Stabilisation of medial shoulder instability by imbrication of the subscapularis muscle tendon of insertion

OBJECTIVES: To evaluate the efficacy of subscapularis muscle tendon of insertion imbrication as a treatment for medial shoulder instability. METHODS: Medial shoulder instability was diagnosed in five dogs. Initial management with medical or arthroscopic treatment failed to fully resolve lameness in four of the cases. Each case was treated by subscapularis muscle tendon of insertion imbrication. An anatomical model of medial shoulder instability was used to assess the effect of subscapularis muscle tendon of insertion imbrication on the angle of abduction of the shoulder. RESULTS: In clinical study, subscapularis muscle tendon of insertion imbrication was performed in five cases. Lameness resolved fully in three cases and partially in two cases. In cadaver study, transection of either the subscapularis muscle tendon of insertion or the subscapularis muscle tendon of insertion and medial glenohumeral ligament significantly increased the angle of abduction. Imbrication of the subscapularis muscle tendon of insertion significantly reduced the angle of abduction. No significant differences were noted between the angle of abduction of normal shoulder and the shoulder with medial shoulder instability treated by subscapularis muscle tendon of insertion imbrication. CLINICAL SIGNIFICANCE: Subscapularis muscle tendon of insertion imbrication is a moderately effective procedure for the management of medial shoulder instability unresponsive to medical and/or arthroscopic management. The angle of abduction of the shoulder was returned to normal in model of medial shoulder instability, following subscapularis muscle tendon of insertion. Subscapularis muscle tendon of insertion imbrication provides a relatively simple method of treating medial shoulder instability in dogs.