Total hip arthroplasty in ankylosing spondylitis. Total hip arthroplasty was performed on 29 hips in 19 patients diagnosed with ankylosing spondylitis over a 13-year period. The results were analyzed retrospectively with an average follow-up period of more than four years. Complete pain relief was achieved in 97%, and significant gains were made in ambulatory capacity. The limited gains in total range of motion (average improvement 75 degrees) were felt to be primarily due to the high incidence of Brooker Class III and IV myositis ossificans (23%) and long-standing soft tissue contractures. 