Techniques in Hand and Upper Extremity Surgery 10(1):14–24, 2006
|
Ó 2006 Lippincott Williams & Wilkins, Philadelphia
R E V I E W A R T I C L E
|
ARM: A Modular Hinged Joint for the AO
Tubular External Fixator
Alfonso Queipo de Llano Temboury, Rafael López Arévalo, and
Felipe Luna González y Enrique Queipo de Lllano Jiménez
Servicio de Cirugı́a Ortopédica y Traumatologı́a
Hospital Clı́nico-Universitario ‘‘Virgen de la Victoria’’ de Málaga
| ABSTRACT
Certain complex traumatic elbow lesions challenge the
orthopaedic and trauma surgeon. If they are not treated
correctly, they cause a high rate of disability, arising
from elbow instablility and stiffness, either by fibrosis
or joint incongruity. Injuries such as complex fractures
of the proximal third of the ulna, coronoid fractures
associated with radial head fractures (the ‘‘terrible
triad’’), are even worse if they are accompanied by soft
tissue lesions.
Hinged external fixators, complemented by other
surgical procedures, are, for many, a recommended
alternative when dealing with irreparable lesions. The
AO tubular external fixator, by virtue of its versatility,
is a very important tool in orthopaedics and trauma, but
there is not the possibility of using it as a hinged fixator.
The authors describe a prototype of a hinged joint that
can be applied easily to the AO tubular external fixator,
converting it into a hinged one.
This hinged joint, in conjunction with the AO
tubular external fixator, has been applied in 5 patients; 2
‘‘terrible triads’’, one posterior elbow fracture-dislocation
with radial head fracture, one Monteggia fracturedislocation and an anterior elbow dislocation that
developed a forearm compartment syndrome.
The patients’ age range was between 20 and 72
years (median 45,6); 4 were male and 1 female. In 3
patients, either a type III coronoid fracture or a radial
head fracture, could not be repaired. One radial head
was totally removed and another one partially removed.
The remaining indications were because of severe soft
tissue lesions. Results were evaluated using the Mayo
Elbow Score Scale and the Broberg and Morrey radiographic evaluation scale.1
The median follow up was 18 months (range 6 to 48
months). All 5 patients got a maximum score of 100
points in the Mayo’s Elbow Score Scale, indicating exAddress correspondence and reprint requests to Dr. Alfonso Queipo de
Llano Temboury, C/Sancha de Lara, 13, 2-, 29010 Málaga. E-mail:
[email protected].
14
cellent results. No patient suffered elbow pain, or any
type of elbow instability. The median range of motion in
flexion was of 127.5- (max. 140- and min. 120-) and the
median extension loss was 20- (max. 25- and min. 15-).
One patient had pronation limited to 70- and one had
supination limited to 70-. Every patient was able to
resume a normal daily life activity and returned to normal
work. In 3 patients the radiographic evaluation was
Grade 0 and in the other 2, Grade I.
Two complications occurred, one was a distal ulnar
Schanz screw loosening with osteolysis and the other
was a superficial infection of one Schanz screw.
It can be concluded that good results can be obtained in
injuries with severe elbow instability and soft tissue
lesions, using this hinged external fixator.
With this new clamp, the AO tubular external fixator
is transformed into a hinged one and a new use is added
to this already very versatile system. This clamp is very
easy to apply.
Keywords: fractures dislocations elbow, elbow instability, Hinged external fixator
| HISTORICAL PERSPECTIVE AND
INDICATIONS
The treatment of the severe osseous and ligamentous
lesions, associated with elbow fractures and dislocations, is a challenge for the fracture surgeon, because of
the potential for instability, and elbow stiffness, either
by fibrosis or joint incongruity. A good example of that
it is the ‘‘terrible triad’’ described by Hotchkiss2
(posterior elbow dislocation associated with a coronoid
and radial head fracture) and conminuted proximal ulnar
fractures. These lesions are even worse if accompanied
by severe soft tissue involvement, such as open injuries
or a compartmental syndrome.
Large incisions and osseous and ligamentous reconstruction at the elbow, as well as a prolonged immobilisation time, are often the causes of stiffness and loss of
function. When the lesions are irreparable, or good
stability could not be achieved after repair, any fracture
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ARM: A Modular Hinged Joint for the AO Tubular External Fixator
surgeon has the option of hinged external fixation.
Many authors are using this type of external fixation
routinely, including distraction arthroplasty for posttraumatic sequelae, because of the possibility of early
elbow mobilisation, combined with sufficient stability
to achieve concentric osseous and ligamentous healing.
In this article, a prototype of a hinged clamp has been
used to convert the versatile AO (Synthes ) tubular
external fixator into a hinged one and thereby increase
its indications. The clamp itself is described, as well as its
placement technique. The clamp modularity allows it to
be positioned to match the rotational centre of the joint
and to modify its position as many times as necessary, in
every spatial plane, before the definitive construct of the
external fixation is applied: this is a property not present
in other current hinged external fixators.
Five clinical cases are presented in which this kind
of fixator has been successfully applied in traumatic
elbow pathology.
A
| DESCRIPTION OF THE MODULAR
HINGED CLAMP (ARM)
Every ARM clamp is made with original Synthes
components, only 2 of them modified, so that constructs
can be achieved with the tubular AO External Fixator,
so-called FEARM. We use 2 universal joints, assembled
together to form a hinge that is mounted sequentially.
The assembly is made over the clamp body, without the
sleeve connecting two flat intermediate pieces, one end
of the flat intermediate piece where the rotational
movement is going to take place has been previously
smoothed to eliminate the interdigitations on both sides.
The ARM is made of the following components
(Fig. 1aYd):
Two flat intermediate pieces ref.393.47, with both sides
of each end smoothed down.
A closed nut ref.392.974.
Two cancellous 6.5 mm screw washers.
A centering device for 2.0 mm Kirschner wires designed
by the author.
For the intra-operative assembly the ARM clamp is
divided into two hemi-clamps; one will be called
HARM1 (hemi-clamp of the ARM), made of one flat
intermediate piece with both sides of one end already
smoothed, with only one connecting clamp joined, and
the hemi-clamp ARM number 2 (HARM2), made of
one flat intermediate piece with both sides smoothed,
together with the clamp without sleeve and a body
clamp on the other side. After the assembling of both
hemi-clamps, 2 washers and a closed nut are placed:
this one was initially designed to dynamize a fracture
with a two parallel tubes construct. When tightening
the closed nut, the flat intermediate piece will not be
compressed and it will allow the two flat pieces to slide
over the rotational body. The rest of the construct is
made using the standard components of the AO tubular
external fixator.
A
Three clamp bodies ref.393.44; one of them without its
sleeve will be the rotational axis, and five nuts
ref.393.36.
| SURGICAL TECHNIQUE
This fixator is applied on the lateral side of the elbow
and is, for that reason, a non-transfixing unilateral
fixator, meaning that it is unnecessary to localize the
ulnar nerve and to carry out a medial approach, unless a
specific indication exists.
Standard Construct in The Elbow
A standard hinged construct for the elbow will be
described, carried out using the following steps.
1. Rotational axis localization and placement of
the humeral part of the fixator
Under radioscopic control, the rotational axis of
the elbow is determined in two orthogonal planes, the
FIGURE 1. A, View of the ARM clamp with its rotational axis and connecting bodies; B, the hemi-clamp HARM1 (Hemiclamp number 1 of the ARM) is placed first and; C, the hemi-clamp number 2 (HARM2) is then assembled with the HARM1
using; D, the washers and the closed nut to form the ARM.
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15
de Llano Temboury et al
on the rotational axis (Fig. 3). To carry out this process
the following steps are required:
FIGURE 2. AYB, Elbow rotational axis localisation placing
a 2.0 mm Kirschner wire through the rotational axis under
X-Ray intensifier control in two perpendicular planes, AP
and saggital.
sagittal and frontal planes, and then a 2.0 mm Kirschner
wire is passed free hand through this axis (Figs. 2aYb).
Over the lateral side of the humerus, avoiding its distal
articular part and the humeral radial canal, two 5 mm
Schanz screws are inserted, and then a tubular bar
attached to them. This bar is orientated towards the
Kirschner wire.
2. Placement of the ARM1 hemi-clamp and
positioning of the rotational axis
To centre the ARM to the rotational axis, it is
necessary first to place the HARM1 so that it is centered
1. Place the HARM1 with the centering device over the
Kirschner wire and. Enough space needs to be left
between the HARM1 and the skin, to allow the other
Mhemi-clamp to be assembled without making skin
contact (Fig. 3aYb).
2. Once the HARM1 has been centered on the Kirschner wire, the clamp is fixed to the universal bar.
When tightening the nuts to the bar, the surgeon must
be careful not to bend the Kirschner wire, which
would cause deviation of the rotational axis (Fig. 3c).
Once this is checked, the centering device is removed
and the correct position and alignment of the
Kirschner wire, centered and perpendicular to the
intermediate flat piece, is confirmed. If it is not
centered, the clamp fixed to the bar has to be
readjusted, and the centering device replaced until a
satisfactory position is achieved (Fig. 3d). When the
centering device is well aligned, it has to pass freely
inside the hole of the flat intermediate piece, with the
Kirschner wire in place (Fig. 4a).
3. It has to be observed that the HARM1 can be
orientated over the K wire in every spatial plane,
coronal, sagittal and transverse, moving the HARM1
on the bar and the flat piece of the clamp.
FIGURE 3. A, The Kirschner wire and the hemi-clamp HARM1 are centred with the open A and B clamps and loosening
the humeral External Fixator clamps the ARM can be oriented in all the spatial planes; B, The centring device is placed
through the K wire. Enough space needs to be left between the HARM1 and the skin to allow the other hemi-clamp to be
assembled without having any contact with it. the surgeon has to be careful when tightening the EF clamps A and B of the
HARM1 not to bend the Kirschner wire, which could cause disorientation of the rotational axis; CYD, if it is not centred the
EF clamps A and B of the HARM1 have to be readjusted over the bar and the centring device replaced until a good position
is achieved.
16
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ARM: A Modular Hinged Joint for the AO Tubular External Fixator
FIGURE 4. AYB, Assemble the HARM2 over the HARM1 that have to be blocked with the C closed nut and the nut D, that
allow a free rotational movement of both clamps; CYD, a new bar is placed along the ulna, tightening the E and F nuts, that
allow the placing of the Schanz screw anywhere we want. In the ulna, apart from exceptions, 4 mm Schanz screws will be
used.
3. Placement of the ARM hemi-clamp 2
(HARM2) over the HARM1.
The K wire is removed, the HARM2 is assembled
with the HARM1 and the D nut is then tightened. Once
both hemi-clamps are assembled, the two washers and
the closed nut (C nut) have to be placed in such a way
that, when tightened, free rotational movement is
allowed (Fig. 4b).
4. Bar placement and fixation on the ulna.
In the distal part of the ARM clamp body, a bar is
positioned along the ulna, fixing it with the E nuts. Given
the great versatility of the AO Tubular External Fixator
FIGURE 5. AYB, Flexion-extension range of motion and joint stability has to be confirmed; C, with two tube-tube clamps
the joint can be blocked in a determined joint angle. Loosening the clamps and removing the connecting bar the elbow can
be mobilised; D, To apply distraction the distractor has to be placed on the ulnar bar, loosening the E of the ARM and the G
proximal ulnar nuts. It is essential to leave enough length of the proximal bar overhanging the E nut for distraction. Turning
the open compressor nut the bar displaces distally.
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17
de Llano Temboury et al
System, the Schanz screws can be inserted anywhere. In
the ulna, other than exceptionally, 4 mm Schanz screws
will be used (Fig. 4cYd).
5. Stability and joint mobility check
Clinically and under radioiscopic control, intraoperative mobility (flexion, extension, as well aspronation and
supination) and joint stability are checked (Fig. 5aYb).
Other Possible Uses
The ARM clamp applied to an AO tubular fixator has
other possible Uses:
1. Temporary joint blocking
The elbow can temporarily be blocked in a certain
position, connecting one bar with two tube-tube clamps,
one on the humeral bar and the other on the ulnar (Fig. 5c).
The elbow can be fixed in the desired degree of flexion
or extension. By loosening the clamps and removing the
connecting bar, the elbow can be mobilised.
Temporary fixation of the elbow can be used,
postoperatively, or as a kind of night splint, as it can
be applied and removed with ease.
2. Use of the ARM for distraction
Distraction can be applied to the distal osseous
segment with the FEARM construct. This distraction is
applied to the affected joint by placing the fully opened
compressor device on the bar pushing the distal ulnar
tube-screw clamp, with the nuts tube-clamp on the bar
loosened (Fig. 5d, nuts G and H). Turning the
compressor nut displaces the bar distally. Once this
process is completed, the nuts G and H are
tightened and the compressor-distractor device can then
be removed.
3. Fixation of an epiphyseal fragment
Adding to the proximal bar a Schanz screw inserted
into an epiphyseal humeral fragment would allow, for
instance, stabilisation of a fragment of a supracondylar
fracture, yet at the same time allow the patient to
mobilise the elbow.
Partially dismantling the external fixator, when the
elbow is stable, removing the ARM, the bar and the
distal ulnar Schanz screws, the external fixator could be
left in place in the humerus, until complete fracture
bone healing. With this technique we should be able to
treat more complex fracture dislocations.
4. Other possible constructs
As the AO Tubular External Fixator is universal,
different types of constructs can be made around other
joints, such as the knee and ankle. We show an
exemplary model in the Figure 6a and 6b.
| PATIENT MATERIAL AND
METHODS OF TREATMENT
Between December 1999 and October 2003, the author
has applied a hinged ARM fixator in 5 patients
(Table 1). The range of patients’ ages was from 20 to
72 years (median 45.6); 4 were male and one female.
Aetiologically, 2 injuries were caused by traffic accidents, 2 others by a fall and one a crush caused when the
patient introduced his arm in an industrial centrifuge.
No patient presented a neurovascular lesion on
arrival at hospital. Two ‘‘terrible triads" were diagnosed,
as well as one multifragmentary fracture of the proximal
ulna with a posterior dislocation, one open Gustilo3 IIIB
Monteggia injury , with an associated proximal humeral
fracture in the same limb, and one case with an anterior
elbow dislocation, associated with ulnar diaphyseal and
radial styloid fractures, who later developed a forearm
compartiment syndrome.
In the two ‘‘terrible triads’’, the coronoid fractures
were of type III, according to of the Reagan and Morrey
classification,4 and none could be fixed. In one 72 year
old patient, a type Mason II radial head fracture5 was
present (Fig. 7a) that was initially treated conservatively
by manipulative reduction and immobilisation with a
posterior plaster splint. One week later a redislocation
occurred (Fig. 7b). In this patient the elbow was again
reduced and a FEARM applied, following the previously described technique, without any other additional
surgical procedure (Fig. 7cYf). In the other ‘‘terrible
triad’’, the radial head fracture was a Mason type III,
and it was necessary to excise the radial head via a
lateral approach; some coronoid fragments were also
removed and a capsular reinsertion made using a
Statack anchorage (Zimmer). The lateral collateral
ligament and the epycondylar muscles were also
reinserted with transosseous sutures.
Another patient with posterior elbow dislocation
presented a multifragmentary proximal ulnar fracture
A
FIGURE 6. Possible knee and ankle constructs respectively.
18
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ARM: A Modular Hinged Joint for the AO Tubular External Fixator
TABLE 1.
Name
ERP
FBR
JMRS
FHK
JSG
Diagnosis
Monteggia fx-dislocation open IIIB
Terrible triad
Olecranon fx-dislocation + radial head fx
Anterior elbow dislocation, compartmental syndrome
Terrible triad
Age
20
72
38
65
Sex
Male
Female
Male
Male
Date
25/12/99
9/5/03
16/6/03
16/10/03
33
Male
17/11/04
Ulna
21-B1.3
AO
R-M III
R-M III
21-B1.3
AO
R-M III
Radius
No
Other lesions
Proximal humeral fx
Mason II
Mason II
No
No
Upper limb blisters
Ulnar fx, radial styloid
fx.
No
Mason IV
Etiology
Traffic accident
Accidental fall
Accidental fall
Arm trapped in a
spinner
Traffic accident
Initial treatment
Surgical debridement + bridge AO ext. fix.
Reduction + plaster splint
LCP plating
Closed reduction + Transarticular K wire +
Fasciotomy
Posterior splint
and a partial, Mason type II radial head fracture: the
radial head fragment was removed via a posterolateral
approach, and by a posterior approach an osteosynthesis
of the ulna was done, using a Locked Compression Plate
(LCP Synthes ). The coronoid fracture could not be
stabilised, resulting in an unstable elbow. The joint was
A
temporarily immobilized with a transarticular K wire. In
the immediate postoperative period, he presented an
intense vesicular and erythematous reaction, probably
due to allergy to to the synthetic cotton bandage, and a
FEARM was applied a week after the osteosynthesis.
This patient retained the FEARM for 4 weeks.
FIGURE 7. A, 72-year-old female. Terrible triad with a coronoid fracture type III (Reagan and Morrey) and radial head
fracture Mason type II; B, Elbow redislocation C, Placement of the FEARM, radiological postoperative view; D, X-Ray AP
and lateral views at five postoperative weeks; E, X-Ray AP and lateral views at 18 postoperative months; F, Final range of
motion 120-Y(j15-) and complete prono-supination with a stable elbow in all the space planes. FEARM was in place 8
weeks.
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de Llano Temboury et al
FIGURE 8. A, 18-year-old male, traffic accident; proximal humerus fracture and open grade IIIB Monteggia fracture
dislocation; b, AO tubular EF with articular blocking and bridging. The proximal forearm scar is atrophic and is adherent to
the underlying ulnar osseous plane; c, There is no sign of callus formation at 6 weeks after the accident; D, X-Ray AP and
lateral views after the FEARM placement; e, Active postoperative range of motion. B: f, Eight weeks after the FEARM
placement there is no sign of fracture healing; g, Without removing the FEARM a Judet decortication was made plus
autologous cancellous bone grafting. X-Ray AP and lateral views; h, Callus radiological evolution eight weeks after the
bone grafting. Callus formation bridging the fracture site can be observed; iYj, Elbow range of motion 16 weeks after the
FEARM placement. C: k, Complete fracture bone healing 20 weeks after the FEARM placement. The loosening of the
ulnar distal Schanz screw that was replaced by another one, has to be observed; l, X-Ray views at 24 weeks with a good
callus; m, Flexo-Extension final range of motion 125--0-25- and; n, Prono-Supination 70--0-90- with a functional elbow that
allowed the patient to return to work.
The patient with an open Grade IIIB Monteggia
fracture dislocation was operated on several times,
surgical débridements etc., and the joint was blocked
in 90- of flexion with an AO tubular external fixator,
locked using one bar and tube-tube clamps. At the
seventh week of follow up, he presented an atrophic
scar at the posterior side of the elbow that made an open
osteosynthesis inadvisable and there was no sign of
fracture healing (Fig. 8a). A FEARM was applied six
20
weeks later, to try to mobilize the elbow, following the
already described technique but without using the
centering device, which was not available at that time
(Fig. 8a, dYe). In the subsequent follow up, the fracture
did not heal, and a Judet decortication plus autologous
cancellous bone graft was performed, with the FEARM
in place, (Fig. 8b, fYh). Although the patient was not
compliant and attended neither the review appointments, nor the rehabilitation therapy was obtaining a
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ARM: A Modular Hinged Joint for the AO Tubular External Fixator
FIGURE 7. (continued).
good functional rage of movement (Fig. 8b, iYj). The
fracture healed at 16 weeks after the FEARM placement
and 8 weeks after bone grafting. The distal ulnar Schanz
screw was loose at the 20th week, which made it
necessary to replace it. Finally, good mobility was
achieved (Fig. 8c, kYn).
On admission, the 65-year-old patient who suffered
an anterior elbow dislocation after trapping his upper
limb inside an industrial centrifuge presented a severe
swelling, distal pulses and normal movement were
present. Three hours after admission he developed pain
in the elbow and paresthesia in the hand. He was
surgically treated immediately by carrying out an
osteosynthesis of the ulnar fracture with a 3.5 mm
LCP plate, via by a medial approach, and a closed
reduction of the elbow dislocation, as well as forearm
palmar and dorsal fasciotomies. The radial styloid
process was fixed with a K wire and the elbow was
then immobilised with a brachio-antebrachial splint.
Three days later, under general anaesthesia, the FEARM
was placed. Ten days later definitive closure of the
palmar fasciotomy was performed with some releasing
incisions. This patient`s outcome was very good.
As a general rule, Schanz screws are temporarily
covered with a dressing for a few days, until any bleeding
stops. Later on, they are left uncovered and are cleaned
with a 50% solution of alcohol and normal saline. In the
immediate postoperative period, starting the following
day, every patient, is encouraged to begin gentle, active
and painless elbow mobilisation, and later on, assisted
elbow movements in flexion, extension, pronation and
supination, as well as, an active mobilization of the
ipsilateral shoulder, wrist and hand.
The mean time of use of the FEARM was 10.8 weeks
(range 4Y20 weeks) (Table 1). All the fixators were
removed, with or without local anaesthesia, in the
hospital outpatient clinic. In no patient was any later
elbow mobilisation under general anaesthesia needed.
Patient’s Evaluation
The patients were evaluated following the Elbow
Assessment Index of the Mayo Clinic, accepted by
many authors and specific for this joint.6
This scale first assesses pain, with a maximum of 45
points in absence of pain, 20 points for a free elbow range
of motion, 25 points for carrying out every day life
activities without any restriction and 10 points for a
complete stability.
An excellent result can be considered with 90Y100
points, good between 75 and 89 points, fair between 60
and 74 points and bad less than 60 points.
Radiological Evaluation
The Broberg and Morrey7 scale was used for assessing
the radiographic follow up. The absence of radiological
osteoarthritis is defined as Grade 0, a slight narrowing
of the cartilage space with a minimum osteophyte
formation is a Grade 1, a moderate narrowing of the
cartilage space with moderate osteophyte formation is a
Grade 2 and severe degenerative changes with complete
loss of the cartilage space is a Grade 3.
| RESULTS
With a median follow up of 18 months (between 6 and
48 months), all the patients returned to work, or to their
usual activity (Table 2). All 5 patients reached the
maximum 100 points in the Mayo Clinic Elbow Assessment Index, constituting for each an excellent result.
No patient suffered from elbow pain, or any type of
instability. The median elbow range of motion was 128-
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de Llano Temboury et al
TABLE 2.
Name
ERP
FBR
JMRS
FHK
JSG
Follow-up (months)
48
18
12
12
6
Pain
No
No
No
No
No
Pain (score)
45
45
45
45
45
Flexion
125
120
125
140
130
Extension
25
15
25
15
10
Pronation
70
90
90
90
90
Supination
90
90
70
90
90
Function
25
25
25
25
25
Score
100
100
100
100
100
Rx.
Grade 0
Grade I
Grade 0
Grade I
Grade 0
Complications
Schanz screw osteolisis
No
No
No
Superficial infection
of flexion (max. 140 and min. 120) and-20 of extension
(max.j25- and min.j15-). Only one patient presented
a slightly limited pronation of 70-, and another a limited
supination of 70-. All the patients returned to full
activities of daily life, or to a normal working life.
The joint was congruent in the radiographic evaluation of the 5 patients; 3 of them obtained a Grade 0 and
the other 2 a Grade 1.
Complications were few: only one patient presented
a distal ulnar Schanz screw loosening, because of osteolysis, which had to be replaced by another more proximal one. One patient got a superficial infection in a
Schanz screw that healed with topical antibiotic. There
was no breakage of any Schanz screw, or neurovascular
lesion, associated with the use of the FEARM. (Table 2).
| DISCUSSION
In the literature there is a consensus for repairing
osseous lesions in elbow fracture dislocations: (1)
anatomic reduction and fixation of the proximal ulna
will prevent future degenerative joint disease, and (2) if
it is possible, reconstruction of the coronoid process and
the radial head, the main elbow osseous stabilisers,8 will
prevent recurrences of dislocations or subluxations.
Doornberg et al.9 concluded that obtaining a good result
depends on the restoration of the osseous architecture
and it is especially important to achieve a stable
humero-ulnar articulation. The usual method of achieving this is ORIF, but, if this is not possible, and given
the failure of the more traditional techniques,10,12,17
there are several alternatives described in the literature,
22
125-Y
120-Y
125-Y
140-Y
130-Y
ROM
(j25-)
(j15-)
(j25-)
(j15-)
(j10-)
100105100125120-
Mobility
20
20
20
20
20
Stability
10
10
10
10
10
such as capsular reinsertion, coronoidoplasty using an
osteochondral graft (of unpredictable results), temporary
joint blocking with transfixing K wires, which can
produce heterotopic calcification, and the use of an
hinged external fixation.
For the radial head, as well as its reconstruction
by ORIF, there is the possibility of removing small
fragments if they cannot be fixed, or prosthetic replacement, procedures that, nevertheless, are not free of
complications.13
Currently, almost every author recommends the use
of hinged external fixators, but the indications differ
between authors. The external fixator has the advantage
of keeping a concentric reduction of the humero-ulnar
joint, at the same time allowing its mobilisation, which
aids collateral ligament healing by maintaining an
appropriate tension and thereby limiting capsular
retractions.14 Ring11 recommends that a repair of the
medial collateral ligament only be done in the most
unstable dislocations and he recommends, in every case,
a hinged external fixator, or a short-lived transfixion of
the humero-ulnar joint, lest joint stiffness supervene.
Pugh15 advises the hinged external fixator only when
surgical reconstruction of the capsule-ligamentous
structures fails to result in sufficient stability to permit
early joint mobilisation.
In this small series, the 2 patients who presented
with a ‘‘terrible triad" were treated in different ways: in
one of them, a 72-year-old lady, the hinged external
fixator only was used for 6 weeks, without carrying out
any capsulo-ligamentous, or osseous, repair, with an
excellent result. In the other case, capsular and
Techniques in Hand and Upper Extremity Surgery
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ARM: A Modular Hinged Joint for the AO Tubular External Fixator
epicondylar muscle reattachments, repair of the lateral
collateral ligament and radial head removal (a prosthetic
replacement was not available), were performed. The
FEARM was retained for 12 weeks, and an excellent result
was also obtained.
The first hinged fixators were employed using the
Ilizarov16 rings with wires transfixing the humerus and
ulna. Later, the Mayo17 distractor fixator was developed, whose rotational distraction axis was maintained
over a nail transfixing the distal end of the humerus; in
order to place it, exposure of the ulnar nerve was
necessary, to prevent damage. In case of infection, the
fixator had to be removed and a secondary septic
arthritis was always a risk. To avoid these disadvantages, unilateral external fixators were designed.
Recently, it has been demonstrated that these types of
fixators are strong enough, and better tolerated by the
patients, than the transfixion external fixators of the
Ilizarov type.18
Ruch,19 using the Orthofix hinged EF obtained a
median range of motion of 120- in 3 patients with acute
lesions, and in 5 patients with a lesion more than 6
weeks old, he reported a median range of motion of 84-.
Only one patient with an acute lesion developed joint
stiffness that needed surgical arthrolysis. The author emphasises the problem of repairing high-energy lesions,
where, not only the bony damage, but also the soft tissue
lesions, make anatomical restoration impossible.
Other fixators, such as the Compass Elbow Hinge
(Smith and Nephew), also avoid the transfixion nail.
McKee20 obtained the following results in 16 patients: a
median flexion-extension range of 105-; in 14 patients
the joint was congruent; he reported one case of
instability and another with a valgus deformity. There
was a 38% complication rate, but only 3 reinterventions
(19%) were needed; one subluxation required the
removal of the fixator because of Schanz screw loosening and 2 more Schanz screws loosened, but fixator
removal was not needed.
Wyrsch et al,21 using the same device, has obtained
a good stabilization in 7 out of 10 patients, although
with 50% complications.
With our fixator we have only had one ulnar Schanz
screw loosening; this was in a non-compliant patient with
an open Grade IIIB Monteggia fracture who presented a
delayed bone healing. The centering devicez could not be
used and the fixator had to be retained for 24 weeks . The
Schanz screw was replaced without removing the fixator.
In this case the soft tissue state indicated the use of the
FEARM, because an adherent and fragile scar prevented
any osteosynthesis.
In the next case, the right upper limb was trapped
inside an industrial centrifuge, causing an anterior
elbow dislocation and, unlike the usual mechanism of
the lesion, a force striking the posterior forearm in the
flexed position22: this was probably produced by torsional mechanism on the forearm, resulting in severe
soft tissue lesions leading to a compartment syndrome,
as well as ulnar and radial styloid fractures. To
stabilized the elbow and manage the soft tissues better
and taking advantage of a surgical intervention on the
forearm, a FEARM was applied, the Schanz screws
being inserted some distance from the soft tissues
exposed by the fasciotomy. The FEARM allowed the
subsequent soft tissue dressings and was left in place for
8 weeks, with a good outcome.
The lack of ease of modification of the rotational
axis and its intraoperative adjustment has been noted by
many authors23Y25 who have reported on the use of
hinged fixators. Broberg11 noted these characteristics of
hinged fixators along with their lilmited availability, the
complicated equipment and the high level of technical
ability needed for their placement.
These lesions are often treated as an emergency and
sometimes the instability is only appreciated intraoperatively, and the fixator may not be readily avai;lable. By
contrast, this FEARM fixator is easy to apply and does
not need complicated instrumentation, just one adapted
clamp and a centering device, which could be packed in
the AO tubular external fixator set. It also offers
freedom of placement of the Schanz screws, and ease
of replacement of screws without removing the whole
fixator. It is also possible to reposition the ARM clamp,
or even remove it intraoperatively without having to
remove the fixator, and to modify its position as often as
may be necessary, in any special plane, properties not
present in other hinged external fixators currently
available. Distraction can be applied, using the standard
compression device included in the normal AO tubular
external fixator set, and it is also possible temporarily to
block the joint simply by adding one bar. All these
procedures can be done as out-patient cases. A potential
disadvantage is that it is not radio-opaque.
| CONCLUSIONS
Good results can be obtained in severe, unstable elbow
injuries, associated with injuries of the soft tissues, using
the described hinged external fixator. The dedicated new
clamp adds another possible use to the modular AO
tubular external fixator system. This hinged external
fixator is very versatile and can be made easily available;
it is easy to apply and presents certain advantages over
other current hinged fixators.
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24
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