Risk Factors for the Development of Heterotopic Ossification Following Acetabular Fractures

BACKGROUND: Heterotopic ossification (HO) following acetabular fractures is a common complication that may affect clinical outcomes. However, the effects of prophylactic treatment with nonsteroidal anti-inflammatory drugs or radiation therapy remain controversial. While several factors have been related to the development of HO, there is considerable uncertainty regarding their importance or effect size in the setting of acetabular surgery. Therefore, this systematic review aims to summarize the risk factors for HO following the operative fixation of acetabular fractures and clarify their interrelationships. METHODS: In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, PubMed, MEDLINE, Embase, and CINAHL databases were searched from inception to February 2021. Studies that assessed factors related to HO development among patients with operatively repaired acetabular fractures were included. Outcomes were risk factors and their effect size (p values, odds ratios, and 95% confidence intervals). RESULTS: Twenty-five studies and 1 conference abstract with a total of 3,940 patients were included. The following risk factors for HO were identified. Patient factors were increased body mass index, male sex, and increased age. Injury factors were intensive care unit (ICU) admission and length of stay, non-ICU hospitalization for >10 days, the need for mechanical ventilation for ≥2 days, abdominal and/or chest injuries, the number and type of associated fractures, traumatic brain injuries, T-type acetabular fractures, pelvic ring injuries, and hip dislocation. Care factors were a delay to surgery, extensile and posterior surgical approaches to the hip, trochanteric osteotomy, postoperative step-off of >3 mm, and a delay to prophylaxis following injury or surgery. Ethnicity, Injury Severity Score, cause of the fracture, femoral head injuries, degloving injuries, comminution, intra-articular debris, the type of bone void filler, gluteus minimus muscle preservation, prolonged operative time, and intraoperative patient position were not risk factors for developing HO. CONCLUSIONS: HO following operative fixation of acetabular fractures is not uncommon, with severe-grade HO associated with substantial disability. Careful consideration of the risk factor effect sizes and interdependencies could aid physicians in identifying patients at risk for developing HO and guide their prophylactic management. The results of this study could establish a framework for future studies. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.