• Liang Zhang, Hui Xu, Xiaozhong Guo, and Yixin Zhou.
• Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2014 Jan 1; 28 (1): 1-6.

ObjectiveTo investigate the clinical and radiographic results of total hip arthroplasty (THA) for the treatment of hip arthrosis in patients with ankylosing spondylitis (AS).MethodsA retrospective analysis was made on the clinical data from 131 patients (195 hips) who underwent THA for AS between September 2001 and August 2011 with a follow-up period of more than 2 years. There were 100 males (152 hips) and 31 females (43 hips), aged 17-69 years (mean, 33.7 years). The average interval between AS onset and THA was 13.7 years (range, 1-50 years). The left hips were involved in 30 cases, the right hips in 37 cases, and bilateral hips in 64 cases. Preoperative Harris hip score was 18.0 +/- 13.7; the sum passive range of motion was (36.2 +/- 51.2) degrees; and the hip passive-flexion arc was (23.4 +/- 32.6) degrees. In 175 hips with passive flexion of less than 90 degrees, 134 hips had flexion contracture. Based on preoperative X-ray films and CT scan, 195 hips were divided into the non-ankylosed subgroup (86 hips), fibrous ankylosed subgroup (43 hips), and bony ankylosed subgroup (66 hips); and the recovery of hip function was compared between subgroups after operation.ResultsIntraoperative complications included linear fractures of femoral calcar in 4 hips, fractures of acetabular posterior column in 1 hip, femoral shaft fractures in 2 hips, and iatrogenic sciatic nerve injury in 3 hips; postoperative complications included anterior dislocation in 2 hips. The average follow-up period was 51.3 months (range, 24-143 months). Bone healing was observed at 3-6 months after operation (mean, 3.9 months). At last follow-up, the average Harris hip score increased to 86.4 +/- 14.1, the sum passive range of motion increased to (202.0 +/- 28.0) degrees, and the hip passive-flexion arc increased to (93.2 +/- 15.3) degrees, all showing significant differences when compared with preoperative ones (P < 0.05). Based on a four-class scale for subjective satisfaction, the patients were very satisfied, satisfied, and not satisfied with the results of THA in 100, 80, and 15 hips respectively. X-ray films showed radiolucent line (< 2 mm) in 5 acetabular components (zones I and II); heterotopic ossification was observed in 49 hips after THA. There was no significant difference in the Harris hip score among 3 subgroups after THA at last follow-up (P > 0.05). At last follow-up, the degree of passive flexion in the fibrous ankylosed subgroup and bony ankylosed subgroup was significantly lower than that in the non-ankylosed subgroup (P < 0.05), and the sum passive range of motion in the fibrous ankylosed subgroup was significantly lower than that in the non-ankylosed subgroup (P < 0.05), but no significant difference was found in the other variables among the 3 sub groups (P > 0.05).ConclusionFor severe hip arthrosis in patients with AS, the overall outcomes after THA are ideal with a good midterm prosthetic survivorship, a low complication rate, and a high satisfaction of patients. However the hip function after THA is still less satisfactory. [Key words] Ankylosing spondylitis Total hip arthroplasty Hip function Mid-term result

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