Avulsion of the extensor digitorum longus muscle in the dog: a report of four cases.

Ill Four similar cases of avulsion of the extensor digitorum longus muscle in large breed dogs are described. Diagnosis was made after a radiological examination of the stifle joint and in each case the avulsed fragment was successfully retained in position using lag screws. INTRODUCTION The extensor digitorum longus muscle of the dog arises on the lateral condyle of the distal femur, traverses the femoro-tibial joint and passes beneath the Tibialis cranialis on the anterolateral aspect of the tibia. The long belly of the muscle terminates just above the tibia-tarsal joint and the tendon continues beneath two transverse fascia! bands across the joint. The tendon splits into four and each branch inserts on a distal phalanx. The action of the muscle is thus extension of the digits and flexion of the tarsus. The muscle has a similar course and action in all the domesticated animals but in man it originates on the proximal tibia. There are no documented cases of lesions specifically involving this muscle and this report describes cases of avulsion of the origin of the muscle in a Dober­ mann Pinscher, a Weimaraner, an Irish Wolfhound and a Russian Wolfhound. CASE 1 A 5-month-old male Dobermann Pinscher became lame in the left hindleg when it slipped on an icy pavement. The local veterinary surgeon examined him one day later and found a gross synovial effusion in the left stifle joint. The joint was