[Effectiveness of total hip arthroplasty in the treatment of involved hips in patients with ankylosing spondylitis].

OBJECTIVE

To summarize the mid- to long-term effectiveness of total hip arthroplasty (THA) in the treatment of the involved hips in patients with ankylosing spondylitis (AS), and to investigate its influencing factors.

METHODS

Between March 1999 and May 2011, 32 patients (42 hips) with AS and involved hip underwent THA. There were 26 males and 6 females with a mean age of 39 years (range, 20-78 years). The disease duration ranged from 2 to 41 years, with a median of 10 years. Metal-on-polyethylene bearings were used in 19 hips, and ceramic-on-ceramic bearings in 23 hips. The diameter of prosthetic femoral head was 36 mm in 15 hips and was 28 mm in 27 hips; and all the prostheses were fixed biologically. The Harris score, visual analogue scale (VAS) score, and total range of motion (ROM) of the hip were compared between at pre- and post-operation to evaluate the effectiveness. The DeLee zone was used for describing acetabular prosthesis, the Gruen zone for describing femoral prosthesis, and the Brooker criterion for evaluating the heterotopic ossification.

RESULTS

Healing of incision by first intention was achieved in all patients after operation. There was no complication of anesthetic accident, infection, or neurovascular injury. Twenty-nine cases (39 hips) were followed up 5-17 years (mean, 9 years). Anterior dislocation of hip joint occurred in 2 hips of 24 hips (28 mm diameter), but did not in 15 hips (36 mm diameter). At last follow-up, the Harris score, VAS score, and the total hip ROM were significantly improved ( <0.05). The shorter the disease duration was, the higher postoperative Harris score and the greater postoperative total hip ROM would be ( <0.05); the bigger diameter of prosthetic femoral head was, the greater postoperative total hip ROM would be ( <0.05). All the acetabular components and femoral stems were well fixed at last follow-up. The osteolysis rate around the acetabular cup in the metal-on-polyethylene bearing group (50%, 9/18) was higher than that in the ceramic-on-ceramic bearing group (0, 0/21). No prosthetic loosening was observed in 2 groups. Seven hips were found to have heterotopic ossification, including 5 hips of Brooker grade I and 2 hips of Brooker grade II.

CONCLUSION

THA is an effective method to treat involved hips in patients with AS; especially for patients having shorter duration of the disease, THA shows better effectiveness when the bigger diameter of prosthetic femoral head and ceramic-on-ceramic bearing are used.