1
Clinical Communication
Tibial plateau levelling osteotomy
in 69 small breed dogs using
conically coupled 1.9/2.5 mm
locking plates
A clinical and radiographic retrospective assessment
G. Cosenza1; U. Reif1; F. M. Martini2
1Tierklinik
Dr. Reif, Böbingen, Germany; 2Unità operativa chirurgia e traumatologia veterinaria, Dipartimento di
scienze medico-veterinarie, Università degli Studi di Parma, Italy
Keywords
Complications, small breed dogs, stifle, retrospective study, TPLO, tibial plateau levelling
osteotomy
Summary
Objective: To report clinical experiences
with the tibial plateau levelling osteotomy
(TPLO) procedure in small breed dogs with
cranial cruciate ligament (CCL) disease using
specific, conically coupled, 1.9/2.5 mm locking plates and evaluating short-term complications and outcome.
Methods: Medical records of small breed
dogs (<15 kg) that underwent TPLO using
1.9/2.5 mm locking plates were reviewed
retrospectively. The preoperative, postoperative and six to eight weeks postoperative tibial plateau angle (TPA) measurements were
determined from the radiographic images.
Lameness evaluation was assessed subjectively preoperatively and six to eight weeks
postoperatively.
Correspondence to:
Dr. Giovanni Cosenza
Schönhardter Straße 36
D-73560 Böbingen-Nord
Germany
Phone: +49 1575 3122744
E-mail: [email protected]
Results: Sixty-nine small breed dogs (n = 79
stifles) were included in the study. Mean (±
SD) preoperative TPA was 29.0 ± 3.4°, postoperative TPA was 5.8 ± 2.5°, and six to
eight weeks postoperative TPA was 7.3 ±
4.1°. Sixteen complications occurred in 12
out of 79 TPLO procedures: three were intraoperative (intra-articular screw placement) and 13 were postoperative complications, of which nine were identified as
minor complications not requiring surgical
reintervention, and four as major complications requiring additional surgical intervention, including tibial tuberosity fracture (n
= 1), osteomyelitis (n = 1), screw failure (n =
1), and plate breakage (n = 1). Lameness
scores by clinical assessment reduced from a
median value of 3/4 preoperatively to 1/4 at
six to eight weeks postoperatively.
Clinical significance: 1.9/2.5 mm locking
plates appear to be a valid choice of implant
for the stabilization of unilateral TPLO in
small breed dogs.
Vet Comp Orthop Traumatol 2015; 28: ••–••
http://dx.doi.org/10.3415/VCOT-14-09-0135
Received: September 1, 2014
Accepted: May 26, 2015
Epub ahead of print: June 3, 2015
Introduction
Cranial cruciate ligament disease has been
recognized as a cause of hindlimb lameness
in both small and large breed dogs since
1926 (1). Cranial tibial thrust is the cranially directed shear force on the tibia with
respect to the femur generated during
weight bearing (2). The cranial cruciate
ligament contributes to passive opposition
of cranial tibial thrust. Deficiency of the
cranial cruciate ligament permits cranial tibial translation during weight bearing, resulting in degradation of the hyaline cartilage matrix, inflammation, and osteoarthritis (3–5). Slocum and Slocum proposed
that cranial tibial thrust magnitude is directly proportional to the tibial plateau
angle (TPA) (6). It has been suggested that
small breed dogs may have a higher TPA
than large breed dogs, with TPA ranging
from 21° to 34° (mean: 27.4°) and 27° to
40° (mean TPA not reported) (7, 8). A high
TPA in small breed dogs has been associated with caudal deformity of the proximal
tibia (9, 10).
Concern about body weight as a variable in the management of dogs with cranial cruciate ligament rupture was first expressed in 1984 (11). In that study, conservative management resulted in acceptable
hindlimb function in up to 85% of small
breed dogs (<15 kg) with cranial cruciate
ligament disease (11, 12). However, recovery time was prolonged (mean: 4
months) and 14.3% of dogs remained lame
(12). Extra-capsular stabilization consists
of placing one or more extracapsular sutures across the joint to neutralize the cranial tibial thrust statically. Extra-capsular
stabilization improves stability and hindlimb function during the postoperative
period (13–15). However, long-term stifle
stability relies on periarticular fibrosis, and
suture failure resulting in joint instability
does occur more commonly than one may
expect, especially in dogs with a high activity level (15–20).
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2
G. Cosenza et al.: A clinical and radiographic retrospective assessment
A greater TPA in smaller dogs may produce a greater cranial tibial thrust and
could theoretically contribute to early failure of extra-capsular stabilization techniques. Therefore, performance of a tibial
osteotomy with the aim of levelling the tibial slope may be more appropriate in this
population of dogs. Tibial plateau levelling
osteotomy provides stifle stability by neutralizing tibiofemoral shear forces dynamically (6, 21).
Increased tibial plateau rotation associated with a high TPA may result in a lack of
buttress support of the tibial tuberosity. It
has been suggested that rotation beyond
the point of patellar ligament insertion
would make the tibial tuberosity more susceptible to fracture (22, 23). To obviate this
problem, a combination of tibial plateau levelling osteotomy and cranial tibial closing
wedge osteotomy has been proposed in
dogs with a steep TPA, however this may
be technically demanding in small breed
dogs due to the small bone (22). Tibial plateau levelling osteotomy in small breed
dogs with a high TPA (>30°) has been reported previously without encountering tibial tuberosity fracture (24).
Both conventional and locking plates
are available for small breed dogs. Locking
screws help maintain the tibial plateau
position during plate application (25).
Small plate contouring discrepancies and
subtle shifts in alignment when tightening
conventional screws can have a great impact on both osteotomy compression and
corrected tibial plateau angle (24–27).
Tibial plateau levelling osteotomy using
a 4-hole 1.9/2.5 mm conically-coupled
locking T-plate in small breed dogs with a
steep TPA has been reported previously
(24). We report our experience using different 1.9/2.5 mm locking plates in small
breed dogs with particular focus on a conically-coupled locking L-plate.
Material and methods
Medical records of dogs that underwent tibial plateau levelling osteotomy utilizing
1.9/2.5 mm conically-coupled locking
platesa at a referral centre (Tierklinik in
Böbingen) between January 2008 and November 2014 were reviewed. Inclusion
criteria included a body weight of less than
15 kg, cranial cruciate ligament disease
confirmed by mini-arthrotomy, complete
medical records including preoperative and
six to eight week postoperative subjective
lameness scoring (0 = no lameness, 1 =
mild, 2 = moderate, 3 = severe, 4 = non
weight-bearing) by a board-certified surgeon (UR), and preoperative, postoperative
and six to eight week postoperative radiographs.
Excluded from the study were dogs with
incomplete medical records that could not
be returned for follow-up examination six
to eight weeks after surgery, dogs with neurological diseases, severe systemic diseases,
or any other injuries or diseases such as patellar luxation, hip dysplasia, Legg-CalvéPerthes disease in the limb being treated
for cranial cruciate ligament disease, and
dogs that underwent surgery on the limb
being treated for cranial cruciate ligament
disease for conditions other than cranial
cruciate ligament disease. Information obtained included breed, sex, age, body
weight, pre-, postoperative and six to eight
week postoperative TPA, meniscal damage
and treatment, saw blade size, implants applied, and complications.
All osteotomies were secured with tibial
plateau levelling osteotomy plates of the
mini-implant series (1.9/2.5 mm system)
which were able to accommodate both 1.9
mm and 2.5 mm screws. The locking plate
consisted of a stainless steel plate with titanium alloy bushing inserts and titanium
self-tapping screws with a conical head that
lock into the bushing inserts of the plate by
conical coupling (28).
Using a standard anaesthesia protocol,
dogs were premedicated with levomethadoneb, and anaesthesia was induced with
propofol and maintained with isoflurane in
oxygen. All dogs received a single administration of cefazolin (22 mg/kg IV) and carprofen or tolfenamic acid preoperatively.
The dogs were positioned in dorsal recumbency with the pelvic limb suspended for
surgery.
All dogs underwent a craniomedial
parapatellar mini-arthrotomy for stifle ex-
ploration, and inspection of both cruciate
ligaments and menisci. Meniscal injuries
were treated by partial meniscectomy.
After fascial incision and reflection of the
sartorius muscle, no additional dissection
of musculature cranial or caudal to the
proximal segment was performed. A semicylindrical osteotomy of 12 or 15 mm
radius was made without use of a jig. Rotation of the proximal fragment was temporarily maintained with an anti-rotational
Kirschner wire and pointed reduction
forceps.
The locking plate was then contoured
such that the proximal two screws would
converge to avoid invasion of the osteotomy gap and to improve fixation of the
caudal part of the proximal tibial bone
fragment. The plate was positioned on the
medial surface of the tibia in a matter that
best fitted the bone contour and osteotomy.
Whenever possible, the plate was oriented
such that the caudal margin was placed
parallel to and adjacent to the caudal cortex
of the tibial shaft. The type of implant was
subjectively chosen by the surgeon preoperatively, considering body weight, the size
and conformation of the tibia, and the
amount of rotation of the proximal fragment. In every case, the plate was secured
with 2.5 mm locking screws in both the
proximal fragment and the tibial diaphysis.
The anti-rotational Kirschner wire was removed and the surgical site closed in layers.
Radiographs were reviewed by one
author (UR), with the observer blinded to
all data. All measurements were made on
digital radiographsc using the built-in tool
on a standard diagnostic imaging software
systemd. The TPA was measured using the
tangential and conventional methods (29).
Postoperative mediolateral radiographs
were also used to determine whether rotation of the proximal fragment was
beyond the point of patellar ligament insertion. Osteotomy healing was assessed on
the six to eight weeks postoperative radiographs using a modified version of a previously developed grading system (International Society of Limb Salvage) (23, 30,
c
a Fixin®: Intrauma S.r.l., Rivoli, Italy
b L-Polamivet®: MSD Animal Health GmbH,
Unterschleißheim, Germany
workstation - easyvet XDR2 cuattro direct digital
detector: Toshi
d easyimage version 8.0.0.05, DICOM-viewer:
Vet Comp Orthop Traumatol 5/2015
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G. Cosenza et al.: A clinical and radiographic retrospective assessment
31). Bone union was defined as fusion of
the osteotomy line, the presence of bridging callus, or the disappearance of the osteotomy lines and scored as follows: 1 =
poor union <25% (no callus); 2 = fair
union 25–50% healing; 3 = good union
>50–75% healing; and 4 = excellent union
>75% healing.
Dogs were typically discharged six to 24
hours after surgery with instructions to the
owner to administer carprofen (2 mg/kg
daily) for 10 days. No routine postoperative
antimicrobial therapy was administered.
Patients were re-examined five to 10 days
after surgery. Postoperative care consisted
of six week confinement to a cage or a
single room except for leash walks of 10–15
minutes two to three times daily.
Complications were defined as any undesirable outcome associated with the surgical procedure and were classified depending on severity as major (surgical intervention required) or minor (managed
nonsurgically).
Statistical analysis
Data were reported as mean ± SD for
normally distributed data, or median and
range for non-parametric data. Distributions of categorical and continuous variables associated with complications were
compared by use of a two-tailed Fisher's
exact test and independent t test, respectively. The two methods of TPA measurement were compared by linear regression
analysis with non-normal errors. For all
analyses, a value of p <0.05 was considered
significant.
Figure 1
Relationship between body weight and the saw blade used to perform the osteotomy.
Breeds were as follows: Jack Russell Terrier (n = 11), West Highland White Terrier
(n = 6), Australian Terrier (n = 4), Havanese (n = 3), Yorkshire Terrier (n = 3), Bichon Frise (n = 2), Bolonka Zwetna (n = 2),
Cairn Terrier (n = 2), Norwich Terrier (n =
2), Shetland Sheepdog (n = 2), Beagle (n =
1), Chihuahua (n = 1), Coton de Tulear (n
= 1), Fox Terrier (n = 1), Lhasa Apso (n =
1), Miniature Schnauzer (n = 1), Patterdale
Terrier (n = 1), Pug (n = 1), Shi Tzu (n = 1),
Toy Poodle (n = 1), Welsh Corg (n = 1).
Twenty-one dogs were mixed-breed. There
were 26 spayed and 16 entire females, and
11 castrated and 16 entire males. Mean age
was 8.5 ± 2.8 years and mean body weight
was 8.8 ± 2.2 kg. Median preoperative subjective lameness score was 3 (range: 2–4).
Surgery
Seventy-nine tibial plateau levelling osteotomy procedures were performed in 69 dogs
by one board-certified surgeon. Bilateral
simultaneous tibial plateau levelling osteotomy procedures were not performed. Meniscal injuries were apparent in 22 stifles
and all were treated by partial meniscectomy. Osteotomy radius was 12 mm in 20
stifles (mean body weight: 6.1 ± 1.2 kg) and
15 mm in 59 stifles (mean body weight 9.7
± 1.7 kg) (▶ Figure 1). The most common
plate used was the 1.2 mm thick and 25
mm long L-platee ( n = 38, ▶ Figure 2), fole
FIXIN® V2007, Intrauma S.r.l., Rivoli, Italy
Results
Signalment
Eighty dogs (96 stifles) fulfilled the initial
criteria for inclusion: all were less than 15
kg in bodyweight and treated by tibial plateau levelling osteotomy using 1.9/2.5 mm
Fixin® plates. However, 11 dogs (17 stifles)
were excluded from the study; five dogs (7
stifles) had medial patellar luxation or were
treated surgically for patellar luxation and
six dogs (10 stifles) were lost to follow-up.
Thus, 69 dogs (79 stifles) were included.
A
B
Figure 2 A) Preoperative mediolateral and caudocranial views of a right tibia and stifle of a dog with
a high tibial plateau angle (34°) and great subluxation of the tibia. B) Immediate postoperative mediolateral and caudocranial views showing rotation of the proximal fragment to level the tibial plateau
and fixation with a locking L-plate and four screws.
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4
G. Cosenza et al.: A clinical and radiographic retrospective assessment
A
B
Figure 3
C
1.9/2.5 mm locking plates used in the study.
lowed by the 1.5 mm thick and 32 mm long
T-platesf ( n = 27), and the 1.2 mm thick
and 25 mm long T-plateg (n = 14, ▶ Figure
3, ▶ Figure 4). Seven dogs were treated
with cephalexin (22–30 mg/kg PO) for 10
days postoperatively.
Radiographic assessment
No significant difference between the two
methods of TPA measurement was ob-
served. Mean (± SD) preoperative TPA was
29.0 ± 3.4°, postoperative TPA, 5.8 ± 2.5°
and six to eight weeks postoperative TPA
7.3 ± 4.1°. The mean change in TPA between postoperative and six to eight weeks
postoperative radiographs was 1.4 ± 1.6°.
The proximal fragment was rotated beyond
the point of patellar ligament insertion in
38 stifles (48.1%). Median osteotomy healing grade was 3 (range: 3–4).
Complications
f FIXIN® V2001/V2021, Intrauma S.r.l., Rivoli, Italy
g FIXIN® V2003, Intrauma S.r.l., Rivoli, Italy
Sixteen complications were recorded in 12
out of 79 tibial plateau levelling osteotomy
Plates
V2001/V2021
V2003
V2007
3
5
7
9
11
13
15
procedures. Intra-operative complications
(intra-articular screw placement) occurred
in three dogs. The malpositioned screws
were replaced with a shorter screw immediately after surgery and radiographs
showing proper screw length and orientation were obtained.
Thirteen postoperative complications
occurred: four major complications
required an additional surgical intervention and the remainder nine were minor
complications. Major complications included one tibial tuberosity fracture, one
osteomyelitis, one screw failure, and one
plate breakage.
Tibial tuberosity fracture was apparent
four weeks after surgery (▶ Figure 5) as the
owner noticed the dog becoming acutely
lame. This was treated with Kirschner wire
fixation and tension band placement. Eight
weeks after revision surgery, osteomyelitis
caused by a multi-resistent Staphylococcus
aureus was diagnosed, thus plate removal
as part of infection treatment was performed. Outcome in terms of radiographic healing and lameness evaluation after eight
weeks was assessed as good.
Failure of the caudal screw in the proximal fragment occurred in one stifle. The
dog had a persistent lameness and a local
infection of the incision site. Radiographs
taken 16 weeks following tibial plateau levelling osteotomy procedure demonstrated
good osteotomy healing and no implant
loosening. However, implant removal led
to the detection of the broken screw just
below the screw head. At the six weeks follow-up examination, the lameness had resolved.
Plate breakage was apparent three weeks
postoperatively in the stifle of a 12 kg
mixed breed dog treated by tibial plateau
levelling osteotomy using the 1.2 mm
L-plate. The owners reported excessive activity within 10 days of surgery. The plate
was removed and the osteotomy re-stabilized by a 3.0/3.5 mm locking T-plateh.
Healing was progressing at six to eight
weeks with active callus formation and no
lameness was noted.
Minor complications included surgical
site infection (n = 6) and seroma (n = 3).
Body weight (kg)
Figure 4
Relationship between body weight and plate used.
h FIXIN® V3001, Intrauma S.r.l., Rivoli, Italy
Vet Comp Orthop Traumatol 5/2015
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G. Cosenza et al.: A clinical and radiographic retrospective assessment
A
B
C
D
E
Figure 5 Mediolateral views of the right stifle of a dog with a tibial tuberosity fracture. A) Radiographic images taken three weeks after surgery. B) Radiographic images following revision surgery, which was performed with two Kirschner wires and a tension band wire. C) Osteomyelitis occurred nine weeks
after revision surgery. D) Following implant removal. E) The osteotomy line was still apparent after three months.
All surgical site infections resolved after
antimicrobial therapy with oral cephalexin
(22–30 mg/kg) for 10 days.
Short-term complications were not significantly associated with sex (p = 0.95),
age (p = 0.67), body weight (p = 0.75), meniscal injury (p = 0.45), preoperative TPA
(p = 0.79), postoperative TPA (p = 1), six to
eight weeks postoperative TPA (p = 1),
change in TPA from postoperatively to six
to eight weeks postoperatively (p = 0.28),
rotation of the proximal fragment beyond
the point of patellar tendon insertion (p =
0.38), saw blade size (p = 0.67), or type of
implant (p = 1) .
Subjectively assessed median lameness
scores six to eight weeks postoperatively
were between 0 (n = 39) and 1 (n = 40).
Discussion
In our study tibial plateau levelling osteotomy procedures utilizing 1.9/2.5 mm conically-coupled locking TPLO plates in 79
stifles of small breed dogs were evaluated.
Mean (± SD) preoperative TPA was 29.0 ±
3.4°, postoperative TPA was 5.8 ± 2.5°, and
six to eight weeks postoperative TPA was
i
FIXIN® V2021 and V2007, Intrauma S.r.l., Rivoli,
Italy
7.3 ± 4.1°. We observed an overall complication rate of 15.2% (12/79 stifles), but no
predisposing factor for postoperative complications was found. The locking plates in
our study resulted in a stable fixation of 77
out of 79 osteotomies. Lameness scores by
clinical assessment reduced from median
3/4 preoperatively to 1/4 at six to eight
weeks postoperatively.
Preoperative TPA of 29.0 ± 3.4° is consistent with the findings of similar studies
in small breed dogs, reporting a higher
TPA compared to other dogs (7, 8, 26).
Possible explanations are that small breed
dogs have a physiologically steeper TPA, or
that small breed dogs with cranial cruciate
ligament disease and a lower TPA respond
well to other treatment options and therefore referral is not sought (7). Moreover,
what in the past has been referred to as a
caudal deformity of the proximal tibia, has
to be considered the physiological tibia
conformation in small breed dogs (9, 10).
Caudal bowing of the proximal tibia associated with caudal sloping of the tibial
plateau is a common finding in small breed
dogs, and it results in a higher TPA compared to medium- and large breed dogs.
Meniscal injuries were found in 27.8%
of stifles, which is similar to the ranges of
10–70% in large breed dogs (32–37). Late
meniscal tears have been reported as fre-
quently occurring complications, but were
not observed in our study (33). This may
be in part attributable to the short followup time in our dogs (33–38). Nevertheless,
thorough evaluation of the meniscus using
a probe should be performed in order to
diagnose latent tears, which may result in
persistent lameness after tibial plateau levelling osteotomy (39, 40).
Intra-articular screw placement occurred in three stifles. The occurrence of
this complication is more of a technical
error (41). Greater experience with tibial
plateau levelling osteotomy using this plate
system in small breed dogs may influence
the type and incidence of complications
over time (42). Since screw direction is imposed in locking plates, contouring of the
plate may redirect the angle of the locking
screws.
Depending on plate availability and
subjective choice of the surgeon, different
1.9/2.5 mm locking plates were used to secure the osteotomy. Special features of
these implants include the plate head that
is specifically designed to facilitate adequate screw purchase in the proximal
bone segment. High TPA resulting in great
rotation causes the caudal portion of the
proximal fragment to protrude beyond the
caudal cortex of the tibial shaft, as a result
the osteotomy fixation becomes technically
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G. Cosenza et al.: A clinical and radiographic retrospective assessment
challenging. For this reason, the L-shaped
plate was designed to ensure appropriate
osteotomy fixation and plate placement
parallel to the caudal cortex of the tibial
diaphysis. Furthermore, temporary stabilization prior to plate fixation is possible in
some platesi by inserting Kirschner wires
through additional plate holes, but was
never performed in our study.
Tables reporting the saw blade size and
the implant used in relation to the body
weight can be used as guidelines when performing tibial plateau levelling osteotomy
in small breed dogs using these plates. Care
must be taken not to undersize the implant,
as it happened in one of our cases. A 1.2
mm L-plate broke three weeks after surgery
in a 12 kg mixed breed dog. This finding
suggests that the use of the 1.2 mm L-plate
should be limited to dogs weighing less
than 12 kg. Finally, factors other than
weight, such as bone size, bone quality, age,
conformation of the tibia, and osteotomy
placement have to be considered when
choosing the type of implant.
High TPA need increased rotation of
the proximal fragment that may result in tibial tuberosity fractures. Risk factors for
this include a thin postoperative tibial
crest, a postoperative increase in TPA, a
gap in the cranial aspect of the osteotomy
after fixation, a single-session bilateral tibial plateau levelling osteotomy procedure,
and lack of osteotomy planning (43–46).
Also, a lack of caudal buttress support due
to rotation beyond the point of patellar
ligament insertion was proposed as a risk
factor, but this was not confirmed by another study (22, 43).
Postoperative tibial tuberosity width
greater than 10 mm has been suggested to
be critical in avoiding tibial tuberosity fractures in large breed dogs, but not in small
breed dogs (24, 43). The tibial crest in dogs
in our study population was usually prominent, but rarely fractured, even in extreme
rotations (maximum TPA: 38.00°) of the tibial plateau. Rotation beyond the patellar
ligament insertion was performed in 38/79
stifles without major complications, suggesting that this condition is not a risk factor for tibial tuberosity fracture in small
breed dogs. An inappropriately placed osteotomy resulting in a narrow tibial crest
was considered to be the cause of a tibial
tuberosity fracture in one dog in our study.
Mean postoperative change in TPA was
1.4 ± 1.6°, which supported previous evidence that use of a locking plate results in
improved maintenance of TPA compared
with non-locking systems (24–26). A minimum of two bicortical locking screws per
fragment are typically recommended (47).
The locking plates used in our study allowed two screws in each fragment, except in
one stifle, as the caudal screw in the proximal fragment was found to be broken at 16
weeks. This complication occurred three
times in another study and has been attributed to the steep TPA in small breed
dogs and the increased degree of rotation
causing the proximal fragment to displace
more caudally (24). The caudal part of the
construct has been suggested to be initially
non-load sharing, potentially explaining
the propensity for failure of the screw at
this point (24).
Plate removal was performed in two
stifles, because of infection, which has been
reported as a complication in 3.6% to 8.4%
of tibial plateau levelling osteotomies
(48–50). A multi-resistent Staphylococcus
aureus was isolated in one stifle following
surgical correction of a tibial tuberosity
fracture. The other stifle had an infection
that was associated with implant failure.
While complication rates in previous
studies reported 14.8% to 28% for tibial
plateau levelling osteotomies using conventional plates in large breed dogs, 9.7% to
11.4% for tibial plateau levelling osteotomies using both conventional and locking
plates in large breed dogs, and 36% in
small-and medium sized dogs, we observed
an overall complication rate of 15.2%
(12/79 dogs presented complications) (26,
33, 41, 45, 51–53). The use of different definitions and classification of complications
could certainly explain complication rate
differences between retrospective studies,
making it difficult to directly compare results of each study. Nevertheless, unlike
comparable retrospective studies, no predisposing factor for postoperative complications was found (33, 41, 45, 51–53). Previously reported risk factors include breed,
sex, body weight, arthrotomy, complete
ligament ruptures and a TPA greater than
30°.
Other types of locking plates for small
breed dog tibial plateau levelling osteotomy
have been developed recently. The Synthes
plates stabilize the osteotomy with three
screws in each fragment and have combiholes that may be used to provide interfragmentary compression. Thus, Synthes
TPLO locking plates theoretically offer improved stability of the fixation. Because of
the often small size of the proximal tibial
fragment, placement of three screws can be
technically demanding. The plates used in
our study provided adequate stability with
just two screws in each fragment, which resulted in healing of all the osteotomies, except for two stifles.
In our opinion, advantages of the Fixin®
TPLO plates include the plate thickness.
Due to the presence of a bushing insert, the
thickness required for adequate conical
coupling is not related to the plate thickness. This allows implants to be thin. Compared to the 2.0/2.4 Synthes® TPLO plates
(2.3 mm thickness), Fixin® plates have a
plate thickness of 1.2 mm or 1.5 mm. Thin
implants are less stiff and much easier to
contour and are ideal for distal extremities
where there is less soft tissue coverage.
However this could predispose to plate
breakage.
Several limitations should be considered
when interpreting the data of this study.
The retrospective nature of our study represents a main limitation. Furthermore,
clinical outcome assessment methods were
limited to physical and radiographic examinations that were performed by one surgeon. Limited data on outcome was tolerated, as the focus of our study was on the
technical feasibility of 1.9/2.5 mm Fixin®
TPLO plates in small breed dogs, rather
than on the clinical outcome. No objective
assessments of limb use, such as force-plate
analyses and kinematic gait evaluations,
were obtained. Therefore, these findings
have to be interpreted in light of this lack of
objective data.
In summary, the tibial plateau levelling
osteotomy procedure was performed in
small breed dogs using 1.9/2.5 mm Fixin®
plates. Short-term complications included
a tibial tuberosity fracture associated with
an inadequate osteotomy placement and a
plate breakage. Plate removal as part of an
infection treatment was performed in two
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G. Cosenza et al.: A clinical and radiographic retrospective assessment
cases, one of which was associated with
screw failure. Complication rate is comparable to large breed dogs, but no predisposing factor for postoperative complications was found. The Fixin® locking
plates used in this study resulted in successful osteotomy healing of 77 out of 79
osteotomies, and were considered to be a
valid choice for the stabilization of tibial
plateau levelling osteotomy in small breed
dogs.
Conflict of interest
The authors declare no conflict of interest
related to this report.
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Vet Comp Orthop Traumatol 5/2015
© Schattauer 2015
Downloaded from www.vcot-online.com on 2015-07-26 | ID: 1000388659 | IP: 78.42.176.219
Note: Uncorrected proof, epub ahead of print online
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