Therapeutic effect of artificial total hip arthroplasty on flexion regidity of hip joint in ankylosing spondylitis

OBJECTIVE To investigate the operative methods, clinical outcomes and complications of total hip arthroplasty (THA) in the treatment of patient with hip joint flexion rigidity due to ankylosing spondylitis (AS). METHODS From May 1992 to July 2004, 56 patients (32 left hips and 39 right hips) with AS received THA through a modified anterolateral approach, including 52 males (67 hips) and 4 females (4 hips) aged 17-48 years with an average of 35.5 years. All the hips were ankylosed in (43.1 +/- 7.2) degrees of flexion and 15 patients had bilaterally ankylosed hips. Preoperatively, Harris hip score was (42.6 +/- 5.3) points and all the hips were classified as stage IV according to the standard of American College of Rheumatology (ACR). And the course of disease was 3-11 years. RESULTS Intraoperatively, 1 patient suffering from proximal femur fracture due to severe osteoporosis was treated with titanium wire fixation, and the fracture was healed 6 weeks later. All the patients were followed up for 3-15 years (average 5.3 years). Postoperatively, 1 patient (1 hip) got subcutaneous soft tissue infection at 8 days, 1 patient (1 hip) got wound disunion at 11 days, 2 patients (2 hips) got infection at 11 months and 3 years, respectively. All the infections were healed after symptomatic treatment. The wounds of the rest 52 patients were healed by first intention without joint infections. The postoperative X-rays demonstrated that 4 hips (5.6%) had loose acetabulum prosthesis, 3 hips (4.2%) had loose femoral prosthesis and 5 hips had loose acetabulum and femoral prosthesis (7.0%), and the total loosening rate was 16.8%. Among which, 8 hips received revision resulting in satisfactory therapeutic effects, and the rest 4 hips had no further treatment. Fifteen hips (21.1%) had heterotopic ossification, which was relieved after taking nonsteroidal anti-inflamatory drugs. Harris hip score at final follow-up was (82.7 +/- 4.1) points, indicating there was a significant difference between before and after operation (P < 0.05). Ten hips were evaluated as excellent, 43 hips good, 14 hips fare, and 4 hips bad, and the excellent and good rate was 74.7%. CONCLUSION THA through the anterolateral approach is effective for the treatment of patient with hip joint flexion rigidity caused by AS.