Arthroplasty is the treatment of choice for severely damaged humeral heads in chronic locked posterior dislocation of the shoulder. We retrospectively reviewed the results of 12 shoulder arthroplasties (11 patients) between 1999 and 2005. Mean follow-up was 37.4 +/- 16.8 months. Mean postoperative Constant score (CS) was 59.4 +/- 21.6 (normative age and gender-related CS 67.1 +/- 24). There was a significant improvement in range of motion for flexion, abduction and external rotation. There was negative correlation (Pearson's coefficient) between the related CS and number of previous operations, pain and duration of symptoms. One patient underwent revision surgery 36 months postoperatively with polyethylene insert exchange. There were two patients with mild and one with severe migration of the humeral head. Shoulder arthroplasty resulted in good midterm results for this patient group with benefits for range of motion, pain and patient satisfaction.