetized 4 inches proximal to the point of the hock on the medial aspect of the
limb, where it can be palpated on the caudal surface of the deep digital flexor muscle,
cranial to the calcaneal tendon only while the limb is flexed. To anesthetize the tibial
nerve with the limb weightbearing, the 1.5-inch, 20-gauge needle is placed from
medial between the DDFT and the calcaneal tendon and 20 mL of local anesthetic
solution is deposited in several planes in the fascia that overlies the deep digital
flexor muscle. To anesthetize the nerve with the limb flexed, the needle is positioned
along the palpable nerve and local anesthetic injected immediately adjacent to it. The
local anesthetic can then be massaged in and around the nerve before the limb is put
down. Failure to block the nerve is common because failure to penetrate the deep
crural fascia between the subcutis and nerve, and therefore subcutaneous injection
of local anesthetic solution does not anesthetize the tibial nerve. Horses may react
violently to needle placement when the needle contacts the nerve. Anesthesia of the
tibial nerve alone can be tested by finding a loss of skin sensation between the heel
bulbs of the heel, but this finding is variable. Amelioration of lameness after the tibial
nerve block alone may incriminate the proximal attachment of the suspensory
ligament as a site of pain.
The deep and superficial fibular nerves must also be anesthetized in order to
desensitize the hock and the limb distal to the hock completely. The site at which
these fibular nerves are usually anesthetized is on the lateral aspect of the crus
about 4 inches proximal to the point of the hock in the groove between the muscle
bellies of the lateral and long digital extensor muscles. Contrary to some reports, the
deep fibular nerve does not lie on the lateral surface of the tibia at this level, but
rather between both muscle bellies at a depth of 1 to 1.5 inches from the skin
surface. A 1.5- to 2-inch, 20- gauge needle is inserted into the groove, directed
slightly craniomedially to stay between the muscle bellies until a depth of 1.5 inches
is reached. Tipping the needle up and down during advancement between the
muscle bellies is helpful to avoid introducing the needle into muscle tissue. Ten mL of
local anesthetic solution is injected at this depth, 10 ml during withdrawal of the
needle into a subcutaneous position and another 5 ml subcutaneously in the
intermuscular groove. The horse may drag the toe of the desensitized limb or
stumble following anesthesia of the deep fibular nerve while loss of skin sensation
over the dorsolateral aspect of hock and metatarsus is inconsistent. Because of the
size and depth of the tibial nerve, it is suggested that up to 40 minutes may be
required to evaluate the effect of this block fully. This offers the opportunity of
sedating the horse with xylazine prior to performing the perineural injection, as the
effect of sedation will have worn off by the time the effect of the nerve block can be
fully evaluated.
Analgesia of the stifle joints
Centesis of the femoropatellar joint involves inserting the hypodermic needle into the
lateral cul-de-sac of the joint. Using this technique, a 1.5-inch, 18- to 20-gauge
needle is inserted perpendicular to the long axis of the limb, approximately 2 inches
proximal to the palpable lateral edge of the lateral tibial condyle, just caudal to the
caudal edge of the palpable lateral patellar ligament. The needle is inserted until its
tip contacts bone, withdrawn slightly and 20 mL local anesthetic injected.
The site of injection of the medial compartment of the femorotibial joint is located
between the medial patellar ligament and the medial femorotibial ligament just
proximal to the palpable proximal border of the medial meniscus. The joint is
penetrated with a 1- to 1.5 inch, 20-gauge needle at a depth of 0.75 to 1 inch and 20
mL of local anesthetic injected.
Centesis of the lateral compartment of the femorotibial joint can be performed most
reliably by inserting a needle into a diverticulum that surrounds the medial aspect of
the tendon of the long digital extensor muscle and extends distally about 3 inches
from the tibial plateau. The combined tendons of the long digital extensor and
peroneus tertius muscles are palpated in the extensor groove that lies between the
tibial tuberosity and the lateral tibial condyle. Centesis of the diverticulum can be
performed by inserting a 1.5 inch, 20-gauge needle directly through the center of the
tendon of the long digital extensor muscle, 0.5 to 1.5 inches distal to craniolateral
edge of the tibia, until the tip of the needle contacts bone. The needle is retracted
slightly before 20 mL local anesthetic solution is injected. Synovial fluid is not
generally observed using this technique, but accuracy of the technique is high.
Analgesia of the coxofemoral joint
The coxofemoral joint of the pelvis is the most difficult joint to enter. The important
landmarks are the cranial and caudal parts of the greater trochanter of the femur,
located two-thirds of the distance between the palpable tuber coxae and the ischiatic
tuberosity. There is a notch between the cranial and caudal parts of the greater
trochanter, through which a 6-inch, 18-gauge spinal needle is directed slightly
downward in a 30 to 45 degrees craniomedial direction. The joint should be
penetrated at a depth of 4 to 5 inches. Twenty to 30 mL of local anesthetic are
injected once successful positioning has been confirmed by aspiration of joint fluid.
Ultrasonographic visualization has been used to improve accuracy of needle
placement.
Analgesia of the trochanteric bursa
The trochanteric bursa is located beneath the flat tendon of the accessory gluteal
muscle, which passes over the cranial part of the greater trochanter and lies tightly
against it when the horse bears weight on the limb. The most reliable bursocentesis
technique is that described by Toth et al. (2011). To access the trochanteric bursa,
the coxofemoral joint is extended by placing the foot caudally to the joint in a
Hickman block. The most proximal aspect of the cranial part of the greater trochanter,
over which the trochanteric bursa is positioned, is palpated. A 3.5 inch, 18-gauge
needle is inserted using ultrasonographic guidance, until the needle contacts bone,
and 15 mL of local anesthetic is injected. Distension of the trochanteric bursa is
observed when local anesthetic solution is injected into the bursa.
References
1. Bassage LH, Ross MW. Diagnostic analgesia. In: Ross MW, Dyson SJ, eds.
Diagnosis and Management of Lameness in the Horse. St.Louis: Elsevier
Science; 2003:93-124.
2. Claunch KM, Eggleston RB, Baxter GM. Anesthetic diffusion following two
approaches to block the deep branch of the lateral plantar nerve, in Proceedings.
Am Assoc Equine Pract 2013;59:84.
3. Contino E, King M, Valdes-Martinez A, et al. In vivo diffusion characteristics after
perineural injection of the deep branch of the lateral plantar nerve with
mepivacaine or iohexol in horses, in Proceedings. Am Assoc Equine Pract
2013;59:85.
4. David F, Rougier M, Alexander K, Morisset S. Utrasound-guided coxofemoral
arthrocentesis in horses. Equine Vet J. 2007;39:79-83.
5. Hinnigan GJ, Singer ER. Distal limb nociceptive threshold measurement following
anaesthesia of the deep branch of the lateral plantar nerve in 20 horses. In
Proceedings, 19th Ann Cong Eur Coll Vet Surgeons 2010;44-45.
6. Hughes TK, Eliashar E, Smith RK. In vitro evaluation of a single injection
technique for diagnostic analgesia of the proximal suspensory ligament of the
equine pelvic limb. Vet Surg. 2007;36:760-764.
7. Moyer W, Schumacher J and Schumacher J. Equine Joint Injections and
Regional Analgesia. (2011) Academic Veterinary Solutions LLC, Chadds Ford,
PA 19317 USA.
8. Schumacher J, Schumacher J, Wilhite R. Comparison of four techniques of
centesis of the lateral compartment of the femorotibial joint of the horse. Equine
Vet J. 2012;44:664-667.
9. Tóth F, Schumacher J, Schramme M, Hecht S. Evaluation of four techniques for
injecting the trochanteric bursa of horses. Vet Surg. 2011;40:489-493
DIFFERENTIATING HIND LIMBS LAMENESS: DOES THE CLINICAL EXAM
ALREADY HIGHLIGHT THE POTENTIAL DIAGNOSIS?
Filip Vandenberghe DrMedVet, Associate (LA) ECVDI
Equine Hospital De Bosdreef, Moerbeke Waas, Belgium
Introduction
A lameness examination consists of a multi-stage protocol that at the end
delivers eventually a conclusive diagnosis. Diagnostic imaging, at the end of this
protocol, mostly visualizes the structural abnormalities, that have to be related to the
clinical presentation, and be named the potential cause of the lameness.
Nevertheless too frequently the first steps in the protocol, i.e. the static and dynamic
examination, are jumped over roughly and clear indications of the relevant diagnosis
are not noticed, where they should. The history and clinical exam remain one of the
most valuable parts in the search to the cause of lameness. Knowledge gained by
advanced imaging in large populations of previous examined horses, might as well
help in ‚detecting’ subtle clinical presentations of certain types of musculoskeletal
disease. During the examination several questions need to be answered. Is the horse
lame? On which limb(s)? From which region on the limb? What’s the structure/tissue
damaged? What’s the possible treatment, prognosis and reconvalescence schedule?
The challenge is to detect as soon as possible in the examination process,
indications that lead to a conclusive diagnosis. A good use of the veterinarians’ eyes
and hands might prevent the owner of expensive and sometimes useless additional
examinations such as MRI, bonescan,… Advanced imaging may never be the
replacement of a badly performed clinical examination.
Lameness examination
If the definition of lameness is an ‚altered gait’ , it can be divided in three large
groups: lameness due to pain, non-pain (mechanical) lameness and neurological
lameness. The vast majority of lameness cases are provoked by pain. Causes of
lameness can be traumatic, single of multiple microtrauma, developmental,
congenital or acquired, infection, metabolic, neurologic.
The examination starts with a good anamnesis. Did the lameness present
acutely or more chronically. What’s the age, breed and use of the horse. On which
grounds is the horse mainly working. Did the lameness present at work or in the field,
stall, paddock. What’s the evolution over time. Are there any treatments installed and
what has been the response. What’s the influence of rest? Preferably the
examination is not performed when the horse has been rested a long time. The risk
of examining coincidental and thus confusing lameness and not the cause of the
original problem is high.
A classic exam consists of a thorough static examination, a dynamic
examination, flexion tests and diagnostic anesthesia.
Static examination
The static examination consists of a visual inspection and palpation. Knowledge
of the normal conformation and what the results of abnormal conformation are, is
crucial. As a normal conformation of the hind limb, seen from the side, a line can be
drawn from the ischiadic tuber region, behind the calcaneus, following the cannon
bone down and hit the ground a bit behind the heel bulbs. If the hind limb is more in
front horses are ‚standing under’ and if more to the back they are ‚post legged’.
Smaller hock angles make the limb sickle hocked and larger angles straight hocked.
Small hock angels (<150°) are more frequently seen in lame horses and almost none
of the elite show jumpers and dressage horses are sickle hocked. Sickle
hocked
limbs are more prone to show synovitis / arthritis / osteoarthritis of stifle and hock. On
the other end extremely straight hocks (>160°) are at higher risk of developing
proximal suspensory disease. Especially in combination with dropped fetlocks. We
have to say that the story of chicken and egg counts here as well… Straight hocked
horses show less flexion of the hock at movement, less propulsion and often lack of
power at the jump or highly collected dressage work.
Seen from the back the hind limb can be base wide or base narrow, often in
combination with closed hocks and open stifles.
At visual inspection the normal positioning of the limbs is evaluated. Neurologic
horses may not correct at stance normally and leave one or another leg a bit
strangely outside of the body. Normal horses do stand more or less symmetrically
and bear weight equally. Muscle atrophy, swellings, joint distensions, tendon
enlargement, scarring are all closely paid attention to. At palpation every anatomical
region is closely evaluated and potential responses to pain are critically monitored.
Passive flexion of every joined individually, as anatomical possible, is performed and
evaluated for stiffness, pain or abnormal instability.
Dynamic examination
Looking at lame horses is an ever ongoing learning curve and training of the
eye is required to look at a moving horse all at once, instead of every limb
individually. Every orthopedic clinician might look slightly differently. As long as the
interpretation and conclusion is similar, there’s no problem. The last decade objective
analysis of lameness, such as the lameness locater, ground plate, force plate,
pressure plate, etc… has made great proces and may help in the training of students
and the evaluation of more subtle lamenesses. Video analysis with slow motion might
help as well in detecting subtle changes. Nevertheless one has to pay attention that
2D evaluation on a screen will always remain different compared to 3D live viewing.
What’s right or wrong is up to debate. Routinely the horse is seen in all gaits on hard
and soft grounds, on straight line and both circles. Seeing the horse under the saddle
might help in identifying the true problem of the rider and horse and prevent from
diagnosing coincidental findings.
Especially the evaluation of the lame hind limb requires some expertise in less
obvious and severe cases. Some subjectivity is seen and between different clinicians
the appreciation and grading differs more on the hind limb than the front limb.
Watching the horse trotting away is often easier to detect pelvic, tuber coxae or
gluteal rise. Evaluation the arc of foot flight, length of the stride, the joint angels and
head movement is more visible, looking from the side.
Generally speaking the lame horse is trying to avoid or unload the affected
limb. This is provoking abnormal movements of the head and neck or the pelvis,
weight shifting, altered phases of the stride, altered joint angles, altered times of
weight bearing… Classification can be made into supporting limb (weight bearing
limb) lameness, swinging limb lameness, mixed lameness, primary or complementary
lameness. If a horse is lame on one limb it might show ‚false lameness’ on another. If
the horse ‚shows’ lameness on a hind limb and the ipsilateral frontlimb, often the hind
limb lameness is true. If lame on the diagonal, often the front lameness is true or the
horse is lame on both. Supporting limb lameness is often said to be related to distal
limb pathologies and swing limb lameness to proximal limb pathologies. This is still
true in a large group of horses. Nevertheless has diagnostic anesthesia and
advanced imaging shown that in several pathologies it might be the other way
around. Differentiation in between hard and soft tissue pathology is often tried as
well, but still remains difficult to predict. Hind limb lameness is very dependent on the
breed and the use of the horse, but around 80% of the causes are located in the
hock and stifle region. In comparison over 95% of the front limb lameness causes are
located in the distal limb.
Different grading systems are used, the AAEP grading system being potentially
the most common. Every grading system has grey zones and none of them is 100%
accurate.
Lameness associated with stifle pathology is rare in the absence of articular
distension. Hip pathology is extremely uncommon. Desmitis or rupture of the
accessory ligament of the femur (lig. capitis femoris) is diagnosed via the
pathognomonic clinical presentation of outwards rotation of the toe and stifle and
inward rotation of the hock. The horses lean over to the opposite site. Sacroiliac joint
related pathology might give a painful response to firm pressure over the tuber
sacrale, but diagnosis is often suspected by the lack of propulsion at canter or bunny
hopping. Distal tarsitis horses are lame in all conditions (hard and soft grounds), inand outside leg. The flexion test of the hock is positive. Remarkably, following the
author, the first steps jogging away after the flexion test might be ok, but the horse
becomes more lame after 5-6 steps. Proximal suspensory disease horses have an
instant positive flexion test of the hock, but often have a more positive response to
distal limb flexion. Fetlock problems resent often passive flexion of the joint and the
flexion test is positive. Interphalangeal joint related pathologies have a positive
flexion as well, but often only slightly and the passive flexion is tolerated better. Most
of the significant soft tissue pathology, except for subtle enthesiopathy of the
proximal suspensory ligament, often shows marked swellings and abnormality at
visual inspection and palpation. The rest of the examination is guided through that.
References
1.
Ross, Dyson in Diagnosis and Management of Lameness in the horse, 2003,
Ed Saunders
2.
Baxter, in Adam’s and Stashak’s Lameness in the horse 6th Ed., Ed Wiley
Blackwell
3.
Keegan KG, Evidence based lameness detection and quantification. Vet. Clin.
Nrth America Eq. Pract. 2007, 23:403-423
4.
Holmstrom et al., Variation in conformation of Swedish Warmblood Horses and
conformational characteristics of elite sports horses; EVJ 1990; 22:186-193
5.
Holmstrom M, The effects of conformation, in Equine Locomotion, Back W,
Clayton, Eds WB Saunders, Philadelphia, 2001:281-296
6.
Gnagey, Clayton, Lannovat, Effect of standing tarsal angle on joint kinematics
and kinetics; EVJ 2006:38, 628-33
SPLINT BONE FRACTURES: SURGERY OR NOT?
Bruce Bladon BVM&S, Cert EP, DESTS, Dipl ECVS, MRCVS
Donnington Grove Veterinary Surgery
Newbury, Berkshire, United Kingdom
The splint bones are the second and fourth metacarpal / metatarsal bones.
These bones are vestigial, having no distal articulation. However they both all four
bones have significant proximal articulation with the distal row of carpal / tarsal bones
in the carpo / tarso meta carpal / tarsal joints. The fourth metatarsal bone, the lateral
splint bone in the hind limb, has the least substantial articular surface, while the
fourth tarsal bone has a substantial articulation with the third metatarsal (cannon)
bone.
Fractures
The splint bones have very limited soft tissue covering and are susceptible to
trauma, as they are relatively flimsy. Fractures of the splint bones are one of the
commonest fractures of the horse. Clients are always determined that their horse’s
injury is caused by a kick. Seldom will you disappoint a client by telling them that the
chronic osteoarthritis which their horse has was caused by a kick when the horse
was a foal. Splint bones fractures, along with olecranon fractures, are one of the few
injuries which are consistently and commonly caused by kicks.
It is common and helpful practice to divide splint bone fractures into three types,
those of the distal, the middle and the proximal third of the bones. It is also
convention to divide the fractures into closed and open. However, this is not helpful,
as the large majority of fractures are open, and closed fractures are very seldom a
therapeutic dilemma.
The diagnosis of splint bone fractures is straightforward. Splint bone fractures
should be anticipated with any wound of the lateral or medial cannon bone region,
particularly if the horse shows significant lameness. It is generally remarkable that a
horse with a large skin laceration will be “sound” as far as a casual examination goes,
i.e weight bearing and walking evenly. Lameness, noted at rest or walking, with any
wound is a serious sign and warrants further investigation. Ironically, the veterinary
surgeon must ignore the petulant whining of their client who will be convinced that
their horse should be lame with such a wound.
The diagnosis is confirmed by radiography. In the majority of cases the
fractures are comminuted, complete and fairly obvious. It is important to take both
oblique views, including the “wrong” one. Thus, a fracture of a lateral splint bone
would traditionally be highlighted by a dorsolateral plantar medial oblique view.
However, a considerable amount of information is often visible on the dorsomedial
plantarlateral oblique view, firing through the cannon bone. Several views may be
necessary to ensure that the fracture is viewed completely “through” the medulla,
with no overlap of the cortex of the third metatarsus.
Occasional cases provide some dilemma, distinguishing between a chronic
fracture or a simple metatarsal exostosis, or “splint”. Again, the relevance of this is
moot, as the treatment is rest, and the diagnosis is often provided to placate the
client - a fracture for those who will not rest the horse, and a “splint” for those who
worry about their horse too much. Advanced imaging, either MRI or CT, is very
seldom of any practical benefit when dealing with splint bone fractures.
Treatment
Fractures of the splint bones are a common surgical condition in the horse.
Various surgeries are used, but usually involve resection of the fractured portion of
the bone, either with or without resection of the distal portion of the bone, and with or
without stabilisation of the proximal portion. One or two screws, placed in lag or
positional fashion, can be used to stabilise the proximal portion of the bone, but these
can pull through. Generally, if stabilisation of the proximal bone is selected then a
plate, contoured over the splint bone and onto the cannon bone is a more secure
repair.
When reviewing surgery it is important to question the rationale for fracture
repair. Distal fractures are usually the result of “internal trauma”. The commonest
condition which results in a fracture of the distal splint bone is desmitis of the branch
of the suspensory ligament. However, many soft tissue conditions of that region may
result in fracture of the distal splint bone, such as collateral ligament desmitis. Non
union is a common result with these fractures, often with some smooth new bone on
either end of the fractured bone. It is evidently very difficult to confirm if lameness is
coming from such a chronic fracture, or if it is coming from the injured soft tissue
structure. Thus many distal fractures undergo surgery to reassure both owner and
veterinary surgeon that the non union is not the source of lameness. It is also
conceivable that a distal fracture may be associated with infection. However,
comminution of these fractures is much less usual, so true sequestration is rare.
Obviously if the fracture is genuinely infected then debridement of the septic parts of
the bone is a very reasonable objective.
Mid body fractures are usually highly comminuted and open. These fractures
often result in sequestration of cortical bone fragments, leading to wound infection,
delayed healing and exuberant granulation tissue. Thus surgery to remove the
fragments is often performed. The necessity for removal of the entire distal portion of
the bone is debated. It can be reasoned that without proximal support and blood
supply the distal portion may not be viable. However, I have always just removed the
fractured portion of the bone, and this approach has been published (Jenson et al
2004).
Proximal fractures usually cause the most concern when it comes to therapy.
These fractures are commonly highly comminuted and are usually open. They can
be articular, raising concerns about septic arthritis. The rationale for surgery is not
obvious. Treatment of septic arthritis is not necessarily enhanced by removal of a
large part of the articular surface. Reconstruction of the articular surface is obviously
ideal, but is often not feasible due to the comminuted nature of the fractures. These
fractures may support infection, with sequestration of some of the many bone
fragments. However, at this level the splint bones have a medulla, a marrow cavity,
and thus the bone has an endosteal as well as a periosteal blood supply. Thus,
infection and sequestration is actually much less common than with fractures of the
mid third, where there is no medullary cavity to the bone.
Having examined the rationale for surgery, the next question to ask is the
complications of surgery. While splint bone fractures are often perceived as a simple
surgical procedure, analysis of the literature suggests complications can be serious.
Analysis of my own surgical series reveals one fatal fracture of the cannon bone, one
fatal luxation of the proximal splint bone, one fatal fracture of the tibia, and one
luxation of the fetlock, which was managed with cast immobilisation successfully.
From 58 cases this is a serious complication rate of 7%. At the ECVS conference in
2012 Caroline Tessier presented a case of a fatal cannon bone fracture following
removal of the fractured portion of the mid third of a splint bone. When questioned,
perhaps half the audience had had a similar experience. Sherlock et al in 2008
reported one fatal cannon bone fracture of 32 surgical cases, Jackson et al in 2007
one from 63 cases, while Jenson et al in 2004 reported no fatalities from 17 cases.
With my series, excluding the fractures other than the fatal cannon bone one, this is
fatality rate of 1.8%. This represents one of the problems with equine veterinary
surgery. Anyone who has performed 30 or so of a particular procedure can
reasonably consider themselves quite experienced in that procedure. However, by
chance, a complication rate of 3% may well not have occurred to them. Such
analysis is the next hurdle for veterinary surgery, moving from analysis and
presentation of tens of cases to that of hundreds of cases. The figures presented
here clearly illustrate this point - surgery of splint bone fractures is dangerous and
results in fatality in approximately 1:50 cases.
If surgery is dangerous, the next question is, is it necessary? Anecdotablly we
had noticed several cases which responded very well to conservative management.
Surgery was recommended in one case, but by the time all the syndicate members
had agreed on surgery the wound had healed! Several cases of proximal fractures
made excellent progress. We conducted a retrospective study of all cases which the
staff of Donnington Grove Veterinary Surgery were consulted about, from 2008 to
2013. It was necessary to include those we were consulted about, as once a
conservative approach is adopted, the supply of horses actually physically
transported to Donnington Grove Veterinary Surgery dries up remarkably quickly,
particularly in this day and age when radiographs can be shared so easily. Sixty six
horses were identified. The fractures were divided into proximal middle and distal
thirds, and into conservative or surgical management. The success rate, comparing
surgical and conservatively managed cases were almost identical.
The most consistent feature was the poor success with distal splint bone
fractures, regardless of management. This was attributed to the frequency of
associated soft tissue injury. It was considered that the surgery was sufficiently
simple that surgical technique could not explain a success rate of < 50% for
amputation of the distal splint bone.
In conclusion, splint bone fractures are a common traumatic injury of the horse.
Distal splint bone fractures are a slightly different injury, secondary to “internal” rather
than external trauma. Surgery for fractured splint bones carries a small but
significant risk of fatal complications. This risk is quite a difficult risk to perceive, as
many surgeons will consider themselves experienced without experiencing this
complication. The results of surgery do not justify taking this risk, as the success with
conservative management is comparable.
References
1. Jenson PW, Gaughan EM, Lillich JD, Bryant JE. Segmental ostectomy of the
second and fourth metacarpal and metatarsal bones in horses: 17 cases (19932002). J Am Vet Med Assoc 2004;224:271–4.
2. Jackson M, Fürst A, Hässig M, Auer J. Splint bone fractures in the horse: a
retrospective study 1992–2001. EqVetEduc 2007;19:329–35.
3. Sherlock CE, Archer RM. A retrospective study comparing conservative and
surgical treatments of open comminuted fractures of the fourth metatarsal bone
in horses. EqVetEduc 2008;20:373–9.
Table 1:
Horses
66
Surgery under GA
Standing surgery
Medical treatment
15
3
48
Di
M
Pr
Di
M
Pr
Di
M
Pr
9
6
0
2
1
0
4
25
19
Returned to exercise
4
5
44%
83%
0
1
1
1
23
17
50%
100%
25%
92%
89%
INJURIES OF THE SUSPENSORY BRANCHES AND BODY
Natasha Werpy, DVM, DACVR
Radiology Department, University of Florida
Laura Axiak, DVM
Introduction
The anatomy of the suspensory ligament (SL) is complicated because multiple
tissue types are present. Specifically ligamentous fibers, as well as regions of fat and
muscle. These various tissue types affect its appearance, particularly with ultrasound
and other advanced imaging such as MRI. Thus, to properly utilize imaging for a
diagnosis, it is imperative to understand the normal anatomy of the structure or
region/structure of interest as well as the associated appearance basted on the
imaging modality.
Anatomy of the Hind Limb Suspensory Ligament
The SL is the hind limb begins as a triangular shape at the proximal aspect of
the third metatarsal bone. The triangle is thinner medially than it is laterally. The
suspensory ligament is closer to the fourth metatarsal bone, with a larger amount of
connective tissue separating it from the second metatarsal bone. The anatomic
relationship between the hind SL and the fourth metatarsal bone is important when
considering ultrasound examination of this structure. As the ligament continues
distally is becomes heart-shaped to round and then oval, until it reaches the level of
the bifurcation. Throughout the transitions in shape of the SL, the apex of the
triangle and the heart shape, which is the plantar margin of the ligament, is directed
plantar lateral. This results in the majority of the SL lateral of midline and adjacent to
the axial margin of the fourth metatarsal bone. The relationship becomes less
important distally as the size of the fourth metatarsal bone decreases relative to the
SL. In contrast to the SL in the forelimb, the hind SL typically has a prominent area
of central fibers as well as peripheral fibers, and is not bilobed. The fat and muscle
distribution is similarly positioned when comparing medial and lateral aspects of the
ligament, in contrast to the variable appearance in the forelimb. However, random
areas of fat and muscle can still dissect through the ligament to the peripheral
margin. These regions should not be mistaken for a tear. Similar to the SL in the
forelimb, regions of fat and muscle converge into a zig-zag pattern as the ligament
takes on an oval shape. The muscle does not continue into the suspensory ligament
branches. However, the connective tissue is represent in the branches in somewhat
of random pattern. The branches change shape, beginning proximally as round or
oval, and then more distally as triangular. They then decrease in size at distal extent
of insertion.
Ultrasound
Ultrasound is an extremely useful tool for the diagnosis of SL injury. However,
as described in this section, diagnosis of SL injury often requires the clinician to go
above and beyond the techniques that can provide a diagnosis for the flexor tendons.
This section will explain why altering the direction of the ultrasound beam is
necessary to visualize the SL anatomy and required to identify pathologic change. It
will cover additional techniques that should be used in conjunction with the standard
technique of SL ultrasound to provide a comprehensive examination. Don’t get put
off by the physics paragraph, it is really straight forward and necessary to properly
ultrasound the SL.
Anisotropy - One of the Ultrasound Physics Principles that REALLY matters!
The complicated anatomy of the SL requires additional ultrasound techniques
to be employed for complete visualization of the ligament and to correctly identify its
anatomy. One of the challenges of SL ultrasound it that the regions of fat and
muscle create variations in the ligament echogenicity. This echo pattern makes it
difficult to determine if these variations in echogenicity are the result of injury or the
normal SL anatomy. A technique that can be used to correctly identify regions of SL
fibers versus areas of fat and muscle is called off angle or oblique incidence imaging.
The basis for this technique is the ultrasound physics principle of anistrophy. We use
this principle every time we adjust the angle of the ultrasound probe proximally or
distally in order to create maximum echogenicity when examining the palmar
metacarpal flexor tendons in transverse plane. When the ultrasound beam is truly
perpendicular to the longitudinal axis of linear fibers within a normal tendon,
maximum echogenicity is created. When the ultrasound beam is not perpendicular to
normal tendon we can create decreased echogenicity in that structure. In contrast to
normal tendon or ligament fibers, the echogenicity of fat and to a lesser degree
muscle is not dependent on the angle of ultrasound beam. The difference between
the echogenicity of SL fibers versus the regions of fat and muscle becomes very
apparent when the ultrasound beam is not perpendicular to the longitudinal axis of
the SL fibers. This change in the position of the probe can be used to identify regions
of fibers versus regions of fat and muscle.
Normal SL fibers will be echogenic when the ultrasound beam is perpendicular to the
longitudinal axis of the fibers and will become hypoechogenic when the ultrasound
beam is no longer perpendicular to the fibers. In contrast, regions of fat and, to a
lesser degree, muscle will remain echogenic regardless of beam angle. Therefore,
comparing the appearance of the SL with the beam both perpendicular and not
perpendicular to the ligament allows identification of fibers versus regions of fat and
muscle. Therefore, regions of mottling or decreased echogenicity identified in the
suspensory ligament with ultrasound can then be further investigated using changes
in beam angle to determine if the source of the decreased echogenicity is normal
ligament fibers or regions of fat and muscle. This technique provides a method for
determining the actual tissue source which allows us to determine if this is part of a
normal pattern of the suspensory ligament or a region of injury.
Similar to the areas of fat and muscle, the echogenicity of the connective tissue
surrounding the SL is not beam angle dependent (remains echogenic regardless of
beam angle). Placing the ultrasound beam slightly oblique to the SL allows
differentiation of the ligament margins from the surrounding echogenic connective
tissue.
Understanding the Effect of Edge Artifacts and Vasculature on the SL when
using the Standard Approach
The importance of understanding the effect of edge artifacts and through
transmission on the appearance of the suspensory ligament when using the standard
ultrasound technique cannot be underestimated. Both artifacts cause alterations in
the echogenicity of the SL as a result of interaction between the US beam and
adjacent structures.
Edge artifact occurs when the sound beam hits a curved surface and is deflected
away from the ultrasound probe. The deflected sound beam then never returns back
to the ultrasound probe, consequently the machine has no information about this
area and it appears as a black line on the image. Using a palmar metacarpal vessel
as an example, the sound wave leaves the ultrasound probe and travels toward the
vessel. When it encounters the palmar and dorsal margins of the vessel it is reflected
back to the ultrasound machine creating an anechoic circular structure bordered by
dorsally and plantarly by white lines. However, the angle of the medial and lateral
vessel margins causes the sound wave to be deflected away from the ultrasound
probe. The medial and lateral vessel walls do not have the same double echogenic
lines seen associated with the dorsal and palmar walls. In addition, extending from
the medial and lateral vessels walls are hypoechoic lines extending through the
tissues deep to the vessel. This can occur with any curved structure when sound
beam encounters the interface at an oblique angle, such as the SDFT in the
metacarpus or the DDFT at the metatarsus.
Through transmission, also called distal acoustic enhancement, causes an artifactual
increase in echogenicity in tissue deep to a fluid filled structure, such as a vessel.
The fluid filled structure does not absorb as much of the sound beam as the adjacent
tissue at the same level. As the sound beam continues along its path, the tissue
deep to the fluid filled structure encounters a stronger or less attenuated US beam. A
stronger beam returns to the ultrasound probe and is interpreted by the machine as
brighter or more echogenic tissue. Any tissue deep to a vessel or other fluid filled
structure will appear brighter than adjacent tissue that is at the same depth.
Edge artifact and through transmission occur simultaneously as the sound beam
encounters a vessel. When trying to decipher this pattern it is easier to identify the
structures that could be affecting the echogenicity of the SL before evaluating the
ligament itself. Using the metacarpal region as an example, identify any edge artifact
resulting from any soft tissue structures, such as the SDFT, and follow it dorsally to
identify where it crosses the SL (Fig – US images vessel). Identify the vessels palmar
to the SL and follow the edge artifact from the margins dorsally and determine where
they cross the SL. Next look at the width and depth of the vessels palmar to the SL
and evaluate the corresponding echo pattern in the SL; the further away the vessel is
located the less effect it will have on the echogenicity of the SL. Follow the vessels
dorsally to the SL, with an expectation of increased echogenicity in the SL relative to
fibers that are dorsal to vessels. Using the same thought process, the regions of the
SL not affected by through transmission (no adjacent vessels) should be relatively
less echogenic when compared to the regions affected by through transmission.
Once this evaluation is completed the SL ligament can be evaluated with an
expected echo pattern based on surrounding structures. Abnormalities in the
ligament will alter this expected echo pattern.
Standard Technique in the Hindlimb
The standard technique for evaluation of the SL in the hindlimb involves using
a medial approach as has been described for the proximal aspect of the suspensory
ligament. (Denoix) In certain cases, the mid to distal aspects of the suspensory
ligament body must be imaged from the plantar aspect of the limb because at this
location the medial aspect of the limb does not provide an adequate contact surface
to allow visualization of the ligament. As discussed in the anatomy section the
majority of the proximal suspensory ligament is lateral of midline. In addition the axial
margin of the fourth metatarsal bone, which is curved, wraps around the lateral
margin of the suspensory ligament and obscures it from view when imaging from the
plantar aspect of the limb. By using the deep digital flexor tendon as a window and
directing the ultrasound beam dorsolaterally the entire suspensory ligament can be
visualized. The hind suspensory ligament changes shape more dramatically than the
front suspensory ligament. In addition, subtle changes in shape are often visible
before ligamentous abnormalities are detected. Therefore, comparison to the
opposite limb is imperative. In addition, the size and shape of the fourth metatarsal
bone changes in similar fashion to the suspensory ligament. The size and shape of
the fourth metatarsal bone and its relationship to the third metatarsal bone can be
used to ensure comparisons between the right and left hind limbs are being made at
the same level. As previously discussed in the standard technique of the forelimb,
standard measurement techniques as well as ultrasound machine settings that
maximize image quality for imaging of the SL should be utilized. Evaluation of the SL
margins for peri-ligamentous tissue proliferation should be performed. The nonweight bearing technique can be applied in the hind limb. In certain cases it is easier
to see the fiber versus fat-muscle regions with the limb in a non-weight bearing
position.
Non-weight Bearing Technique
In addition to the standard technique, the suspensory ligament should be
examined with the limb mildly flexed at the tarsus and fetlock, with the limb in a
resting position. If the horse is resistant in maintaining this position, the limb can be
held in a more flexed position for this examination. Examining the suspensory
ligament with the limb in a non-weight bearing position allows improved visualization
of the suspensory ligament when compared to the standard technique. Flexion of the
limb results in relaxation of the plantar soft tissues. The flexor tendons can then be
manipulated, which will increase the contact area for the ultrasound probe. The entire
SL is now visible in one image with the US beam oriented in a dorsal to plantar
dimension, as opposed to the standard technique. The manipulation of the flexor
tendons decreases the depth between the ultrasound probe and the suspensory
ligament, thereby increasing image detail by allowing the use of a higher frequency.
This method allows visualization of the relationship between the second and fourth
metatarsal bones and the suspensory ligament.
Identifying Pathologic Change in the Hind Limb SL using Ultrasound
Abnormalities in the size, shape, margin and echogenicity can all indicate
abnormalities in the SL. Focal variations in the ligament echogenicity identified using
the standard technique require further investigation with the limb in a non-weight
bearing position. Reexamining these regions with the limb in a non-weight bearing
position and varying US beam angles will establish if they are associated with SL
fibers or regions of fat and muscle. It is important to note the dorsal aspect of the SL
may have decreased echogenicity when compared to the rest of the ligament. This
may be the result of relaxation artifact. Further investigation of this appearance is
warranted, but diffuse subtle decreased echogenicity in a ligament with a normal size
and shape should be interpreted with caution. Regions of injury in the SL fibers will
have decreased echogenicity regardless of beam angle. They will appear as
decreased echogenicity with the beam angle not perpendicular to the fibers. Their
appearance will remain unchanged as the beam is moved perpendicular to the SL
ligament and the surrounding normal fibers become echogenic. In contrast, scarring
will be echogenic regardless of beam angle and can have associated ligament
enlargement. The echogenicity of mature fibrous tissue is independent of beam
angle, creating its echogenic appearance despite changes in beam angle.
Often injury to the SL alters the fat and muscle distribution, and creates indistinct
margins between regions of fibers and areas of fat and muscle. The regions of fat
and muscle can become less evident with diffuse enlargement of the ligament and
with focal regions of fiber injury and enlargement. Loss of the normal fat-muscle
distribution in combination with abnormal fibers is often seen in conjunction with SL
injury.
The margins of the SL should be closely examined. This is best done with the limb in
a non-weight bearing position and the US beam not perpendicular to the SL. Dorsal
margin fraying or tears and focal areas of enlargement along the dorsal border of the
SL are best identified using this technique. Abnormalities in the SL margin will be
evident adjacent to echogenic connective tissue. It is important to recognize that
some amount of edge artifact is present on the medial and lateral margins of the hind
SL using this technique. Therefore, margin tears or peri-ligamentous tissue
proliferation on the medial and lateral margins of the SL will be best visualized using
a medial approach. Abnormalities in the plantar margin of the third metatarsal bone
will be recognized with the beam angle both perpendicular and not perpendicular to
the osseous surface and best identified using the plantar approach. The beam angle
that best characterizes the appearance will depend on the lesion margins and
configuration. The axial margins of the second and fourth metatarsal bones and their
relationship to the SL should be assessed.
Identifying abnormalities in the suspensory ligament branches is more easily
achieved than evaluation of the suspensory ligament body. The lack of muscle tissue
at the level is beneficial in decreasing the ambiguity of the images at this level. The
branches should be evaluated for the presence of enlargement, fiber abnormalities
and enthesopathy (proliferative or resorptive) at the suspensor ligament attachment
on the sesamoid bones. In addition, the per-ligamentous tissues should also be
evaluated.
In all cases comparison to the opposite leg is imperative. In many cases bilateral
disease is present. However, one limb is often more affected than the other so
comparison of limbs can still be beneficial. When possible the SL should be
reexamined 2-4 weeks following the initial diagnosis. In certain cases the injury will
be worse in this time frame despite treatment. Additional rechecks and treatment
plan can be made by visualizing full extent of injury which should be evident with the
combination of these two US examination approaches.
DIAGNOSIS OF PROXIMAL METATARSAL AND TARSAL PAIN
Michael Schramme DrMedVet, CertEO, PhD, DECVS, DACVS, AssocECVDI
Campus Vétérinaire de Lyon, VetAgro Sup
Université de Lyon, France
Proximal plantar metatarsal pain can be defined as lameness that improves following
anesthesia of the deep branch of the lateral plantar nerve or other forms of subtarsal
anesthesia. Proximal plantar metatarsal pain appears to have become the most
commonly diagnosed cause of hindlimb lameness in Sports Horses, even more
common than distal tarsal joint pain. While the diagnosis of proximal suspensory
desmitis (PSD) in Sports Horses appears to have increased in recent years, the
reasons for this remain poorly understood. Improved recognition not only by
veterinarians but also by equestrian professionals certainly has played a role. Modern
training demands, regimes and surfaces may also contribute. Predisposing factors
have been identified as dressage training not only at advanced level but also at
lower, non-elite levels, straight hocks and hyperextended fetlock conformation.
History and clinical signs
PSD is frequently, though not always, associated with a straight hock and
hyperextension of the MCP/MTP joint. It is not always clear if this appearance is a
primary risk factor or a secondary postural change due to loss of strength of the stay
apparatus in affected horses. The reason for presentation of the horse to a
veterinarian may vary from subtle loss of performance to marked, unilateral
lameness. Loss of performance during ridden work may present itself as bilateral
stiffness, loss of hindlimb impulsion, difficulties in transitions, resistance to lateral
exercises, flying changes or canter pirouettes, evasive behavior, or reduced power
when jumping. Horses tend to warm out of early injuries fairly quickly. Lameness may
be absent or present as mild with an insidious progression or severe with an acute
onset. Bilateral lameness is common and can be mild to moderate in degree.
Clinical signs of acute inflammation of the suspensory ligament (swelling, heat and
pain over the affected ligament) may be evident in acute cases but are more
frequently absent. The presence of swelling is best identified by palpation in the
standing limb. Swelling will result in some loss of the concave profile of the skin on
the plantarolateral aspect of the limb, between the plantar border of the lateral splint
bone and the lateral margin of the superficial digital flexor tendon in the proximal
metatarsal region. This is a highly specific clinical finding, even when mild and it
should always be compared with the same area in the contralateral limb. Pain on
palpation is easier to detect in the raised limb even though the proximal part of the
suspensory ligament is difficult to palpate in the hindlimb because it is largely
covered by the heads of the lateral and medial splint bones and lies deep to the
digital flexor tendons. The best technique here is to exert pressure on the proximal
part of the suspensory ligament by compressing the flexor tendons dorsally. Horses
with PSD may also resent pressure between the head of the lateral or medial splint
bone, and the lateral or medial margin of the superficial digital flexor tendon. Some
clinicians believe the Churchill test to be particularly useful in identifying pain in the
proximal part of the hind suspensory ligament. Bony enlargement on the medial
aspect of the hock may occur in advanced stages of distal tarsal joint disease but
earlier stages may not be apparent in many horses.
Evaluation of lameness should be performed with the horse trotting in straight lines
and lunging in circles both on a hard and a soft surface. As in many horses with
hindlimb lameness, both distal tarsal joint pain and proximal suspensory pain present
with a reduced arc of foot flight, reduced extension of the fetlock joint and shortening
of the cranial phase of the stride. Horses with distal hock pain may carry the limb
medially during protraction and land more on the lateral aspect of the foot leading to
increased wear of the toe and lateral branch of the shoe. When examining horses
with hindlimb lameness, the use of a wireless, inertial, sensor-based system of
lameness quantification (Lameness Locator® - EquinosisTM) can be of tremendous
help to quantify the degree of lameness objectively and to characterize the nature of
the asymmetry in vertical displacement of the pelvis between strides. Horses with
PSD often show push-off lameness during the second part of the weight bearing
phase of the stride while horses with distal tarsal joint pain more frequently tend to
show an impact lameness during the early part of weight bearing. The effect of
circling and surface variation on lameness arising from PSD is less predictable than
the effect on lameness arising from distal tarsal joint pain. There is frequently but not
always a moderately positive response to both distal and proximal flexion tests for
PSD, while distal tarsal joint pain generally results in a positive proximal flexion test.
In some horses with PSD, lameness is only obvious under saddle, especially when
the rider is sitting on the diagonal of the lame limb.
Diagnostic anesthesia
There are many different ways of removing sensation from the proximal plantar
metatarsal region, in particular from the origin and body of the suspensory ligament.
Techniques include the high 6-point nerve block, the tibial nerve block, direct
infiltration of local anesthetic solution around the origin of the suspensory ligament
and anesthesia of the deep branch of the lateral plantar nerve. This latter technique
has a better chance of improving the specificity of diagnostic anesthesia compared to
the other techniques. The horse is restrained with a twitch, the affected hindlimb lifted
and the fetlock supported on the clinician’s knee with the hock flexed at 90 degrees
and the third metatarsal bone positioned vertically. The superficial digital flexor
tendon is deflected medially and a 25 mm, 23 G needle inserted perpendicular to the
skin surface, 15mm distal to the head of the fourth metatarsal bone, on the
plantarolateral surface of the metatarsal region. The needle is advanced in a slightly
dorsomedial direction between the fourth metatarsal bone and the lateral border of
the SDFT up to the hub and 3-4 ml of mepivacaine is injected without resistance.
Occasionally blood is seen to flow freely from the needle indicating puncture of the
venous portion of the (proximal) deep plantar arch, in which case the needle should
be re-directed slightly more dorsolaterally to avoid intravascular injection. The lateral
placement of the needle in this technique reduces the risk of inadvertent penetration
of the tarsometatarsal joint and the tarsal sheath, when compared to other methods
of subtarsal anesthesia. However, in up to 20% of horses in which 2.5 ml of
mepivacaine was injected at this site, the lateral plantar nerve also appeared to have
been desensitized. Therefore it is always advisable to assess the effect of anesthesia
of the distal limb with a low 6-point nerve block first, prior to performing diagnostic
anesthesia of the deep branch of the lateral plantar nerve.
Lameness is assessed 10-15 minutes after injection. Critical evaluation of the degree
of improvement can be performed accurately and objectively with a wireless, inertial,
sensor-based system of lameness quantification (Lameness Locator® - EquinosisTM).
This is essential when considering treatment by neurectomy. It is also important
when comparing the degree of improvement with that seen after intra-articular
anesthesia of the distal tarsal joints. Subtarsal anesthesia may improve
tarsometatarsal joint pain and vice-versa, but most improvement in suspensory pain
is usually seen following anesthesia of the deep branch of the lateral plantar nerve. It
has been suggested that pain is less successfully alleviated by anesthesia of the
deep branch if enthesopathy of the proximal plantar portion of the metatarsal cortex
is present. In these cases, direct deeper infiltration of 2-4 cc of mepivacaine at the
bone surface may be more effective in abolishing lameness. Anesthesia of the tibial
nerve alone eliminates suspensory ligament pain without completely removing
sensation from the distal tarsal joints.
Differential diagnosis
Some clinicians have suggested that the differences in clinical signs between
proximal metatarsal pain and distal tarsal joint pain are best summarized as shown in
the table below, even though it makes some generalisations.
PROXIMAL SUSPENSORY
DESMITIS
Worse with exercise
Avoid fetlock loading
Push-off lameness
Positive nerve block of the deep
branch of the lateral plantar nerve
Mild response intra-articular
anesthesia
Mild or no response to intra-articular
therapy
DISTAL TARSAL JOINT PAIN
Better with exercise
Normal fetlock loading
Impact lameness
Negative nerve block of the deep
branch of the lateral plantar nerve
Positive response intra-articular
anesthesia
Positive response to intra-articular
therapy
Table 1: Comparison of clinical features of proximal suspensory pain and distal tarsal
joint pain.
Imaging
An accurate imaging diagnosis of proximal metatarsal pain or distal tarsal
osteoarthritis (OA) is of great importance as recommended options for management
are costly and time demanding. This diagnosis can be based on radiographic,
scintigraphic, sonographic and MR imaging findings. It is well known that the severity
of lameness in horses with distal tarsal joint pain does not correlate well with the
severity of radiographic disease. Radiographic and scintigraphic findings are useful
for the detection of bone injuries associated with PSD but are frequently nonspecific.
Sonographic assessment of the proximal portion of the suspensory ligament is
difficult. High-field MR imaging was recently shown to be the most reliable technique
for accurate diagnosis of the causes of proximal metatarsal pain.
It is recommended that a complete radiographic examination of the tarsus and
proximal metatarsal regions is always performed as distal hock joint pain and PSD
may coexist in horses with proximal metatarsal pain. Though increased radiopacity in
the proximal plantar metatarsal region may be more extensive in horses with chronic
PSD, these radiographic findings are frequently not specific. In a recent review of 155
horses with PSD, 21% of lame limbs had a spur on the dorsoproximal aspect of the
third metatarsal bone, 30% had mild, diffusely increased radiopacity proximolaterally
in the third metatarsal bone, 3% focal areas of intensely increased radiopacity, and
6% low-grade osteoarthritis of the distal tarsal joints.
Ultrasonographic examination of the proximal portion of the suspensory ligament is
performed using a 7.5 or higher MHz linear-array transducer and must always include
comparison with the contralateral limb. A delay of 1 - 2 days after diagnostic
anesthesia is useful to avoid imaging artefacts caused by air in the tissues.
Alternatively the ultrasonographic examination may precede the use of nerve blocks.
Even with careful attention to detail, ultrasonographic examination of the proximal
metatarsal region is a difficult technique. Modifications to ultrasonographic technique
that have been suggested to improve accuracy include a plantaromedial position for
the ultrasound probe, holding the limb in a non-weight-bearing position and using an
off-incidence ultrasound beam. In addition, the use of stand-off pads and convex
array or virtual convex array transducers may offer a wider field-of-view on the
proximal portion of the suspensory ligament. It has been suggested that the presence
of injury of the proximal part of the suspensory ligament is most commonly
recognized by the presence of ultrasonographic enlargement with poor demarcation
of the borders and diffuse reduction of the echogenicity rather than by the presence
of focal areas of hypoechogenicity, but this is not in accordance with the focal nature
of many lesions as observed on high-field MR images. The cross-sectional area of
the suspensory ligament is difficult to measure at this level as the lateral and medial
margins of the ligament are usually invisible. Even so, the cross-sectional area of
normal suspensory ligaments was measured on MR images as 0.86 cm2 at the level
of the tarsometatarsal joint, 2.08 cm2 at 2 cm, 1.81 cm2 at 4 cm, 1.69 cm2 at 6 cm and
1.57 cm2 at 8 cm distal to the level of the tarsometatarsal joint.
Nuclear scintigraphy can not be considered a sensitive tool for the detection of PSD
in the hindlimbs of lame horses. Both pool and bone phase images were found to be
abnormal in only 15 % of horses with ultrasonographic evidence of PSD. Increased
radiopharmaceutical uptake was associated with more severe ultrasonographic
lesions. Increased radiopharmaceutical uptake in the proximoplantar aspect of the
third metatarsal bone without detectable ultrasonographic or radiographic
abnormalities represents primary osseous pathology such as stress injury or
enthesopathy at the origin of the suspensory ligament, rather than PSD per se.
Recent high-field MR imaging studies of horses with proximal plantar metatarsal pain
have indicated that proximal suspensory desmopathy and/or enthesopathy (PSD)
was identified as the cause of lameness in the majority of them (55-80 %), while in
20-25% of horses a pathologic process unrelated to the suspensory ligament was
documented, and in 10-20% of cases no reason for the lameness could be found in
the proximal metatarsal or distal tarsal regions. Lesions that were considered
responsible for lameness but were unrelated to the suspensory ligament included
osteoarthritis of the distal tarsal joints, osseous cyst-like lesions of the tarsal bones,
tarsal bone edema, enthesopathy of the intertarsal ligaments, osseous injury of the
third or fourth metatarsal bones, tendinopathy of the deep or superficial digital flexor
tendon, and desmopathy of the plantar ligament. Other injuries that should be
considered in the proximal plantar metatarsal region are stress fractures of the
plantar metatarsal cortex and avulsion fractures of the origin of the suspensory
ligament. Neuropathy of the deep branch of the lateral plantar nerve may be the
cause of pain in horses without imaging abnormalities.
High-field MR imaging findings in lame horses indicated that lesions of the proximal
part of the suspensory ligament consisted predominantly of focal areas of signal
increase, that extended on average from 14.2 mm to 50.4 mm distal to the level of
the tarsometatarsal joint, with lesion length varying from 4.3 mm to 107 mm. When
comparing ultrasonographic with MR imaging findings, ultrasonography was found to
have a sensitivity of 66% and a specificity of 31% for the diagnosis of confirmed PSD.
Because of the high incidence of false positive ultrasonographic diagnoses,
ultrasonography was considered of limited value for the detection of PSD. In
comparison with high-field magnets, low-field MR imaging on standing horses only
has a limited ability to show anatomic detail of the proximal portion of the suspensory
ligament and to detect soft tissue lesions accurately, mainly due to imaging artefacts
caused by movement of the horse.
References
1. Brokken MT, Schneider RK, Sampson SN, Tucker RL, Gavin PR, Ho CP.
Magnetic resonance imaging features of proximal metacarpal and metatarsal
injuries in the horse. Vet Radiol Ultrasound 2007;48:507–517.
2. Labens R, Schramme MC, Robertson ID, Thrall DE, Redding WR. Clinical, MR
and sonographic imaging findings in horses with proximal plantar metatarsal
pain. Vet Radiol and Ultrasound. 2010;51:11-18.
3. Toth F, Schumacher J, Schramme M, Holder T, Adair HS, Donnell RL.
Compressive damage to the deep branch of the lateral plantar nerve associated
with lameness caused by proximal suspensory desmitis. Veterinary Surgery,
2008; 37:328-335.
4. Murray RC, Dyson SJ, Tranquille C, Adams V. Association of type of sport and
performance level with anatomical site of orthopaedic injury diagnosis. Equine
Vet J Suppl. 2006;36:411-416.
5. Dyson SJ and Murray RM. Management of hindlimb proximal suspensory
desmopathy by neurectomy of the deep branch of the lateral plantar nerve and
plantar fasciotomy: 155 horses (2003-2008). Equine Vet J. 2012;44:361-367.
6. Hughes TK, Eliashar E, Smith RK. In vitro evaluation of a single injection
technique for diagnostic analgesia of the proximal suspensory ligament of the
equine pelvic limb. Vet Surg. 2007;36:760-764.
7. Hinnigan GJ, Singer ER. Distal limb nociceptive threshold measurement following
anaesthesia of the deep branch of the lateral plantar nerve in 20 horses. In
Proceedings, 19th Ann Cong Eur Coll Vet Surgeons 2010;44-45.
8. Denoix JM, Coudry V, Jacquet S. Ultrasonographic procedure for a complete
examination of the proximal third interosseous muscle (proximal suspensory
ligament) in the equine forelimbs. Equine Vet Educ 2008;20:148–153.
9. Pond V. and Smith RKW. A comparison of the ultrasonographic and histological
appearance of the origin of the suspensory ligament and the insertion of the
straight distal sesamoidean ligament. In Proceedings, 36th BEVA Congress
1997; 132.
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normal equine rear suspensory ligament using ultrasonography, magnetic
resonance imaging, and histology. Vet Radiol Ultrasound. 2012;53:318-328.
Further references available from author upon request.
PROXIMAL METATARSAL PAIN
A Diagnostic Dilemma
History + risk factors + lameness or poor performance
Tentative
diagnosis of
PSD?
Recumbent MRI ?
+ DBLPN block
A BUCKET
DIAGNOSIS?
Standing MRI = may be difficult
Ultrasound unreliable
Radiography and
scintigraphy non-specific
RADIOGRAPHY AND RADIOLOGY OF THE TARSUS
Roger Smith MA VetMB, DEO, PhD, DECVS, AssocECVDI
Dept. of Veterinary Clinical Sciences, The Royal Veterinary College, Hawkshead
Lane, North Mymms, Hatfield, Herts. AL9 7TA. U.K.
Indications
- Effusion in the tarsocrural joint
- Lameness localised to the tarsal region
- Developmental orthopaedic disease candidates (eg osteochondrosis)
- Trauma to the hock
Radiographic technique and anatomy
The four standard projections of the equine hock are:1.
Lateromedial (LM) projection
This is particularly useful for evaluating the medial trochlear ridge of the talus,
the calcaneus and the dorsal aspects of the proximal intertarsal, distal intertarsal
and tarsometatarsal joints.
2.
Dorsoplantar (DP) projection
This is particularly useful for evaluating the medial aspects of the proximal
intertarsal, distal intertarsal and tarsometatarsal joints. However, it is relatively
difficult to produce well-aligned images of the distal tarsal joints in this view,
compared to the DLPMO.
3.
Dorso-45-lateral plantaromedial oblique (DLPMO) projection
This is useful for evaluating the dorsomedial aspects of the proximal intertarsal,
distal intertarsal and tarsometatarsal joints, the calcaneus, the fourth tarsal bone
and the fourth metatarsal (splint) bone.
4.
Plantaro-45-lateral dorsomedial oblique (PLDMO) projection
This is the view of choice for evaluation of the lateral trochlear ridge of the tibial
tarsal bone and the sustentaculum tali of the fibular tarsal bone. It also skylines
the second metatarsal bone and the dorsolateral aspects of the proximal
intertarsal, distal intertarsal and tarsometatarsal joints.
The anatomy of all these projections is illustrated in the line drawings.
Further projections which may be of use are:5.
Flexed LM projection
This is useful for evaluating the caudal aspect of the distal tibia.
6.
Flexed DP projection of the calcaneus and sustentaculum tali
This allows these structures to be evaluated in a DP projection without
superimposition of the tibia.
7.
Various lesion-oriented obliques can be designed to look at pathology in
individual animals based on findings in the "standard" projections.
Radiographic abnormalities
1.
(a)
Soft Tissue Problems
Tenosynovitis of the tarsal sheath
In some animals, tenosynovitis (thoroughpin) is associated with lameness. In
these cases, the sustentaculum tali should be evaluated to look for roughening
and new bone formation which is damaging the deep digital flexor tendon.
Alternatively, a few cases of thoroughpin may be associated with ossification of
the tarsal sheath, rather than new bone formation on the sustentaculum tali.
(b)
Other synovial distensions
Enlargement of various bursae, other tendon sheaths or the tarsocrural joint can
be assessed using contrast radiography if required. This is also useful for
assessing communication between structures and leakage from them if there is
an overlying wound.
(c)
Calcinosis
Although classically associated with the shoulder and stifle joints in the horse,
calcinosis can be seen as circular or oval granular deposits adjacent to the hock
joint.
2.
Infective Arthritis
In its early stages, this will be recognised as soft tissue swelling alone; later,
there will be variable degrees of destruction of subchondral bone, together with
new bone formation around the joints. This will generally be more extensive and
irregular than that related to degenerative joint disease.
3.
Osteoarthritis (Degenerative Joint Disease)
This affects both the high motion (tarsocrural) joint but more commonly the low
motion (proximal intertarsal, distal intertarsal and tarsometatarsal) joints of the
hock. New bone formation is more limited in the case of the tarsocrural joint,
and will be recognised on the distal tibia in the lateromedial projection and on the
medial malleolus in the dorsoplantar projection. The low-motion joints will
demonstrate variable degrees of new bone formation and subchondral bone
destruction, usually best visualised in the DLPMO view.
4.
Osteochondrosis Dissecans
This affects most commonly the distal intermediate ridge of the tibia and, less
commonly, the lateral trochlear ridge and medial malleolous. Both lesions are
best evaluated in the PLDMO projection.
5.
Bone Cysts
These may be found in the small tarsal bones, as elsewhere.
6.
Fractures
These take various configurations, and their clinical significance will depend on
their effect on stability of the hock and the individual joints affected.
7.
Tarsal Collapse
In young foals, tarsal collapse involving the central and third tarsal bones may
cause a "curby-hocked" appearance, associated with dorsal movement of the
proximal part of the calcaneus. This may also lead to slab fractures of the dorsal
aspects of these bones.
8.
Luxation/Subluxation
This may affect any of the joints, but clearly luxation of the tarsocrural joint is
more of a disaster than luxations affecting the other joints!
9.
Angular Deformities
These are associated with the distal tibia and, like the carpus, are usually valgus.
Line drawings of the radiographic anatomy of the hock
ULTRASONOGRAPHIC EVALUATION OF THE TARSUS
Natasha Werpy, DVM, DACVR
Radiology Department, University of Florida
Laura Axiak, DVM
Introduction
The tarsus is a common source of performance limitations and equine hind
limb lameness. Radiography is the most commonly used diagnostic modality for the
tarsus. Radiography in the tarsus can be used for detection of joint arthrosis,
developmental orthopedic disease, trauma or infection. Joint arthrosis is
characterized by periarticular osteophyte production, subchondral bone sclerosis or
lysis and joint space narrowing. Scintigraphic examination of the tarsus can be used
as an adjunct to radiographs to evaluation the physiologic state of osseous
abnormalities. Scintigraphic examination can be used for detection of incomplete or
non-displaced fractures. Enthesopathy at soft tissue attachments and osteoarthritis
can be evaluated using scintigraphy. Reassessment of osseous lesions that may not
change on radiographs can provide useful clinical information. A lack of radiographic
abnormalities or radiographic abnormalities confined to soft tissue attachments, as
well as certain scintigraphic findings may indicate soft tissue injury of the tarsus
which can be further investigated with ultrasound. In addition, swelling of the tarsus,
synovial distention and/or wounds can be examined with ultrasound to determine the
extent of the injury and the involved structures. However, ultrasound of the tarsus can
be challenging due to the anatomic complexity of the region.
The process for a standardized comprehensive and thorough examination of the
structures of the tarsus has been described and illustrated.1 Common tarsal region
injuries diagnosed with ultrasound include tarsocrural joint synovitis and/or arthrosis,
tarsal sheath distention, collateral ligament injury, peroneus tertius tendonitis or
rupture, cranial tibialis muscle and cunean tendonitis, fragments and/or mineralization
of the tarsus, and calcaneal bursitis.2,3 The interosseous ligaments of the tarsus
cannot be visualized with ultrasound and are best evaluated with MR imaging. In
addition, MR images best demonstrate fluid in the bones of the tarsus compared with
other imaging modalities.
Techniques for Ultrasound of the Tarsus
Ultrasound of the tarsus requires a linear transducer with a 7.5 to 12 MHz
range of frequency and a depth of 2 to 6 cm. Use of a standoff pad is necessary for
superficial structures. Due to the complex anatomy the tarsus can be systematically
divided into four regions – dorsal, plantar, medial and lateral.
Tarsal Structures to Evaluate with Ultrasound
 Dorsal structures
o Tibia
o Cranial tibialis muscle and cunean tendon
o Peroneus tertius muscle tendon
 Origin: extensor fossa of the lateral femoral condyle
 Insertion: inserts with four distinct tendons to the tarsus
 Ruptured tendon = tarsal joint can be extended while stifle is
flexed
o Long digital extensor muscle tendon


Plantar structures
o Tuber calcanei
o Superficial and deep digital flexor tendons
o Tarsal tendon sheath
o Long plantar ligament
o Proximal branch of the suspensory ligament
o Calcaneal bursae
 Subcutaneous calcaneal bursa: superficial to the SDFT and
variably present
 Intertendinous calcaneal bursa: between SDFT and
gastrocnemius tendon
 Gastrocnemius bursa: cranial to the insertion of the
gastrocnemius tendon on the tuber calcanei
Collateral ligaments of the tarsocrural joint
o Medial collateral ligament
 Long part
 Superficial
 Origin
o Caudal medial malleolus
 Insertion
o Distal tuberosity of the talus
o Distal tarsal bones
o Proximal second and third metatarsal bones
 Short part
 Origin
o Cranial medial malleolus
 Continues plantar distal to insertion
 Insertion
o Branches
 Proximal tuberosity of the talus and the
sustentaculum tali
o Lateral collateral ligament
 Superficial part
 Origin
o Caudal lateral malleolus
 Insertion
o Calcaneus, fourth tarsal bone, third tarsal bone and
fourth metatarsal bone
 Deep part
 Origin
o Cranial lateral malleolus
 Directed caudally
 Insertion
o Lateral talus and calcaneus
Conclusions
Horses with swelling of the tarsal region, wounds or distention of the synovial
structures should be referred for ultrasonographic examination to determine extent of
injury and involved anatomical structures. Tarsal region injuries diagnosed with
ultrasound may include collateral ligament injury, joint or synovial structures
abnormalities, or injury to the peroneus tertius or superficial digital flexor tendons.
Careful systemic ultrasound technique is important due to the complex anatomy of
this region.
References
1. Vilar, JM, Rivero MA, Arencibia A, et al. Systematic exploration of the equine
tarsus by ultrasonography. Anat. Histol. Embryol. 2008;37:338-343.
2. Raes, EV, Vanderperren, K, Pille, F, et al. Ultrasonographic findings in 100
horses with tarsal region disorders. The Veterinary Journal 2010;186:201-209.
3. Vanderperren, K, Raes, E, Hoegaerts, M, et al. Diagnostic imaging of the equine
tarsal region using radiography and ultrasonography. Part 1: the soft tissues. The
Veterinary Journal 2009;179:179-197.
THE USE OF STANDING MRI IN THE DIAGNOSIS OF HINDLIMB LAMENESS
Filip Vandenberghe DrMedVet, Associate (LA) ECVDI
Equine Hospital De Bosdreef, Moerbeke Waas, Belgium
Introduction
The last decade MRI has revolutionized our understanding in a large group of
musculoskeletal pathology causing lameness. Especially in the foot MRI has given a
better insight in the different potential causes of foot pain, previously undetected by
radiography and ultrasonography. Magnetic resonance imaging is, whether it’s high
field or low field, mainly limited to the distal limb. Images can be obtained from the
foot to the carpus or tarsus. In some limited MRI machines images of the equine
stifle, under general anesthesia, can be produced. Over 90% of the lameness in a
fore limb is located in the distal limb, whereas about 80% of the causes of hind limb
lameness is located either in the hock or stifle region. Indications for hind limb MRI
examinations are thus less common. Especially as hind foot lameness is less
common, diagnosis in hind limb lameness is often already made through the more
classic diagnostic procedures.
The equine distal hind limb
Just as in any other region, hind limb lameness is tried to be localized to a
certain region, before diagnostic imaging is performed. In case diagnostic anesthesia
is failing, the help of bone scintigraphy can especially in the hind limb be beneficial.
Nevertheless lameness then often is coming from regions inaccessible for MRI. An
important anatomical region where the classic diagnostic modalities often fail to give
a reliable conclusive and clinically significant diagnosis is the distal and plantar hock
region, including the origin of the suspensory ligament. Seen the often confusing
normal ultrasonographic appearance and the questionable clinical value of minor
ultrasonographic changes at the proximal third and origin of the suspensory ligament,
MRI (and bone scintigraphy) are of great value in the examination of that region.
Diagnostic anesthesia localizing lameness to that region often interferes with
potential lameness coming from the distal tarsus (TMT, DIT joint). As the treatment
and management of proximal suspensory disease and distal tarsitis (bone spavin) is
very different, it’s of great importance to diagnose the true site of pain. Combination
of both pathologies is not uncommon in sports horses and are a diagnostic and
management challenge. MRI of the proximal metatarsal and distal tarsal region has
significantly clarified some of the misunderstandings from the past. In the acute
presentation of proximal suspensory disease, where ultrasound doesn’t reveal major
abnormalities, MRI is capable to demonstrate increased STIR signal at the endosteal
margin of the origin. In the more chronic stage even with MRI it might be very difficult
to evaluate the true source of pain and cause of lameness. (Standing) MRI of the
distal row of tarsal bones frequently only shows some increased subchondral bone
densification. Nevertheless those horses might have a truly significant increased
uptake on bone scintigraphy in that region and treatment is often directed based on
the bone scan findings.
The metatarsophalangeal joint is examined with MRI as well. Pathologies are
more or less similar to the findings in the front limb, with a high percentage (70%) of
subchondral bone changes such as sclerosis, bone-edema due to inflammation of
due to necrosis. Incomplete ‚fissures’ midsagitally in proximal P1 is, as in front
fetlocks, not uncommon. Contrary to the front limbs in the phalanges of the hind limb
more ‚dramatic’ STIR increased signal is often detected. Soft tissue pathologies in
the pastern and fetlock region are in our hospital less frequently detected. Especially
for pathology of and in the digital flexor tendon sheath, ultrasonography and
tenoscopy are preferred over MRI in the diagnostic process. Longitudinal fibrillation of
the borders of DDFT, SDFT or manica flexoria is in subtle cases not easily picked up
on standing MRI. Contrary to literature (Biggi, Dyson) significant soft tissue pathology
in the foot is not commonly seen either. Especially the evaluation of the collateral
ligaments of the DIP joint and the proximal collateral ligaments of the distal
sesamoidean bone are blurred because of magic angle artefact and often falsely
diagnosed. Performing standing MRI of a hind foot is often a challenge. Horses
naturally point out a bit the toe when they are positioned in the magnet, influencing
massively the presence of magic angle artefact in the collateral ligaments, de
sesamoidean ligaments and even the DDFT. A proper foot placement in the magnet,
instead of correcting the pilots, is crucial in performing MRI of the hind foot (and
fetlock). Besides the obvious bone pathologies and the occasional soft tissue
pathology (DDFT tear) at our hospital MRI of the hind foot often doesn’t reveal major
pathologies. The lameness is often located to the foot by an intra-articular anesthesia
of the distal interphalangeal joint, only being positive after 10 minutes of waiting time.
The cause of lameness is then often concluded to be in the pododerm / cushion /
sole, regions where the sensitivity and specificity of (low field) MRI in detecting
pathology is lower.
References
1.
Murray, 2011, Equine MRI, ed: Wiley Blackwell
2.
Biggi M, Dyson S, Hind foot lameness: results of magnetic resonance imaging
in 38 horses (2001-2011), Equine Vet J, 2013, Jul; 45(4):427-434
3.
Daniel AJ et al., Comparsion of radiography, nuclear scintigraphy and magnetic
resonance imaging for conditions of the distal tarsal bones of horses: 20 cases
(2006-2010). JAVMA 2012 May 1;240(9):1109-14
4.
Schramme M et al., Characterization of the origin and body of the normal
equine rear suspensory ligament using ultrasonography, MRI and histology. Vet
Radiology Ultrasound 2012 May-Jun;53(3):318-28
5.
Labens R et al. Clinical, magnetic resonance, and sonogrpahic imaging findings
in horses with proximal plantar metatarsal pain. Vet Radiology Ultrasound 2010
Jan-Feb;51(1):11-8
6.
Bischofberger AS et al., Magnetic resonance imaging, ultrasonography and
histology of the suspensory ligament origin: a comparative study of normal
anatomy of warmblood horses. Equine Vet J 2006 Nov;38(6):508-16
7.
Werpy NM, Denoix JM, Imaging of the equine proximal suspensory ligament,
Vet Clin North Amr Equine Pract. 2012 Dec;28(3):507-25
SURGERY FOR PROXIMAL SUSPENSORY DESMITIS
TO CUT IS TO CURE?
Bruce Bladon BVM&S, Cert EP, DESTS, Dipl ECVS, MRCVS
Donnington Grove Veterinary Surgery
Newbury, Berkshire, United Kingdom
Diagnosis
Proximal suspensory desmitis is a well recognised, common, and extremely
badly defined cause of lameness. Though proximal suspensory desmitis is the
accepted terminology, proximal metatarsal pain would be a more accurate
description. Pathological studies have inconsistently demonstrated abnormalities,
and diagnostic imaging has also yielded variable findings. The condition has
remarkable similarities with “tennis elbow” in humans. This condition is also rather
poorly defined, but is clinically consistent. Tennis elbow is not characterised by
inflammation, rather by degeneration, and the pain experienced is not predicted by
diagnostic imaging.
Proximal suspensory desmitis is a condition which causes moderate lameness in
either front limb or hindlimb. Bilateral cases, particularly in the hindlimb, can present
as poor performance, with loss of impulsion or reduced jumping performance. There
are few localising clinical signs. Pain on palpation of the proximal suspensory
ligament is common in the forelimb, and is rare in the hindlimb. I have not found pain
on palpation of the suspensory to be helpful diagnostically. Many normal horses
have marked pain on palpation of the ligament. It is helpful in detecting whether a
nerve block has anaesthetised the proximal suspensory ligament.
The lameness is localised to the proximal suspensory ligament by nerve blocks.
Particularly in the forelimb, many cases are exacerbated by an abaxial sesamoid
nerve block.
Whether a “four point nerve block” can diffuse proximally to
anaesthetise the proximal suspensory ligament is controversial. However, in my
opinion it is common, and a positive response to a four point nerve block cannot be
interpreted as diagnostic of fetlock pain. Lameness is abolished by a sub tarsal or
sub carpal nerve block. There are more ways to perform these nerve blocks than it is
possible to imagine. In the hindlimb, my favoured block is anaesthesia of the lateral
plantar nerve, by injection of 3ml of local anaesthetic between the superficial digital
flexor tendon and the head of the lateral splint bone. There is loose connective
tissue in this area and there should be no resistance to injection. We perform this
nerve block with the limb elevated and partly flexed. The tendon and splint bone are
digitally separated and a 1” needle is directed straight in between the two. An
alternative technique, which we use in cases which have not responded to a “lateral
plantar block” is to inject 5ml of local anaesthetic adjacent to the plantar surface of
the cannon bone, immediately axial to either splint bone, just distal to the origin of the
suspensory ligament. Some horses do respond to this block and not the former.
In the forelimb, the nerve block injecting either side of the suspensory ligament,
adjacent to the palmar cannon bone, is relatively simple. Care must be taken with
asepsis as penetration of the palmar pouch of the carpometacarpal joint is common.
An alternative is to inject just deep to the accessorioquatral ligament, between the
head of the lateral splint bone and the accessory carpal bone. A ⅝” needle is
directed straight through the ligament and 3ml of local anaesthetic is deposited. I
favour this technique, but penetration of the carpal sheath is common, so care must
be taken with asepsis. A third technique is to inject 3ml of local anaesthetic on the
axial border of the accessory carpal bone, where there is a palpable ridge,
immediately palmar to the insertion of the carpal retinaculum. A violent reaction is
sometimes noted with this block, possibly the result of “hitting the nerve”. As noted,
the efficacy of the blocks is assessed by palpation of the suspensory ligament.
The effects of local diffusion of anaesthetic and inadvertent intra articular
administration are widely acknowledged now. Thus, with any of these nerve blocks it
is useful to compare the effect of the nerve block with intra-articular anaesthesia of
the inter carpal or tarsometatarsal joints. Radiography of both joints is also indicated.
Radiographs of the proximal cannon are also obtained. Sometimes these show a
clear diagnosis, particularly in the forelimb where fractures of the cannon, both linear
and avulsion fractures, are identified. In the hindlimb, diffuse sclerosis is often the
only sign.
I do not intend to say anything about ultrasonography, other than there is a wide
overlap with normal and disease. Loss of echogenicity of the dorsal border, and core
lesions are usually the commonly cited findings. In my hands ultrasonography is
difficult, particularly in the hindlimb. Measurement of the suspensory ligament is
unreliable because of the difficulty of imaging the margins of the structure. In my
opinion the overlap between normal and disease is such as to make the technique of
questionable diagnostic value. In my hands, the reality is that proximal suspensory
desmitis is diagnosed by a positive response with a sub carpal or tarsal nerve block,
no abnormalities on radiographs, and any ultrasonographic findings.
Treatment
It is widely acknowledged that the prognosis with proximal suspensory desmitis
differs widely between the forelimb and the hindlimb. In the forelimb, the prognosis is
good. The large majority of cases resolve with rest. I recommend six weeks of box
rest followed by six weeks in a restricted paddock. In the hindlbimb the prognosis is
poor. When originally reported, the prognosis was 15%. This was possibly a little
negative, and may contribute to the positive benefit suggested with shock wave
treatment. However, it is widely agreed that the prognosis is poor and many horses
remain lame despite well structured rest regimes.
Surgery for proximal suspensory desmitis has been popularised by Bathe. The
theory behind surgery is that proximal suspensory desmitis in the hindlimb may be a
compressive neuropathy. The suspensory ligament is located between the two large
“splint” bones and the plantar cannon bone, and is overlain by a layer of fascia, the
deep plantar laminar fascia. If the suspensory ligament was injured and swelled,
may be it will compress the deep branch of the lateral plantar nerve as it runs into this
canal, resulting in persistent lameness. Thus the proposed procedure was a
combined neurectomy and a fasciotomy, to decompress and desensitise the
ligament. Good results have been reported, with 81% and 79% of horses returning
to ridden exercise.
The technique is relatively straightforward but it can be difficult to perform neatly
through a small incision. Surgery is performed under general anaesthesia in dorsal
recumbency. A linear incision is made at the level of the head of the lateral splint
bone. Sharp dissection is continued through the subcutaneous tissues, and through
the superficial fascia, a distinct layer, which envelops all the structures of the plantar
hock. Blunt dissection is then used down the axial margin of the lateral splint bone,
to isolate the deep branch of the lateral plantar nerve. It is usually quite
straightforward to identify blood vessels in this area, they are at the level of the deep
digital flexor tendon or deeper, not at the level of the superficial digital flexor tendon.
The nerve is usually identified deep to these vessels. Some hook ended tonsil
forceps are ideal for elevating the vessels. It is perfectly acceptable to elevate all
structures and then separate the nerve from the vessels. I always treat the nerve
with topical local anaesthetic prior to further nerve manipulation as stimulation at this
stage can result in movement of the horse under anaesthesia. The nerve has a
typical "gritty" sensation when a fingernail is run over the nerve on a metal surface.
The nerve is observed running relatively deep, and usually dividing into two or more
branches distally. One of the most useful tips to distinguish the deep branch from the
lateral plantar nerve itself is that the deep branch can usually only be retracted to
wound level, while the lateral plantar nerve itself can be retracted several centimetres
away from the surgical wound. The nerve is clamped with mosquito forceps and
approximately 3 cm is resected using guillotine technique with a new #15 blade.
The deep plantar laminar fashion is identified in the distal margins of the incision.
A crescent of white tissue is usually identified overlying the deepest structures. This
has to be transected blind, as the fascia extends from the distal margins of the
incision distally for 10 cm. This can be undertaken using Metzenbaum scissors, but a
split in the surface of the suspensory ligament is almost inevitable. This finding was
documented by Dyson, who showed linear hypoechoic defects in the suspensory
ligament on post-operative ultrasonography. A custom fasciotome is manufactured
by Dr Fitz, and use of this is preferred. Even so the fascia has to be transected blind.
The incision is repaired using simple continuous sutures of absorbable material
(I use three metric Monocryl®) in the superficial plantar fascia. Theoretically skin
sutures would be quite satisfactory at this stage, but we have observed when
breakdown on several occasions. Therefore, we use a second layer of simple
continuous sutures in the subcutaneous tissues, followed by intradermal sutures
again of three metric Monocryl®. Bandaging of the wound is relatively difficult due to
its location at the back of the hock. Generally, we use a bandage of the cannon bone
extending over the distal hock, and then cover the hock with custom Pressage®
bandages. Post operatively, a three-month regime is recommended, commencing
with three weeks box rest and progressively increasing the amount of turnout and
walking exercise.
One study documented linear hypoechoic lesions in the suspensory ligament on
post operative ultrasonographic examination [3].
Another study documented
significant neurogenic atrophy of the suspensory ligament following neurectomy [4].
Finally, excellent results have been reported following neurectomy of the deep
branch of the lateral plantar nerve alone [5]. Based on this information we
hypothesised that plantar fasciotomy may be unnecessary, or indeed detrimental
In August 2010, in the light of the above information, plantar fasciotomy was
discarded, and neurectomy of the deep branch of the lateral plantar nerve alone was
performed in appropriate cases. This resulted in two separate but non randomised
populations which had undergone neurectomy of the deep branch of the lateral
plantar nerve, with or without deep plantar laminar fasciotomy. A retrospective study
was conducted, to compare the success rate with or without fasciotomy. Information
on post operative progress was obtained by telephone questionnaire of the owners or
rider. The proportion of horses returning to previous levels of athletic activity, and of
those which returned to ridden activity, were compared for each procedure using
Fisher’s Exact test.
171 horses were included in the study, of which 86 (50%) had undergone plantar
neurectomy alone. Follow up information was available for 135 horses, of which 91
(67%) had return to ridden exercise, including 63 (46%) at the same or higher level of
athletic activity. Following combined fasciotomy and neurectomy, 33 horses (54%)
returned to previous levels of activity, and a further 8 (13%) horses returned to ridden
exercise. Following neurectomy of the deep branch of the lateral plantar nerve alone,
30 horses (41%) returned to previous levels of athletic activity and a further 20
horses (27%) returned to ridden exercise. The proportion of horses returning to
ridden activity was identical with or without fasciotomy, and though the proportion
returning to original levels of athletic use was lower (54% v 41%), this was not
statistically different, p value = 0.12 (Fishers Exact Test).
The hypothesis that fasciotomy did not alter the outcome following surgical
neurectomy of the deep branch of the lateral plantar nerve was not rejected, but the p
value was low. Other factors may have influenced the outcome due to lack of
randomisation. It has been shown that horses with primary proximal suspensory
desmitis, in the absence of any other musculoskeletal conditions, have a better
outcome than those with concurrent conditions such as sacroiliac region pain, and
particularly, straight hock with hyperextended metatarsophalangeal joint conformation
[3]. It is conceivable that the change of surgical procedure occurred at a time when
the surgeons were encouraged by good results and had widened their selection
criteria to include such cases. We are still obtaining follow up data, but are likely to
reinstate the fasciotomy soon.
Surgery can be performed in the fore limb. Chronic proximal suspensory
desmitis is much less frequent in this limb, with the large majority of horses
responding to rest alone. However, persistent or recurrent cases are occasionally
encountered. Treatment by neurectomy of the deep branch of the lateral palmar
nerve has been reported. The principles are very similar, but there is no deep plantar
laminar fascia overlying the suspensory ligament in the forelimb. The nerve is
isolated between the accessory carpal bone and the head of the lateral splint bone.
Again the surgery is performed in dorsal recumbency. We find dorsal recumbency
much easier, with natural control of haemorrhage and easier access to the other limb.
The limb is supported in extension. If not fully extended, it should be possible to
manually extend the limb, to identify the accessorioquatral ligament, between
accessory carpal and splint bones. An oblique incision is made immediately distal to
this. This is critical, and we have consistently found that the nerves are just distal to
the ligament and not directly underneath it. The ligament is consistent with the
palmar fascia, and so sharp dissection through the distal margin of the ligament is
necessary. This exposes the loose underlying connective tissue, and a large venous
structure is usually evident. Careful blunt dissection will isolate the nerves. The
deep branch is, as in the hindlimb, about ⅔ the size of the lateral palmar nerve itself.
It is also positioned more proximally, though both nerves run in a palmar proximal
dorsodistal oblique direction. I usually try to identify both nerves. Several
centimetres are removed using exactly the same technique as the hindlimb.
The published prognosis is good, with 4/4 horses remaining sound for one year.
References
1. Crowe OM, Dyson SJ, Wright I, Schramme MC, Smith RKW. Treatment of
chronic or recurrent proximal suspensory desmitis using radial pressure wave
therapy in the horse. Equine Vet J 2004;36:316.
2. Bathe A. Plantar metatarsal neurectomy and fasciotomy for the treatment of
hindlimb proximal suspensory desmitis. Proc ACVS 2007.
3. Dyson S, Murray R. Management of hindlimb proximal suspensory desmopathy
by neurectomy of the deep branch of the lateral plantar nerve and plantar
fasciotomy: 155 horses (2003-2008). Equine Vet J 2011:no–no.
4. Pauwels FE, Schumacher J, Mayhew IG, Sickle DC. Neurectomy of the deep
branch of the lateral plantar nerve can cause neurogenic atrophy of the muscle
fibres in the proximal part of the suspensory ligament (M. interosseous III).
Equine Vet J 2010;41:508–10.
5. Kelly G. Results of neurectomy of the deep branch of the lateral plantar nerve for
the treatment of proximal suspensory desmitis. Proc ECVS, Dublin, 2007, 130 134.
TREATMENT OF DISTAL TARSAL JOINT PAIN
Michael Schramme DrMedVet, CertEO, PhD, HDR, DECVS, DACVS
Campus Vétérinaire de Lyon, VetAgro Sup
Université de Lyon, France
Spavin, or osteoarthritis of the tarsometatarsal, distal and/or proximal intertarsal
joints, is an insidious onset, slowly progressive, degenerative joint disease of the low
motion joint type. Complete fusion of the central and third tarsal bones resulting in the
total disappearance of the tarsometatarsal and distal intertarsal joints has been
observed radiographically and has been considered as the end-stage of chronic
osteoarthritis. Nevertheless spontaneous progression of joint destruction from early
degeneration, through active osteoarthritis, to bony ankylosis has not been
documented. It is clear however, that the state of ankylosis is generally associated
with a pain-free limb. Treatment of osteoarthritis is always palliative and is aimed at
eliminating pain and rendering the horse useful, rather than restoring to joint function
to normal. Both non invasive and invasive techniques have been used to achieve this
objective. Conservative (non-invasive) treatments consist of systemic or intraarticular medication, corrective shoeing and/or adaptation of the horse’s exercise
regimen. Invasive treatments for bone spavin have been designed to remove direct
pressure over the affected area, to promote fusion of the affected joints, to remove
sensory perception from painful joints or to reduce the subchondral bone pressure
adjacent to affected joints. The plethora of treatment options available appears to
indicate that none of them is totally effective.
Shoeing
Hoof care preference is to balance the foot and achieve a dorsal hoof angle 1° to 2°
steeper than the pastern and square or roll the toe. As much foot as possible should
be removed in the process to improve stability. The most commonly used shoeing
adaptations consist of lateral extensions or trailers, heel elevations and rolled toes.
Lateral extension shoes aim to minimize the axial swing of the foot. Wide-webbed
wedged (flat) aluminum shoes, help achieve the angle and support the foot that may
tend to land unevenly, particularly in show horses. In a recent study however, we
found that neither the lateral extension shoe nor the rolled toe shoe with elevated
heels had a consistent effect on the position of point of zero moment (point of force)
of the foot during stance, on the orientation of the hindlimbs during flight nor on the
clinical lameness of these horses, thereby questioning their efficacy.
Anti-inflammatory medication
Anti-inflammatory therapy is required to resolve or control the pain resulting in
lameness. Generally, the best plan is to do the minimum required to keep the horse
effectively in work, because more treatment will probably be required eventually.
Each horse is different and requires discovery of an effective treatment schedule.
A starting point includes systemic phenylbutazone (2.2 mg/kg, BID), which can be
continued for an extended period of time in most horses or given only when the horse
is worked.
Intra-articular corticosteroids
Intra-articular medication with corticosteroids (40-80 mg methylprednisolone, 6-12 mg
bethamethasone or 6-12 mg triamcinolone acetonide) is more predictably successful
in rendering horses sound, although reported success rates vary from 35% to 70% of
horses injected being improved (Labens et al. 2007; Byam-Cook et al. 2009).
Therapeutic concentrations of methylprednisolone have been measured in both the
TMT and DIT joints following injection of the TMT joint only (Serena et al. 2005).
When the horse responds poorly to initial treatment with intra-articular steroids, a
second injection 3 to 4 weeks later is often more effective. Using triamcinolone (6 mg/
joint) for the first injection and scheduling a second injection with 80 mg
methylprednisolone makes sense in horses for which long-term pain control is
needed. A period of reduced activity after medication usually improves the result; the
rest period has subjectively varied from 5 to 14 days in show horses
Tiludronate
Tiludronate inhibits osteoclast activity and has been used in horses with distal tarsal
pain. In a limited double-blind clinical trial of 8 horses with lameness confirmed to
originate in the distal tarsal joints given 1 or 2 single IV doses, 1 horse improved
(Dyson 2004). More recently, a larger study using 86 horses showed an average
improvement of 2 (out of 10) lameness grades in horses treated with an infusion of
tiludronate and a controlled exercise regime which was significantly better than the
improvement seen in horses in the placebo group (Gough et al. 2010).
Failing the above conservative measures, a more aggressive approach is required.
Cunean Tenectomy
Cunean tenectomy and the Wamberg modification of this procedure are purported to
alleviate pressure over the dorsomedial aspect of the small tarsal joints. One survey
of the owners of 285 performance horses with bone spavin, reported that results of
cunean tenectomy were rated as excellent or good in 83% of patients and that
lameness resolved within 8 weeks following cunean tenectomy. The authors
speculated that tenectomy reduced rotational and shearing forces during contraction
of the tibialis cranialis muscle, resulting in less pain (Eastman 1997). Calling the
procedure into question are reports describing similar results between 2 groups of
racing Thoroughbreds. One group was treated with cunean tenectomy in addition to
other medical therapy and shoeing changes, and the other group had the same
measures without surgery (Gabel et al. 1979).
Arthrodesis
The aim of surgical arthrodesis is to remove sufficient cartilage to allow continuity of
bone across the joint space. In spite of many variations of this technique having been
used, the success rate of surgical arthrodesis is consistently reported to lie between
59 and 85% (Dechant 1999; Zubrod et al. 2005). The most common cause for
dissatisfaction following surgical arthrodesis is the protracted convalescence to
soundness (average 7.5 months; range 3.5 to 12 months) (Edwards 1980).
Techniques creating 3 single distinct drill paths have proven to cause minimal
postoperative morbidity with generally good outcomes. Drill size varies from 2.7 to
4.5 mm with similar results. A 3.2-mm drill bit compromises nicely between sufficient
rigidity to drill without breaking while having just enough flexibility to follow the joint
space without bypassing islands of cartilage, and 3 drill paths seem to suffice. The
success of the procedure depends upon creating solid spot welds of bony bridging to
immobilize the joints. Most surgeons treat both the TMT and DIT joints regardless of
diagnostic indications of the source of pain. The drill bit must stay within the joint
space and therefore intra-operative imaging is considered imperative. While minor
distal penetrations do not affect the outcome, damage to the margins of the joints
may cause exostoses, enlargement, and potential gait compromise. If the PIT joint is
involved, the prognosis is less favorable, but it too should be operated, because this
offers the best hope of a complete recovery. Horses are stall rested until the skin
sutures are removed and hand walking is allowed for an additional 2 weeks, when
light riding is begun. Horses should not be turned out for a minimum of 2 months to
avoid joint instability.
Facilitated ankylosis
Techniques of chemical arthrodesis (monoiodoacetic acid or ethyl alcohol) have been
proposed to require a shorter convalescence time in comparison with surgical
arthrodesis. Intra-articular sodium monoiodioacetate (MIA) has been used to induce
cartilage necrosis, presumably leading to ankylosis of the DIT and TMT joints.
Soundness in horses 12 months after MIA injection of the distal tarsal joints has been
reported in several studies. The results seem to be somewhat dose-related, and
reported doses include 100 mg/joint, up to mean doses per joint of 250 mg. Contrast
arthrograms must be performed to confirm location of the needle and to rule out
communication of the TMT or DIT joint with the PIT/TC joint or the tarsal canal. If the
arthrogram reveals contrast in the PIT/TC joints or tarsal canal or failure to fill the
intended joint, the procedure is aborted. Leakage of MIA into the subcutaneous
space also produces noticeable inflammation that may lead to a tissue slough. Pain
in the immediate post-injection period can be profound but varies among reports.
Complications that have been observed include soft tissue necrosis at the injection
site, septic arthritis, unexplained increased lameness, and delayed PIT/TC joint OA.
This potential for serious complications must be weighed against the appeal of the
simplicity and minimal cost of the procedure. We perfomed a study with 60 horses in
which bone spavin was treated with intra-articular injection of MIA. The procedure
was performed under general anaesthesia with the patient in dorsal recumbency.
Prior to injection of MIA, contrast arthrography was performed to confirm intraarticular placement of the needles and to rule out undesirable communications
between the affected distal tarsal joints and the adjacent, unaffected proximal
intertarsal and tibiotarsal joints. A solution containing 100 mg MIA in 2 ml of 0.9%
saline (sterilised using 0.22 ul filtration) was injected aseptically into each of the
affected joints. Postoperative walking exercise was initiated within 24 h and patients
were returned to full ridden work within 7 days. Owners were informed of the absolute
necessity of 1 hour of ridden exercise daily until fusion occurred. Long-term
soundness was only obtained in 22% of horses, although lameness improved in
another 30% of patients (Schramme et al. 2000). Marked post-injection pain was
present in most horses but subsided after 24 hours. These results were considerably
less favourable than those reported in an earlier study by Bohanon (1995) and a later
study by Dowling et al. (2004). In this latter study, horses were injected twice the
concentration of MIA under standing sedation (200 mg MIA per joint).
Ethanol solubilizes lipids and induces nonspecific protein denaturation, cellular
dehydration, and precipitation of protoplasm. As such, it affects chondrocytes in a
similar manner as MIA. Ethanol has neurolytic properties that could contribute to its
reported early resolution of lameness. In normal horses, no significant post-injection
local reaction occurred and no persisting lameness was induced. After 12 months,
the TMT joints were largely ankylosed and the horses were not lame (Shoemaker et
al. 2006). Facilitated ankylosis with ethyl alcohol in the tarsometatarsal joint has
reportedly resulted in significant improvement in lameness in 52% and deterioration
in 19% of horses. 75% of owners were pleased with treatment results (Carmalt et al.
2010; Lamas et al. 2011).
Laser energy (Nd : YAG or 980-nm gallium-aluminum-arsenide diode laser) applied
to the TMT and DIT joints has been reported to relieve distal tarsal pain (Hague et al.
2000) All horses in a series of 24 Standardbreds and Western performance horses
improved. Stall confinement was enforced for 2 days followed by progressive return
to full activity in approximately 2 weeks. The horses were reported to become sound
before fusion could have occurred. Comparison of laser, MIA and drilled arthrodesis
in horses without abnormalities of the distal tarsal joints suggested that laser resulted
in more extensive chondrocyte death although the effect appeared focal, while drilled
arthrodesis resulted in more evidence of joint space narrowing and fusion (Scruton et
al. 2005). Experimental laser treatment of normal distal tarsal joints produced minimal
localized cartilage necrosis and the defects eventually filled with mostly fibrous tissue
(Scruton et al. 2005; Zubrod et al. 2005). The authors concluded that ankylosis
occurred earlier after intra-articular drilling of the distal tarsal joints than after laserfacilitated arthrodesis, although clinically affected horses may respond differently. In
a similar study comparing the effects of MIA, surgical drilling and laser on distal tarsal
joints without osteoarthritis, Zubrod et al. (2005) concluded that surgical drilling and
MIA resulted in more bone bridging of the distal 2 tarsal joints, than laser surgery.
However, laser surgery seemingly caused less pain and discomfort to horses in the
immediate postoperative period.
It is possible that the mechanism of action of laser is elimination of sensation in the
fibrous joint capsule from “boiling” of intrasynovial fluid. The advantage of laser
treatment compared to surgical drilling of the joint spaces is a more rapid return to
activity. Horses treated with the laser returned to normal activity in a few weeks
compared to 6 to 17 months after surgical drilling.
Subchondral fenestration
Elevated intramedullary bone pressure has been proposed as a source of lameness
in horses with OA; pressure in horses with diseased tarsi approximated 50% more
than that from normal horses (Sonnichsen and Svalastoga 1985). A modified drilling
procedure coursing obliquely distad to proximad through MT3, DIT, and TMT joints
terminating within the central tarsal bone has been described (Jansson 1995).
Although it is not possible to separate the effect of medullary decompression from
immobilization due to bone healing across the drill sites, this technique appears to be
approximately as effective as other techniques described. Although this technique
has been shown to reduce intraosseous pressures effectively, it has proved
disappointing in alleviating lameness in the author's experience.
Neurectomy of the Tibial and Deep Peroneal Nerves
The results of an improved method of partial tibial and deep peroneal neurectomy
were reported in 24 Warmblood horses (Imschoot et al. 1990). Complete tibial and
peroneal neurectomy as previously reported is said to have caused proprioceptive,
sensory, and trophic complications and hyperextension of the tarsus.
The revised procedure is performed with the horse in lateral recumbency, rolling the
horse when the first side has been completed. Using a tourniquet proximally, 3 15-cm
medial skin incisions are used to expose the tibial nerve and its branches into the
medial and lateral plantar nerves. All the branches from the exposed nerves are
transected. After rolling the horse, another incision is created between the long and
lateral digital extensor muscles proximal to the tarsus to expose and resect a 3- 4-cm
segment of the deep peroneal nerve.
Postoperative care includes stall rest for 2 months with progressive increases in hand
walking after the incisions have healed. Deficits from denervation were not observed.
Results were gathered 1 to 3 years after surgery from telephone conversations with
owners. Of 21 horses to follow up, 14 were used for dressage, riding, jumping, or
eventing for 14 to 36 months. Five horses relapsed 6 to 14 months after surgery, and
2 failed to improve. Radiographic follow-up revealed variable stasis or progression of
the OA. The authors’ conclusion was that the convalescence was shorter than that
following surgical arthrodesis, but that the surgery time was long due to the sizeable
incisions that must be closed. A blemish usually developed at the lateral incision site.
References
1. Bohanon TC, Schneider RK, Weisbrode SE. Fusion of the distal intertarsal and
tarsometatarsal joints in the horse using intra-articular sodium monoiodoacetate.
Equine Vet J 1991;23: 289–295.
2. Byam-Cook KL, Singer ER. Is there a relationship between clinical presentation,
diagnostic and radiographic findings and outcome in horses with osteoarthritis of
the small tarsal joints? Equine Vet J 2009;41:118–123.
3. Carmalt JL, Bell CD, Panizzi L, Wolker RR, Lanovaz JL, Bracamonte JL, Wilson
DG. Alcohol-facilitated ankylosis of the distal intertarsal and tarsometatarsal
joints in horses with osteoarthritis. J Am Vet Med Assoc. 2012;240:199-204.
4. Carmalt JL, Wilson DG. Alcohol facilitated ankylosis of the distal intertarsal and
tarsometatarsal joints in the horse. Vet Surg 2009;38:E28.
5. Dechant JE, Southwood LL, Baxter GM, et al. Treatment of distal tarsal
osteoarthritis using a 3-drill technique in 36 horses. Proceedings Am Assoc Eq
Pract 1999;45:160–161.
6. Dowling BA, Dart AJ, Matthews SM. Chemical arthrodesis of the distal tarsal
joints using sodium monoiodoacetate in 104 horses. Aust Vet J 2004;82:38–42.
7. Dyson S. Are there any advances in the treatment of distal hock joint pain? Int
Symp on Dis of the Icelandic Horse 2004;1111.0604.
8. Eastman T, Bohanon T, Beeman G, et al. Owner survey on cunean tenectomy as
a treatment for bone spavin in performance horses. Proceedings Am Assoc Eq
Pract 1997;43:121–122.
9. Edwards GB. Surgical arthrodesis for the treatment of bone spavin in 20 horses.
Equine Vet J 1982;14:117–121.
10. Gabel AA. Treatment and prognosis for cunean tendon bursitis-tarsitis of
standardbred horses. J Am Vet Med Assoc 1979;175:1086–1088.
11. Gough MR, Thibaud D, Smith RK Tiludronate infusion in the treatment of bone
spavin: a double blind placebo-controlled trial. Equine Vet J. 2010;42:381-387.
12. Hague BA, Guccione A. Clinical impression of a new technique utilizing a nd :
Yag laser to arthrodese the distal tarsal joints. Vet Surg 2000;29:464.
13. Imschoot J, Verschooten F, Moor Ad, et al. Partial tibial neurectomy and
neurectomy of the deep peroneal nerve as a treatment for bone spavin in the
horse. Vla Dierg Tijd 1990;59:222–224.
14. Jansson N, Sonnichesen H, Hansen E. Bone spavin in the horse: Fenestration
technique. A retrospective study. Pferd 1995;11: 97–100.
15. Kristoffersen K. Investigations of aseptic hock diseases in the horse.
Copenhagen: The Royal Veterinary and Agricultural University, 1981.
16. Labens R, Mellor DJ, Voute LC. Retrospective study of the effect of intra-articular
treatment of osteoarthritis of the distal tarsal joints in 51 horses. Vet Rec
2007;161:611–616.
17. Lamas LP, Edmonds J, Hodge W, Zamora-Vera L, Burford J, Coomer R, Munroe
G. Use of ethanol in the treatment of distal tarsal joint osteoarthritis: 24 cases.
Equine Vet J. 2012;44:399-403.
18. Moyer W, Brokken TD, Raker CW. Bone spavin in throughbread race horses.
Proceedings Am Assoc Equine Pract 1983;29: 81–92.
19. Schramme M, Platt D, Smith RK. Treatment of osteoarthritis of the
tarsometatarsal and distal intertarsal joints of the horse (spavin) with
monoiodoacetate: Preliminary results. Vet Surg 1998;27:296.
20. Scruton C, Baxter GM, Cross MW, et al. Comparison of intra-articular drilling and
diode laser treatment for arthrodesis of the distal tarsal joints in normal horses.
Equine Vet J 2005;37:81–86.
21. Serena A, Schumacher J, Schramme MC, Degraves F, Bell E, Ravis W.
Concentration of methylprednisolone in the centrodistal joint after administration
of methylprednisolone acetate in the tarsometatarsal joint. Equine Vet J.
2005;37:172-174
22. Shoemaker RW, Allen AL, Richardson CE, et al. Use of intra-articular
administration of ethyl alcohol for arthrodesis of the tarsometatarsal joint in
healthy horses. Am J Vet Res 2006;67:850–857.
23. Sonnichsen HV, Svalastoga E. Surgical treatment of bone spavin in the horse.
Eq Pract 1985;7:6–9.
24. Wyn-Jones G, May SA. Surgical arthrodesis for the treatment of osteoarthrosis of
the proximal intertarsal, distal intertarsal and tarsometatarsal joints in 30 horses:
A comparison of four different techniques. Equine Vet J 1986;18:59–64.
25. Zubrod CJ, Schneider RK, Hague BA, et al. Comparison of three methods for
arthrodesis of the distal intertarsal and tarsometatarsal joints in horses. Vet Surg
2005;34:372–382.
MANAGEMENT OF SOFT TISSUE INJURIES OF THE TARSUS
Roger Smith MA VetMB, DEO, PhD, DECVS, AssocECVDI
Dept. of Veterinary Clinical Sciences, The Royal Veterinary College, Hawkshead
Lane, North Mymms, Hatfield, Herts. AL9 7TA. U.K.
Introduction
For the purpose of discussion of the myriad of soft tissue lesions of the hock, the
tarsus can be divided into four regions – dorsal, medial, lateral and plantar. The
dorsal, medial and lateral areas are related to the tarsocrural and small tarsal joints
and their accompanying periarticular tendons and ligaments, while the plantar aspect
is associated with the plantar tendons of the hock and metatarsal regions.
Dorsal aspect
There is a complex arrangement of the tendons on the dorsal aspect. Trauma
and wounds are the most common injury in this location, especially wire injuries
where the hindlimb gets caught in wire fences and cuts through the dorsal aspect of
the hock, potentially lacerating the extensor tendons (of minor clinical significance)
and the perineus tertius (resulting in a characteristic mechanical lameness, where the
hock remains extended when the stifle is flexed, and the calcaneal tendon becomes
slack).
Management of these injuries requires careful assessment for synovial
involvement (necessitating arthroscopic/tenoscopic lavage and debridement).
Significant damage to the peri-articular structures on the dorsal aspect of the small
tarsal joints can result in subluxation which requires full limb casting for effective
treatment.
Injuries to the soft tissue structures on the dorsal aspect of the hock that do not
involve the underlying joints rarely result in significant complications and are usually
managed conservatively with routine wound management and rest. Perineus tertius
ruptures respond well to conservative treatment and function of this structure in coordinating stifle and hock flexion will return while healing can be monitored
ultrasonographically.
Lateral and medial aspects
Collateral ligament desmitis is often associated with tarsocrural joint distension
and filling (and pain) over the affected ligament. Ultrasonography is particularly
helpful for identifying collateral ligament desmitis and any associated avulsion
fractures (most commonly involving the lateral malleolus). Desmitis can affect both
long and short collateral ligaments on either side of the tarsocrural joint and are
manifest as areas of reduced echogenicity with altered longitudinal pattern and
periligamentar oedema in acute, and fibrosis in chronic stages. Pathology in the
short collateral ligaments is more likely to involve the tarsocrural joint and if
tarsocrural joint effusion is marked and persistent, arthroscopic assessment and
debridement is indicated [1].
Significant pathology of the cunean tendon and bursa is almost never identified
and this structure is primarily used to identify the surgical site for drilling of the small
tarsal joint to achieve surgical arthrodesis.
Plantar aspect
Calcaneal bursa, gastrocnemius and subcutaneous bursae
The calcaneal bursa separates the SDFT from the gastrocnemius tendon, but in
normal horses contains only a small amount of fluid. The calcaneal bursa usually
communicates with the bursa lying beneath the insertion of the gastrocnemius tendon
(gastrocnemius bursa). An acquired subcutaneous bursa is variably present
superficial to the SDFT over the point of the hock.
Distension of the calcaneal bursa can be due to the presence of gastrocnemius
tendinopathy (see below), defects in the surface of the adjacent tendons, or sepsis
following penetrating injuries. Sepsis requires bursoscopic lavage and debridement
although hese carry a guarded prognosis if there is tendon or bony involvement [2].
Sepsis of the subcutaneous bursa is easily treated with local drainage and carries an
excellent prognosis [2].
Gastrocnemius tendon, deep tarsal tendons and superficial digital flexor
tendon over the point of the hock
The gastrocnemius tendon wraps around the SDFT laterally proximal to the point
of the hock and comes to lie deep to the SDFT at the point of the hock. Tendinitis of
the gastrocnemius tendon and/or the deep tarsal ligaments has been described and
is manifest as enlargement and heterogeneity of the affected tendons and is
commonly associated with calcaneal bursal distension [3]. The treatment of choice is
prolonged period of rest and a period of 6-12 months is often necessary for the
condition to heal, but lesions can persist.
Rupture of the medial retinacular band or a longitudinal split in the SDFT can be
identified in cases of persistent or intermittent dislocation of the tendon from the point
of the hock. In some cases, the disruption can involve the superficial digital flexor
tendon which can explain some, if not most, of the intermittent displacements and
which may be amenable to surgical resection of the torn tendon [4]. Ultrasonography
can be used to identify the location of the tear and hence inform suitable cases for
bursoscopy. Tears involving the tendon rather than the retinaculae in smaller ponies
can be repaired and managed in a full limb cast.
Tarsal sheath and deep digital flexor tendon
The tarsal sheath extends from above to below hock on the plantaromedial
aspect. Pathology observed includes idiopathic tenosynovitis (with or without
thickened synovium), deep digital flexor tendon tears, sepsis associated with
penetrating wounds which frequently follow kicks to this region which can also
damage the DDFT and sustentaculum tali.
When distension is marked, the most evident site is proximal to the hock and
dorsal to the calcaneal tendon (so-called ‘thoroughpin’). Distension of the tarsal
sheath is not always associated with lameness but those that are, can be
investigated with ultrasonography and radiography to identify the primary pathology.
Treatment depends on the primary pathology but frequently tenoscopy can offer both
diagnostic and therapeutic benefits although fractures of the sustentaculum tali usally
require an open surgical approach for their removal due to their usual extra-thecal
location.
Recently, acquired synovioceoles on the plantar aspect of the hock have been
related to disruption of the tarsal sheath, resulting in a ‘one-way valve’[5]. Such
cases should be evaluated ultrasonographically both weight-bearing and non-weightbearing to assist in the identification of the communication with the tarsal sheath.
Contrast studies can also help demonstrate communication, showing up as
horseshoe-shaped structures dorsal to the common calcaneal tendon. Due to the
‘one-way valve’, contrast may not pass into the tarsal sheath while this is more
consistent from the tarsal sheath to the synoviocoele. Treatment is either rest and
spontaneous resolution or require tenoscopy of the tarsal sheath and enlargement of
the communication between the two.
Plantar ligament
The plantar ligament lies lateral to the superficial (proximally) and deep (distally)
digital flexor tendons, emanating from the plantarolateral aspect of the calcaneus and
predominatly inserting on the fourth tarsal metatarsal bone. Overstrain injuries to this
structure are rare although are one cause of a ‘curb’ (see below). Treatment is
conservative consisting of rest and then a gradual ascending exercise regime based
on clinical and ultrasonographic healing.
Soft tissue swellings in the region of the plantar hock
A ‘curb’ is a swelling located on the plantar aspect of the distal hock – it can be a
conformational abnormality due to prominence of the head of the fourth metatarsal
bone or due to a variety of soft tissue pathologies - subcutaneous fibrosis, superficial
digital flexor tendonitis, desmitis of the accessory ligament of the deep digital flexor
tendon, proximal suspensory desmitis, or, rarely, plantar ligament desmitis.
Ultrasonography is useful to differentiate these causes. Treatment is rarely indicated
but soft tissue pathologies are managed conservatively.
Proximal suspensory desmitis
Proximal suspensory desmitis is a very common cause of hindlimb lameness and
is closely associated with the hock, bringing with challenges in differentiating
lameness originating in this structure with other adjacent sites in the hock. The
proximal region of the suspensory ligament in the hindlimb is contained within a more
restricted canal made up of the large head of the lateral splint bone, the head of the
medial splint bone and the overlying fascia. This anatomy has suggested that
lameness related to the proximal suspensory ligament injury may arise from
compression of the adjacent nerves rather than from the ligament itself [6]. Initial
treatment is usually conservative which involves initial box-rest with walking exercise
for, in the first instance 3 months which is often extended for up to 6 months, followed
by an ascending exercise regime.
Refractory cases can be managed with extracorporeal shock wave therapy which
has shown significant improvements in prognosis in chronic hindlimb cases [7].
Periligamentar injection of corticosteroids may also result in improvement but this is
usually not sustained if the primary pathology is not addressed and can adversely
affect ligament healing (if damage is evident).
Should this therapy be unsuccessful, a surgical option of local neurectomy and
fasciotomy has been proposed for hindlimb cases [8]. Care should be made in
selecting the appropriate cases – horses with ultrasonographically apparent marked
disruption to the proximal suspensory ligament are less appropriate because of the
risk of subsequent exacerbation or rupture and a neurectomised horse is not officially
allowed to compete under FEI rules.
Intra-lesional injections of mesenchymal stem cells, platelet-rich plasma or ACell
have more recently been recommended although there is concern that these
injections in the absence of a fasciotomy can increase the risk of a compressive
neuropathy which is thought to be involved in the aetiopathogenesis of many
hindlimb proximal suspensory desmitides. No significant comparative case series
has been published to determine which of these intralesional treatments is the most
effective.
The prognosis for acute desmitis is poor (13% sound and in full work at 6
months; [9]), with the prognosis for chronic cases approaching 0%. Shockwave has
been shown to return 43% of chronic hindlimb cases to full work after 6 months [7]
while fasciotomy and neurectomy has been reported to have a higher success rate of
79% [8].
References
1. Barker, W.H., et al., Soft tissue injuries of the tarsocrural joint: a retrospective
analysis of 30 cases evaluated arthroscopically. Equine Vet J, 2013. 45(4): p.
435-41.
2. Post, E.M., et al., Retrospective study of 24 cases of septic calcaneal bursitis in
the horse. Equine Vet J, 2003. 35(7): p. 662-8.
3. Dyson, S.J. and L. Kidd, Five cases of gastrocnemius tendinitis in the horse.
Equine Vet J, 1992. 24(5): p. 351-6.
4. Wright, I.M. and G.J. Minshall, Injuries of the calcaneal insertions of the
superficial digital flexor tendon in 19 horses. Equine Vet J, 2012. 44(2): p. 13642.
5. Minshall, G.J. and I.M. Wright, Synoviocoeles associated with the tarsal sheath:
description of the lesion and treatment in 15 horses. Equine Vet J, 2012. 44(1): p.
71-5.
6. Toth, F., et al., Compressive damage to the deep branch of the lateral plantar
nerve associated with lameness caused by proximal suspensory desmitis. Vet
Surg, 2008. 37(4): p. 328-35.
7. Crowe, O.M., et al., Treatment of chronic or recurrent proximal suspensory
desmitis using radial pressure wave therapy in the horse. Equine Vet J, 2004.
36(4): p. 313-6.
8. Dyson, S. and R. Murray, Management of hindlimb proximal suspensory
desmopathy by neurectomy of the deep branch of the lateral plantar nerve and
plantar fasciotomy: 155 horses (2003-2008). Equine Vet J, 2012. 44(3): p. 361-7.
9. Dyson, S., Proximal suspensory desmitis in the hindlimb: 42 cases. Br Vet J,
1994. 150(3): p. 279-91.
SHOEING SOLUTIONS FOR HINDLIMB LAMENESS PART 1
PERFORMANCE
Hans Castelijns
D.V.M. – Certified Farrier
Equine Podiatry Consults and Referrals
Loc. Valecchie n° 11/A, Cortona 52040 (AR) Italia
Mob:+39.333 7716663 -Tel & Fax +39.0575.614335
E.mail : [email protected]
Web site : farriery.eu
Introduction
Normal Biomechanics of the equine hind limb is quite different from the fore limb.
Hilary Clayton has compared the horse’s front limb to a weight supporting “elephant
like” limb, the hind limb to a propulsive “cat-like” limb.
Faulty conformation of the hind limb , as of the fore limb can only be corrected during
the fast growth phase of the foal.
The knowledge of growth plate closure times is essential, with as general rules that
angular deviations around the fetlock should be addressed within the first three
months of the foal’s life and that varus deviations are more necessary and more
difficult to treat, as growth and increase in weight tend to make them worse.(fig.1)
A good example, which illustrates this point is the frequently encountered “wind
swept” conformation of new born foals. The hardest limb to correct is almost always
the varus one, so an early lateral extension on this limb is of the utmost
importance.(fig.2)
Performance
In the adult horse, performance enhancing shoeing has to be approached carefully,
taking discipline, ground/arena quality and penetrability and individual conformation
in to account.
Interference involving hint limbs is an important issue in performance and injury
prevention, especially in some high-speed disciplines like harness racing.
An invaluable , modern, tool in the analysis of the exact mechanisms of interference ,
is the use of high-speed cameras, the author preferring a 300 frame per second
setting. (the human eye has a frequency of 50Hz ).
Two examples of frequently encountered interference involving hind limbs, may
illustrate the importance of careful motion analysis:
1) Brushing - the interference of one hind limb against the contralateral hind
limb, usually at the pastern or fetlock , can often be addressed by braking the
inside of the hind feet with a small medial heel stud or prolonged inside branch
for example.
2) Scalping – on the other hand, the interference of a front limb which touches its
ipsilateral hind limb, usually at the inside of the metatarsus , can be addressed
by a prolonged or trailered outside branch of the hind shoes.(fig.3)
Tools and means
The author has adopted a fairly uniform trimming protocol for both front and hind feet,
based on the philosophy of leaving what belongs to the foot and trimming away what
has grown in excess.
In more scientific terms this means trimming to a uniform sole thickness level at the
bottom of the hoof;
That is , trimming away only the exfoliated horn of the sole and the hoof wall which
protrudes from this level.
The underpinning of this trimming method has been researched by Michael Savoldi
and more recently by Michael.E.Miller.(fig.4, courtesy M. Savoldi)
Hoof distortion, when present, is addressed by removing flares and realigning bulb
heights when necessary.
This implies that the main means for both performance enhancing and therapeutic
shoeing , do not involve leaving the hoof asymmetric in height, either lateral to medial
or toe to heels, but in modifying shoe shape, placement and its break-over features
on the normally trimmed hoof.
These are essentially:
Increased surface or extensions of the shoe, relative to the trimmed hoof capsule, at
the toe, the heels or at the lateral or medial side of the hoof.(fig.5)
Break-over enhancement , like rockered or rolled toes, heals or lateral or medial
branches.(fig.6)
Other tools in the box of therapeutic farriery include the different weights of different
shoes e.g. alloy shoes versus steel and shock absorbing and even flexible shoeing
materials.
In some performance sports, like show jumping and polo, improved grip through shoe
design (concave shoes) or stud use is also important.
Selected bibliography
1. Hoefverzorging en hoefbeslag, W.A. Hermans, Uitgeverij Terra Zutphen, 1984.
2. Tratado de las Enfermedades del Pie del Caballo, A. Pires, C.H. Lightowler,
Editorial Hemisferio Sur, 1991.
3. Notes de Marechalerie, J.M. Denoix, J.L. Brochet, D. Houliez, Unité Clinique
Equine-CIRALE, Ecole Nationale
4. Vétérinaire d’Alfort.
5. Farriery- Foal to Race Horse, S. Curtis, Newmarket Farriery Consultancy, 1999.
6. Equine Locomotion, W. Back, H. Clayton, WB Saunders, 2001.
7. Shoeing and balancing the Trotter, C.A. McLellan, Lessiter Publications, Inc.
2001.
8. Hoof Problems, R. van Nassau, Kenilworth Press, 2007.
9. The Mirage of the Natural Foot, M.E.Miller, 2010.
10. Therapeutic Farriery, Veterinary clinics of North America, Volume 28, number 2,
August 2012.
Figure 1: Figure 2:
Figure 3:
Figure 4:
Figure 5:
Figure 6:
RADIOGRAPHY AND RADIOLOGY OF THE STIFLE
Roger Smith MA VetMB, DEO, PhD, DECVS, AssocECVDI
Dept. of Veterinary Clinical Sciences, The Royal Veterinary College, Hawkshead
Lane, North Mymms, Hatfield, Herts. AL9 7TA. U.K.
Indications
- Effusion in the femoropatellar, medial and/or lateral femorotibial joints
- Lameness localised to the stifle
- Developmental orthopaedic disease candidates (eg osteochondrosis,
subchondral cystic lesions)
- Trauma to the stifle
RADIOGRAPHIC TECHNIQUE AND ANATOMY
Two projections are usually obtained for “routine” examination:
1. Lateromedial or Caudo30°Lateral-Craniomedial Oblique Projections:
- Adequate exposures differ between the femoropatellar joint and the femorotibial
joints unless an aluminum wedge filter is used to filter incoming radiation over
the cranial part of the articulation to avoid overexposure.
- A large cassette is advanced into the inguinal region from cranial or from behind
the stifle. Handheld large cassettes, lead gloves and coning down of the central
beam help to avoid exposure of gloved fingers in the primary beam. Sedation,
nose twitch and a cassette stand are often required. The cassette should
remain as close as possible parallel to the sagittal plane of the stifle (which is
usually rotated slightly outwards).
- The central beam is aimed at the level of the femorotibial joint, just proximal to
the tibial crest and approximately10cm caudal to the cranial contour of the limb
whilst trying to be as perpendicular as possible to the sagittal plane of the stifle.
- A true lateromedial projection is often difficult to perform due to the inability to
align the cassette truly with the sagittal plane of the limb. The caudo30°lateral
craniomedial oblique projection is a valuable alternative and allows for:
 Greater ease of cassette placement
 Separation of the trochlear ridges and the femoral condyles
 Centered over the trochlear ridges, this projection provides a clear view
of the femoropatellar joint, with lower exposures than needed for the full
LM projection.
- Angling the primary beam 10° down (proximodistally) increases the ease of
cassette alignment further and separates the lateral and medial joint
compartments slightly in a proximodistal direction.
- The medial trochlear ridge is larger and projects more cranially. There is
irregular transition into the diaphysis proximally. The lateral trochlear ridge is
much smaller.
- The medial femoral condyle has a characteristic caudal notch; the lateral
condyle has a smooth transition into the femoral diaphysis caudally.
- The line extending from craniodistal to caudoproximal over the condylar area
indicates the base of the intercondylar fossa. Another radiodense structure that
crosses this line is the extensor fossa.
- The lateral tibial plateau and the tibio-fibular articulation project further caudally
than the medial tibial plateau.
- The medial intercondylar tubercle is larger and extends further cranially than the
lateral tubercle.
- The small depression in the tibia, cranial to medial intercondylar tubercle is the
site of attachment of both cranial meniscal ligaments and anterior cruciate
ligament.
- The patella is fully ossified at 4 months of age. Its longest measurement should
equal the distance from the patella to the tibial tuberosity in all projections.
- The area of decreased radiodensity proximal to the patella is a fat pad.
- The growth traction apophysis of the tibial tuberosity is visible up to 2.5 - 3 years
of age.
- The rough and irregular outline of the trochlear ridges of the femur is due to
incomplete ossification and is normal up to 3 months of age. Both trochlear
ridges are similar in size from birth to 2 months of age. The femoral condyles
should have a smooth curved contour. Irregularity in their outline is considered
pathological at any age.
- Cortical roughening at the level of the distal caudal femoral metaphysis near the
physis can occur.
- Occasionally, a small area of flattening can be observed at the most distal
aspect of the lateral trochlear ridge at the level of its transition into the lateral
condyle. Additionally, a small area of radiolucency is often detected just
proximal to this flattening. This is normal and should not be confused with
osteochondritis dissecans (OCD) of the lateral femoral trochlear ridge.
- In more oblique projections (>30°), the proximal extent of the lateral trochlear
ridge often appears indistinctly outlined with a "fuzzy" contour. This is a
projection artifact and usually not OCD.
- Fabellae are extremely rare but may occasionally occur in the horse.
2. Caudocranial Projection:
- The tube is positioned directly behind the horse with the central beam aimed at
the tibial tuberosity and angled down 10°. The central beam should further be
parallel to the sagittal plane of the limb. The cassette is brought in form lateral
over the front of the stifle, perpendicular to the incoming central beam.
- The patella is situated more laterally (bears on the lateral trochlear ridge).
- The lateral femoral condyle is smaller and more pointed distally.
- The medial femoral condyle has usually a smoothly rounded contour, but some
flattening of the weight-bearing surface may be acceptable if the trabecular
pattern of the subchondral bone is of normal radiodensity.
- The medial intercondylar tubercle is larger and more pointed than the lateral
one. Both tubercles project proximally into intercondylar fossa.
- The lateral femorotibial joint space is usually narrower than the medial, although
this can be strongly affected by positioning of the animal.
- The fibula often shows radiolucent defect line(s) which are of no clinical
significance. The ossification process which starts at 2 months of age from one
or more ossification centers and remains often incomplete throughout the
horse's adult life.
Other projections
3. Flexed Lateromedial Projection:
- The leg is held in flexion with the tibia nearly horizontally aligned. The cassette
is brought in from cranial over the medial surface of the stifle, parallel to the
sagittal plane of the limb and perpendicular to the incoming beam. The beam is
centred on the femoral condyles.
- The tibial plateau is displaced caudally and distally away from the weightbearing surface of the femoral condyles. This allows for better assessment of
the condyles. Simultaneously, the patella moves down in the intertrochlear
groove.
4. Cranioproximal-Craniodistal Oblique Projection (Skyline View Patella):
- The limb is held flexed with the tibia positioned as close as possible to
horizontal. The cassette is brought in from cranial and held horizontally, ventral
to the patella. The central beam is directed downwards, centering on the
patella. Slight angulation of the X-ray beam from lateral to medial is often
necessary to avoid the abdominal wall in the field of view. This projection
provides additional information about the patella, its position in the intertrochlear
groove and the trochlear ridges.
5. 45° Oblique Projections:
- These oblique projections are not routinely used in the radiographic examination
of the stifle. However, they can provide invaluable additional information if
particular areas of suspicion are identified on the standard projections.
RADIOGRAPHIC ABNORMALITIES
1. Osteochondritis Dissecans (OCD):
- Lesions are most commonly located on the lateral trochlear ridge of the femur,
more specifically in its middle third. Lesions of the medial femoral trochlear ridge
or of the articular surface of the patella are considerably less common.
- Two clinical syndromes appear to be recognized in practice:
a. Foals and yearlings with severe joint swelling and lameness
b. Young horses in work with exercise-induced mild to moderate lameness and
joint effusion. OCD lesions appear usually less severe when problems are
detected later in life.
- OCD lesions on the lateral femoral trochlear ridge are most easily detected on
the Ca30°Lat-CdMed Oblique projection. Abnormalities include:
 Flattening of the lateral trochlear ridge
 Irregular outline of the lateral trochlear ridge
 Focal radiolucencies within the lateral trochlear ridge
 Osteochondral fragments within defects in the lateral trochlear ridge
 Osteochondral fragments attached to the synovial membrane
 Free osteochondral fragments with varying locations in the joint on
consecutive studies (most commonly in the dependent parts of the
femoropatellar joint).
 Undersized and flattened lateral trochlear ridge due to chronic
remodeling in long-standing cases.
 Irregular outline to the articular surface of the patella with/without
fragmentation.
- There is (limited) evidence describing radiographic resolution of early detected
mild abnormalities of the lateral trochlear ridge in young foals. Surgical
treatment (arthroscopy) is generally indicated if lameness and joint effusion are
present (at the latest when the animal enters athletic activity).
- Secondary DJD can occur in chronic cases.
- OCD lesions are frequently bilateral: Examine both limbs!
2. Subchondral Cyst-Like Lesions (SCL):
- SCL are commonly observed in young and mature horses, rarely in ponies.
- Cystic lesions have been classified in two groups (Jeffcott 1986):
A. Group A lesions are most common and are located on the weight-bearing
surface of the medial femoral condyle:
 Type 1 configuration is a shallow saucer-shaped to dome-shaped
lucent area which is confluent with the flattened joint surface of the
medial femoral condyle.
 Type 2 configuration describes a circular lucent area within the medial
femoral condyle, usually with a thinner radiolucent "neck" connecting it
to the articular surface.
 The aetiopathogenesis of these lesions remains unclear:
Osteochondrosis and aseptic posttraumatic bone necrosis have been
suggested. Osteochondrosis is supported by the observations in young
animals, with bilateral involvement and improvement with rest. There is
some evidence that type 2 lesions may evolve from a type 1 lesion in
these cases. Posttraumatic aseptic necrosis has been suggested to
explain a history of related trauma, pain, and the occurrence in older
animals with unilateral involvement.
B. Group B lesions:
 Other osseous cyst-like lesions in other locations in the stifle are
relatively rare and have been described in the proximal tibia and in the
femoral condyles.
 Explanations for these lesions have included osteochondrosis and
trauma. Cyst-like radiolucencies in the intercondylar area have been
associated with chronic damage to the origin/insertion of the cruciate
ligaments.
- Cysts rarely “fill in” or change radiographically after surgical or medical
treatment, but radiographic resolution is not necessary for a satisfactory clinical
outcome.
- Intense osteosclerotic margination around the cyst cavity indicates an attempt at
demarcation of the affected area by the surrounding normal reactive bone, and
indicates chronicity. Vague, poorly defined loss of radiodensity with poor
definition to cyst margins indicates a more recent, active process with little
"healing" response from the surrounding bone.
- Long standing lesions may be associated with signs of DJD.
- SCL are most easily detected on caudocranial projections.
3. Degenerative Joint Disease:
- The radiographic appearance of DJD is usually less dramatic than the clinical
signs.
- Radiographic abnormalities observed with DJD of the stifle joints include:
- Periarticular osteophyte formation at the following locations:
- Patellar apex
- Medial border of the tibial plateau
- Intercondylar area.
- Subchondral lucencies
- Entheseous or capsular new bone formation along the axial surface of the
medial femoral condyle.
- The most commonly affected joints are:
- Femoropatellar joint secondary to chronic OCD. Femoropatellar DJD is best
observed on the LM projection.
- Medial femorotibial joint secondary to chronic SCL or ligament trauma.
Infectious arthritis (joint ill) in foals commonly localizes in the medial
femorotibial joint. This is commonly characterized by extensive osteolysis of
the medial femoral condyle and widening of the joint space. Femorotibial
DJD is best identified on the caudocranial projection.
4. Soft Tissue Injuries:
- The complex of soft tissue injuries in the equine stifle is still poorly understood.
It is generally postulated that injuries of the medial meniscus, medial collateral
ligament and anterior cruciate ligament occur simultaneously. However, clinical
practice shows that this is not always the case. There are often little or no
radiographic abnormalities detectable in acute cases. Arthroscopic examination
is commonly necessary to make an accurate diagnosis.
A. Meniscal damage:
 Collapse of the affected femorotibial joint compartment, only identified on
perfectly weight-bearing projections.
 Irregular new bone formation along the attachment of medial collateral
ligament on the medial epicondyle of the femur.
 Marginal osteophyte formation along the medial proximal tibial plateau.
 Mineralization within chronically damaged menisci.
 Consider use of ultrasonography to evaluate meniscus
B. Cruciate ligament damage:
 Anterior cruciate ligament: Avulsion fractures, osteolytic changes at the
insertion and/or origin sites, occasionally fragmentation off the medial
intercondylar eminence, entheseophyte formation on the medial
intercondylar eminence.
 Posterior cruciate ligament: Avulsion fractures caudal lateral margin of the
tibial plateau.
C. Medial (or lateral) collateral ligament damage:
 Irregular new bone formation along the attachment of medial collateral
ligament on the medial femoral epicondyle or on the proximomedial surface
of the tibia.
 Widening of the medial joint space on stressed views.
 Avulsion of fragments or dystrophic calcification within the ligament.
D. Patellar ligament damage:
 Dystrophic calcification in the patellar ligaments.
 Entheseophyte formation at the attachment to the patella and the tibial
tuberosity.
 Remodeling/fragmentation of the patellar apex following medial patellar
ligament desmotomy for treatment of upward fixation of the patella.
5. Fractures:
A. Patellar fractures:
- Fracture configurations:
 Medial wing fractures
 Horizontal fractures
 Sagittal fractures
 Osteochondral fractures off the apical margin
 Comminuted fractures
- Skyline projection of the patella (CrProx-CrDistO projection) often provides
valuable additional information.
B. Osteochondral fractures off the intercondylar tubercles
- Sometimes in association with anterior cruciate ruptures, although this
association appears to have been overemphasized.
C. Tibial tuberosity fractures
- Caused by external trauma.
- Severity depends on the remaining attachment of the middle patellar
ligament.
D. Tibial stress fractures
- The most common location is the proximolateral cortex of the tibia,
approximately 8 cm distal to the lateral femorotibial joint.
- Periosteal and endosteal callus are some of the more common radiographic
features. Occasionally there is a faint radiolucent line indicating an
incomplete cortical fracture through the callus.
- Delayed-phase nuclear scintigraphy (bone scan) to confirm diagnosis and
monitor convalescence.
E. Fibular fractures
- Differentiation from incomplete ossification lines in their more oblique
orientation and through the presence of callus. Rare.
6. Miscellaneous Conditions:
- Calcinosis circumscripta is present on the lateral aspect of the stifle, often in
close association with the lateral femorotibial joint. It consists of a soft tissue
mass containing multiple amorphous areas of mineralization. These lesions can
have highly increased radiopharmaceutical uptake in nuclear scintigraphy
examinations.
- Lateral patellar luxation
 Hypoplasia lateral femoral trochlear ridge in Shetland ponies.
 Severe OCD in the lateral femoral trochlear ridge.
 Femoral nerve paralysis with quadriceps wastage.
‐
Upward fixation of the patella
 Usually minimal radiographic signs but primary pathology may be evident.
 Fragmentation of the apex of the patella may be evident if the horse has
undergone medial patellar ligament desmotomy
ULTRASONOGRAPHIC EXAMINATION OF THE EQUINE STIFLE: BASIC AND
ADVANCED TECHNIQUES
Natasha Werpy, DVM, DACVR
Radiology Department, University of Florida
Introduction
The stifle is a significant source of equine hind limb lameness. Radiography,
ultrasound and arthroscopy, in addition to a physical exam, comprise the diagnostic
evaluation for equine stifle injuries. Radiography is the most commonly used
diagnostic modality for the equine stifle. However, ultrasound remains the most
common method for imaging the soft tissues of the stifle and provides important
information about osseous injuries of this joint.
Techniques for Ultrasound of the Stifle Joint
In the standing horse, the medial, lateral and caudal aspects of the stifle as
well as the patellar ligaments can be examined. Examination of the medial aspect of
the stifle allows visualization of the medial meniscus, medial collateral ligament and
the medial femorotibial joint. Examination of the lateral aspect of the joint allows
visualization of the lateral meniscus, the lateral collateral ligament, and the popliteus
tendon. The caudal horns of the menisci can be evaluated from the caudal aspect of
the limb. The probe is angled toward the joint to identify the margins of the femur
and tibia and locate the meniscus. The increased depth and necessary adjustments
in probe frequency required to visualize the caudal horn may obscure subtle
abnormalities. In addition to abnormalities of the soft tissue structures, ultrasound of
the stifle allows identification of joint arthrosis characterized by peri-articular
osteophyte formation, enthesophytes and abnormalities in the articular surfaces.
Evaluation of the stifle joint with the limb in a weight bearing and non-weight
bearing position is required for complete evaluation of the stifle. The limb must be
flexed to allow examination of the cranial aspect of the stifle, specifically the cranial
horns of the menisci and cranial tibial meniscal ligaments. The linear areas of
decreased echogenicity or striated pattern in the meniscus can be found in many
sound horses and the clinical significance of this finding is poorly understood. Digital
ultrasound systems tend to enhance tissue interfaces. Therefore this pattern is more
evident on digital ultrasound systems.
The striations and the meniscus should
maintain the same size, shape and echogenicity with the limb in weight- bearing and
non-weight bearing positions.
Flexion of the stifle allows visualization of the distal articular surface of the
femoral condyles. Defects in the subchondral bone can be easily identified. This is
an effective method for evaluating the subchondral bone surface if there are
questionable findings on radiographic examination. In the case where a lesion is
identified on radiographs the overlying articular cartilage can be evaluated.
Structures to Evaluate in the Stifle on Ultrasound Examination
Synovial Fluid:
Normal synovial fluid appears anechoic and is easily identified, especially when fluid
distension is present. When evaluating a joint for effusion, the amount of pressure
applied with the probe should be kept to a minimum to prevent the collapse of the
synovial structure being examined. Increased cellularity, tissue debris, fibrin clots,
fragments of cartilage, menisci or calcified bodies can all affect the echogenicity of
the synovial fluid. When cartilaginous or meniscal fragments are present in synovial
fluid, they appear as floating echogenic bodies/debris, which can be moved by
manipulating the pressure in the joint capsule.5
The medial femorotibial joint compartment is identified cranial to the medial
collateral ligament at the level of the femur. The medial femorotibial compartment
contains anechogenic synovial fluid with few to no synovial villi, whereas the lateral
femorotibial compartment contains no synovial fluid in normal stifles.6 The normal
lateral femorotibial joint compartment contains no fluid in the recess deep to the
long digital extensor tendon. The femoropatellar joint compartment has medial and
lateral recesses with synovial fluid that are both identified caudal to their respective
medial and lateral patellar ligaments. The synovial villi are high and thick in the
medial femoropatellar recess.6
Articular cartilage:
Normal articular cartilage is a hypoechoic line formed by the echogenic
smooth articular surface and the hyperechoic subchondral bone.6 The superficial
surface of the articular cartilage is best defined when the ultrasound beam is
perpendicular to the articular surface.5 As most joint surfaces are curved, continued
changes in beam angles are required to properly evaluate the articular surfaces. The
margin, thickness and echogenicity of the articular cartilage should be evaluated. As
cartilage thickness varies by joint and age, the contralateral limb should be examined
to determine what is normal.6 The articular cartilage of the lateral trochlea is thicker
when compared to the medial trochlea. The articular cartilage of the trochlear and the
femoral condyles can be well evaluated with ultrasound.
Joint Capsule and Synovial Membrane:
The normal joint capsule is thin and appears homogeneously echogenic,
which allows it to be identified from the surrounding soft tissue structures. The
normal synovial membrane is hypoechoic, therefore detecting loss of echogenicity
may be difficult. Technique is important when evaluating the synovial membrane,
due to the effect of pressure with the transducer as well as the effect of limb position
on the image. Minimal pressure with the transducer is necessary to properly image
the superficial membrane. The limb should be positioned so that the joint capsule
and synovial membrane are distended, allowing separation from the articular
cartilage.5
Acute and chronic injury can result in thickening of the joint capsule. Edema
and/or hemorrhage from a recent injury will result in a hypoechoic thickened joint
capsule. Fibrosis from a chronic or old injury will result in a hyperechoic, thickened
and irregular joint capsule. The medial femorotibial joint capsule becomes more
pronounced with chronic injury and fibrosis. Rupture of the joint capsule results in a
hypo-to-anechoic region superficial to the capsule due to the accumulation of fluid.5,7
Acute synovitis has several common ultrasonographic characteristics which
include thickening of the synovial membrane, edema of the synovial villi, and synovial
fluid effusion.5 Chronic synovitis can appear as diffuse hyperechoic areas due to
fibrosis. There may also be focal hyperechoic areas with acoustic shadows due to
osteochondral fragments or dystrophic mineralization of the synovial membrane.5
Peri-Articular Margins:
Compared to radiography, ultrasonography is more sensitive to abnormalities
of the peri-articular joint margins. Peri-articular margins appear as a smooth
hyperechoic lines due to the subchondral bone. Osteophytes create an abnormal
shape compared to normal. Osteophytes can have smooth or irregular margins.
Focal hyperechoic material with acoustic shadows that is separated from the articular
margin indicates periarticular bony fragments.5 When radiographing joints, such as
the stifle, there is extensive superimposition of bone that may obscure the
visualization of peri-articular osteophytes. Alternatively, ultrasound allows for the periarticular osteophytes to be easily identified.
Subchondral Bone:
The subchondral bone surface appears as a smooth hyperechoic line in the
adult horse.6 Similar to the articular cartilage, optimal imaging occurs when the beam
is perpendicular to the subchondral bone. Injury to subchondral bone will appear as
an irregular margin, abnormal shape or a defect in the bone margin. Cysts that
extend into the subchondral bone appear as a large focal defect due to discontinuity
of the echogenic margin produced by the subchondral bone. The contents of the
cyst determine the echogenicity in the defect ranging from anechoic for fluid to
echogenic for tissue.6 The articular cartilage overlying the region of the cyst can be
evaluated. The quality of the assessment depends on whether a perpendicular beam
angle can be achieved.
Collateral Ligaments:
Accurate imaging of ligaments requires that the ultrasound beam is
perpendicular to the longitudinal axis of the ligament fibers. Ligaments can have
variable fiber orientations. Ligaments with parallel fibers will have homogeneous
echogenicity. Examples of ligaments with parallel fibers include the patellar ligaments
and the medial collateral ligaments of the stifle. It is important to note that the
proximal aspect of the medial collateral ligament curves towards the femur as it
attaches to the medial epicondyle of the femur. Complete examination this region
requires that the angle of the transducer to be adjusted to allow visualization of the
normal fiber pattern.
Injuries that disrupt ligament fibers typically present as an anechoic region with
disruption of the normal fiber architecture. These injuries can occur in the central
aspect of the ligament or on the margin, consequently the entire ligament must be
evaluated. Diffuse desmopathies can appear as a separation of normal fibers along
the length of the ligament. The severity of ligament injury can be categorized as mild,
moderate, severe or complete rupture. Mild lesions generally have separation of the
fibers, with little to no disruption of the linear architecture of the fibers. These lesions
will appear only slightly less echogenic than normal ligaments. Moderate lesions are
indicative of disruption of normal architecture of the fibers. These lesions have areas
of decreased echogenecity when examined in transverse and long axis with loss of
the linear fiber pattern in long axis. Severe lesions correspond to substantial fiber
tearing. When a complete tear of a ligament occurs, there can be considerable
relaxation artifact and hematoma formation. These injuries appear anechoic due to
the discontinuity in the ligament and retraction of the fibers. However, if portions of
the ligament have strong fascial plane attachments these regions can have linear
echogenic fibers even with complete rupture of the ligament. Complete rupture of
the medial and lateral collateral ligaments with an echogenic distal portion has been
identified in the stifle. Severe injury and subsequent soft tissue swelling can result in
distortion of the normal anatomy. Using knowledge of normal anatomical landmarks,
it is possible to determine the extent of injury even with distortion of the anatomy.8
Insertion desmopathies can be identified as abnormalities in thickness, shape,
and echogenicity. Bone resorption caused by chronic stress at a ligamentous
attachment site can result in an enlargement and deepening of the normal insertion
site. Tearing of the ligament fibers away from the bone at an attachment site leads to
osseous proliferation or enthesophyte formation.9
Menisci and Cranial Tibial Meniscal Ligaments:
Normal menisci will appear homogenously echogenic with visibility of the
internal structure, or striations. The curvature of the meniscus requires the
ultrasonographic examination to be performed in a radial direction, ensuring that the
beam is perpendicular to the meniscal fibers. This means the ultrasound probe must
be continuously repositioned so the beam remains perpendicular to the ligament
fibers producing echogenicity in the meniscus. Due to the superficial location of the
medial meniscus of the femorotibial joint, evaluation of the medial meniscus is easier
than the lateral meniscus. Using a radial technique, the menisci can be examined
completely. Increased depth may be required to image the cranial horn of the
meniscus and will be required to visualize the cranial tibial meniscus ligament. As
the probe is moved cranially to image the cranial horn and cranial tibial meniscal
ligament the orientation of the probe should be altered so that the US beam is
perpendicular to the surface structure being examined. Examination of the cranial
tibial meniscal ligaments and cranial horns requires flexion of the limb and should be
imaged in two orthogonal planes (longitudinal and transverse). The caudal horns
should be evaluated from the plantar aspect of the limb.8
When viewed in a longitudinal section relative to the limb, the medial meniscus
will appear as a homogeneous echogenic triangular shape with the boundaries
formed by the anechoic articular cartilage of the femur and tibia. The meniscus
appears concave at the proximal border due to its contact with the medial femoral
condyle.5,6 Within the homogeneous meniscus, a variable number of linear
echolucencies consistent with the normal striations will be present. The landmarks for
viewing the lateral meniscus are the long digital extensor tendon and lateral collateral
ligament in combination with the tendon of the popliteus muscle.8 Ultrasonographic
examination of the body of the lateral meniscus will appear trapezoidal. However the
cranial and caudal horns appear triangular.5
Ultrasonographic findings of injury to the menisci can present in several ways.
Meniscal tears appear as linear hypoechoic areas with discontinuity of the meniscal
margin. Changes in the size, shape, echogenicity and position of the menisci are also
indicative of meniscal injury.5,7 Hyperechoic areas with acoustic shadowing is
indicative of calcification usually due to chronic meniscal damage.6
Evaluation of the stifle joint with the limb in a weight bearing and non-weight
bearing position is required for complete evaluation of the stifle. The limb must be
flexed to allow examination of the cranial aspect of the stifle, specifically the cranial
horns of the menisci and cranial tibial meniscal ligaments. Furthermore, fissures or
tears of a meniscus may not be visible with the limb in a weight-bearing position, due
to compression of the tear under the weight of the femur. With the limb in a nonweight bearing position, synovial fluid can enter the tear creating a larger separation
between the edges of the tear making it more apparent. A small tear or fissure can be
difficult to differentiate from focal areas of linear decreased echogenicity. The linear
areas of decreased echogenicity or striated pattern in the meniscus can be found in
many sound horses and the clinical significance of this finding is poorly understood.
Digital ultrasound systems tend to enhance tissue interfaces. Therefore this pattern
is more evident on digital ultrasound systems. The striations and the meniscus
should maintain the same size, shape and echogenicity with the limb in weightbearing and non-weight bearing positions. If focal areas of decreased echogenicity
within the meniscus increase in size and/or change shape with the limb in a nonweight bearing position compared to a weight-bearing position then fiber
degeneration or intra-substance tearing should be considered. Protrusion of the
meniscus can be more easily identified by comparing the position of the meniscus
with the limb in weight-bearing and non-weight bearing positions. In many cases the
meniscus will be further displaced outside the joint margins with the limb in a weight
bearing position and then will return within the joint space with the limb in a nonweight bearing position.
Examination of the meniscus while taking the limb through a range of motion
can provide further information about a region of abnormal echogenicity as well as
demonstrate changes in position of the meniscus indicating pathologic change.
Injury to the cranial tibial meniscal ligament as well as other support structures of the
meniscus will allow the meniscus to slide or protrude medially along the medial
margin of the femur. A change in the position of the meniscus confirms injury to the
soft tissue support structures of the meniscus or injury to the meniscus and should
prompt a thorough investigation to determine the affected structure(s). It is important
to note that in the author’s opinion, Quarter Horse’s medial menisci frequently extend
beyond the peri-articular margin in horses free from lameness. This is a bilaterally
symmetrical finding in horses that are determined to not have clinically significant
findings. Comparison to the opposite limb is important.
Patellar Ligaments:
The medial patellar ligament, middle patellar ligament and the lateral patellar
ligament are examined in the longitudinal and transverse planes using ultrasound.
These three ligaments have different anatomical shapes in the transverse plane. The
medial patellar ligament is triangular, the middle patellar ligament is round, and the
lateral patellar ligament is flat and wide.6
Cruciate Ligaments:
The cranial and caudal cruciate ligaments can appear hypoechogenic
because it is not always possible to place the beam angle perpendicular to the
ligament fibers. Therefore they are often difficult to image and differentiate from
surrounding structures. The insertion surfaces of the ligaments can be examined with
a cranial approach to a flexed stifle.6 The distal extent and the insertion of the caudal
cruciate ligament can be identified with the limb in a weight bearing position. It is
immediately adjacent to the medial extend of the caudal horn of the medial meniscus
in the intercondylar region.
Meniscofemoral Ligament:
The mensicofemoral ligament extends from the caudal horn of the lateral
meniscus and attaches on the intercondyloid fossa of the femur. It traverses obliquely
extending in the proximomedial direction from the caudal horn. It is covered by the
superficial digital flexor tendon and the popliteal vasculature.
Conclusion
Radiographs and ultrasound are valuable tools for the diagnosis of stifle injury.
Radiographic evaluation of the stifle requires appropriate positioning and the best
approach will depend somewhat on the conformation and temperament of the horse,
plate size and type of x-ray generator. Ultrasound requires a consistent and thorough
examination method with an extensive knowledge of the anatomy and continued
practice.
References
1. Adams WM, Thiisted JP. Radiographic Appearance of the Equine Stifle from
Birth to 6 Months. Veterinary Radiology. 1985;26(4):126–32.
2. Dyson S, Wright I, Kold S, Vatistas N. Clinical and radiographic features,
treatment and outcome in 15 horses with fracture of the medial aspect of the
patella. Equine Vet. J. 1992 Jul;24(4):264–8.
3. Arnold CE, Schaer TP, Baird DL, Martin BB. Conservative management of 17
horses with nonarticular fractures of the tibial tuberosity. Equine Vet. J. 2003
Mar;35(2):202–6.
4. Prades M, Grant BD, Turner TA, Nixon AJ, Brown MP. Injuries to the cranial
cruciate ligament and associated structures: summary of clinical, radiographic,
arthroscopic and pathological findings from 10 horses. Equine Vet. J. 1989
Sep;21(5):354–7.
5. McIlwraith CW. Joint disease in the horse. Philadelphia: W.B. Saunders; 1996.
6. Denoix, J.-M., Audigie’. Ultrasonographic Examination of Joints in Horses
[Internet]. [cited 2012 Nov 21]. Available from:
http://www.ivis.org/proceedings/AAEP/2001/contents01.pdf
7. White NA, Moore JN, editors. Current techniques in equine surgery and
lameness. 2nd ed. Philadelphia, Pa: W.B. Saunders; 1998.
8. Reef VB. Equine diagnostic ultrasound. Philadelphia: W.B. Saunders; 1998.
9. Rantanen NW, McKinnon AO, editors. Equine diagnostic ultrasonography. 1st ed.
Baltimore: Williams & Wilkins; 1998.
SOFT TISSUE INJURIES OF THE STIFLE: MENISCUS AND CRUCIATE
LIGAMENTS
Michael Schramme DrMedVet, CertEO, PhD, HDR, DECVS, DACVS
Campus Vétérinaire de Lyon, VetAgro Sup
Université de Lyon, France
Roger Smith MA VetMB, DEO, PhD, DECVS, AssocECVDI
Dept. of Veterinary Clinical Sciences, The Royal Veterinary College, Hawkshead
Lane, North Mymms, Hatfield, Herts. AL9 7TA. U.K.
Introduction
The stifle is not an unusual site of lameness in the Sporthorse. While it is a common
site of developmental conditions such as osteochondrosis in the young animal, soft
tissue injuries are a common cause of lameness arising from the stifle in adult
Sportshorses.
Clinical examination of stifle lameness
Traumatic injuries to the stifle are commonly seen in association with external trauma
from a kick or a collision with a fixed or moving heavy object. Typically this occurs in
event horses that hit cross-country fences with the stifle region of one or both
hindlimbs. However, stifle injuries have also been observed in horses turned out at
pasture without any history of trauma.
In comparison with other diarthrodial joints, the stifle is characterised by the poor
congruity between the spherical femoral condyles and the flat plateau at the proximal
end of the tibia, and by an intricate support system of extra- and intra-articular
ligaments and two fibrocartilagenous menisci. These structures are at risk of injury
when the loaded stifle is subject to craniocaudal, lateromedial or twisting forces
outside of the normal physiological range.
Careful clinical examination by inspection and palpation of an injured stifle can be
rewarding. The landmarks for palpation are the patella, the tibial crest, the patellar
ligaments, the combined tendon of the peroneus tertius and the long digital extensor,
the collateral ligaments, the proximal medial articular margin of the tibia, and the
medial border of the medial meniscus immediately proximal to it. The presence of
stifle effusion is significant. Diffuse swelling over the cranial aspect of the stifle
causes loss of the characteristic cranial silhouette of the stifle region and is
commonly associated with periarticular bruising following acute trauma. Effusion of
the femoropatellar joint is most prominent just distal to the distal border of the patella,
proximally between the patellar ligaments. It causes a characteristic bulge in the
cranial silhouette of the stifle just distal to the patella. Effusion of the medial
femorotibial joint is best appreciated as a medial bulge of the joint capsule through a
window bordered by the medial collateral ligament caudally, the proximal medial
articular margin of the tibia with the medial border of the medial meniscus distally, the
medial patellar ligament cranially and the medial femoral metaphysis proximally.
Distension of this joint is a serious clinical sign, most commonly associated with
traumatic arthritis of the medial femorotibial joint. Effusion of the lateral femorotibial
joint is less easily identified because of the presence of the broad common tendon of
the long digital extensor and the peroneus tertius in the extensor fossa overlying the
craniolateral aspect of this joint.
Hindlimb flexion and abduction tests have been described but are of limited
specificity in the identification of stifle pathology. A drawer test is occasionally used in
the cranial-cruciate-deficient stifle.
Lameness is highly variable and is not specific to the stifle. However as the stifle is
responsible for a considerable amount of the protraction phase of the stride, the
cranial phase of the stride is often reduced and the lameness is usually as evident, or
worse, on soft ground compared to on hard ground.
Diagnostic analgesia of all three joints should be performed in those cases were the
location of the lameness is unknown because of variable physical and functional
communication between the three separate stifle joint compartments (Reeves et al.
1991; Toth et al. 2014).
Diagnostic Imaging of stifle lameness
Diagnostic imaging should include a minimum of radiography (lateromedial,
caudocranial and flexed lateromedial views) and ultrasonography (cranial, medial and
lateral aspects), which, when combined with arthroscopy provides the most efficient
definition of the soft tissue injury. Gamma scintigraphy and, in some limited centres,
MRI or CT, are alternatives.
Diagnostic imaging
Ultrasonography is a very useful technique to image the peri- and intra-articular soft
tissues of the stifle, but its usefulness is limited to the patellar ligaments, the collateral
ligaments of the femorotibial joints and the medial and lateral horns of the medial and
lateral menisci respectively. Meniscal tears are classified according to their
orientation and extent. The cranial and caudal portions of the femorotibial joints are
more difficult to image and ultrasonographic recognition of pathological changes in
the cruciate ligaments, meniscal ligaments and cranial horns of the menisci continue
to elude us in many cases.
During a scintigraphic examination, lateral, caudal and sometimes flexed cranial
images are obtained of the injured stifle and the contralateral normal stifle for
comparison, on standing, sedated patients for 120 seconds each. Movement
correction of the image is particularly useful for scintigraphic examination of the stifle.
In our clinic, this technique, though rewarding for the identification of acute skeletal
damage, has been less sensitive in the diagnosis of soft tissue injuries that
accompany traumatic arthritis of the stifle.
Specific soft tissue pathologies
Bruising
When Sporthorses hit a fence, trauma to the cranial aspect of the stifle is common.
Bruising in this area results in haematoma of the cranial periarticular tissues,
characterised by a fluctuant swelling which is compressible and heterogenous in
echogenicity on ultrasound. These cases should also be evaluated using sky-line
(cranioproximal-craniodistal oblique) radiographs for possible medial pole fractures of
the patella which can be easily missed on standard radiographs.
Patellar ligament desmitis
In order to identify the patellar ligaments ultrasonographically, the transducer is
positioned transversely and moved distoproximally from the tibial crest to the patella.
Over-strain injury to these ligaments is rare. The most commonly affected ligament is
the middle patellar ligament. Clinical signs include swelling surrounding the ligament
with pain on palpation with the stifle semi-flexed. Results of diagnostic analgesia of
the stifle is variable and can be negative. Treatment is conservative. There are
limited clinical data available on outcome but the prognosis is considered to be
guarded.
The ‘terrible triad’ – cranial cruciate, medial meniscus and medial collateral ligament
This concept of a ‘triad of injuries’ is derived from human and small animal clinical
practice but is actually rare in horses except with severe impact trauma to the stifle.
Meniscal tears are most frequently seen in isolation with a much lower frequency of
injury affecting the cranial cruciate and medial collateral ligaments.
Cruciate ligament desmitis/rupture
Cruciate ligament injuries are much rarer than in small animals and are difficult to
diagnose with confidence without arthroscopy. The cruciate ligaments lie under a
thin layer of synovial membrane (subsynovially). Damage is usually manifest by
visual recognition of fibre rupture or haemorrhage. In addition, avulsion fragments of
bone can be seen radiographically at the origin and insertion sites of the ligaments.
Walmsley (1996) graded cranial cruciate tears in a similar fashion to mensical tears:
(I) superficial haemorrhage and fibrin deposition (cruciate sprain); (II) superficial
separation of ligament fibers; (III) deep sparation of fibers or rupture. Most cranial
cruciate injuries seem to occur in its body or towards the tibial insertion. New bone on
the cranial edge of the medial intercondylar eminence of the tibia is believed to be
more indicative of meniscal ligament pathology than cruciate damage, although
fragmentation of the medial (or lateral) intercondylar eminence is occasionally (but
not always) associated with cruciate ligament injury. Careful assessment of other soft
tissue structures of the stifle is important to rule out other concurrent pathology.
Treatment consists of arthroscopic debridement and rest. Arthroscopic assessment
and debridement can be facilitated by removal of the median septum. Debridement
using motorized resectors is recommended for some grade 2 and for grade 3 tears,
followed by a prolonged period of rest and controlled exercise (up to 6 months).
Selected results suggest that this may lead to favourable outcome in some cases.
Some contained injuries have been treated with arthroscopically guided intraligamentous injections with mesenchymal stem cells.
Fractures of the medial intercondylar eminence have long been regarded as avulsion
injuries of the cranial cruciate ligament. Arthroscopic exploration of such injuries
however has shown that they may occur without significant ligament disruption.
Arthroscopic removal of fracture fragments or internal fixation with a lag screw may
result in good functional outcome.
Collateral ligament desmitis
These injuries are rare. Severe injury results in a widening of the joint space on the
side of the injury. Enlargement of the ligament is the most obvious sign recognized
during ultrasonographic examination. In some cases, avulsion fractures of the
insertion sites of the ligament can occur. If the damage to the ligament produces
significant joint instability, the prognosis is poor.
Meniscal tears
The meniscus can not be comprehensively evaluated with any one imaging
technique only and the best evaluation is achieved by a combination of radiography,
ultrasonography, and arthroscopy (Schramme et al. 2006). Arthroscopy will enable
the cranial and caudal poles of the menisci to be evaluated while ultrasonography
allows the identification of pathology within the medial or lateral portion of the body of
the meniscus, not visible arthroscopically.
Ultrasonography of the menisci is
relatively easily performed. The transducer should be aligned vertically along the
longitudinal axis of the limb and moved in a craniocaudal direction. The meniscus
and the collateral ligament can be identified (and the popliteal tendon lying between
the lateral meniscus and the collateral ligament on the lateral aspect).
Injury is invariably associated with moderate to severe lameness and frequently (but
not always) with distension of the femorotibial (and sometimes also the
femoropatellar) joints. Medial meniscal injuries are more common than lateral and
based on recent biomechanical studies, are believed to occur because the cranial
horn of medial meniscus is compressed and minimally mobile when the stifle is
extended (Fowlie et al. 2012). This also explains why most tears arise in the cranial
aspect of the menisci and extend variably caudally.
Chronic meniscal pathology often results in osteoarthritis of the femorotbial joints
identified by osteophytes on the medial intercondylar eminence of the tibia and on
the perimeter of the tibial plateau. Pathognomonic for tearing of the cranial ligament
of the meniscus is the presence of entheseous new bone on the cranial surface of
the medial intercondylar eminence of the tibia, as seen most easily on flexed
lateromedial views of the stifle.
Meniscal tears have been classified into three categories arthroscopically:
 Grade I – confined to the cranial ligament of the meniscus
 Grade II – tears extending from the cranial ligament of the meniscus
into the meniscus but where the entire tear is visible
arthroscopically.
 Grade III – a tear in the meniscus which extends beyond the field of
view.
 In addition, a fourth grade representing meniscal tears occurring within the
body of the ligament that can not be seen arthroscopically can be included
(Schramme et al., 2006).
Arthroscopic debridement is the treatment of choice. Grade I tears are left untreated,
while grade II and grade III tears are debrided as effectively as possible.
Postoperatively horses are maintained on controlled exercise for up to 6 months. The
prognosis for return to exercise in grade I injuries is 63%, 56% for grade II, and 6%
for grade III (Walmsley, 2005). More recently, concurrent biological therapies (such
as intra-articular or intra-lesional mesenchymal stem cells) have also been used
based on evidence of meniscal regeneration in experimental animal models (Murphy
et al. 2003). In a limited number of reported case series, this appears to have
improved the outcome (Ferris et al. 2014) although the use of MSCs is only
recommended in those cases with a stable stifle joint and without meniscal
displacement.
References
1. Fowlie JG, Arnoczky SP, Lavagnino M, Stick JA. Stifle extension results in
differential tensile forces developing between abaxial and axial components of
the cranial meniscotibial ligament of the equine medial meniscus: a mechanistic
explanation for meniscal tear patterns. Equine Vet J. 2012 Sep;44(5):554-8.
2. Ferris DJ, Frisbie DD, Kisiday JD, McIlwraith CW, Hague BA, Major MD,
Schneider RK, Zubrod CJ, Kawcak CE, Goodrich LR. Clinical Outcome After
3.
4.
5.
6.
7.
Intra-Articular Administration of Bone Marrow Derived Mesenchymal Stem Cells
in 33 Horses With Stifle Injury. Vet Surg. 2014 Jan 16. doi: 10.1111/j.1532950X.2014.12100.x
Murphy JM, Fink DJ, Hunziker EB, Barry FP. Stem cell therapy in a caprine
model of osteoarthritis. Arthritis Rheum. 2003 Dec;48(12):3464-74.
Reeves MJ, Trotter GW, Kainer RA. Anatomical and functional communications
between the synovial sacs of the equine stifle joint. Equine Vet J. 1991 May;
23(3):215-8.
Schramme, M.C., Smith, R.K., Jones, R.M. and Dyson, S.J. (2006) Comparison
of radiographic, ultrasonographic and arthroscopic findings in 29 horses with
meniscal injury. In: Proceedings of the 16th Annual Meeting of the American
College of Veterinary Surgeons.
Tóth F, Schumacher J, Schramme MC, Hecht S. Effect of anesthetizing individual
compartments of the stifle joint in horses with experimentally induced stifle joint
lameness. Am J Vet Res. 2014 Jan;75(1):19-25.
Walmsley JP. Diagnosis and treatment of ligamentous and meniscal injuries in
the equine stifle. Vet Clin North Am Equine Pract. 2005 Dec;21(3):651-72.
SUBCHONDRAL BONE CYSTS OF THE STIFLE
Roger Smith MA VetMB, DEO, PhD, DECVS, AssocECVDI
Dept. of Veterinary Clinical Sciences, The Royal Veterinary College, Hawkshead
Lane, North Mymms, Hatfield, Herts. AL9 7TA. U.K.
Aetiopathogenesis
There are 2 possible causes for the development of subchondral bone cysts.
1.
They may be a manifestation of osteochondrosis with thickened necrotic
cartilage persisting as a localized defect within the subchondral bone.
2.
They may result from localized trauma damaging primarily either
•
The articular cartilage.
•
The underlying subchondral bone.
Clinical signs
 Generally found in young horses but can also present in middle aged to older
horses. It is unclear if older horses have had the lesions since they were young
without showing signs or whether a different aetiology exists in these patients
such as secondary formation to other joint pathology.
 Usually presents clinically as persistent mild to moderate lameness, although it
may be intermittent in nature (and sometimes severe depending on concurrent
pathology)
Diagnosis
 Intra-articular analgesia of the medial femorotibial joint (or of all three
compartments). May not result in complete soundness
 Radiology.
Cysts are seen best on the caudocranial projection or the
cuadolateral-craniomedial oblique. They appear as large circular or domeshaped cysts in the medial femoral condyle, usually with a distinct
communication with the medial femorotibial joint.
Treatment
 Conservative management (i.e. 6 months rest) may restore soundness but only
in a limited number of cases.
 In the young animal the first line treatment is usually injection of the cyst lining.
This can be done either standing or under general anaesthesia with ultrasound
guidance with a flexed stifle, or under general anaesthesia with arthroscopic
control. The latter enables concurrent assessment for any concurrent joint
pathology, removal of necrotic cartilage from the cloaca of the cyst, and improves
accuracy of injecting the corticosteroid beneath of the surface of the cyst lining at
multiple sites.
 Older horse cysts or those where corticosteroid injection has failed can be
treated by surgical debridement of the cyst while maintaining as much of the
subchondral bone in the region of the cloaca.
 Additional surgical procedures such as forage of the bone surrounding the cyst or
packing the cyst with an autogenic cancellous bone graft have been reported but
are now infrequently used due to their limited success.
 More recently cartilage resurfacing techniques using autogenic chondrocyte or
stem cell implantation or autogenic bone-cartilage transplants have been
reported to have better success.
Prognosis
 Corticosteroids – 67% (Wallis et al., 2008)
 Surgical debridement - 50-75% depending on concurrent pathology. Older horse
cysts (not all of which may have been due to osteochondrosis) had a prognosis
of ~30% (Smith et al., 2005).

ULTRASONOGRAPIC EXAMINATION OF THE PELVIS AND COXOFEMORAL
JOINTS
Natasha Werpy, DVM, DACVR
Radiology Department, University of Florida
Journal of Equine Veterinary Science 32 (2012) 222-230
Journal of Equine Veterinary Science
journal homepage: www.j-evs.com
Clinical Technique
Procedure for the Transrectal and Transcutaneous Ultrasonographic
Diagnosis of Pelvic Fractures in the Horse
Wade T. Walker DVM, Natasha M. Werpy DVM, DACVR, Laurie R. Goodrich DVM, PhD, DACVS
Gail Holmes Equine Orthopaedic Research Center, Colorado State University, Fort Collins, CO
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 June 2011
Received in revised form
29 August 2011
Accepted 8 September 2011
Available online 29 October 2011
Recent advancements in the quality and availability of imaging modalities have allowed
clinicians to diagnose fractures in horses with hindlimb lameness. Many imaging
modalities aid in the diagnosis of pelvic fractures, including radiography, nuclear scintigraphy, computed tomography, and ultrasonography. Ultrasonography is an appropriate
initial diagnostic tool when a pelvic fracture is suspected. The use of ultrasonography
minimizes many of the risks and complications associated with the radiographic, scintigraphic, and computed tomographic evaluation of pelvic fractures, and is readily
available to equine practitioners. This manuscript provides a detailed description of
a complete transrectal and transcutaneous ultrasonographic examination of the equine
pelvis. The described method has been effective in the diagnosis of pelvic fractures in
a series of eight cases. Transrectal ultrasonography was found effective in revealing
fractures of the ischiatic table, acetabulum, pubis, and ilium. Transcutaneous ultrasonography effectively identified fractures of the ilium, acetabular rim, femoral neck,
greater trochanter, and a capital physeal fracture with a subluxated femoral head.
Ó 2012 Elsevier Inc. All rights reserved.
Keywords:
Diagnostic
Equine
Fracture
Pelvis
Ultrasound
1. Introduction
In horses, hindlimb lameness caused by pelvic fractures
is far more common than previously appreciated. Early
retrospective studies report that 4.4% of all hindlimb lameness was a result of pelvic fractures [1]. More recent studies
performed on Thoroughbreds have demonstrated a much
higher frequency of hindlimb lameness resulting from
pelvic fractures than reported by original studies [2-4].
Recent recognition of the incidence and implications of
pelvic fractures in the horse have facilitated advancements
in their diagnosis.
Pelvic fractures can have a nonspecific clinical
presentation [5]. Soft tissue swelling, unilateral hindlimb
W.T.W. is currently at Arizona Equine Medical and Surgical Centre,
1685 S. Gilbert Rd., Gilbert, AZ 85296.
Corresponding author at: Natasha M. Werpy, DVM, DACVR, Gail
Holmes Equine Orthopaedic Research Center, Colorado State University,
300 W. Drake Rd., Fort Collins, CO 80523-1678.
E-mail address: [email protected] (N.M. Werpy).
0737-0806/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved.
doi:10.1016/j.jevs.2011.09.067
lameness, gluteal muscle atrophy, as well as crepitation
and muscle spasm on palpation are often indicative of
pelvic injury [5-7]. Asymmetry of the pelvic canal, crepitus, hematomas, as well as the pubic bone, ventral
sacroiliac joint, and internal surface of the ilium can all be
evaluated by rectal palpation. Abnormalities on rectal
palpation may suggest the presence of a pelvic fracture
[5-8].
Various techniques for the radiographic evaluation of
the equine pelvis have been described [9-11]. Radiographic
imaging is performed under general anesthesia to obtain
a ventrodorsal projection to evaluate pelvic symmetry
followed by an oblique image with the affected side down
[9-11]. This protocol has proven to be 70% effective in
confirming the diagnosis of pelvic fractures [10]. However,
anesthetizing a horse with a pelvic fracture may illicit
complications such as fracture displacement which could
potentially lacerate the internal iliac vessels [12]. Because
of the risks associated with obtaining radiographs under
general anesthesia, many clinicians are hesitant to use this
technique when a pelvic fracture is suspected.
W.T. Walker et al. / Journal of Equine Veterinary Science 32 (2012) 222-230
Standing ventrodorsal, ventrodorsal oblique, lateral, and
lateral oblique radiographic techniques of the equine pelvis
have been described [13-15]. These methods avoid the
associated risk of fracture displacement with general
anesthesia and offer visualization of the caudal pelvis and
cranial acetabular rim [13]. Pelvic radiography in the
standing horse may decrease the associated risks of
recumbency; however, these techniques require high
exposure tubes and antiscatter equipment [13-15]. Additionally, the unwillingness of horses in pain to stand square
often complicates standing techniques [15].
Detection of pelvic fractures using nuclear scintigraphy
has been described [16-20]. Nuclear scintigraphy can be
effective for diagnosing fractures of the tuber coxae, tuber
ischii, greater trochanter, and third trochanter [19-21]. In
addition, it has been used to identify bone remodeling
of the ilial body, which could be a precursor to catastrophic failure [17-19]. A study suggests that nuclear
scintigraphy is unreliable for diagnosing pubic bone
fractures because of radiopharmaceutical uptake in the
urinary bladder [19]. Furthermore, nuclear scintigraphy
does not reveal detail of the fracture configuration and is
complicated by pelvic asymmetry, muscle atrophy, and
motion [19].
Computed tomography has been recently described in
the diagnosis of pelvic fractures in two fillies [22]. This can
be an effective diagnostic aid in young horses and potentially ponies or other small breed horses; however, general
anesthesia is required, and computed tomography is only
available at a select number of referral veterinary
hospitals.
Ultrasonography of the equine pelvis has been validated
using computed tomography, magnetic resonance imaging,
and frozen sections [23]. This modality has proven to be an
effective method for the diagnosis of pelvic fractures [3,
24-27] and coxofemoral subluxation in horses [28].
Owing to the risks associated with recumbent radiographic
techniques and the inability to perform this technique in
the field, clinical examination followed by ultrasonographic
imaging of the pelvis is an effective and inexpensive way
for equine practitioners to diagnose pelvic fractures
[23-27]. Furthermore, the relatively noninvasive technique
of pelvic ultrasonography is useful to monitor the
progression of pelvic fractures, determine prognosis, and
prescribe therapeutic modalities [6,26].
Recently, transcutaneous and transrectal ultrasonographic examinations have been deemed appropriate
diagnostic procedures to precede radiographic examinations when a pelvic fracture is suspected [29]. Studies have
described the normal ultrasonographic appearance of the
pelvis [23-25] and the abnormal ultrasonographic findings
associated with the diagnosis of pelvic fractures [25,26]. A
detailed description of the transrectal ultrasonographic
diagnosis of pelvic fractures has yet to be described. The
purpose of this study is to describe a thorough ultrasonographic examination of the bony structures of the pelvis. In
addition, the subsequently described technique was used
along with other diagnostic aids and postmortem confirmation to effectively diagnose pelvic fractures in eight
horses. The signalment, clinical examination findings,
ultrasonographic findings, and results of other diagnostic
imaging modalities in these horses are presented.
223
2. Methods and Materials
A thorough clinical and ultrasonographic examination
was performed on eight horses admitted to the Colorado
State University Veterinary Teaching Hospital for suspected
pelvic fractures from 2005 to 2008. The subsequently
reported technique for the transrectal and transcutaneous
ultrasonographic diagnosis of pelvic fractures was used on
10 horses with no history of hindlimb lameness. Normal
(Figs.1-4) and pathologic ultrasonographic images (Figs. 5-9)
oriented with cranial to the left and caudal to the right are
included. Ultrasonographic results were confirmed with
clinical examination, radiography, nuclear scintigraphy, or
postmortem findings (Table 1).
2.1. Clinical Examination
After performing a thorough physical and lameness
examination, the pelvis was visually and manually examined to evaluate external symmetry. The tuber sacrale,
tuber coxae, and tuber ischii were physically manipulated
bilaterally to elicit pain or crepitus. Other areas of the pelvis
such as the region of the coxofemoral joint and ventral
pelvis were palpated for heat, pain, and hematomas.
Patient preparation included intravenous administration of
0.02-mg/kg detomidine hydrochloride (Pfizer Animal
Health, Exton, PA), evacuation of feces from the rectum, and
an intrarectal infusion of 60-mL 2% lidocaine via an
extension set. A rectal examination was then performed to
assess internal symmetry, pain, crepitus, callus, and the
presence of hematomas in the pelvic canal.
2.2. Approach to Transrectal Ultrasonographic Examination
For the ultrasonographer’s safety, the transrectal
examination was performed before the transcutaneous
examination while the horse was sedated. A 7.5-10-MHz
linear rectal transducer was used transrectally to evaluate
the osseous integrity of the pelvic canal. Orientation of the
probe alternated between transverse and longitudinal
direction to perform a thorough transrectal examination
(Fig. 1A). During the examination, the probe was advanced
slightly less than one probe length with each change of
direction to ensure that the entire osseous surface of the
pelvis was imaged. To assess the ischiatic table, the probe
was placed midsagitally on the most caudal margin of the
ischium. The probe was advanced laterad (away from
midline) along the caudal border of the ischiatic arch until
the ischiatic tuberosity was reached. From the ischiatic
tuberosity, the probe was swept craniomediad (toward
midline) until the pelvic symphysis was reached one probe
length cranial to the lesser ischiatic arch. The probe was
advanced laterad along the concave dorsal surface of the
ischiatic table until the lesser ischiatic notch was reached at
the most lateral margin of the ischium. From the dorsal
border of the lesser ischiatic notch, the probe was returned
craniomediad reaching the pelvic symphysis two probe
lengths cranial to the lesser ischiatic arch. The probe was
advanced laterad to image the caudal border of the obturator foramen until the ischiatic spine was reached.
Advancing the probe craniomediad allowed for the
remaining ischiatic and pubic borders of the obturator
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W.T. Walker et al. / Journal of Equine Veterinary Science 32 (2012) 222-230
Fig. 1. Internal structures of the equine pelvis (A), including the pelvic symphysis (1), ischiatic table (2), tuber ischii (3), ischiatic arch (4), lesser ischiatic notch (5),
obturator foramen (6), ischiatic spine (7), pubic bone (8), acetabulum (9), body of the ilium (10), wing of the ilium (11), tuber sacrale (12), and tuber coxae (13).
Normal transverse transrectal image (B) of the pelvic symphysis on midline (arrow) and axial aspect of the ischiatic tables (arrowheads). Normal sagittal
transrectal image of the caudal border of the obturator foramen (C) consisting of the soft tissues within the obturator foramen (arrowhead) and cranial ischium
(arrows). Normal sagittal transrectal image of the pubic bone (D, arrows) and soft tissues within the obturator foramen (arrowhead).
foramen to be imaged until the pelvic symphysis was
reached on midline. The aforementioned examination was
repeated on the contralateral hemipelvis for comparison of
symmetry and echogenicity.
The acetabulum, ilium, and sacrum were examined
transrectally by placing the probe at the most cranial aspect
of the pelvic symphysis and advancing the probe laterad
over the pubic bone to the level of the acetabulum (Fig. 2A).
When examining the medial aspect of the left ilium and
ventral sacrum, the probe was in the right hand; examination of the contralateral structures was performed with
the probe in the left hand. After proper orientation of the
probe was achieved, the probe was advanced dorsad to
examine the medial surface of the ilial body between the
borders of the greater sciatic notch and arcuate line of the
ilium. As the probe continued dorsomediad along the body
of the ilium, the ventral aspect sacroiliac joint was examined. From this point, the ventral sacrum was examined,
including the ventral sacral foramina and the promontory
of the sacrum at midline (Fig. 3A). The aforementioned
examination was repeated on the contralateral hemipelvis
for comparison of symmetry and echogenicity.
Fig. 2. Internal structures of the equine pelvis visualized from the medial aspect (A), including the ischiatic table (1), pubic bone (2), arcuate line of the ilium (3),
ischiatic spine (4), and the medial surface of the ilium (5). Normal sagittal transrectal image of the medial surface of the acetabulum (B, arrows) and obturator
vessels (arrowheads). Normal sagittal transrectal image of the medial surface of the body of the ilium (C, arrows) between the greater sciatic notch and arcuate
line of the ilium.
W.T. Walker et al. / Journal of Equine Veterinary Science 32 (2012) 222-230
225
Fig. 3. Ventral view of the equine pelvis (A), including the tuber ischii (1), ischiatic table (2), obturator foramen (3), acetabulum (4), pubic bone (5), ventral sacral
foramina (6), promontory of the sacrum (7), ventral sacroiliac joint (8), and the wing of the sacrum (9). Normal transverse transrectal image of the sacroiliac joint
(B, accent), including the ventral surface of the ilium (arrowheads) and the ventral sacrum (arrows). Normal sagittal transrectal image of a ventral sacral foramina
(C), including the ventral sacral nerve root (arrows), a branch of the caudal gluteal artery within the nerve root (accent), and the ventral aspect of the sacrum
(arrowheads).
2.3. Approach to Transcutaneous Ultrasonographic
Examination
A transcutaneous ultrasonographic examination was
then performed similar to those previously described
[23,25] (Fig. 4A). A 3-5-MHz curvilinear transducer was
used alternating between transverse and longitudinal
orientation to better visualize the osseous structures of the
pelvis transcutaneously. The tuber sacrale was imaged from
its most dorsal margin craniolaterad over the concave crest
of the ilium to the tuber coxae (Fig. 4A). The probe was
swept caudodistad across the gluteal surface of the ilial
wing between its most lateral and medial margins until
reaching the body of the ilium. From the caudal ilium, the
probe was advanced caudad to view the dorsal aspect of the
acetabulum, the coxofemoral joint, as well as the head,
neck, and greater trochanter of the femur. The probe was
moved further caudad to image the lateral aspect of the
ischium along the caudal portions of the lesser ischiatic
notch. At the most caudal aspect of the pelvis, the tuber
ischii was palpated and imaged with the probe in a vertical
orientation. The aforementioned examination was
repeated on the contralateral hemipelvis for comparison of
symmetry and echogenicity.
3. Results
3.1. Normal Transrectal Ultrasonographic Findings
The pelvic symphysis was identified with the probe in
transverse orientation, midsagittally as a thin linear hypoechoic region separated by the hyperechoic osseous
Fig. 4. Structures of the normal pelvis evaluated with transcutaneous ultrasonography (A), including the wing of the ilium (1), tuber coxae (2), body of the ilium
(3), acetabular rim (4), coxofemoral joint (5), greater trochanter of the femur (6), and the tuber ischii (7). Normal longitudinal transcutaneous image the tuber
sacrale (B, arrow) and the iliac crest (arrowheads). Normal transcutaneous image of the coxofemoral joint (C, accent), acetabular rim (arrows), and greater
trochanter (arrowheads) with the probe directed dorsoventrally.
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W.T. Walker et al. / Journal of Equine Veterinary Science 32 (2012) 222-230
Fig. 5. Transverse transrectal image of case 2 demonstrating the pelvic
symphysis (accent), normal section of ischium (arrowhead), and a callus on
the ischium due to a previous fracture (arrows). See Figure 1B for normal
ultrasonographic appearance.
structures of the ischiatic table (Fig. 1B). The ischiatic table
was identified as a smooth concave hyperechoic line. This
line led to a rough hyperechoic convex surface near the
lateral margin of the caudal ischium representing the tuber
ischii. The dorsal margin of the lesser ischiatic notch was
delineated by a smooth transition of hyperechogenicity
into an area of mixed echogenicity representing the overlying musculature.
The obturator foramen was easily identified with the
probe in sagittal orientation as an area of mixed echogenicity surrounded by the ischiatic and pubic margins of the
obturator foramen. These margins were identified as
a smooth convex hyperechoic line (Fig. 1C). The pubic bone
was identified in sagittal orientation as a smooth hyperechoic line that did not span the entire length of the probe
(Fig. 1D). As the probe was moved laterad on the body of
the pubic bone, the length of the pubic bone widened until
reaching the medial surface of the acetabulum. The medial
surface of the acetabulum was identified in sagittal orientation as a smooth and wide hyperechoic line between the
region of the pubic bone and ischial spine. We found that
the medial surface of the acetabulum was wider than the
margins of the probe and required sweeping the probe in
a cranial to caudal manner to examine its entire surface.
Fig. 7. Gross (A) and dorsoventral transcutaneous image (B) of case 4
demonstrating a greater trochanteric and capital physeal fracture and
a subluxated coxofemoral joint. The acetabular rim (arrow), femoral head
(accent), and greater trochanter (arrowheads) are all imaged with the probe
in longitudinal orientation. The femoral head is subluxated and there is
a step fracture on the femoral neck. See Figure 4C for normal ultrasonographic appearance.
Two hypoechoic circular structures in the obturator groove
on the medial aspect of the acetabulum were consistently
identified with the probe in sagittal orientation representing the obturator artery and vein (Fig. 2B). The obturator nerve also occupies this region but could not be
imaged consistently.
Dorsolateral to the acetabulum, the medial surface of
the body of the ilium was visualized with the probe in
sagittal orientation. This congruent hyperechoic line
between the greater sciatic notch and arcuate line of the
ilium was imaged within the length of the probe (Fig. 2C).
The ventral aspect of the sacroiliac joint was imaged as
a hypoechoic gap between the hyperechoic wing of the
ilium and the sacrum [23] (Fig. 3B). The ventral sacral
foramina were identified in sagittal orientation as halfcircles of mixed echogenicity perpendicular to the plane
of imaging (Fig. 3C). The promontory of the sacrum was
identified midsagittally in transverse orientation as
a convex hyperechoic prominence.
3.2. Normal Transcutaneous Ultrasonographic Findings
Fig. 6. Sagittal transrectal image of case 2 at the medial aspect of the
acetabulum demonstrating displacement of the obturator vessels (arrowheads) and extensive callus (arrows). See Figure 2B for normal ultrasonographic appearance.
The tuber sacrale was identified as a smooth hyperechoic prominence (Fig. 4B), and the tuber coxae was
identified as a hyperechoic convex line at the craniolateral
aspect of the pelvis. The crest of the ilium was imaged with
the probe in longitudinal orientation as a smooth concave
W.T. Walker et al. / Journal of Equine Veterinary Science 32 (2012) 222-230
227
Fig. 8. Sagittal transrectal image of case 5 demonstrating an ischial step
fracture. The fracture (arrows) is displaced from the ischium (arrowheads).
hyperechoic line spanning the region between the tuber
sacrale and tuber coxae. The gluteal surface of the ilial wing
was identified as a smooth concave hyperechoic line
(Fig. 4B). The lateral and medial margins of the ilial wing
narrowed caudal in direction until the body of the ilium
was imaged as a narrow convex hyperechoic line viewed
entirely within the length of the probe in transverse
orientation. Caudal to this, the body of the ilium widened
until the acetabular rim was identified as a small convex
hyperechoic line (Fig. 4C). The coxofemoral joint was
identified as a small hypoechoic line in apposition to the
hyperechoic lines of acetabular rim and head of the femur
(Fig. 4C). The femoral neck was identified as a smooth
hyperechoic line extending dorsad and superficially until
a large hyperechoic prominence was imaged representing
the greater trochanter. The lateral aspect of the caudal
ischium at the lesser ischiatic notch was identified as
a smooth hyperechoic line. The tuber ischii was identified
as a smooth hyperechoic prominence at the origins of the
caudal thigh muscles.
3.3. Ultrasonographic Diagnosis of Pelvic Fractures
Seven horses referred to the Colorado State University
Veterinary Teaching Hospital for a suspected pelvic fracture
received a complete ultrasonographic examination. Transcutaneous ultrasonography was performed on one additional horse without a transrectal examination because of
his young age and because a fracture was readily diagnosed
on transcutaneous examination. Fractures were identified
in three cases on both transrectal and transcutaneous
examinations. Fractures of the ischium and pubis were only
identified on the transrectal examination (Fig. 5). Transrectal ultrasonographic examination of the acetabulum
indicated a high suspicion of fracture that was verified with
other diagnostic aids (Fig. 6, Table 1). Bony proliferation of
the acetabular rim was evident on transcutaneous ultrasonographic examinations where acetabular fractures were
highly suspicious transrectally in all cases except horse 8.
The acetabular fracture in this case was acute. We were not
able to differentiate between articular fracture or
osteoarthritis in the coxofemoral joint on transcutaneous
ultrasonography without transrectal ultrasonographic
examination. A femoral fracture and femoral subluxation
Fig. 9. Transverse transcutaneous image of case 7 with two displaced
fragments on the wing of the ilium (arrows). See Figure 4B for normal
ultrasonographic appearance. Image courtesy of Dr. Myra Barrett.
were only identified on the transcutaneous examination
(Fig. 7B). Fractures of the ischium (Fig. 8), pubis, and ilium
were only diagnosed using transrectal ultrasonography.
Pelvic fractures were highly suspicious using transrectal
ultrasonography in six of eight cases and were confirmed
with other diagnostic aids. Two cases were diagnosed with
transcutaneous ultrasonographic examination and were
negative on transrectal examination. Bony proliferation
and irregularities of the acetabular rim and greater
trochanter were diagnosed only on transcutaneous examination (Fig. 7B). Although case 7 did not receive a transrectal ultrasonographic examination because of his small
size, an ilial wing fracture (Fig. 9) was diagnosed on the
transcutaneous examination. Recumbent ventrodorsal
radiographs indicated that there was no further involvement of the pelvis in this case.
In this series of cases, transrectal ultrasonographic
examination of the pelvis was an effective diagnostic aid in
revealing fractures of the pubis, acetabulum, ischium, and
internal ilium (Table 1). Transcutaneous ultrasonographic
examination of the pelvis effectively identified fractures of
the body of the ilium, femoral neck, and greater trochanter,
as well as bony proliferation on the acetabular rim and
a subluxated femoral head.
4. Discussion
In the present case series, case 5 and 8 had fractures of
ischium, pubis, and ilium that were diagnosed with transrectal ultrasonography and could not be detected with the
transcutaneous approach. Other studies support that
transrectal ultrasonography is diagnostic for ischial and
pubic bone fractures [26,29].
Performing a thorough clinical and lameness examination followed by a transrectal and transcutaneous ultrasonographic examination has been shown to be effective for
the diagnosis of pelvic fractures [26,29]. Our results support
work from two other studies [26,29] that demonstrate the
reliability of transrectal and transcutaneous ultrasonographic examinations in the evaluation of pelvic fractures.
Horse
Age
Sex
Breed
Physical
Ultrasonographic Findings
Transrectal
Transcutaneous
25
MC
QH
4/5 left hind lame, stifle
effusion, quadriceps
atrophy, tuber coxae
pain
Negative
Ill-defined irregularities
of L greater
trochanter and
acetabular rim
2
2
FI
TB
4/5 left hind lame, pain
and swelling over L
coxofemoral joint
Misshapen L
acetabulum with
extensive callus
extending to the
ischium
Bony proliferation of
the L acetabular rim
3
1
FI
QH
1
MI
QH
Proliferative bony
callus on R ischiatic
table
Negative
Bony proliferation of
the R acetabular rim
4
5/5 right hind lame
with gluteal atrophy
and pain
5/5 right hind lame
with stifle swelling
and toed out stance
with elevated R hock
5
17
MC
TB
5/5 left hind lame with
abduction and ataxia
at walk
Multiple step fractures
in L ischium and
pubis with multiple
hematomas,
irregularities in body
of ilium
Negative
R coxofemoral joint and
femoral head
visualized within
acetabulum but not
continuous with
femoral neck and
greater trochanter
6
4 months
MI
QH
5/5 right hind lame
with swelling and
pain on R
coxofemoral joint
with toed out stance
Irregular step in medial
margin of R
acetabulum
Bony proliferation of
the R acetabular rim
7
2 months
MI
QH
FI
QH
5/5 right hind lame
with swelling and
pain ventrolateral to
the tuber coxae
5/5 left hind lame with
a palpable mass
medial to the L
acetabulum
Not performed due to
age and diagnosis
with other
modalities
Fracture of the L pubic
bone and
acetabulum with
displaced iliac
vessels and a large
hematoma
Step fractures on the
lateral aspect of the R
ilium just distal to
the tuber coxae
None
8
17
Additional Diagnostics
Diagnosis
Diagnostic Aid Leading
to Diagnosis
Ventrodorsal: L greater
trochanter avulsion
and L cranial
acetabulum bony
changes
Ventrodorsal: L
acetabular fracture
with osteophytes,
bony callus and
fractured L puboiliac
junction
Findings from R stifle
radiographs were
negative
Findings from R stifle
radiographs were
negative, standing
pelvic radiographs
not diagnostic due to
overexposure,
capital physeal
fracture confirmed at
necropsy
Rectal palpation was
severely painful with
crepitus on the floor
of the pubis;
abdominocentesis
revealed
hemoabdomen; R
stifle radiographs
were negative
Ventrodorsal:
caudolateral
displacement of R
pubis at iliopubic
physis and irregular
R dorsal acetabular
rim
Ventrodorsal: non
displaced fractures of
the caudal R ilial
body
Nuclear scintigraphy:
focal uptake at the L
pubic bone
Fracture of the left
greater trochanter
and osteoarthritis of
the coxofemoral
joint
Fracture of the left
acetabulum and
ischium
Radiographs,
ultrasonography was
only suggestive of
a fracture
Radiographs,
ultrasound was only
suggestive of
fractures
Fracture of the right
ischiatic table
Ultrasound
Fracture of the right
greater trochanter
and capital physis
with a femoral head
subluxation
Ultrasound and
necropsy
Fracture of the left
ischium and pubis
Ultrasound
Fracture of the right
pubis and
acetabulum
Ultrasound and
radiographs
Fracture of the right
ilial body
Ultrasonography and
radiographs
Fracture of the left
pubic bone and
acetabulum
Ultrasonography,
nuclear scintigraphy
was only suggestive
of a fracture
W.T. Walker et al. / Journal of Equine Veterinary Science 32 (2012) 222-230
1
228
Table 1
Signalment, transrectal, and transcutaneous ultrasonographic findings, results of other diagnostic aids, and final diagnosis of eight horses presenting for a suspected pelvic fracture
W.T. Walker et al. / Journal of Equine Veterinary Science 32 (2012) 222-230
In one study [26], initial transrectal ultrasonographic
examinations effectively diagnosed pelvic fractures in
seven of nine cases. The two cases in that study which were
negative revealed pelvic fractures on a follow-up transrectal ultrasonographic examination [26]. Another study
[29] demonstrated that the ultrasonographic yield for the
diagnosis of pelvic fractures was approximately the same as
a radiographic examination (73%). In this study, five fractures were diagnosed by ultrasonography and not by
radiography. All fractures were suspected with ultrasonography but three were confirmed with radiography. This
study reported that radiography better characterized three
fractures that were diagnosed using ultrasonography [29].
In this study, only five of nine acetabular fractures were
definitively diagnosed with ultrasonography, although
fractures were suspected in the other four cases. The
authors could not definitively diagnose acetabular fractures
using transrectal ultrasonography in the four other cases.
However, this modality suggested the presence of an
acetabular fracture in all of the cases with acetabular
pathology [29]. Acetabular rim fractures can be diagnosed
with the probe directed dorsoventrally and oriented
parallel to the longitudinal surface of the ilial body [28,29].
Furthermore, a novel ultrasonographic technique which
images the coxofemoral joint during weight-bearing and
noneweight-bearing stance can be used to diagnose coxofemoral joint subluxation [28]. Transcutaneous ultrasonographic examination of the acetabulum in our case series
effectively revealed bony changes in the acetabular rim in
four cases where pathologic change was present. In case 8,
transcutaneous ultrasonographic examination did not
reveal acetabular rim changes, although an acetabular
fracture was diagnosed transrectally. The acute nature of
this fracture may have resulted in the discrepancy between
transcutaneous and transrectal ultrasonographic findings,
as bony changes on the acetabular rim were not yet
present.
Similar to ultrasonographic studies elsewhere on the
horse, ultrasonography requires familiarity with the
machine, an in-depth understanding of equine pelvic
anatomy, and experience to achieve competency. Having
a dry gross specimen of the equine pelvis available can aid
in the recognition of normal anatomy [6]. It is important to
compare one side of the hemipelvis with its contralateral
counterpart to evaluate bilateral symmetry [6], which can
be of assistance when diagnosing less apparent lesions.
It is imperative that transrectal and transcutaneous
ultrasonographic examinations are performed and include
all bony surfaces of the pelvis when a pelvic fracture is
suspected. One case report discussed a false-negative
transcutaneous ultrasonographic pelvic examination
where the greater trochanter blocked visualization of
a craniolateral ischial fracture. However, transrectal ultrasonography was not performed in this case leading to many
other diagnostic tests at the owners’ expense [30]. In
another study, transrectal ultrasonography was not performed because the horse was negative to rectal palpation.
A pelvic fracture was later diagnosed on a follow-up
transrectal ultrasonographic examination [26]. These
examples highlight the importance of performing a thorough transrectal and transcutaneous ultrasonographic
examination [26].
229
As with any rectal examination, the potential complication of a rectal tear exists. Sedation and a transrectal
infusion of 60-mL 2% lidocaine via an extension set will
enhance the comfort of the patient, limit resistance, and
decrease peristalsis and straining. Although we did not
find it necessary, the administration of an antispasmotic
may be beneficial in horses that are straining against the
examiner. Using these precautions, the authors feel that
transrectal ultrasonography is safer than general anesthesia because it eliminates the risk of fracture displacement to the patient and avoids repeated exposure of the
staff to radiation.
Although the present ultrasonographic technique
successfully diagnosed or confirmed the diagnosis of pelvic
fractures in this case series, several limitations exist. We
describe a specific technique that has been found to be
useful in a limited number of cases. Previous studies have
used ultrasound to effectively diagnose pelvic fractures in
far more cases [26,29]; however, a thorough verbal and
pictoral description of the approach was not included.
Several approaches can be used as long as the entire bony
surface of the pelvis is visualized. Only 25% of horses
included in our case series were <1 year of age; however,
37% [8]-42% [5] of pelvic fractures occur in horses <1 year
of age. Transrectal ultrasonography can be dangerous in
this demographic because of their small size and flighty
nature. Additionally, radiographs and nuclear scintigraphy
can be complicated by the presence of open physes. If
available, computed tomography can be an effective alternative for the diagnosis of pelvic fractures in young horses;
however, this modality requires general anesthesia [22].
Finally, although offered to owners, pelvic radiography
under general anesthesia was only performed in 50% of the
presented cases. Because of the small number of cases and
the lack of consistency in diagnostic approach, direct
comparisons between the efficacy of ultrasonography and
other diagnostic aids could not be made.
5. Conclusion
Transrectal and transcutaneous ultrasonographic
examination of the pelvis can be an effective, sensitive, and
inexpensive modality for the diagnosis of pelvic fractures in
the horse [24-28] and is most useful in concert with other
diagnostic aids. Transrectal and transcutaneous ultrasonographic examination has been deemed an appropriate
initial imaging examination following a clinical and lameness examination when a pelvic fracture is suspected [29].
This study describes a detailed transrectal and transcutaneous ultrasonographic technique for the diagnosis of
pelvic fractures and presents figures of both the normal and
pathologic appearance of the pelvis. In addition to a valuable aid in the diagnosis of pelvic fractures, this modality
provides an effective way to monitor the progression of
pelvic fractures, determine prognosis, and recommend
specific therapeutic modalities [6,26]. Ultrasound is readily
available to equine practitioners and can be a helpful aid for
diagnosing pelvic fractures in the field where high-power
X-ray equipment, computed tomography, or nuclear scintigraphy are not available. When ultrasonographic findings
are unclear or the ultrasonographer is uncomfortable with
230
W.T. Walker et al. / Journal of Equine Veterinary Science 32 (2012) 222-230
the findings, radiography, nuclear scintigraphy, and
computed tomography can be used effectively.
Acknowledgments
The authors thank Dr. Anna D. Fails and Heather Miller
for their artistic contributions.
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performance: 128 cases (1993-2000). J Am Vet Med Assoc
2004;224:88-95.
[20] Geissbühler U, Busato A, Ueltschi G. Abnormal bone scan findings of
the equine ischial tuberosity and third trochanter. Vet Radiol
Ultrasound 1998;39:572-7.
[21] Dewé TCM, Fulton IC, Anderson BH. Scintigraphic diagnosis of
greater trochanter, third trochanter, tuber coxae and tuber ischii
injuries in the racing Thoroughbred: 43 cases (2002-2008). Aust
Equine Vet 2008;27:48.
[22] Trump M, Kircher PR, Fürst A. The use of computed tomography in
the diagnosis of pelvic fractures involving the acetabulum in two
fillies. Vet Comp Orthop Traumatol 2011;24:68-71.
[23] Tomlinson JE, Sage AM, Turner TA, Feeney DA. Detailed ultrasonographic mapping of the pelvis in clinically normal horses and
ponies. Am J Vet Res 2001;62:1768-75.
[24] Goodrich LR, Werpy NM, Armentrout A. How to ultrasound the
normal pelvis for aiding diagnosis of pelvic fractures using rectal
and transcutaneous ultrasound examination. Proc Am Assoc Equine
Pract 2006;52:609-12.
[25] Shepherd MC, Pilsworth RC. The use of ultrasound in the diagnosis
of pelvic fractures. Equine Vet Educ 1994;6:223-7.
[26] Almanza A, Whitcomb MB. Ultrasonographic diagnosis of pelvic
fractures in 28 horses. Proc Am Assoc Equine Pract 2003;49:50-4.
[27] Shepherd ML, Pilsworth RC, Hopes R, Steven WN, Bathe AP. Clinical
signs, diagnosis, management and outcome of complete and
incomplete fracture to the ilium: a review of 20 cases. Proc Am
Assoc Equine Pract 1994;40:177-80.
[28] Brenner S, Whitcomb MB. Ultrasonographic diagnosis of coxofemoral subluxation in horses. Vet Radiol Ultrasound 2009;50:423-8.
[29] Geburek F, Rotting AK, Stadler PM. Comparison of the diagnostic
value of ultrasonography and standing radiography for pelvicfemoral disorders in horses. Vet Surg 2009;38:310-7.
[30] Driver AJ, Nagy A. Fracture of the ischium in an eight-year-old
Arabian gelding: a diagnostic challenge. Equine Vet Educ
2008;20:127-30.
PELVIC AND COXOFEMORAL LAMENESS
Roger Smith MA VetMB, DEO, PhD, DECVS, AssocECVDI
Dept. of Veterinary Clinical Sciences, The Royal Veterinary College, Hawkshead
Lane, North Mymms, Hatfield, Herts. AL9 7TA. U.K.
Michael Schramme DrMedVet, CertEO, PhD, HDR, DECVS, DACVS
Campus Vétérinaire de Lyon, VetAgro Sup
Université de Lyon, France
Introduction
Controversy exists as to the frequency of lameness located in the pelvic and
coxofemoral region which is largely because of the difficulties in identifying and
defining pathology in a region covered by a large muscle mass. This paper will focus
on the clinical approach to the diagnosis of injuries in this region and the
management of typical conditions.
History
Injuries in this region are mostly traumatic, although sacro-iliac disease is
believed to be responsible for lower grade lameness and poor performance in the
absence of overt trauma. For traumatic pelvic injury, there is usually a history of
acute, severe hindlimb lameness preceded by a traumatic event, such as a fall,
rearing and falling over backwards, becoming cast in the stable or sustaining an
injury during transport. When there is no history of trauma, it is generally necessary
to exclude all possible sources of pain in the distal limb before focusing on the pelvic
region.
Clinical signs
The first clue of a pelvic injury is usually gained from a careful clinical
assessment of the pelvic region. The horse should be standing completely squarely
behind, on a firm, level surface for accurate evaluation of symmetry of the
musculature and bony elements of the pelvic region. Detailed visual examination and
palpation should include the bony landmarks of the tubera coxae (TC), tubera sacrale
(TS), and tubera ischii (TI) of the pelvis, and the greater trochanter (GT) and third
trochanter (3T) of the femur, as well the covering musculature (gluteus medius,
gluteus superficialis, semitendinosus, semimembranosus, biceps femoris, the caudal
aspect of the longissimus dorsi and the muscles around the tailhead. Asymmetry of
the height of the TS may be seen in normal horses, horses with poor performance
and horses with hindlimb lameness. Firm pressure should be applied to the bony
prominences to test if an abnormal response or pain can be induced.
Mild to moderate atrophy of the hindquarter musculature is frequently
nonspecific and can reflect disuse due to pain arising anywhere in the limb. More
specific of pelvic injury are more severe hindquarter muscle atrophy, muscle atrophy
around the tailhead and marked muscle atrophy in the caudal lumbar region resulting
in increased prominence of the TS.
Attention should also be paid to the posture of the lame limb. An abnormally
straight limb conformation may be caused by proximal luxation of the coxofemoral
(CF) joint, sometimes accompanied by secondary upward fixation of the patella and
an outwardly rotated limb.
A rectal examination is always indicated if pelvic injury is suspected in order to
assess internal symmetry of the caudal aspect of the ilial shaft, the pubis and
ischium.
Manipulation of the limb is frequently resented if there is pain associated with
the CF joint. Resistence to abduction is rather nonspecific but may be associated
with pain in the contralateral sacroiliac joint. Horses with pain arising from either the
SI or CF joints may be reluctant to stand on one limb, with the other limb raised.
Gait evaluation
The degree and character of lameness associated with the pelvic region
depend on the underlying cause. Fractures or luxation of the CF joint result in acute
onset, severe lameness. All other lesions in the pelvic region more typically result in
mild to moderate lameness with non-specific characteristics. Plaiting behind, i.e. the
horse crossing over each hindlimb at the trot, is often considered characteristic of SI
region pain although neither is it specific. In many horses with SI joint pain this is
accompanied by a bilaterally “shuffling” gait, with a reduced height of foot flight and
reduced stride length. The resulting restriction in gait and loss of hindlimb impulsion
may be much more obvious when the horse is ridden, where occasional kicking out
with one hindlimb has also been reported as a characteristic of SI disease.
The response to flexion tests is nonspecific except for the odd paradoxical
response in horses with SI joint pain, where flexion and abduction of the contralateral
limb results in accentuating lameness in the weight-bearing limb. Although ridden
exercise may accentuate lameness in horses presenting with a history of poor
performance or loss of hindlimb impulsion, observation of lameness under saddle can
be difficult and is highly subjective.
Diagnostic analgesic techniques
In horses with mild to moderate lameness without external clinical signs, it is
critical that pain in all other areas of the limb is eliminated by reliable regional
anesthesia of the tibial and fibular nerves and all 3 compartments of the stifle joint,
before attention is directed toward the pelvic region.
CF joint
The hip joint is difficult to enter, and with improper needle placement, the
sciatic nerve can be damaged. The procedure is performed with the limb bearing
weight and positioned vertically. The site of needle placement is the notch between
the caudal and cranial protuberances of the GT. An 18-gauge, 6-inch spinal needle
is introduced and advanced at an angle of 45° to 60° to the sagittal plane of the
horse, in an attempt to follow the femoral neck towards the joint capsule. This is
usually breached at a depth of approximately 12 cm. In order to avoid advancing the
needle too dorsal to the joint (dorsal to or against the ischiatic spine), a slight
downwards angle of advancement is useful (15° to30°). Twenty to thirty ml of local
anaesthetic solution is adequate for intra-articular analgesia. The only secure test of
successful arthrocentesis is aspiration of joint fluid. Failing this, aspiration of local
anesthetic solution after administration is also likely to indicate proper needle
placement. Remember that extra-articular deposition of local anaesthetic solution
may result in temporary obturator nerve or sciatic nerve paralysis. As the bony
landmarks for injection can be difficult to palpate in well-muscled, mature horses it is
useful to determine their position ultrasonographically. A successful ultrasoundguided technique for arthrocentesis of the CF joint has recently been described1.
Synovial fluid analysis
Synovial fluid aspirated from the CF joint can help establish a more specific
diagnosis. Idiopathic joint sepsis has been described and is characterized by
elevation of neutrophils and total protein in the joint. Tearing of the teres ligament or
intra-articular fractures may result in the presence of erythrocytes,
haemosiderophages or varying degrees of reddish discolouration.
Sacroiliac (SI) joint
SI injection techniques have been reviewed by Engeli and Haussler2 and
Cousty et al.3 The optimal technique involves a needle entry site located 2–3 cm
cranial to the contralateral TS. An 18-15 gauge, 25 cm spinal needle, pre-bent to an
angle of 40°, is inserted towards the targeted SI joint at an angle of 45° relative to the
vertical plane until it firmly engages as far lateral as possible, periarticularly to the SI
joint on the dorsal surface of the sacral wing or abaxial surface of the ilial wing. It is
recommended to use ultrasound to help guide the needle under the iliac wing. 1020ml of local anaesthetic solution is deposited next to the SI joint, to allow for
maximal diffusion into the joint with minimal diffusion across the entire SI region.
Radiographic examination
Because the advent of nuclear scintigraphy and diagnostic ultrasonography,
the indications for radiographic examination of the pelvis have reduced. Radiographic
examination of the pelvic region of a horse can be performed either with the horse
anesthetized and positioned in dorsal recumbency, or in the standing position. The
use of grids can help to reduce scattered radiation. Radiographs are usually obtained
with the patient in the frog-leg position, but fractures of the GT may be missed unless
another ventrodorsal view is obtained with the limbs extended backwards. In addition to
the ventrodorsal view, an oblique view of the CF joint (ventral 45medial- dorsolateral
oblique) will provide additional information on the femoral neck and GT. Standing
ventrodorsal radiography of the pelvis involves positioning the X-ray tube ventral to the
horse's abdomen in front of its hindlegs. The cassette and grid sit on top of the animal's
quarters following the inclination of the pelvis, and are held in place with a long-handled
cassette holder or a fixed rotatable bucky. Exposures are similar to those used for the
recumbent technique and range from 70 - 100 kVp and 300 - 600 mAs. The central
beam is variably angled depending on the area of interest. An angle of 20 to 25 to the
vertical produces a good view of the ilial shaft. A 30-35 angled beam produces good
images of the acetabulum and caudal pelvis.
If lameness has been localized to the CF joint, radiographic examination is
indicated to determine the nature of the pathology and, hence, prognosis. Even
though the best quality radiographs are obtained with the horse positioned in dorsal
recumbency under general anesthesia, radiographs obtained in the standing position
may be satisfactory for confirmation of suspected luxation or subluxation of the CF
joint, or determining if a pelvic fracture has an acetabular component, especially in
smaller equids. Dorsolateral-ventrolateral obliques can also be used in small equids.
If standing radiographs and scintigraphy remain inconclusive with regard to the
fracture configuration, recumbent radiography of a suspected pelvic fracture is best
delayed for 8 weeks after the onset of lameness to determine whether or not a
suspected fracture involves the CF joint.
Radiographic evaluation of the SI joints is difficult because the joint slopes at
approximately 30 to the horizontal and abdominal viscera are superimposed on the
area of interest. The radiographic characteristics of SI joint disease are minimal.
Identification of new bone formation on the caudal aspect of the joint, or irregular
joint-space width are poor prognostic indicators.
Ultrasonographic examination
Diagnostic ultrasonography of the pelvic region can be performed either
transcutaneously, or per rectum. Tomlinson4 mapped the normal anatomy of the
equine pelvis in longitudinal and cross-sectional planes using a 7.5 MHz linear array
transducer for the SI area, TC and TI, and rectal examination; the ilial wing, ilial body,
and CF joints were imaged with a 3.5 MHz sector transducer. Bone surfaces produce
smooth echoes with the exception of the TC and the GT. The caudal aspect of the TS
may appear roughened or even produce acoustic shadowing due to the presence of
secondary ossification.5 Diagnostic ultrasonography is useful in the evaluation of
fractures, including fractures of the third trochanter, assessment of the SI ligaments
and determination of aortic and craniomesenteric blood-vessel patency. Fractures of
the ilial wing can be recognized readily with ultrasonography and appear as a
discontinuity of the contour of the ilial wing, with changes ranging from a clear
fracture gap to small irregular echogenic areas on the dorsal surface, representing
periosteal new bone formation. The most common ultrasonographic diagnosis in a
series of 20 horses with upper hindlimb pain was dorsal sacroiliac ligament desmitis,
often characterized by a change in size of the affected ligament6. However, Engeli5
has attributed incongruency in size and shape between both dorsal SI ligaments to
differences in height of the TS and does not necessarily consider this finding
indicative of desmitis. In addition he found that these ligaments have a variable
echogenicity and size. Only the ventral aspect of the SI joint can be evaluated for
periarticular remodeling, but even the ultrasonographic recognition of new bone
formation at the joint margins is considered of questionable clinical significance5.
Scintigraphic examination
Due to the limited ability of other imaging modalities to provide ready access to
all structures of the pelvic region, the scintigraphic appearance of the pelvis
frequently forms the cornerstone for diagnosis of injury of this region. Scintigraphy is
the most sensitive indicator of pelvic pathology available. Complete evaluation of the
pelvic region requires dorsal views of the SI joints, oblique views of the ilial wings,
caudodorsal and caudal views of the TI, and lateral views of the CF joints. Many
technical factors need to be considered during pelvic scintigraphy, that may improve
the diagnostic yield of pelvic scans (effective motion correction, empyting of the
bladder and/or post acquisition masking out of the bladder region, rotating the image
and accounting for degree of overlying muscle mass). The thickness of muscle
resulting in 50% attenuation of gamma radiation from Technetium99m is reportedly 4
cm. It will therefore be clear that asymmetric gluteal muscle mass will result in
apparently asymmetric radionuclide uptake between both halves of the pelvis.
Nuclear scintigraphic evaluation of the pelvic region is useful for the identification of
fractures, stress reactions in bone, increased bone modeling associated with OA and
other bony lesions, evidence of recurrent exertional rhabdomyolysis (RER),
evaluation of blood flow in the aorta, iliac and femoral arteries, and assessment of the
SI joints. Initial scintigraphic examination of a suspected pelvic fracture may yield
negative results, even in if the fracture is complete and displaced. In these patients
scintigraphy should be repeated at least 10 days from the time of injury. Care must
also be taken in interpretation of the appearance of the SI joints because there are
age-related changes that occur in normal horses.
Conditions
Luxation
Luxation of the hip is rare in the horse. It usually occurs as a result of trauma. The
femoral head is usually displaced craniodorsally. The limb may be rotated outwards
and appears shortened. The greater trochanter may appear particularly prominent
and crepitus may be palpable externally or per rectum on manipulation. The
diagnosis may be confirmed radiographically or ultrasonographically. The
radiographs should be carefully scrutinised for accompanying fractures of the dorsal
rim of the acetabulum although high detail images are often difficult to obtain.
Closed reduction under general anaesthesia may be possible in recent injury,
though recurrence is common. Both open reduction and salvage by femoral head
excision have also been reported and are recommended for luxations that have been
present for more than a few days.
Pelvic and proximal femoral fractures
Fractures involving the hip region are usually the result of trauma from falls or
collisions but may occur as a result of stress fractures in racehorses. Theoretically
any configuration is possible. If articular, the prognosis for future soundness is very
poor, but rare cases return to training. Diagnosis can be frustratingly difficult but
scintigraphy is usually helpful (although transport to a suitable centre may not be
viable). Ultrasound examination, transcutaneous and per rectum, can be a very
useful technique as the dorsomedial aspect of the acetabulum, the ischium and part
of the ilial shaft can all be assessed; however, false negatives are possible.
Displaced ilial shaft fractures can sever the iliac or gluteal arteries and result in fatal
haemorrhage. Femoral head fractures can resemble luxations and can be repaired
using lag screws or removed in small equids.
Third trochanter fractures are most easily identified uswing gamma scintigraphy
and confirmed using ultrasonography although the fracture plane is usually
perpendicular to the ultrasound beam and there can be difficult to identify. Evidence
of bony fragmentation, callus in more chronic cases, and surrounding haemorrhage
are indicative of the presence of a fracture. A standing craniolateral-caudomedial 25°
oblique radiographic view has been reported to demonstrate the fracture in some
horses6. Treatment is by rest and can be successful although numbers of cases
reported are small.
Osteoarthritis
Osteoarthritis of the hip and adjacent sacral joints in the horse is rare, but also
difficult to diagnose so its prevalence may be underestimated. It may occur
secondary to trauma which may cause rupture of the round ligament and consequent
instability (subluxation). Clinically, the horse may show outward rotation of the
affected limb at rest. Crepitus may be palpable externally or on rectal examination.
Scintigraphy and/or radiography may help confirm the diagnosis and ultrasonography
can also be useful either percutaneously or per rectum. Localisation can be aided
with intra-articular anaesthesia. The prognosis is usually poor.
Intermittent claudication/thrombosis of the aortoiliac vessels
This condition usually presents as an intermittent lameness brought on my
exercise. A absence of a distal limb pulse can be suggestive but confirmation of the
diagnosis can be achieved by ultrasonographic examination per rectum. Treatment
is often conservative but medical treatment is usually unsuccessful. Surgical
thrombectomy has been suggested as an alternative approach7.
Sepsis
Infection of the hip joint is rare in foals (usually haematogenous) and almost
unheard of in mature horses unless associated with significant trauma or rare
haematogenous spread/local invasion from abscesses8. It can be difficult to diagnose
as, although synoviocentesis should be clear-cut evidence, the hip is not a joint many
clinicians routinely enter. Waiting for radiographs (again sometimes difficult to obtain)
to show changes and confirm the diagnosis means missing the treatment opportunity.
If suspected, for example in a foal with lameness and other signs of sepsis with no
obvious cause, consider prompt referral. Synoviocentesis of the hip joint can be
aided by ultrasound guidance.
References
1. David F, Rougier M, Alexander K et al. : Ultrasound-guided coxofemoral
arthrocentesis in horses. Proc 15th Ann Scientific Meeting ECVS 15, 2006. In
press.
2. Engeli E, Haussler KK : Review of sacroiliac injection techniques. Proc Am Ass
Eq Pract 50:372-378, 2004.
3. Cousty M, Rossier Y, David F. Ultrasound-guided periarticular injections of the
sacroiliac region in horses: a cadaveric study. Equine Vet J. 2008 Mar;40(2):1606.
4. Tomlinson JE, Sage AM, Turner TA: Ultrasonographic examination of the normal
and diseased equine pelvis. Proc Am Ass Eq Pract 46: 375-377, 2000.
5. Engeli E, Yaeger A, Haussler KK : Use and limitations of ultrasonography in
sacroiliac disease. Proc Am Ass Eq Pract 50:385-391, 2004.
6. Bertoni L, Seignour M, de Mira MC, Coudry V, Audigie F, Denoix JM. Fractures of
the third trochanter in horses: 8 cases (2000-2012). J Am Vet Med Assoc. 2013
Jul 15;243(2):261-6.
7. Rijkenhuizen AB, Sinclair D, Jahn W. Surgical thrombectomy in horses with
aortoiliac thrombosis: 17 cases. Equine Vet J. 2009 Nov;41(8):754-8.
8. Clegg PD. Idiopathic infective arthritis of the coxofemoral joint in a mature horse.
Vet Rec. 1995 Oct 28;137(18):460-4.
MANAGEMENT OF PELVIC FRACTURES:
BAD NEWS?
Bruce Bladon BVM&S, Cert EP, DESTS, Dipl ECVS, MRCVS
Donnington Grove Veterinary Surgery
Newbury, Berkshire, United Kingdom
It is still reported in the veterinary literature that pelvic fractures in horses are
rare and are the result of severe trauma such as accidents while jumping at high
speed. This is simply incorrect. Pilsworth first began to report the frequency of this
injury at BEVA in 1993. Since then it has become recognised that pelvic fractures
are one of the commonest “stress” fractures of the athletic horse1. Fractures of the
ilium represent 15% of all fractures in a survey of Thoroughbreds in race training in
Britain2. Traumatic fractures undoubtedly exist, such as can be seen in ponies
following trailer accidents. However many “traumatic” pelvic fractures, such as
horses becoming cast in a stable, are almost certainly pre-existing stress fractures,
which have become complete fractures following a minor trauma.
The anatomy of the pelvis is relatively straightforward. As with all anatomy the
terminology is adapted rather slavishly from human anatomy. Thus the key point is
the level of the pelvic brim, the cranial edge of the ventral portion of the pelvis.
Cranial to this is the greater pelvis and the bone is known as the ilium. In the horse
the ilium is divided into the shaft, going cranially and the wing heading mediolaterally. The lesser pelvis, caudal to the pelvic brim, is a complete cavity. The bone
is termed the ischium dorsally and the pubis ventrally, and it passes caudally to the
tuber ischii. The wing of the ilium is the origin of gluteal musculature.
Pelvic fractures appear to be commonest in the Thoroughbred, but do occur in
all athletic horses. Therefore the pathogenesis may involve galloping, however little
detail is known of the pathogenesis of these fractures relative to condylar fractures of
the fetlock. The fractures are not the preserve of two year-old horses and occur in
many ages. Fractures are frequently seen in National Hunt horses (usually 4 years
of age or older, which race over jumps). They are also seen in point-to-point horses
as well (a form of less regulated racing over jumps for hunt horses, not necessarily
Thoroughbred) but are unusual in eventers and other slower horses.
The clinical signs of pelvic fractures are variable depending on the fracture site.
Incomplete stress fractures of the ilial wing generally present as a low-grade non
specific hind limb lameness. There are frequently no localising clinical signs and
there is no pain on palpation of the area. Pelvic asymmetry may be present, however
this can be present in normal horses as well. Pain on direct downward pressure on
the tuber sacrale is noticed in some horses. Rest for a limited period – (one to two
weeks) usually resolves the signs of lameness and the horse can be put back into
exercise. However lameness will usually recur. This is the clinical challenge of
pelvic fractures, identifying them at this stage. If the horse is repeatedly exercised
and rested the fracture will progress and will become complete. By then it is less of a
diagnostic and more of a therapeutic challenge.
Complete displaced pelvic fractures are a life threatening condition depending
on the location of the fracture. There is usually severe pain, presenting as severe
lameness or even signs of colic. Horses can be difficult to control and to keep
standing. There is frequently severe swelling of the pelvic region, or frequently of the
thigh, as the haemorrhage “runs downwards”. There may be obvious pelvic
asymmetry, though this may be more subtle.
The progression of the condition depends on the location of the fracture. Some
of the most dramatic signs can be associated with fractures of the tuber coxa, abaxial
to the ilial shaft. In this situation the “box” of the pelvis is not disrupted and the signs
of lameness will subside over a few days. Horses with these fractures are left with
obvious asymmetry but have a reasonable prognosis for athletic activity. A horse
with such a fracture was the subject of a well publicised legal claim in the UK. The
horse was “passed” at a pre-purchase examination, and went on to race 17 times,
winning twice, being placed five times and winning £23,137. Despite this the owners
managed to supplement their income by successfully suing the vet, mostly due to
poor certification.
Complete displaced fractures axial to this, particularly if they involve the ilial
shaft have a grave prognosis. Fatal haemorrhage from the obturator or external iliac
artery is a frequent complication if the vessel is lacerated by the sharp edges of the
fractured bone. Many horses even without fatal haemorrhage will be euthanased
due to the severe signs of pain. A crucial part of management of these fractures is
preventing the horse from becoming recumbent. Normal recumbency in the box may
result in the sharp edges of bone lacerating the blood vessels and subsequent fatal
haemorrhage. Therefore horses with severe pelvic fractures should be tied up to
prevent them lying down. Obviously a break string is used, so some horses will still
become recumbent. We keep severe pelvic fractures tied up for six weeks. We offer
hay and water from head height. However, twice daily we feed the horse from the
floor, while an attendant holds the horse. This is to allow the horse to get its head
down and drain the airway secretions. One of the most important complications of
“cross tying” a horse is pleuropneumonia, particularly (for us) at the hotter times of
year.
In severe cases as much analgesia as possible is necessary. Non-steroidal
anti-inflammatory drugs are indicated and are usually supplemented with anti-ulcer
drugs – a bout of colic once the acute crisis has been averted is not helpful. We use
epidural analgesia, with detomidine, morphine and mepivicaine, if indicated. In
dwelling epidural catheters can be used to provide more prolonged analgesia.
If there is displacement of the fracture then changes may be demonstrated on
ultrasonography of the ilial wing. New bone is also easily visualised but recent
irregular new bone can be difficult to interpret, as it disrupts the echo from the bone
surface. Using a low frequency, curvilinear probe, a good image of the smoothly
curved ilial wing can be achieved. Clipping of the coat is seldom necessary if the hair
is soaked with iso-propyl alcohol. Surgical spirit can be used, but this has some
castor oil in it, which causes delamination of ultrasound probes, so the probe must be
shielded. Great care must be taken with pelvic ultrasonography, as artifacts are
easily created. There is a consistent blood vessel in the musculature above the mid
ilial wing, which creates a “lens” effect and produces an apparent step in the bone
surface, particularly at the caudal edge.
Scintigraphy is the diagnostic technique of choice for pelvic fractures. Using a
gamma camera a simple 2D image of the pelvis is acquired, though motion correction
software is helpful as sedated horses do sway. The only artefact issue is the
bladder, which generally shows as a very bright area due to the urinary excretion of
the diphosphonate. It is our policy to scan around the bladder, ensuring that is does
not obscure the relevant region, and to mask it with software after acquisition. We do
not scan if the bladder is particularly full (usually the case on first scanning the horse)
and return the horse to the stable until urination. With the use of alpha 2 agonist
agents for sedation urination is usually rapid. We only occasionally use furosemide,
on horses that appear reluctant to urinate. It is remarkably ineffective. Horses
appear able to urinate by emptying the top half of the bladder only, keeping
radioactive material behind, and it greatly increases the chance of the horse
producing radioactive urine in the bone scan room. Both dorsal views (cranial and
caudal) and oblique views of each ilial wing should be acquired.
Much as described with hindlimb lameness in the racehorse in general,
diagnosis is an economic rather than clinical challenge. A case can be made for
doing a “bone scan” on all non specific hindlimb lameness cases in racehorses, but
this is frequently not financially possible. Equally, the situation has to be avoided
where an “X-Ray safari” is followed by a few desultory and inconclusive nerve blocks,
generating a significant bill before undertaking scintigraphy.
The issue of
destabilisation of a hindlimb fracture during examination should also not be
dismissed. The author has observed fatal destabilisation of a pelvic fracture and
destabilization of a split pastern during lameness examination.
The results of pelvic fractures have not been widely analysed. We conducted a
retrospective study of all Thorougbred racehorses diagnosed with a pelvic stress
fracture by scintigraphy at Donnington Grove Veterinary Surgery. It is widely stated
that the prognosis for non or minimally displaced fractures of the ilium is good,
comparable to other stress fractures of the limb. We analysed the results of 95
horses with pelvic fractures of which only 58 (61%) raced again, less than
anticipated. The median duration of return to racing was 288 days, (79 – 739), with
53% of horses returning to racing between 250 and 350 days.
The age range was from 2 – 11. Two year old horses were the most frequently
affected (25%) but the median age was 4 and 32% of horses were aged 6 or more.
Pelvic fractures were commonest in flat racehorses (55% in our series) but occurred
in National Hunt horses (24%) as well as dual purpose animals. Fractures were left
sided in 45% of horses, right sided in 31% and bilateral in 24%. In five horses the
lameness was noted to be in the contra-lateral limb to a unilateral fracture, and in a
further two horses the lameness was noted to be in the less severely afflicted limb
with bilateral fractures.
Loss of speed did not appear to be a serious issue for horses which returned to
racing. Of 39 horses which raced before and after bone scan, 17 (44%) of horses
achieved a rating higher than before fracture diagnosis, with 6 gaining a rating 25lb
or more higher. These results are similar to control studies we have conducted for
other conditions. Only 5 horses were rated 25lb or more worse than before fracture
diagnosis.
Ultrasonographic abnormalities were identified subsequent to bone scan
diagnosis in 35 horses (though only 51 – 60% underwent post scintigraphy
ultrasound) 69%. It should be noted that a large number of horses had pelvic
fractures diagnosed by ultrasonography and thus did not undergo scintigraphy and
were excluded from the study.
We classified the fractures into five separate types:
1) from the ilial shaft along the caudal edge of the ilium towards the tuber sacrale
21, of which 13 (62%) raced again
2) transverse across the ilium axial to the ilial shaft
30, of which 20 (67%) raced again
3) from the ilial shaft along the caudal edge of the ilium towards the tuber coxa
25 of which 13 (52%) raced again
4) fractures of the ilial shaft
2 of which 0 raced again
5) fractures of the ilial wing right across from tuber sacrale to tuber coxa
12, of which 8 (67%) raced again
6) fractures of the tuber ischii
6, of which 4 (80%) raced again.
We hypothesised that the fractures abaxial to the ilial shaft (type 3) would have
a better prognosis than fractures axial to the ilial shaft (type 1, 2 and 5) as they would
not destabilise the “box” of the pelvis, or that fractures which involved the ilial shaft
(type 1, 3 and 4) would have a worse outlook than fractures which only involve the
rest of the pelvis, (type 2, 5 and 6). While there were some differences on univariate
analysis, these results did not stand up to multivariate analysis, suggesting there was
unlikely to be a marked difference in prognosis between fracture types.
These results are difficult to interpret due to the case selection - by scintigraphy.
Many cases of pelvic fractures will not have warranted the expense of a bone scan,
will not have been diagnosed, but will have been rested and resolved. Other more
serious cases will have been diagnosed on clinical grounds and will not have
undergone scintigraphy, and another group will have been diagnosed by
ultrasonography alone. However we concluded that pelvic fractures have a worse
outlook than previously suggested. For instance Verheyen (2004) showed that 75%
of British Thoroughbred horses managed non surgically for stress fractures returned
to racing2. We did compare the success rate for racing again (61%) with that of tibial
stress fractures (68%) but again were not able to show a difference on multivariate
analysis.
Acknowledgement. This project was commenced by Lilly Beever while she was
an intern at Donnington Grove Veterinary Surgery. She was tragically killed in a train
crash in Sardinia in 2007.
References
1.
Pilsworth RC, Shepherd MC, Herinckx BM, Holmes MA. Fracture of the wing of
the ilium, adjacent to the sacroiliac joint, in thoroughbred racehorses. Equine
Vet J 1994;26:94–9.
2.
Verheyen K, Wood J. Descriptive epidemiology of fractures occurring in British
Thoroughbred racehorses in training 2004;36:167–73.
CLINICAL AND IMAGING EVALUATION OF THE VERTEBRAL COLUMN:
HOW TO RECOGNIZE THE PRESENCE OF PAIN
Filip Vandenberghe DrMedVet, Associate (LA) ECVDI
Equine Hospital De Bosdreef, Moerbeke Waas, Belgium
Introduction
The last decade the vertebral column is more frequently recognized as a source
of primary pain and potentially cause lameness or poor performance in the more
subtle case. Previously the equine back was only briefly examined and back
problems were often waived as only secondary to underlying primary lameness. The
latter is still existing, but primary lesions are nicely documented and there influence
on equine locomotion and biomechanics are more and more described. Making the
correlation between the complaint, the clinical examination not only of the back, but
the whole horse and diagnostic imaging still remains a challenge though. Often
vertebral column disorders are the acute clinical presentation of more chronic
underlying pathology, visualized on diagnostic imaging. Understanding of the
anatomy and biomechanics are detrimental in the evaluation and examination of ‚the
painful back’.
Clinical examination
As in any other examination the clinical examination of a vertebral column
related problem starts with a good anamnesis. Especially with these kind of
pathologies the complaints are often vague and well directed questions are
necessary to obtain valuable information. Commonly heard complaints are: difficulties
bending, refusal or gait abnormalities at side work, being hard on the bridle or refusal
to accept the bridle, kicking, bucking, violent behavior, lack of propulsion, bunny
hopping, cross canter, generalized stiffness, … Discipline specific problems are often
encountered. Dressage horses have difficulties with the high collected work such as
piaffe and passage or show irregular side work. Jumping horses lack power at the
jumps, are ‚afraid’ of landing, or don’t get to the last pole in combination jumps.
Specific problems in reining horses are beyond the expertise of the author.
The clinical exam consist of a visual inspection, looking for asymmetries,
muscle atrophy or swellings and take the conformation of the back in the individual
into account. Nevertheless a sometimes poorer conformation some horses might
manage it very well in sports and not necessarily develop pathology. The whole
vertebral column is palpated first superficially and, after going the horse some time to
adapt, more firmly. Interpretation of a painful response always remains a bit
subjective and reproducibility of the painful response is valuable. Dorsal, ventral and
lateroflexion is elicited. Symmetrical movements left and right are important. In subtle
cases abnormalities at visual inspection and palpation are frequently very little or
absent.
The dynamic horse is invaluable in the evaluation of back movement. The horse
is seen like in a classic orthopedic examination, but seeing the horse in their actual
tack and ridden is important. A good saddle and bridle fit are often overseen. Just as
obvious dental disease. Potential lameness is evaluated as well and might be related
or not to the vertebral column pathology. The appreciation of a back problem still can
be secondary to an underlying lameness problem. The main example is the bilateral
navicular disease horse moving with a stiff back. Nevertheless those horses don’t
necessarily develop true back problems, but only show signs of back pain. Once the
primary problem is properly treated, the back problem fades. Developing true
vertebral column lesions as a secondary effect is unlikely. Horses have a relative
short athletic career and might not get old enough to develop the pathology. On the
other end vertebral column lesions are often identified in young horses as well and
are thus more and more considered as primary. They even might be responsible in
provoking (secondary) limb lameness. The trigger point why clinically silent vertebral
column disorders, such as kissing spines, facet osteoarthritis, overriding transverse
processes or sacroiliac disease, all of a sudden become clinically ‚active’ and
provoke performance issues still remains often unknown. The value of proper training
management and riding skills is probably higher as previously expected.
Diagnostic anesthesia in vertebral column pathology is only rarely performed,
because of the lack of specificity and even sometimes dangerous side effects (e.g.
coincidental ischiadic nerve anesthesia in an attempt to desensitize (parts) of the
sacroiliac joint.
Diagnostic imaging
The recent powerful generators (100kW) are capable in producing radiographs
of diagnostic value of the whole vertebral column, including thoracic and lumbar
region. Nevertheless are subtle changes difficult to identify. Superposition is as well
blurring the correct interpretation. The correlation between radiography and the
clinical complaint is as well relatively low. (Transrectal) Ultrasonography is a valuable
tool in the detection of facetosteoarthritis, overriding transverse processes, lumbar
disc degeneration, sacroiliac abnormalities and more. But just as radiography it’s
visualizing structural abnormalities being an anatomical diagnostic modality. The
author prefers the addition of bone scintigraphy to be routinely included in a case of
potential vertebral column pathology of poor performance, in an attempt to evaluate
potential lesions a bit in closer correlation to the clinical complaint and ‚activity’ of the
structural lesion. Having said this, increased radiopharmaceutical uptake doesn’t
mean blindly that the highlighted site is a source of pain.
Conclusion
The detection of true vertebral pathology being the source of pain and thus the
cause of the poorly performing horse, remains up-to-date a diagnostic challenge.
Critical evaluation of multiple modalities in relation to the clinical exam is mandatory.
The result of installed specific treatments might help retrospectively to confirm or
deny the diagnosis. Especially in the management of vertebral column disease the
value of good common sense physiotherapy can’t be over emphasized.
References
1. Cauvin E. Assessment of back pain in horses. Equine Practice 1997;19:522-533.
2. Denoix JM, Audigié F. The neck and back. In Equine Locomotion. Back W,
Clayton HM, eds. WB Saunders, London, 2001;167-191.
3. Jeffcott LB. Historical perspective and clinical indications. Vet Clinics North
America Equine Pract. 1999;15:1-12.
4. van Wessum R. Evaulation of back pain by clinical examination. In Current
Therapy in Equine Medicine, 6th Ed. Robinson NE, Sprayberry KA, eds.
Saunders, St. Louis, 2009;469-473.
IMAGING FEATURES OF SACROILIAC JOINT PAIN
Natasha Werpy, DVM, DACVR
Radiology Department, University of Florida
Introduction
Back problems can be a cause of poor performance and lameness in horses.
Diagnosis of back pain is a challenge and requires a thorough clinical examination
combined with imaging techniques. Imaging allows localization of lesions, which is
one of the difficulties in diagnosis of back pain. Palpation can be yield valuable
information. However, certain areas are not accessible with palpation. Radiographs
can identify osseous lesions. General anesthesia is required for radiography of the
sacroiliac joint in an adult horse, making this technique undesirable in many cases.
Nuclear scintigraphy provides useful information on the location and physiology of
lesions. Nuclear scintigraphy is often used to localize lameness to the sacroiliac
region. However, it is important to recognize the limitations of nuclear scintigraphy
examination, as patient motion, positioning and muscle asymmetry can cause errors
in interpretation. Ultrasound can be used to document osseous and soft tissue
lesions and is easily used in the field. Therefore it is most frequently used to
investigate the sacroiliac region.
Ultrasound Technique for Imaging of the Sacroiliac Region
Complete ultrasound examination of the pelvis requires transrectal and
transcutaneous examination. Transrectal examination allows visualization of the
ventral spine margin, the intervertebral discs (L4-S1), the intertransverse lumbars
joints, the sacral foramina and associated nerve roots, and the sacroiliac joints. In
addition, the ilial wing and body, medial acetabular margin, pubis, and ischium can
also be evaluated. Transrectal examination should be performed with a high
frequency linear probe, such as a 7.5 MHz probe. Small rectal ultrasound probes
can be used to image certain structures in both longitudinal and transverse planes,
this is especially helpful when evaluating the intervertebral discs. Transcutaneous
examination allows visualization of the dorsal sacroiliac ligaments and the ilium.
Transcutaneous examination of dorsal sacroiliac ligaments and tuber sacrale can be
performed by a high frequency probe, while examination of the ilial wing and body
requires a lower frequency probe (2-5 MHZ) probe for depth penetration.
Ultrasound examination should be performed percutaneously and transrectally
to evaluate the sacroiliac joint margins and associated structures. Whenever
possible, transrectal ultrasound examination should be performed in all cases with
suspected sacroiliac region pain. Osseous and soft tissue abnormalities can be
identified with ultrasound examination can be identified in the sacroiliac joint region.
The transrectal ultrasound technique for sacroiliac joint evaluation is performed by
placing the ultrasound probe on the ventral margin of the spine on midline, directing
the ultrasound beam directly dorsally and locating the lumbosacral disc space and
identifying the sacrum. The sacroiliac joints are then identified by sliding the probe
slightly caudally from the lumbosacral junction onto the cranial aspect of the sacrum
to identify the first and second sacral foramina. The probe is directed abaxially until
the joint is identified. The intervertebral discs, sacral foramina and associated nerve
roots and intertransverse lumbar joins in this region should also be evaluated.
The L6-S1 intervertebral disc is normally the most caudally visible intervertebral
disc after imaging in cranial direction along the ventral midline margin of the sacrum.
Ankylosis or sacralization of the L6 can obscure visualization of the lumbosacral
junction. Continuing cranially from the lumbosacral junction along the ventral margin
of the vertebral bodies will allow visualization of the intervertebral discs of L5-L6 and
L4-L5, depending on horse size as well as the arm length and size. It is important to
note that the fibers within the intervertebral disc are curved. Therefore, the disc will
not be uniformly echogenic with the probe angled parallel to the ventral spine margin.
The ultrasound probe must be tipped at multiple angles from cranial to caudal to
create echogenicity in all aspects of the intervertebral disc. Moving the probe in an
abaxial or lateral direction from midline will allow visualization of the sacral nerve
roots and foramina. Continuing cranially will allow visualization of the intertransverse
lumbar joint. The lumbosacral intertransverse joints are imaged laterally to the L6
ventral intervertebral foramen. Only the medial aspect of this joint can be examined.
The lateral part is obscured by the iliopsoas muscles.
Dynamic examination of the lumbosacral joint can be used to assess the
intervertebral disc during flexion and extension. During flexion the intervertebral disc
bulges ventrally and the ventral intervertebral disc space narrows as the lumbosacral
joint angulation decreases.1 During extension, the ventral aspect of the intervertebral
disc straightens due to increased tension and the intervertebral disc space thickness
widens as the lumbosacral joint angulation increases.1
In normal horses, the L4-L5 and L5-L6 intervertebral disc spaces are thinner
than the lumbosacral disc space, and only the ventral aspect of these intervertebral
discs is consistently imaged. The curvature of the vertebral body endplates partially
obscures the joint space. The ultrasound beam angle can be directed from maximum
visualization of the joint space. The normal intertransverse lumbar joint is imaged as
a small anechoic line created by the hyperechoic ventral bone surfaces of the
transverse processes of the L6 and S1 vertebrae.
Directing the probe caudally to the intertransverse lumbar joint and abaxially to
the first and second sacral foramina allows identification of the sacroiliac joint region.
The sacrum will be cranial to the ilium when imaged using this technique. The normal
sacroiliac joint has smooth curved to flat margins depending on where along the joint
margins the ultrasound probe is placed, and the ventral sacroiliac ligament can be
identified ventral to the joint margins. The ventral sacroiliac ligament is triangular in
shape and uniformly echogenic. Transcutaneous examination can be used to
evaluate the dorsal sacroiliac ligaments, the margins of the tuber sacrale and the
caudal extent of the sacroiliac joint. Due its position in the pelvis the interosseous
ligament of the sacroiliac joint can’t be imaged with ultrasound.
Abnormalities Identified with Ultrasound
Narrowing of part or the entire intervertebral disc is indicative of intervertebral
disc disease. Ankylosis of the joint space or sacralization of L6 will prevent
identification of the lumbosacral joint space. Anklyosis of the lumbosacral joint can
put additional stress on the L5-L6 joint space and intervertebral disc predisposing it
to injury. Widening of this joint space has been detected in horses with lumbosacral
ankylosis.1 Abnormalities in echogenecity of the intervertbral disc can provide
additional evidence of disc disease. Decreased echogenecity in the disc can indicate
disc degeneration, fiber rupture or focal cavitation. Focal hyperechoic regions with
and without shadowing can represent mineralization or fibrosis in the disc. Ventral
spondylosis of the spine can also be detected.
Abnormalities identified in an
intervertebral disc space require careful examination of surrounding intervertebral
discs and joint for associated abnormalities. Peri-articular proliferation, ankylosis,
and focal bone resorption and/or osteolysis can be identified in the intertransverse
lumbar joint. Peri-articular proliferation on the joint margins and abnormalities
(thickening, scarring, fiber disruption, enlargement) of ventral sacroiliac ligament can
be identified with transrectal examination of the sacroiliac joint. Injury to the dorsal
sacroiliac ligaments characterized by abnormalities in echogenecity and fiber can be
identified with transcutanous examination. Enthesopathy at the attachment of the
dorsal sacroiliac ligaments on the tuber sacrale can also be identified.
Multiple abnormalities can be identified with ultrasound in the sacroiliac joint region.
However, it is important to have clinical correlation with the ultrasound findings to
better determine their relevance. Moderate or greater osteophytosis and/or ventral
sacroiliac ligament injury is typically a clinically significant finding. However, mild
injury can be more difficult to interpret, especially in horses that present for poor
performance. In these cases, the significance of the finding is determined in light of
the horse’s complete clinical examination and any other areas of concern identified
during a complete lameness assessment. In certain cases when subtle clinical and/or
imaging findings are present, response to treatment can provide valuable information.
References
1. Denoix JM. Ultrasonographic evaluation of back lesions. Vet Clin North Am
Equine Pract 1999;15:1;131-159.
2. May SA, Patterson LJ, Peacock, PJ et al. Radiographic Technique for the pelvis
in the standing horse. Equine Vet J 1991;23:312.
ULTRASOUND-GUIDED INJECTION OF THE CERVICAL INTERVERTEBRAL
FACET JOINTS: TECHNIQUE AND OUTCOME
Filip Vandenberghe DrMedVet, Associate (LA) ECVDI
Equine Hospital De Bosdreef, Moerbeke Waas, Belgium
Introduction
Arthropathy of the cervical articular process joints is more and more frequently
considered as a potential cause of a range of orthopedic and neurologic disorders,
including front- and hindlimb lameness, neck pain, poor performance and ataxia.
Diagnosis is commonly based on radiographic appearance, eventually supplemented
by scintigraphy, ultrasonography or TMS (transcranial magnetic stimulation).
Temporary relief of symptoms can be achieved by local injection of steroids.
Ultrasonography is indispensable to achieve correct intra-articular injection.
Anatomy
Vertebrae are articulating via 2 articular process joints dorsally and one large
intervertebral joint containing a disc. The articular process joints (= facet joints) are
synovial joints consisting of hyaline cartilage, a synovial membrane and synovial
fluid. The bony parts are the caudal process of the more rostral vertebra and the
cranial process of the more caudal vertebra. Both of the facetjoints are in close
relation to the vertebral canal.
Osteoarthritis is seen in many synovial joints, just as the facet joints. Process
fractures, malformations, instability or more general degenerative disease can all
result in arthropathy with new bone formation, subchondral bone lysis and sclerosis,
capsule thickening and joint distension. As in other joints, joint inflammation can
cause clinical symptoms of neck pain, and reduced mobility. Because of the close
relationship of the facet joints to the vertebral canal and spinal cord, excessive joint
distension, capsule thickening and new bone formation can cause spinal cord
compression and thus neurological symptoms of ataxia. Symptoms of paresis (lower
motor neuron) are assumed as well.
Diagnosis
Careful interpretation of the radiographs in close relation to the clinical exam is
important as radiography of the especially caudal facets is often showing minor to
moderate changes, not necessarily causing clinical symptoms. True confirmation of
facet arthropathy as the cause of the clinical symptoms still remains a diagnostic
challenge. Additional diagnostic modalities such as scintigraphy and transcranial
stimulation may help to document and objectify the diagnosis.
Treatment
The neck is properly prepared for intra-articular injection. The probe of the
ultrasound is covered in a sterile glove. The author doesn’t use sterile gel, but liberal
amounts of alcohol, to obtain nice ultrasonographic guiding images. A spinal
20Gauche needle is driven in the beam of the ultrasound probe until the tip of the
needle touches the cervical processes nearby the articular line. Mostly a low dose
and small volume of triamcinolone is injected. Complementary treatment may be a
mesotherapy of the neck and Tildren perfusion. Aftercare of the horses consists of 2
weeks of free movement and lunging with a free head and neck position. After 2
weeks work can be progressively resumed.
The preliminary data of an ongoing study will be presented.
Reasons for performing the study
Local treatment of the cervical facets is performed more frequently. Data on
indications and outcome are only poorly described.
Objective
An attempt to gain some more objective information on the outcome of local
caudal neck facet injection.
Methods
Horses being diagnosed with caudal neck facet osteoarthritis, based on the
clinical presentation, radiography, ultrasonography or scintigraphy were included in
the study. Horses presented with the complaint or suspicion of a caudal neck
problem were not necessarily included. A large number of the horses were presented
with a general complaint of ‚poor performance’. All horses had a thorough clinical
examination and radiography. Scintigraphy was performed in the majority of cases
and TMS (transcranial magnet stimulation) in a selected group. Clinical symptoms
varied from an acutely ‚blocked’ neck to reduced flexion to one or both sides or even
fore limb or hind limb lameness. The affected facet joints were treated intra-articularly
under ultrasonographic guidance with triamcinolone. Some horses received a
supplementary tiludronate perfusion, based on scintigraphic findings, or additional
mesotherapy of the neck. Follow up information was obtained via telephone or
personal contact. Horses being back in full work or competing better at the same or
at a higher level were considered successfully treated.
Results
At the time of writing the questionnaire is still ongoing. Numbers will be
presented at the presentation.
Conclusions and potential relevance
Preliminary results indicate that a combination of diagnostic modalities, gamma
scintigraphy specifically, narrows down the true diagnosis of clinically relevant facet
osteoarthritis of the cervical vertebrae. The vast majority of those horses were treated
with a positive response for over 6 months.
MANAGEMENT OF THORACOLUMBAR AND SACROILIAC PAIN:
KISSING SPINES, SACROILIAC DISEASE AND OTHER MADE UP STUFF…
Bruce Bladon BVM&S, Cert EP, DESTS, Dipl ECVS, MRCVS
Donnington Grove Veterinary Surgery
Newbury, Berkshire, United Kingdom
There are few more controversial conditions in the horse than thoracolumbar or
sacroiliac pain. Back pain in the horse is notoriously difficult to objectively assess.
The clinical signs are nebulous and are best assessed by a rider, who may be a
skilled and reliable judge of the horse’s condition, or may be slightly lacking in talent
and seeking an excuse for their own poor performance. CEVA data shows that back
pain and/or kissing spines is the commonest “off label” indication in France for
tiludronate treatment with a high instance of veterinarian satisfaction. Clinical signs
vary from bucking under rider or even during tacking up, through to “limited
impulsion” or “jumping flat”.
Diagnosis
At Donnington Grove Veterinary Surgery we rely heavily on scintigraphy in the
investigation of cases presented with this type of history. We try not to neglect
clinical examination, but do find the signs very variable. The scintigraphic findings
can also require careful interpretation. In a series we showed that in two-year old
horses the uptake in the dorsal spinous processes was considerably more (when
compared to the uptake of a rib, usually T14), than it was for older horses. Whether
this reflects more disease in younger horses, or that increased uptake is a “normal
abnormality” in younger horses is unclear. However we interpret increased uptake of
radioisotope in the dorsal spinous processes of younger horses with caution. It has
been suggested that the increased uptake can occur in normal horses, questioning
the validity of any scintigraphic diagnosis [1].
Scintigraphy can also be useful in the investigation of sacroiliac disease.
Generally, the intense uptake in the tuber coxa and tuber sacrale becomes less
marked with age. Thus, the image will be “flatter” in older horses. The sacroiliac joint
is quite markedly abaxial to the tuber sacrale and can be observed. Sometimes an
increase in uptake can be quite apparent. It has been suggested that asymmetry of
uptake is the most important diagnostic criteria, and that “profiling” or even comparing
regions of interest is the most reliable criteria [2]. However, sacroiliac disease is
often a bilateral condition and we will rely on a visual impression of increased uptake,
rather than requiring asymmetric uptake.
Radiography correlates better with scintigraphy for kissing spines than widely
believed [3]. Early in 2002 46 two year old horses had their knees and fetlocks
radiographed at the request of a trainer – all these horses had a single radiograph of
the dorsal spinous processes as well. Only six horses had any abnormality and no
horse had severe abnormalities. It is very rare that scintigraphic increased uptake is
not associated with quite obvious and often severe radiographic changes [1]. Finally
radiographic findings which are scintigraphically “cold” are unusual – in our
experience more so than published [1]. However we do not have objective data on
this and most horses undergoing back investigations at Donnington Grove Veterinary
Surgery are bone scanned first.
Treatment
Kissing spines
The principle therapy for “kissing spines” at Donnington Grove Veterinary
Surgery is intra-lesional medication with methyl prednisolone acetate, usually
combined with local anaesthetic. Radiographic screening is preferred and is usually
used. Occasional cases are combined with shockwave therapy and tiludronate
treatment. Response to treatment can be used as part of the diagnostic process.
We have observed two cases of infection following injection, which have both
responded to a combination of topical and systemic antibiotics.
The use of methyl prednisolone acetate, particularly in a fibrous area does give
concern for drug withdrawal times but horses are seldom fit enough to compete. The
prognosis with back injection is fair. Many horses respond very favourably. Whether
this is because of the treatment, despite it, or due to the intra-muscular injection of
cortico-steroid is unclear. A proportion of horses return at the start of each season
for follow up treatment. Many other horses appear to “grow out” of the condition and
further injection is not necessary.
It is considered a good prognostic indicator if the injection can be made.
Frequently the area is too fibrous and the spinous processes are too close to permit
medication. In this situation a peri-lesional intra-muscular injection is made, by
directing the needle off the midline. For us radiographically and scintigraphically
marked “kissing spines” remains a surgical disease
“Blocking” the back – assessing ridden exercise before and after intra-lesional
medication is widely recommended and is simply performed. It is quite common to
add corticosteroids into the protocol, though this can require some explaining if the
investigation turns out to be negative. However, in our experience it is very rare to
block a back and have a rider pronounce no change. Generally if this does happen it
is a highly competent individual. The majority of riders who compete at a low level
will perceive an improvement following blocking the back. It is unclear if they are
subject to a “placebo” effect, if there is a genuine improvement, or if the horse is
moving better because the “unbalancing” effect of a poor rider is somewhat
anaesthetised. Hence the logic of using corticosteroids at the same time, to allow a
few weeks for the placebo effect to wear off, for both horse and rider.
Sacroiliac pain
“Blocking” the sacroiliac joint is also commonly performed. Multiple injection
techniques have been described [4]. Generally, we use an 8” needle, which is
slightly curved. A site cranial to the two tuber sacrale is prepared for aseptic
injection, but is not necessarily clipped. The skin is anaesthetised with a bleb of local
anaesthetic. Ultrasound can be used but the benefits of ultrasonographic monitoring
are quite limited. An injection is made immediately cranial to one tuber sacrale with
the needle directed to the contralateral side, underneath the contralateral wing of the
ilium, and aiming for a point half way between the tuber coxa and the greater
trochanter of the femur. The needle is advanced until it hits bone, when an injection
totalling 8ml is made.
Sacroiliac injection is not without risk. We have caused temporary but complete
paralysis in one horse, and ataxia in many others. There are reported cases of
permanent paralysis of the bladder, and of permanent focal loss of pelvic
musculature. A few general points can be made. Complications are more likely if the
injection is made further caudally. Thus the target point should be midway caudo-
cranial under the wing of the ilium. Complications are also more likely with deeper
injections. Some people use a 3.5” spinal needle, and claim good response to nerve
blocks, suggesting that local diffusion is adequate to anaesthetise the affected
structures. We have remained with the long needle technique. Complications are
not necessarily more frequent, but they are more likely to be permanent with
sclerosing agents. It was considered that instability of the sacroiliac joint was the
underlying problem, and thus attempts to build up scar tissue in the area might
increase stability. The favoured sclerosing agent was P2G, a mixture of phenol and
glycerol. We have discarded this agent in favour of corticosteroids.
Surgical treatment
Surgical resection of the summits of the dorsal spinous processes has been
described for many years. Perhaps like superior check ligament desmotomy it is a
surgery which waxes and wanes in popularity. Extensive reviews of cases have
been published [5] and the surgery has recently been described in the standing
sedated horse [6] as well as an endoscopic technique [7], a wedge resection
technique [8], and a minimally invasive technique. At Donnington Grove Veterinary
Surgery we do not have experience of the endoscopic technique.
The technique of standing kissing spine resection is relatively straightforward,
certainly easier than under general anaesthesia. We have not performed any
procedures under general anaesthesia since 2008. Pre-operative radiography is
used to identify the processes scheduled for removal – these are then marked using
a skin staple placed just off the midline. The horse is sedated and positioned in
stocks. We use detomidine with an opiate usually butorphanol or morphine.
Sedation can be continued with a drip but topping up with further injection appears to
work satisfactorily and does work out substantially cheaper. The surgical field is
anaesthetised with injection of copious amounts of local anaesthetic. We use
subcutaneous injection along the incision line, followed by deeper injection in the
region of the spines to be resected. Significant volumes of local anaesthetic are
used, usually ~ 150ml of lidocaine with adrenaline for typical resection of three
spinous processes. The secret to standing surgery is achieving adequate analgesia,
and we have not observed wound healing problems secondary to this volume of local
anaesthetic.
For conventional surgery an incision is made over the selected spinous process,
approximately double the length of the spinous process. Sharp dissection is
continued through the supraspinous ligament down to the surface of the bone. Using
a #11 scalpel blade the soft tissue attachements of the ligament to the spinous
process are sharply transected. Once the supraspinous ligament is separated from
the process rib spreaders are introduced into the incision and are opened to retract
the surgical site. Muscular attachments to the lateral borders of the supraspinous
ligament are minimal and are easily separated by further sharp dissection. The
dorsal spinous process is then resected using an oscillating saw, or osteotome and
mallet. An oscillating saw is preferred and we have not observed complications with
conscious horses objecting to the noise or vibration. A cut is made obliquely across
the spinous process, from caudo dorsal to cranio ventral. The cut is then repeated in
the opposite diagonal, to remove a wedge shape from the centre of the process.
Further cuts are made to remove as much spinous process as possible, but complete
resection cannot be achieved with the saw. Large duck billed rongeurs are then
used to remove the remainder of the dorsal aspect of the dorsal spinous process, to
a depth of 3 - 4 cm.
The incision is then repaired using simple continuous sutures of thick material in
the supraspinous ligament, we use 5 metric Vicryl®. Following this subcutaneous
sutures and skin staples are used, the skin staples are reinforced with simple
interrupted skin sutures every 2cm. The procedure is then repeated over the next
spinous process. It is quite possible to remove alternate spinous processes from
individual skin incisions, particularly caudally where the processes are wider. It may
be convenient to remove two processes together (to ensure all the “kissing spines”
are removed. The two adjacent processes are removed from the cranial edge of the
incision where the processes are narrower. Thus a typical case might involve
resection of T13 and 14, T16 and T18, through three separate incisions.
The intra-operative pathology is frequently very impressive. There is flaring of
the spinous processes, wrapping around the opposing vertebra, and the spinous
process has to be ripped off its neighbour, separating tight fibrous tissue. It is very
difficult to believe that the condition is an insignificant finding when performing
surgery.
Post operative management is box rest for three weeks, followed by paddock
rest for a further nine weeks. Lunging exercise is introduced at this stage with a view
to ridden exercise being underway by six months.
The results of kissing spine surgery are consistently quite encouraging.
Walmsley et al (2002, EqVetJ) reported 72% of horses returned to full athletic
activity. Perkins et al (2005, Vet Surg) reported 100% of horses returned to previous
activity, of which 80% where athletic animals (two broodmares were treated for
osteomyelitis of the spinous processes). Of horses we have performed the surgery
standing, in one horse sedation was excessive and marked swaying interfered with
surgery. This horse developed a wound infection which required further surgery to
resect another spinous process and necrotic tissue. Of 19 operated under general
anaesthesia, two have developed post-operative infection. One horse resolved over
a prolonged time – six months, and the other underwent a second standing
procedure to resect another spinous process and necrotic tissue. Obviously the
infection rate is the same for standing and general anaesthesia surgery.
A retrospective study of our cases several years ago revealed of 29 procedures
on 27 horses at Donnington Grove Veterinary Surgery. Three were considered
complete failures – either the same or worse after surgery and were ultimately
euthanased. One is lost to follow up, of the remainder 6 were a qualified success.
Two horses were reported as being functionally cured but “mentally” never the same,
returning to a lower level of competition, one became a broodmare as it was
purchased (rather than failing to train) and one was involved in a significant debt
between trainer and owner, so was not trained. One raced in Ireland at lower level
than hoped for by connections, one raced and was retired with carpal osteo-arthritis.
The remaining 17 (63%) were considered a complete success by connections.
These were athletic horses returning to the same level of competition. The case
series includes 7 racehorses, of which one (flat) horse raced at a lower level, one
(National Hunt) horse developed carpal osteo-arthritis and one (National Hunt) was
not re-trained (qualified successes).
Four (57%) are considered unqualified
successes, have returned to racing, and include a flat horse rated 109 and three
National Hunt horses.
The minimally invasive surgery, the “Coomer” technique has been the key
innovation in kissing spines surgery in recent years [9]. This surgical procedure was
described and compared with medication of the inter spinous processes. The
conclusion of the paper was that surgery was more effective than medication and the
rest period was minimally longer.
The surgical technique is relatively straightforward. The horse is radiographed
and the interspinous spaces for surgery are selected. These are marked using a skin
staple. The area is anaesthetised by subcutaneous injection of local anaesthetic, we
use lidocaine with adrenaline, followed by deeper intramuscular injection on either
side of the spinous processes. Copious volumes of local anaesthetic are used, we
consider it quite normal to use 100 ml of anaesthetic for typical surgery on five or six
interspinous spaces. A 1 cm in incision is made immediately parasagittal, in a lateral
medial plane. A dissection plane is then established by blunt dissection underneath
the supraspinous ligament, until the instrument can be palpated subcutaneously on
the contralateral side. A blunt dissection plane is then established between the dorsal
spinous processes, to a depth of 5cm or so. This can require considerable force. I
use a combination of an osteotome, a solid scalpel, large stout blunt ended Mayo
scissors, and some intervertebral disc rongeurs. Over time we have become more
aggressive at this stage, not hesitating to use some rongeurs to try and establish a
significant dissection plane between the spinous processes. Frequently the key to
this step is identifying which plane the spinous processes are overlapping in, and
directing the instruments appropriately. The spinous processes are often obliquely
arranged, cranial left to caudal right or cranial right to caudal left. The bone of the
dorsal spinous processes is remarkably soft and it is quite possible to split the
spinous processes with stout scissors. We have done this, and treated it by removal
of the affected bone using rongeurs. Again, this is quite possible to do through a
relatively small incision. Intraoperative radiography is recommended and is used far
more frequently than when doing the traditional more open procedure. Skin closure
alone is sufficient and we usually use two or three simple interrupted sutures of
monofilament nylon.
Post operatively, horses have made very good progress. It is normal for horses
to show significant post operative pain following conventional open surgery of the
dorsal spinous process. Following the minimally invasive procedure post-operative
pain is unusual. Horses generally are discharged the following day with oral
antibiotics and analgesics. We usually recommend three weeks of box rest, followed
by three weeks of light lunging exercise, prior to reassessment and reintroduction of
ridden exercise. We have observed one case of sub optimal wound healing. Onehorse developed swelling and focal pain possibly associated with infection of
adjacent bone. This resolved satisfactorily with antibiotic treatment and rest but did
take some time. Despite resolution, the client was very unhappy and started legal
action as they had anticipated a very limited convalescence. Managing client
expectation can be difficult.
We conducted a retrospective study of this procedure at Donnington Grove
Veterinary Surgery a year ago. At that stage we had performed this procedure on 18
horses. The results are comparable to conventional open surgery. One horse has
been put down as the clinical signs of bucking severely were not altered by surgery.
Two horses have been put down after developing other lameness. One horse
represented for conventional open surgery, which was performed, despite
radiographically much improved appearance. Of 11 horses with appropriate follow
up, 6 have excellent results, based on telephone follow up.
Exactly as with conventional “open” surgery, conducting follow up on Kissing
Spines cases is enormously satisfying, due to the enthusiasm of owners for the
procedure. It is quite frequent to be told how the horse’s personality has been
transformed, and a miserable horse has now become a delight to own. My personal
favourite was a client who described the surgery as “the most successful operation
they had ever had done”, which considering they had also had a horse with a colon
torsion which was still alive three years later seemed a little surprising.
References
1. Erichsen, C., Eksell, P., Holm, K., Lord, P. and Johnston, C. (2004) Relationship
between scintigraphic and radiographic evaluations of spinous processes in the
thoracolumbar spine in riding horses without clinical signs of back problems. 36,
458–465.
2. Dyson, S., Murray, R., Branch, M. and Harding, E. (2006) The sacroiliac joints:
evaluation using nuclear scintigraphy. Part 2: Lame horses. 1–7.
3. Zimmerman, M., Dyson, S. and Murray, R. (2011) Close, impinging and
overriding spinous processes in the thoracolumbar spine: The relationship
between radiological and scintigraphic findings and clinical signs. Equine Vet J
44, 178–184.
4. Engeli, E., Haussler, K. and Erb, H. (2004) Development and validation of a
periarticular injection technique of the sacroiliac joint in horses. 36, 324–330.
5. Walmsley, J., Pettersson, H., Winberg, F. and McEvoy, F. (2002) Impingement
of the dorsal spinous processes in two hundred and fifteen horses: case
selection, surgical technique and results. 34, 23–28.
6. Perkins, J.D., Schumacher, J., Kelly, G., Pollock, P. and Harty, M. (2005)
Subtotal ostectomy of dorsal spinous processes performed in nine standing
horses. Vet Surg 34, 625–629.
7. Desbrosse, F.G., Perrin, R., Launois, T., Vandeweerd, J.-M.E. and CLEGG, P.D.
(2007) Endoscopic resection of dorsal spinous processes and interspinous
ligament in ten horses. Vet Surg 36, 149–155.
8. Jacklin, B.D., Minshall, G.J. and Wright, I. (2014) A new technique for subtotal
(cranial wedge) ostectomy in the treatment of impinging/overriding spinous
processes: Description of technique and outcome of 25 cases. n/a–n/a.
9. Coomer, R.P.C., McKane, S.A., Smith, N. and Vandeweerd, J.-M.E. (2012) A
controlled study evaluating a novel surgical treatment for kissing spines in
standing sedated horses. Vet Surg 41, 890–897.
SHOEING SOLUTIONS FOR HINDLIMB LAMENESS PART 2
LAMENESS
Hans Castelijns
D.V.M. – Certified Farrier
Equine Podiatry Consults and Referrals
Loc. Valecchie n° 11/A, Cortona 52040 (AR) Italia
Mob:+39.333 7716663 -Tel & Fax +39.0575.614335
E.mail : [email protected]
Web site : farriery.eu
Lameness
Lameness of the hind limb is clinically evaluated in movement by observing foot
placement, hip hike, the stride’s length, its cranial and caudal phases and fetlock
descent.
Subtle differences in movement between hind limbs are often on the border of being
a conformation/performance issue versus a true lameness one (especially in the
dressage world!).
Hind limbs are different from front limbs , both anatomically and functionally, even in
the pes, below the hock.
The hoof and distal phalanx shape are less rounded with a more pointed toe. The
extendibility of its MIO III or suspensory ligament (SL) is probably larger, with a
narrower channel between the accessory metatarsal bones in which its proximal part
runs. Innervation is different. The superficial digital flexor tendon (SDFT) does not
originate from contractible muscle bellies.
Causes of hind limb lameness in the lower limb are also quite differently distributed.
Hoof diseases - canker, cheratomas, quarter and toe cracks, onicomycosis,
abscesses, penetrating wounds- are however fairly similar in frequency and
treatment.
Navicular disease is rare. The hind limb seems to suffer less from distal
interphalangeal joint (DIP) disease, including collateral ligament desmitis. Arthrosis of
the proximal interphalangeal (PIP) joint has a better prognosis.
Distal phalanx (DP) fractures are perhaps as, or more frequent than in front limbs,
due to kicking against solid objects.
Plantar hoof pain and plantar process osteitis and sole bruising at the seat of corn is
encountered in horses with negative plantar angles of the DP. This condition is fairly
frequent, probably due to under treatment of flexor flaccidity of the hinds in new born
foals.
Tendonitis of the DDFT and the SDFT are often the consequence of external trauma,
like wire or sheet metal cuts, as is the case for the digital extensor tendon, which may
also suffer from blunt trauma in certain sports.
Suspensory Ligament Desmitis (SLD)
The incidence of SLD , especially of the origin but also of the branches, seems to
become higher in sport horses , due to the stiffer modern riding arenas. It is
something of a professional disease in dressage, Icelandic and standard bred
horses.Prognosis for hind limb SLD is poorer than for front limb SLD.
Shoeing for hind limb SLD is controversial.
The underlying biomechanics are as follows, according to Jean Marie Denoix: DP
orientation in the sagittal plane influences DDFT tension, which in turn influences
SDFT and SL loading- the tighter the deep, the less load on the superficial and the
suspensory in their role to hold the fetlock up. Thus, by prescribing a wide web toenarrow heeled shoe during rehab on penetrable ground, the increased ground
reaction force in the toe area prevents the toe from digging in to the ground , with the
extended Dip joint maintaining a tighter DDFT, limiting hyper-extension of the
fetlock.(fig.7, courtesy L. Entwistle)
Other practitioners swear by egg-bar shoes for Hind limb SLD. On biomechanical
grounds this would seem to be counterproductive, as the bar behind the heels
increases ground reaction force in the caudal area , promoting toe penetration on
penetrable ground and therefore increased fetlock extension in the mid stance
phase.
A theoretical explanation of the benefit of the rounded bar at the heels could be a
more harmonious, latero-medial landing phase. This could benefit even high SL
lesions, as the medial fibers of the SL at its proximal origin cross over distally to form
the lateral branch and vice-versa.
Denis Leveillard has developed the “ diplomatic” SLD shoe for hind limbs, which
features a wide web at the toe and a short- rounded-bar, which protrudes less
caudally than a regular egg-bar.(fig.8, courtesy D. Leveillard)
Francis Desbrosse advises a slight bending upwards of the heels of the shoe, so
called heel rockering, in horses with strong heeled feet. The benefits are not only less
ground reaction force at the heels, but also a lessening of angular velocity of the
heel-toe slap on landing at speed.
Suspensory ligament branch desmitis can be treated with wide toe-single wide
branch shoes, the wider branch corresponding to the side of the injured branch
(Denoix). Alternatively, especially on harness racing horses, going on relatively un
penetrable ground surfaces, Desbrosse proposes the shock absorbing PG shoe with
its short latero-medial leaver arms.(fig.9)
Light weight alloy shoes are certainly use full in the treatment of SLD and SDFT
tendonitis, as they reduce the whip lash like effect of the tendons and ligaments on
protraction in the flight phase of the lower limb. This can be even more important with
shoes which become heavier by supplying them with wider webs .
Many horses however wear aluminum shoes on their hind feet strongly at the toes,
therefore increasing toe penetration and consequently fetlock extension at the end of
their shoeing period.
Shock absorbing shoes tend to diminish both fetlock joint and digital synovial sheath
ectasia (wind galls).
Suspensory breakdown
A high degree of hyper extension of the fetlock together with a straightening of the
hock is often, but not exclusively, observed in older brood mares. This condition
usually goes together with a lateral slipping- and distension- of the SDFT of the point
of the hock.(fig.10) The hyper extended fetlock is held up by the two remaining
structures, the DDFT and the overstretched and often extremely painful SL. The
lateral and medial flexor muscles of the phalanxes contract to increase the tension on
the DDFT, causing the toe to dig in to the ground and to wear excessively. These
horses undoubtedly benefit from a wider surface of the shoe at the toe, placed in line
with the original toe wall if this one has been worn back. It is also important to trim the
heels of these feet well down to the natural sole depth.
In extreme cases or in cases with traumatic rupture of one or more of the two flexor
tendons and or of the SL, it may be necessary to apply a fetlock support shoe with a
padded rigid spoon upholding the fetlock and the pastern. These orthosomas on the
hind limbs should always be made adjustable and in at least 2 pieces with the
supporting spoon to be applied to the base shoe after this one has been nailed on to
the hoof, as the fetlock is in a flexed position when nailing on the shoe. If the DDFT is
ruptured ,a plantar extension (fish bar shoe) is necessary as otherwise the toe of the
foot will lift of the ground.
Bone spavin
Osteoarthritis of the medio-dorsal aspect of the distal inter tarsal and tarso-metatarsal
joints is probably the most common form of hock disease in hard working horses,
especially if they have a bow legged (varus hock) conformation. The author uses a
wide lateral web shoe with a marked medial toe rocker. On penetrable ground the
wider lateral branch will take up more of the ground reaction force, diminishing
compression on the medial aspect of the hock on weight bearing. On break-over the
rocker at the medial toe will diminish pressure on the dorso-medial aspect of the
affected joints.
Stifle
The outward twist of the hock, together with an inward rotation of the foot on weight
bearing which can be observed on some horses, especially at a walk is due to
incongruity of the femoral condyles and or trochlear ridges of the talus. Many horses
are able to perform quite well with this defect and trying to eliminate this stubbing
movement, by increasing the grip of the shoe is counter indicated as it will increase
torsion on the digital joints. Excessive wear on the outside toe and quarter of the
shoe can become a problem and should be addressed by the use of a wider web
and/or a slight rocker at this part of the shoe which will actually facilitate this
movement and prolong the shoe’s durability.
For arthrosis of the stifle some practitioners recommend a full rolling motion type of
shoe, well set back at the toe.(fig.11)
Upward fixation of the patella and in broader terms laxity of the medial patellar
ligament, has been addressed in contradictory ways in different shoeing traditions. All
agree on keeping short the toe, but while the Dutch will raise the outer branch with a
wedge, the Germans would traditionally raise the inner branch. Rob Renieri explains
the partial success of both methods with the fact that both change the tension on the
medial patellar ligament through asymmetrical weight bearing at the hoof. The author
favors a short, set back, rockered toe shoe with a widened lateral branch, as wedging
has been shown to distort the hoof capsule.
As is to be expected, the further away (proximal to) the source of lameness is from
the hoof, the less demonstrable effect is obtained with shoeing modifications. A
notable exception is muscle pain in the croup, which Richard Mansmann found to be
directly related to toe length ( the longer the toes, the more pain).
It can perhaps be stated that proximal causes of pain on weight bearing in the midstance phase, like for example sacro-iliac pain, have less of a shoeing solution than
sources of pain during propulsion, where facilitating break-over may be helpful. In this
context it should be noted that no matter how well executed a therapeutic or
performance shoeing job is, it will grow forward and downward, increasing dorsal and
latero-medial leaver arms, if left on for too long. Short shoeing intervals are a must in
performance and therapy.
A final word of caution on the prevention of weight bearing laminitis. It is the authors
conviction that horses can cope even less with a single hind leg bearing weight for an
extended period of time, than with a single front limb. This may be due to the horse’s
natural attitude at rest, of periodic weight shifting between hind limbs. The severity
and speed of onset of hind limb weight bearing founder, can quite literally send a
horse to its end. This is especially sad in those cases where the original, contralateral
limb’s lesion, might have had a decent prognosis. Getting the originally injured limb to
bear weight as soon as possible and protective measures for the weight bearing foot,
like caudal support or roller motion type shoes, are of paramount importance.
Selected bibliography
11. Hoefverzorging en hoefbeslag, W.A. Hermans, Uitgeverij Terra Zutphen, 1984.
12. Tratado de las Enfermedades del Pie del Caballo, A. Pires, C.H. Lightowler,
Editorial Hemisferio Sur, 1991.
13. Notes de Marechalerie, J.M. Denoix, J.L. Brochet, D. Houliez, Unité Clinique
Equine-CIRALE, Ecole Nationale
14. Vétérinaire d’Alfort.
15. Farriery- Foal to Race Horse, S. Curtis, Newmarket Farriery Consultancy, 1999.
16. Equine Locomotion, W. Back, H. Clayton, WB Saunders, 2001.
17. Shoeing and balancing the Trotter, C.A. McLellan, Lessiter Publications, Inc.
2001.
18. Hoof Problems, R. van Nassau, Kenilworth Press, 2007.
19. The Mirage of the Natural Foot, M.E.Miller, 2010.
20. Therapeutic Farriery, Veterinary clinics of North America, Volume 28, number 2,
August 2012.
Figure 7:
Figure 8:
Figure 9:
Figure 10:
Figure 11:
LOW GRADE ATAXIA AS A CAUSE OF OCCULT LAMENESS AND POOR
PERFORMANCE
Filip Vandenberghe DrMedVet, Associate (LA) ECVDI
Katleen Vanschandevijl, DVM, Dipl. ECEIM
Dierenkliniek De Bosdreef, Moerbeke Waas, Belgium
Poor performance is a common reason nowadays to present a horse for a
veterinary examination. Owners, trainers and riders are more professionally
involved in the management and training of their horses and because of that,
subtle dysfunctions or low-grade locomotive abnormalities are detected
sooner. Poor performance poses a diagnostic challenge to the veterinarian as
there’s a very wide variety of possible underlying causes and the examination
requires expertise, time and variable diagnostic modalities.
Anamnesis
A good and detailed anamnesis is invaluable and the first step in
detecting ‘true’ from ‘false’ veterinary pathology. Rider induced resistance to
work, bad riding or training or behaviour problems are not uncommon. Good
communication is important and it’s not always easy to convince the rider as
being a potential cause of the problem. Often preliminary to further diagnostic
procedures, the horses are trained under non-steroidal anti-inflammatories. In
case of significant improvement the focus of the examination is the search for
musculoskeletal inflammation or pain. A strictly behavioural malfunction will
not improve after administration of pain-killers. Often is an abrupt change in
behaviour triggered by a period of pain and can even persist when the pain
has already disappeared.
Clinical examination
The focus of the examination is on the locomotor apparatus. Cardiorespiratory causes of poor performance are not included in this talk. Routinely
a standard orthopaedic work up is performed. Close attention is paid to subtle
swellings or localised muscle atrophy, pain responses to pressure, extension
or flexion, lack of mobility or low grade lameness. Often horses are sound
while being lunged on hard and soft surfaces and an evaluation while being
ridden is necessary. Subtle soft tissue injuries, e.g. proximal suspensory
desmitis, often give more pronounced lameness when the horses are ridden.
Diagnostic anesthesia can be evaluated under the saddle as well. The first
intention of any poor performance examination is to rule out any obvious
lameness or orthopaedic condition. Examination of the axial skeleton (neck
and back) requires specific knowledge and expertise. Back mobility is
evaluated at stance, while being lunged and while being ridden.
Diagnostic imaging
Gamma scintigraphy is a valuable tool in detecting potentially underlying
causes of poor performance. Especially for proximally located and back
related problems bone scintigraphy is of major interest in giving objective
information. Together with its high sensibility, the low specificity of the modality
should be assessed and a good correlation with the clinical examination and
the anamnesis is crucial. Often in the examination of those cases we have no
starting point and so gamma scintigraphy is an excellent first screening tool.
Once scintigraphy has highlighted a region of increased uptake, radiography
and ultrasonography are the invaluable tools to visualise and diagnose the
lesions. In cases of (low grade) lameness, MRI might contribute as well to
deliver the diagnosis. Thermography is a nice tool to document a case, but will
rarely deliver crucial information.
Transcranial magnetic stimulation (= mmep test)
Low grade ataxia is a common cause of lack of performance and is until
today often not diagnosed because the clinical assessment can be very
difficult, especially in subtle cases. Transcranial magnetic stimulation (TMS) is
invaluable in the objective determination of the presence of ataxia and will be
discussed in detail later.
Treatment
A successful treatment is of course dependant on the exact diagnosis. In
some cases the correlation between diagnostic imaging findings and the
anamnesis is only made by installing a diagnostic treatment. Good follow-up
and reliable feedback from the rider are helping to solve future cases.
Neurology
Introduction
Horses presented with abnormal, poor or decreased performance are a
diagnostic challenge for every veterinarian, especially in those cases where any
obvious pathology is absent and signs are subtle. Normal performance and normal
locomotion is dependent of normal function of the neurological system as well as the
musculoskeletal system. When the horse is not performing as he used to or when he
does not meet the expectations, a diagnostic process is indispensable. The
orthopedic examination in this process is discussed above. The neurological
examination includes the clinical neurological examination, the transcranial magnetic
stimulation (TMS of MMEP test), radiography of the cervical vertebrae and
myelography.
Clinical neurological examination
This presentation is limited to the pathology of spinal ataxia. Other neurological
disorders are not discussed. The basic tests that can be included in a physical
examination to assist in the detection of a spinal cord disorder are: flexion of head
and neck, evaluation of symmetry of neck, trunk and pelvis, the postures adopted at
rest, evaluation of the gait at walk, trot and canter, evaluation of transitions walk-trotcanter-trot-walk, evaluating the horse whilst turning at stance and when the horse is
maneuvered rapidly and stopped abruptly. In the horses that are examined for poor
performance, signs will be subtle. With mild cervical spinal cord lesions, signs of
ataxia and weakness may be evident in the pelvic limbs only. We will look for
degrees of weakness and ataxia: easily stumbling, horses will show buckling on a
limb when turning, they will circumduct a limb when turning, horses will be more
easily pulled to the side by the tail while standing still and whilst moving, dragging of
a toe and a low foot flight and awkward placement of a limb when the horse is
stopped abruptly. Still, in subtle cases, it remains difficult to make an accurate
diagnosis and other diagnostic tests are necessary. Next cervical vertebral
radiography and transcranial magnetic stimulation are indicated. First TMS is
performed to identify the presence of a functional spinal cord lesion and make a
localization of the lesions, i.e. cervical spinal cord of after the 2nd thoracic vertebra,
allowing the use of more specific test (cervical radiography, myelography).
TMS
TMT is a non-invasive, objective, painless and sensitive neurological test that is
performed on the standing, sedated horse. TMS in the horse is used for objective
assessment of motor function, i.e. assessment of the motor tracts in the spinal cord.
Both in human and animals with spinal cord lesions, magnetic stimulation of the brain
is proven to be a valuable diagnostic tool for detection of lesions along the spinal
cord. A magnetic stimulus (painless!!) is given, through the skull, to the cerebral
motor cortex and subsequently electrical activity will pass through the motor tracts in
the spinal cord and elicit a response in the musculature of the horse. This response is
measured in the forelimbs in the extensor carpi radials muscle and in the hind limbs
in the extensor carpi radialis muscle with electromyography. These
electromyographic responses (MMEP’s, magnetic motor evoked potentials) are
measured: the onset latency and the amplitude are determined. In horses suffering
from spinal cord lesions the MMEP’s will demonstrate several typical abnormal
features (even in mild spinal cord lesions): prolonged and variable latency, low
amplitude and frequently polyphasic waveforms (Nollet, 2002). MMEP’s are always
recorded in all 4 limbs. Recordings of the forelimbs and hind limbs are compared and
the recordings of the left and right are compared to respectively distinct cervical
spinal cord lesions from lesions located ofter the 2nd thoracic vertebra and to detect
asymmetrical lesions. In Europe spinal ataxia is mostly caused by lesions in the
cervical part of the spinal cord and most cases these lesions are the result of cervical
vertebral malformation (CVM) or the so called ‚Wobbler’ syndrome. Other possibilities
are infectious disease (EHV), trauma, fractures, tumors. When the lesion is located in
the cervical spinal cord, radiography is performed. If the lesion is located caudal of
Th2, final diagnosis is more difficult to obtain in the horse. Scintigraphy, radiography
of thoracic and lumbar vertebra and rectal ultrasound are indicated.
Cervical vertebral radiography
It is important to obtain true lateral radiographs. This can be achieved in the
standing, sedated horse. The radiographs will be assessed for: encroachment of the
caudal physics dorsally into the vertebral canal (ski jumps), caudal extension of the
dorsal aspect of the arch of the vertebral canal, dorsal angulation and arhtropathy of
the articular facets. In addition to these characteristics of CVM (Wobbler Syndrome),
examination for other abnormalities such as fractures, malformations and tumoral
lesions should be performed. When diagnosing CVM, it is mostly important to identify
the presence of stenosis of the cervical vertebral canal. Therefore measurement of
intra- and intervertebral sagittal ratio’s is indispensable. The addition of these
measurements improved accuracy of radiography in diagnosing CVM. A ratio less
than 52% for C3 to C5 and less than 56% for C6 and C7 (Moore, 1994) or a ratio of <
0,485 (Hahn, 2008) at any inter-or intravertebral site is strongly indicative of CVM.
Myelography
Cervical myelography can also be a useful asset in helping to confirm a
diagnosis of CVM or to help determine the exact site of compression especially when
surgery is an option. False negative as well as false positive results are not
uncommon, so it is important to be careful in interpretation. It should be considered
as one of the tests performed in the work-up for spinal cord problems. Nevertheless,
to obtain high quality images, general anesthesia is required.
Conclusion
The diagnostic process in a horse with poor performance includes a lameness
examination and potentially a neurological examination to detect subtle signs of
spinal ataxia. Subsequently to confirm the presence of a spinal cord lesion and spinal
ataxia, TMS is performed. When TMT confirms the presence of a lesion in the
cervical part of the spinal cord, radiographs are taken. In the diagnosis of CVM it’s
important to detect stenosis of the vertebral canal. Inter-and intravertabral sagittal
ratio’s should be routinely determined. Cervical myelography can be performed to
help determine the exact site and might become more frequently used if it’s done in
the standing horse.
In this diagnostic work up TMT is a useful tool to detect the presence of spinal
ataxia and to determine whether radiographic abnormalities are functionally and
clinically relevant and may contribute to the complaints of the poor performing horse.
References
1. Nollet H. et al., The use of motor evoked potentials in horses with cervical spinal
cord disease. Equine Vet J 2002; 34:156-163
2. Moore BR et al., Assessment of vertebral canal diameter and bony malformation
of the cervical part of the spine in horses with cervical stenotic myelopathy. Am J
Vet Res 1994; 55:5-13
3. Hahn CN et al., Assessment of the utility of using intra- and intervertebral sagittal
diameter ratio’s in the diagnosis of cervical vertebral malformation in horses. Vet
Radiology Ultrasound 2008; 49:1-6