Total hip replacement in patients with ankylosing spondylitis with involvement of the hip.

Twenty-three patients with ankylosing spondylitis underwent thirty-four total hip arthroplasties with an average follow-up of 42.5 months. The over-all results were rated good in all but two patients. Significant benefit was obtained in posture and function so that these patients could be gainfully employed. Improvement in the sum total range of motion was 96.1 degrees in patients with bone ankylosis and 150 degrees in those with fibrous ankylosis. The preoperative sum total range of motion was maintained or improved in hips with a painful arc of motion. Most of the limited motion in patients with ankylosed hips was due to myositis ossificans.