[Medium-term follow-up outcomes of total hip arthroplasty for patients with ankylosing spondylitis]

To retrospectively study medium-term follow-up outcomes of total hip arthroplasty (THA) for patients with ankylosing spondylitis (AS).

From January 2000 to December 2008, 67 patients (88 hip joints) with AS were treated with all ceramic interface THA. And 55 patients (74 hips) were finally followed up. Among them, there were 30 males and 25 females, with an average age of 32.6 (ranged 19 to 58) years old. Sixty-one hips were treated with biological prosthesis and 13 hips were treated with hybrid prosthesis. Fifty-five patients were followed up at least 5 years, with an average of (75.2 +/- 8.6) months. Clinical symptoms and radiography information were evaluated after follow-up.

Harris hip score were significantly improved from 30.8 +/- 7.0 preoperatively to 85.2 +/- 5.5 at the last follow-up (P<0.01). The hip movement range increased from (21.2 +/- 8.5) degrees preoperatively to (142.0 +/- 10.2) degrees postoperatively (P<0.01). The 5-year survival of prosthesis was 95.9%. One patient were renovated because of internal wall broken caused by injury, 1 was renovated for infection, 1 was renovated for fracture arround femoral stem prostheses, and 1 was treated with conservative treatment by dislocation. Three cases with abnormal sound were cured with non-operation. 7 cases with heterotopic ossification were not treated, 2 cases with thigh pain received conservative treatment. Bone dissolve around prosthesis, loose and sink of femur and acetabulum prosthesis were occurred in other cases.

THA for the treatment of AS is a reliable method, which has a satisfied medium-term follow-up outcomes.