Risk Factors for Deep Infection and Conversion Total Hip Arthroplasty After Operative Combined Pelvic Ring and Acetabular Fractures

Objectives: To determine risk factors for deep infection and conversion total hip arthroplasty (THA) after operative management of combined pelvic ring and acetabular injuries. Design: Retrospective case control study. Setting: Level 1 trauma center. Patients and Intervention: We reviewed 150 operative combined pelvic ring and acetabular injuries at our institution from 2010 to 2019, with an average follow-up of 690 (90–3282) days. Main Outcome Measurements: Deep infection and conversion THA. Results: Patients who developed deep infection (N = 17, 11.3%) had higher rates of hip dislocation ( P = 0.030), intraoperative transfusion ( P = 0.030), higher body mass index (BMI) ( P = 0.046), increased estimated blood loss ( P < 0.001), more intraoperative units transfused ( P = 0.004), and longer operative times ( P = 0.035). Of the 84 patients with 1-year follow-up, 24 (28.6%) required conversion to THA. Patients requiring conversion THA were older ( P = 0.022) and had higher rates of transverse posterior wall fracture pattern ( P = 0.034), posterior wall involvement ( P < 0.001), hip dislocation ( P = 0.031), wall comminution ( P = 0.002), and increased estimated blood loss ( P = 0.024). The order of the pelvic ring versus acetabular fixation did not affect rates of conversion to THA ( P = 0.109). Multiple logistic regression showed that an increased number of intraoperative units transfused [adjusted odds ratio (aOR) = 1.56, 95% confidence interval (CI) = 1.16–2.09, P = 0.003] and higher BMI (aOR = 1.10, 95% CI = 1.01–1.16, P = 0.024) were independently associated with an increased odds of deep infection. Posterior wall involvement was independently associated with an increased odds of conversion THA (aOR = 5.73, 95% CI = 1.17–27.04, P = 0.031). Conclusions: Rates of deep infection and conversion THA after operative fixation of combined injuries were 11.3% and 28.6%, respectively. Higher average BMI and number of intraoperative units of blood transfused were independently associated with deep infection, whereas posterior wall involvement was independently associated with conversion to THA in these patients. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.