Anatomic Shoulder Arthroplasty as Treatment for Locked Posterior Dislocation of the Shoulder

Abstract

Chronic locked shoulder dislocations account for 2% to 5% of all shoulder dislocations. There is little information regarding the mid-term to long-term results of anatomic shoulder arthroplasty for treatment of this problem. Thirty-two shoulder arthroplasties were performed in thirty-two patients who had chronic locked posterior dislocation of the shoulder. Eighteen patients were treated with a hemiarthroplasty and fourteen, with a total shoulder arthroplasty. Inclusion criteria included moderate or severe pain and functional limitations. Structural indications included an impression fracture involving ≥45% of the humeral head, fibrosis of the articular cartilage, and/or severe osteopenia of the humeral head. When one-third or more of the glenoid was devoid of articular cartilage, a glenoid component was placed. All patients were followed for a minimum of two years (mean, 8.2 years) or until a reoperation. The operations led to pain relief, with the median pain score decreasing from 4 (on a 5-point scale) preoperatively to 3 postoperatively (p < 0.01), and improvement in shoulder external rotation, from a preoperative median of -15° to a postoperative median of 50° (p < 0.001). Instability recurred in three patients in the early postoperative period. Nine patients underwent a reoperation for various reasons. According to a modified Neer rating system, there were four excellent, fifteen satisfactory, and thirteen unsatisfactory outcomes. Although shoulder arthroplasty for locked posterior dislocation can provide pain relief, improved shoulder external rotation, and a low risk of recurrent instability, the overall rate of satisfaction is inferior to that following anatomic arthroplasty for treatment of glenohumeral osteoarthritis.