Effects of tendon transfer on the canine scapulohumeral joint.

Surgical techniques for correcting medial or lateral instability of the scapulohumeral joint in conditioned research dogs were evaluated. Lateral instability was created by severing the lateral joint capsule and the tendon of insertion of the infraspinatus muscle. In 4 dogs, the tendon of origin of the biceps brachii muscle was then transferred to a position lateral to the greater tubercle in an effort to improve lateral stability. In 3 control dogs, lateral instability was induced, but attempt was not made to stabilize the joint. Medial instability was created by severing the tendon of insertion of the subscapularis muscle and the medial joint capsule. In 3 dogs, the tendon of origin of the biceps brachii muscle was transferred to a position under the lesser tubercle. In 2 dogs, a portion of the tendon of insertion of the supraspinatus muscle was transferred to a medial location. In 3 control dogs, attempt was not made to stabilize the joint. The control dogs (n = 6) demonstrated mild-to-moderate weight-bearing lameness for 7 to 14 days after surgical induction of joint instability and thereafter had normal limb usage. Dogs having had tendon transfer procedures recovered normal limb usage in 4 to 6 weeks and thereafter behaved normally. At necropsy, all joints appeared stable, and the surgical repairs were intact. A variety of joint surface abnormalities consistent with degenerative joint disease was observed, but no consistent pattern was assignable to any given surgical manipulation.