Background: We are not aware of any large published studies regarding the intermediate to long-term results of shoulder arthroplasty performed for the treatment of osteoarthritis after instability surgery. Therefore, we reviewed the results of this procedure, the risk factors for an unsatisfactory outcome, and the rates of failure in our patients.

Methods: Between January 1, 1978, and December 31, 1997, thirty-three patients (thirty-three shoulders) with glenohumeral arthritis after instability surgery were treated with a shoulder arthroplasty at our institution. Two patients were excluded from the study: one died less than two years postoperatively, and one had not been managed by the senior surgeon. The remaining thirty-one patients, including twenty-one patients who had had a total shoulder arthroplasty and ten who had had a hemiarthroplasty, were followed for a minimum of two years (mean, seven years) or until the time of revision surgery. The mean age at the time of the shoulder arthroplasty was forty-six years.

Results: Shoulder arthroplasty was associated with significant pain relief (p < 0.001) as well as significant improvement in external rotation (from 4° to 43°; p < 0.001) and active abduction (from 94° to 141°; p < 0.001). There was not a significant difference between the hemiarthroplasty group and the total shoulder arthroplasty group with regard to postoperative external rotation, active abduction, or pain. According to a modification of the rating system of Neer et al., there were four excellent, two satisfactory, and four unsatisfactory results in the hemiarthroplasty group and three excellent, five satisfactory, and thirteen unsatisfactory results in the total shoulder arthroplasty group. Three patients in the hemiarthroplasty group and eight patients in the total shoulder arthroplasty group underwent revision surgery. The estimated survival of the components (and 95% confidence interval) was 97% (91% to 100%) at two years, 86% (74% to 99%) at five years, and 61% (42% to 86%) at ten years.

Conclusions: The data from the present study suggest that shoulder arthroplasty for the treatment of osteoarthritis of the glenohumeral joint following instability surgery in this relatively young group of patients provides pain relief and improved motion but is associated with high rates of revision surgery and unsatisfactory results due to component failure, instability, and pain due to glenoid arthritis.