Risk Factors of Heterotopic Ossification Following Total Hip Arthroplasty in Patients With Ankylosing Spondylitis.

This study was to identify the risk factors of heterotopic ossification (HO) after total hip arthroplasty (THA) in ankylosing spondylitis. We analyzed 47 hips (24 patients) with ankylosing spondylitis that underwent primary THA. The incidence of HO was 14.9%. The risk factors were divided into modifiable and nonmodifiable factors. Female gender (P=0.008), preoperative ankylosed hip (P<0.001), occurrence of HO in previous surgery (P=0.036) were nonmodifiable risk factors which increased the prevalence of HO. Of the various modifiable risk factors, elevated preoperative ESR (P=0.007), elevated preoperative CRP (P=0.004) and prolonged duration of surgery (P=0.014) were associated with increased occurrence of HO. Perioperative medical intervention to reduce inflammation (ESR and CRP) may help to decrease HO.