Posterior glenohumeral instability

The posterior instability of the shoulder is a more difficult diagnostic and therapeutic challenge than the anterior instability. There are many etiologies and causes of posterior instability. Most studies in the literature are retrospective and yield a great variation in therapeutic recommendations. Generally it has to be separated in traumatic and atraumatic instabilities. Most of the traumatic dislocations are impaction fractures of the humeral head against the dorsal glenoid. Therapy is depending on the size of the humeral defect, the duration of dislocation and the functional demand of the patient. Therapeutic possibilities are closed reduction and fixation with a cast, open reduction and the transfer of the lower tubercule (McLaughlin's procedure), lifting of the defect and supporting with cancellous bone, subcapital rotational osteotomy or arthroplasty. The therapy of choice for atraumatic instability is a individualized rehabilitation program with strengthening and balancing of rotatator cuff muscles and scapular stabilizers. Psychologic abnormalities and emotional problems have to be recognized prior to any operative procedure. These patients are no operative candidates. Operative treatment of choice is the posterior capsular shift adressing the causative redundancy or laxity of the postero-inferior capsule. Posterior bony procedures as glenoid osteotomy or bone block transfers are indicated, if the pathologic geometry of the glenoid is primarily responsible for posterior instability. It is strongly recommended to combine them with a capsular shift to adress the secondary capsular redundancy.