PAPER 159: INSTABILITY AFTER REVERSE SHOULDER ARTHROPLASTY

Abstract

Purpose: Reverse shoulder arthroplasty (RSA) is becoming increasingly common for a variety of indications. The most common postoperative complication is instability. The objectives of this study are to describe causes of RSA instability and preventive and treatment recommendations.

Method: All members of the American Shoulder and Elbow Society were asked for cases of RSA instability. We retrospectively reviewed 52 cases in 52 patients, performed by 13 surgeons. The mean age was 67.5 years (range, 36–83). The mean follow-up was 32.7 months (range, 3–43).

Results: The etiology included: cuff tear arthropathy (14 patients); revision arthroplasty (13 patients); fracture sequelae (6 patients); and other (6 patients). Twenty-four patients had previous shoulder surgery. All patients had a deltopectoral approach. Anterior deltoid deficiency was noted in 3 cases. Subscapularis insufficiency was noted in 27 cases. Humeral component dissociation occurred in 2 patients. The instability was: anterior (27 patients); posterior (5 patients); or inferior (3 patients). Instability occurred: in the first 48 hours (10 cases); between 2 to 30 days (13 cases); or after one month (12 cases). Causes of instability included: inadequate soft-tissue tension (23 patients); a large antero-inferior release (22 patients); subscapularis insufficiency (7 patients); hematoma (2 patients); trauma (2 patients), deltoid insufficiency (2 patients); glenosphere malposition (2 patients); acromion fracture (2 patients); and other (4 patients). Initial treatment included: non-operative (6 patients); closed reduction (23 patients); open reduction (3 patients); and revision arthroplasty (11 patients). Final outcomes included: persistent instability (7 patients); humeral revision (19 patients); glenoid revision (one patient); hemiarthroplasty (3 patients); and resection arthroplasty (2 patients).

Conclusion: Main causes of RSA instability include inadequate soft tissue tension, large anteroinferior release and subscapularis insufficiency. Preventive measures include careful patient selection, restoration of humeral length, minimizing anteroinferior releases, maximizing soft-tissue tension, maintaining or restoring subscapularis integrity, immobilization in the case of subscapularis insufficiency and use of a postoperative drain. Treatment recommendations include restoration of humeral length, soft-tissue retensioning and prolonged immobilization.