Risk Factors for the Development of Heterotopic Ossification After Conversion Total Hip Arthroplasty

BACKGROUND: Heterotopic ossification (HO) is an extensively studied complication of primary total hip arthroplasty (THA); however, there remains a paucity of research as to its incidence with conversion to THA from prior internal fixation of acetabular or hip fractures. METHODS: The authors conducted a single-center retrospective chart review of patients who underwent conversion to THA following open reduction internal fixation of acetabular fractures or intramedullary nailing of hip fractures, focusing on analysis of demographics, comorbidities, surgical details, prophylaxis methods, and radiographic Brooker classification. RESULTS: Among 75 hips, 25 (33.3%) developed progressive HO following conversion surgery. Of these 25 hips, 14 (56.0%) had prior HO following initial surgery, showing a statistically significant three-time increased risk of developing HO in patients who had prior ectopic bone about the operative hip compared to those who did not. Longer operative times at conversion surgery and African American race also led to a significantly increased risk for HO. There was no significant association observed between prophylaxis following initial surgery and the development of HO following conversion. CONCLUSIONS: Our results demonstrated a significantly higher risk of HO following conversion to THA in patients who had prior postoperative HO in the operative hip compared to those who did not, prolonged operative times, and African American race. Prophylaxis after initial surgery had no effect on HO development following subsequent conversion to THA. This study highlights the need for further research on HO following conversion THA and consideration of prophylactic HO treatment in high-risk patients.