When the Subscapularis muscle is incompetent either due to a failure of its tendinous insertion to heal after previous surgery or following post-traumatic injury, the shoulder may be unstable.
Episodes of slipping out the front (subluxation) or dislocation are best treated by re-repair of the subscapularis tendon, but if that tendon is not repairable then a tendon transfer may be required.
The pectoralis major muscle is an ideal donor--routed deep to the conjoint tendon and inserted onto the greater tuberosity with the shoulder reduced and in external rotation. Stability and functional use can be restored with little risk of complication, by as early as 2 months after surgery.
