Keywords
tenotomy - Achilles tendon - superficial digital flexor tendon - contracture - arthrodesis
- dog
Introduction
Spontaneous partial disruption of the Achilles tendon—avulsion of the gastrocnemius
tendon from the tuber calcanei—is a recognized condition in dogs.[1] The clinical presentation includes lameness, swelling of the tendon insertion, hyperflexion
of the tarsocrural joint and flexion of the digits caused by stretching of the superficial
digital flexor tendon (SDFT).[1]
[2] The most common treatment that aims to restore tendon function is surgical reattachment
to the tuber calcanei using locking-loop or modified three-loop pulley suture patterns.[3] These tendon repair techniques are reported to achieve a good or excellent outcome
in 70 to 94% of cases.[3] Most complications are associated with the method used to maintain tarsocrural extension,
especially with external skeletal fixation.[1] Where repair fails, options are limited. Pantarsal arthrodesis is a salvage procedure
that effectively treats the tarsal hyperflexion associated with avulsion of the gastrocnemius
tendon. The current authors have experienced subjectively greater rates of repair
failure than those reported and offer pantarsal arthrodesis as a primary treatment
for avulsion of the gastrocnemius tendon, where owners wish to avoid the risk of repair
failure and the need for a second surgery. We understand others take a similar approach,
and in a recent retrospective study of pantarsal arthrodesis, 12 of 30 arthrodeses
were performed to treat avulsion of the gastrocnemius tendon.[4] Reported complications following pantarsal arthrodesis are implant loosening or
breakage, calcaneal fracture, persistent lameness, deformity of the limb, distal limb
swelling, pressure sores, sepsis, wound dehiscence, metatarsal fracture, plantar necrosis
and gastrocnemius tendon pain causing ongoing lameness.[4]
[5]
[6]
[7]
Musculotendinous contractures in dogs are usually caused by overstretching or overuse
of the muscle, or by trauma, and are characterized by a pathological shortening of
the musculotendinous unit.[8] Clinical signs include swelling, lameness, weakness, firmness through the muscle,
characteristically abnormal gait and pain in the muscle.[8] Contracture has been reported to affect the teres minor, supraspinatus, infraspinatus,
brachialis, quadriceps, the deep digital flexor tendon (DDFT) and SDFT of the thoracic
limb.[8]
[9]
[10]
Superficial digital flexor tendon contracture in the canine hindlimb has not been
reported in isolation, in dogs with gastrocnemius tendinopathy, or as a complication
of pantarsal arthrodesis. Here we describe a case of contracture of the SDFT in a
dog with chronic avulsion of the gastrocnemius tendon from the tuber calcanei (treated
by pantarsal arthrodesis) and its successful surgical treatment.
Case Description
A 7.5-year-old female neutered Weimaraner presented to the University of Glasgow Small
Animal Hospital with persistent left hindlimb lameness of 4 months duration. The dog
displayed hyperflexion of the tarsus and flexion of the digits, characteristic of
avulsion of the gastrocnemius tendon from the tuber calcanei ([Fig. 1]). The gastrocnemius was severely mineralized radiographically and pantarsal arthrodesis
was performed as the risk of failure of a sutured repair was considered high. Pantarsal
arthrodesis was performed through a standard medial approach[11] and stabilized using a 3.5/2.7 mm medial plate and 3.5 mm calcaneotibial screw.
The calcaneotibial screw was placed through the tuber calcanei after reflection of
the SDFT laterally. There were no intraoperative or immediately postoperative complications;
however, moderate left hind lameness caused by hyperflexion of the digits persisted,
despite consistent weight-bearing on the affected limb, progressively increasing controlled
exercise, non-steroidal anti-inflammatory medications and physiotherapy. By 7 months
postoperatively, the foot posture was unchanged, despite a stable pantarsal arthrodesis.
Radiographically the tarsus showed replacement of all joint spaces with bone, consistent
with complete fusion, there was new bone surrounding the plate proximally and distally,
and lucency surrounding the calcaneotibial screw within the tuber calcanei. The calcaneotibial
screw protruded caudally a few millimetres from the tuber calcanei due to the density
of soft tissue overlying it. We believe this tissue prevented the screw head from
seating on the bone ([Fig. 2]).
Fig. 1 Hyperflexion of the tarsus and flexion of the digits consistent with superficial
digital flexor tendon contracture.
Fig. 2 Plantarodorsal (A) and mediolateral (B) radiographs 7 months following pantarsal arthrodesis.
Because digital flexion and lameness persisted despite non-surgical treatment, contracture
of the SDFT was diagnosed. Tenotomy of the SDFT to allow digit extension and removal
of the calcaneotibial screw (which appeared loose radiographically) were recommended.
The dog was premedicated with medetomidine (5 µg/kg) and methadone (0.3 mg/kg), induced
with propofol to effect and maintained under general anaesthesia using isoflurane
in oxygen. The degree of metatarsophalangeal extension (extending all digits as a
unit) was reassessed under anaesthesia and measured around 15 degrees goniometrically
([Fig. 3] and [Video 1]). The dog was positioned in sternal recumbency and the left hindlimb extended caudally.
The tarsus was prepared aseptically. A vertical incision was made over the SDFT, on
the plantar aspect of the distal portion of the calcaneus and proximal portion of
the metatarsal bones. The SDFT was isolated and transected at the level of distal
calcaneus ([Fig. 4]). Extension of the digits was notably improved immediately and measured around 40 degrees
goniometrically ([Fig. 5] and [Video 2]). A separate small incision was made directly over the head of the calcaneotibial
screw and it was removed. The incisions were closed routinely and the dog made a good
recovery from anaesthesia. Postoperative analgesia was provided using buprenorphine
(0.02 mg/kg) and meloxicam (0.1 mg/kg).
Fig. 3 Extension of the digits measured around 15 degrees goniometrically, before tenotomy
surgery.
Fig. 4 Transected superficial digital flexor tendon at the level of the distal calcaneus.
Fig. 5 Extension of the digits measured around 40 degrees goniometrically, after tenotomy.
Video 1 Poor range of digital extension before superficial digital flexor tendon tenotomy.
Video 2 Improved range of digital extension intraoperatively after tenotomy.
The dog was discharged with meloxicam daily for 1 week (to be extended if necessary).
The owner was advised to restrict exercise to 10 minutes on a short lead, two to three
times daily for 2 weeks. It was advised that once the skin incision had healed, exercise
could be slowly increased over 2 more weeks.
A follow-up video was sent by the owners 2 weeks after surgery ([Video 3]). The dog's owner reported a significant improvement in foot posture, lameness and
ability to exercise. We re-examined the dog 2 years postoperatively and found a good
long-term functional outcome ([Video 4]). The owner reported minimal lameness, though the nails of the affected digits would
drag on the floor at times. The dog was able to exercise normally. On examination
there was a mild mechanical lameness, the left hind foot was flat ([Fig. 6]) and the nails of digits 3 and 4 were shorter than those of 2 and 5. There were
no abnormalities of the pads or interdigital skin and manipulation was well tolerated.
Fig. 6 Flat left hind foot, 2 years after tenotomy surgery.
Video 3 Follow-up [video 2] weeks after tenotomy surgery.
Video 4 Follow-up [video 2] years after tenotomy surgery. Good functional outcome.
Discussion
This is the first case report describing SDFT contracture alone in the hindlimb, and
a successful surgical treatment. We have re-examined the dog more than 2 years after
the surgery, and she has maintained an excellent improvement in her gait. No minor
or major complications occurred with this procedure.
The action of the SDFT is to flex the digits, extend and fix the tarsus and flex the
stifle joint.[12] It is, therefore, logical that contracture of the SDFT could cause flexion of one
or more digits, as in the case described. It was expected that after restoration of
a more normal tarsal flexion angle through pantarsal arthrodesis, and with use of
the limb after surgery, the foot posture would return to normal. The aetiology of
the SDFT contracture in this case is uncertain, but we speculate that the chronicity
of the gastrocnemius avulsion and resulting prolonged repetitive strain injury to
the SDFT may be significant. Also, the pantarsal arthrodesis surgery may have caused
the significant injury to the SDFT. If there is damage to a muscle and/or associated
tendon, with replacement of normal tissue by fibrous connective tissue, the fibrosis
causes permanent shortening of the musculotendinous unit. This will limit the range
of movement in any joints that the unit crosses.[8] Other differentials for the presenting signs must also be considered. Contracture
of the DDFT or both SDFT and DDFT could have caused the persistent flexion of the
digits.[9] Ankylosis of the metatarsophalangeal joints was also a differential, but there was
no radiographic evidence of this. Finally, the suboptimal positioning of the calcaneotibial
screw, with the screw head elevated from the bone surface, may have interfered with
the function of the SDFT, though we think this unlikely because the SDFT was reflected,
and the screw placed deep to it. It is true that our presumed diagnosis was only confirmed
when tenotomy of the SDFT permitted extension of the digits.
Musculotendinous contractures may be treated non-surgically with non-steroidal anti-inflammatories,
or steroids, and rest.[8] Surgical treatment is recommended for the treatment of specific muscle tendinopathies,
such as teres minor myopathy, supraspinatus, infraspinatus, brachialis, and quadriceps
contracture.[8] Deep digital flexor tendon contracture has been diagnosed in one dog after combined
tibial plateau levelling osteotomy and cranial closing wedge osteotomy for the treatment
of cranial cruciate ligament disease. This case was treated with a z-plasty procedure
which resolved the flexion of the digits. This case did have a similar clinical presentation
to ours, and at surgery the SDFT was described as ‘mildly taut’, but the pathology
primarily affected the DDFT and no surgery of the SDFT was performed.[9] Superficial flexor tendinopathy was reported to affect the forelimb of a dog and
an idiopathic aetiology was suspected. The surgery performed was lengthening of the
tendon using a modified z-tenotomy technique.[10] In a case series and recent case report of cats with digital flexor muscle contracture
in the forepaws, tenectomy surgery was successful.[13]
[14] Tenotomy of the SDFT is also reported for the treatment of chronic corns in sighthounds,
unloading the pad and reducing pain when weightbearing, and in many cases causing
the corn to exfoliate.[15] Tenotomy of the SDFT tendon for the treatment of corns is typically performed on
individual digits. In our case, all four digits were abnormally flexed. The tenotomy
was performed at the level of the proximal metatarsus, before the SDFT divides into
four branches, releasing the contraction of digits II, III, IV, and V. Tenotomy was
not expected to adversely affect the other function of the SDFT (extension of the
tarsus) since an arthrodesis had been performed.
In conclusion, we have described for the first-time contracture of the SDFT tendon
in a dog with avulsion of the gastrocnemius tendon, and a simple surgical technique
that managed it successfully.
