Anatomic shoulder arthroplasty as treatment for locked posterior dislocation of the shoulder.

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.