Risk factors for heterotopic ossification following total hip arthroplasty in patients with ankylosing spondylitis

Liu Yong; Huo Shao-chuan; Zhou Chi; Tang Hong-yu; Chen De-long; Chen Jian-fa; Guo Hai; Deng Zhang-rong; Wang Hai-bin

doi:10.3969/j.issn.2095-4344.2017.11.001

Abstract：BACKGROUND: Heterotopic ossification (HO) is common following primary total hip arthroplasty (THA) in patients with ankylosing spondylitis (AS), which may cause certain influence on functional recovery.OBJECTIVE: To explore the risk factors for HO after primary THA in AS patients.METHODS: The clinical and radiological data from 87 patients (132 hips) with AS undergoing primary THA between June 2011 and December 2015 were retrospectively analyzed, and followed up for more than 6 months. The radiological information included preoperative and postoperative hip anteroposterior and lateral radiographs. The presence of HO surrounding the prosthesis was evaluated on the radiographs at the last follow-up and graded according to the Brooker classification. Risk factors for HO were divided into invariable factors (age, sex, course and with or without ankylosed hip) and variable factors (preoperative C-reactive protein level, preoperative erythrocyte sedimentation rate, intraoperative blood loss, operation time, prosthesis types and anesthesia methods) to determine the pertinent risk factors.RESULTS AND CONCLUSION: (1) Totally 43 hips (32.6%) were found to have developed into HO. (2) Invariable risk factors including male (P=0.029), preoperative ankylosed hip (P < 0.001), and course (P=0.029) increased the prevalence of HO. Among the variable risk factors, prolonged operation time (P=0.031) and general anesthesia (P=0.003)were associated with the increased occurrence of HO. Age, preoperative C-reactive protein level and erythrocyte sedimentation rate, intraoperative blood loss, and prosthesis types had no obvious correlation with HO. (3) These results suggest that to prevent the formation of HO following THA in AS, efforts to reduce the operation time and avoid general anesthesia should be considered.