The goal of this study was to assess the clinical and radiological outcome of bipolar shoulder prosthesis in twelve shoulders with rheumatoid arthritis (RA) and irreparable rotator cuff tears.
The follow-up was more than five years (range 2-9 years). In addition, in order to investigate the effect of rheumatoid arthritis on outcome, results were compared with ten bipolar shoulder prostheses implanted for osteoarthritis with massive rotator cuff tears.
The mean preoperative Constant score was 16.9 points with 2.6 points for pain, 4.2 points for activity, 9.5 points for motion and 0.6 points for force. The preoperative active motion was 63.8 degrees for forward flexion, 45 degrees for abduction and 12 degrees for active external rotation. At last follow-up, the average Constant score was 39.4 points with 10.7 points for pain, 10.8 points for activity, 13.8 points for motion and 4.1 points for force. Regarding the active motion, mean forward flexion was 83.7 degrees, 70.4 degrees for abduction and 29.1 degrees for external rotation. The complication rate was low, mainly superior migration due to infraspinatus tear and glenoid wear. Satisfactory deltoid arm level was achieved in all patients and no loosening was observed. Preoperative and postoperative scores of the rheumatoid group were not significantly different from the arthritis group (p<0.001).
Our findings suggest that bipolar shoulder prosthesis provides a viable replacement alternative in RA combined with massive rotator cuff tear with a low rate of complication. Bipolar shoulder prosthesis demonstrates no clear superiority over conventional hemiarthroplasty regarding improved motion and glenoid wear. In addition, no significant difference with arthritis was observed (p<0.05), assuming that outcome depends principally on the preoperative condition of the rotator cuff.
Some massive tears involving the subscapularis tendon can lead to anterior recurrence after bipolar shoulder prosthesis. They might be a limit to the procedure and require a reversed shoulder prosthesis or a glenohumeral arthrodesis.