Analysis Of Early And Medium Term Results Of Total Hip Arthroplasty For Treatment Of Ankylosing Spondylitis

Objective:To observe and study the early and medium stage results of total hip arthroplasty for treatment of ankylosing spondylitis,and carry on postoperative evaluation and analysis of efficacy. Methods:A retrospective analysis was made on the clinical data and image results from 37 patients(59 hips) who underwent THA for AS between December 2008 and December 2014 in our department.There were 31males(48hips) and 6 females(11hips),aged 21-70 years(mean,37.8 years).Preoperative Harris score was 8(4,20);preoperative WOMAC score was 83(60,89);preoperative Oxford hips score was 42(38,47);preoperative sum passive hip range of motion was 0(0,60);preoperative hip passive-flexion arc was 0(0,40).In 57 hips with passive flexion of less than 90°,32 hips had flexion contracture.Based on whether the preoperative sum passive hip range of motion was 0°,38 hips were divided into the ankylosed subgroup and 21 hips were divided into the non-ankylosed subgroup.The recovery of hip function including Harris score、WOMAC score、Oxford hips score、hip passive-flexion arc、sum passive hip range of motion was compared between preoperative and postoperative and between subgroups after operation and observing whether there will postoperative complications. Results:A total of 37 patients(59 hips)was followed up and the average follow-up period was 44.4 months(range,16 months-85 months).At last follow up,the average Harris score increased to 84(77,91),WOMAC score increased to 22(18,30),Oxford hips score increased to 9(7,12),hip passive-flexion arc increased to 90(85,100),and sum passive hip range of motion increased to 158(140,202),all showing significant differences when compared with preoperative ones( P < 0.05).There was no significant difference in the WOMAC score and Oxford hips score among 2 subgroups after THA at last follow up(P>0.05).Hip passive-flexion arc,sum passive hip range of motion and Harris score in ankylosed subgroup was significantly lower than non- ankylosed subgroup(P<0.05)at last follow up. In postoperative the rate of good and fine was 66.1% and only 2 hips have mild pain and the rest of hips have no pain.Based on a foul-class scale for subjective satisfaction,the patients were very satisfied, satisfied,dissatisfied and very dissatisfied with the results of THA in 32(86.49%),5( 13.51%),0,and 0 patients respectively.Main causes of dissatisfaction was pain in 1 patients,leg length discrepancy in 2 patients and limited flexion in 2 patients.Both 2 patients had flexion contracture.Among these 2 patients in the last follow up,hip passive-flexion arc was 90°in one patient and hip passive-flexion arc was 70° in another.Intraoperative complications including linear fractures of femoral calcar in 3 hips; postoperative complications including hip dislocation in 2 hip.X-ray films in the last follow up showed heterotopic ossification in 3 hips(Brooker I);radiolucent line(<2mm) in 3 acetabular components(zones I and II). Conclusion:Although the rate of good and fine was only 66.1% in postoperative,the satisfaction of patient was very high and there was no signs of loosening.THA is a feasible and effective treatment for AS with hip stiffness and the overall outcomes after THA are ideal with a good early and medium stage prosthetic survivorship,a high satisfaction of patients and a low complication rate,but improvement of postoperative hip joint mobility was poor when compared with THA.