Abstract：Objective To investigate the clinical significance and effect of total hip arthroplasty (THA) in treatment of bony ankylosis of the hip in patients with ankylosing spondylitis (AS).Methods The study enrolled 23 patients (35 hips) undergone THA for bony ankylosis of the hip in AS between March 2008 and November 2012.Postoperative outcome was measured based on Harris hip score and Xray images.Results Preoperative Harris hip score of (27.6 ± 2.3) points increased to (86.7 ± 2.6)points postoperatively.Hip flexion and adduction deformity presented correction postoperatively.Total hip range of motion (flexion,adduction,abduction,and external rotation) improved from (45.7 ±5.3) o preoperatively to (206.9-±4.7) °postoperatively and mean hip flexion activity was 81 °.Hip activity achieved significant improvement and pain was relieved.X-ray films revealed proper position of prostheses without the presence of loosening or subsidence.Two patients (3 hips) experienced mild pain after a long period of walking.Four patients had heterotypic ossification including Brooker grade Ⅱ in one patient and Brooker grade Ⅰ in three.Conclusion THA is an effective treatment for bony ankylosis of the hip in AS,for it rebuilds joint function,relieves pain of the hip and improves patients' quality of life.
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