Also known as: Fibrotic Myopathy
Introduction
Contracture of a muscle occurs to some degree secondary to any muscle contusion that heals primarily by scar tissue.
Muscle contracture or fibrotic myopathy is characterised by the replacement of most or all of a muscle by fibrous scar tissue that contracts to an inelastic band. Therefore normal motion of the related joints is decreased or lost.
Muscles most commonly affected include: infraspinatus, quadriceps, gracilis and semitendinosus.
Infraspinatus Contracture
This commonly occurs in medium-large working dogs, with a lifestyle of repetitive minor trauma, such as hunting.
Clinical Features
Palpation of the infraspinatus fossa is not painful and reveals marked atrophy and an inability to fully extend or internally rotate the shoulder.
The dog holds the limb in external rotation and slight abduction.
If the contracture is severe the limb may not reach the ground.
The gait is characteristic, and includes marked circumduction and abduction of the forepaw with a carpal 'flip'.
Treatment
Transection of the infraspinatus muscle is curative. Adhesions around the muscle should be broken down at surgery by sharp dissection, until full range of motion is restored.
Conservative therapy is not effective.
Quardriceps Contracture
This typically occurs secondary to a distal femoral fracture in young dogs.
Tight adhesions develop between the femur and quadriceps muscle.
Clinical Features
The condition causes limited motion of the stifle and hock joints and is associated with severe ankylosis and degenerative joint disease of the stifle. When complete, the stifle and hock are locked in full extension.
There is usually marked atrophy of the quadriceps, and then atrophy of the other muscles of the limb.
Treatment
Treatment is only effective if performed early, and the muscle should be kept in motion to prevent excessive scar formation.
Salvage techniques include release of the quadriceps muscle from the proximal femur and pelvis, arthrodesis of the stifle and hock, and amputation.
Conservative treatment can be considered, but the limb is useless and the toes may become abraded and infected.
Gracilis Contracture
This occurs most commonly in German Shepherd dogs with an active, working lifestyle.
Repeated strain injuries are thought to be the cause.
Clinical Features
Clinical signs are progressive but tend to plateau. The condition internally rotates the leg during stifle extension, shortens the strike, and leads to a characteristic jerky gait.
The gracilis palpates very firm and distinct from the other muscles.
Treatment
Transection of the muscle does not seem to work and recurrence of signs is common.
Affected dogs usually remain active despite the lameness, and pain does not usually occur.
Semitendinosus Contracture
This also occurs in German Shepherds.
Clinical Features
Palpable bands are present, and prevent full extension of the stifle. The gait abnormality is similar to that described for gracilis contracture. The hock is rotated out and the stifle is rotated inwards, and the paw slaps down at the end of the stride.
Treatment
Surgical transection only resolves the lameness temporarily and is therefore not advised.
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Small Animal Orthopaedics Q&A 14 |
References
Pasquini, C. (1999) Tschauner's Guide to Small Animal Clinics Sudz Publishing
Slatter, D. (2002) Textbook of Small Animal Surgery Elsevier Health Sciences
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