Heterotopic ossification after total hip arthroplasty: radiological comparison between a direct anterior approach without an orthopaedic table and a posterior approach.

Abstract

Heterotopic ossification (HO) occurs in almost ⅓ of total hip arthroplasties (THAs). A direct anterior approach (DAA) with an orthopaedic table is less likely to cause HO than a posterior approach. Without an orthopaedic table, the exposure of the femur requires additional soft tissue release. Soft tissue trauma leads to the production of HO inductors. Our study evaluated the incidence of HO 6 months after THA and compared the results between DAAs without an orthopaedic table and posterior approaches. Retrospectively, 164 consecutive, primary THAs were included: 76 through a posterior approach and 88 through a DAA. The main objective was to measure the presence of HO on pelvis radiography 6 months after surgery. The incidence of HO was significantly higher in the DAA group than in the posterior approach group (47.7% vs. 27.6%, respectively; p < 0.01). The overall incidence of HO was 38.4%. No significant difference was found between the 2 approaches regarding the severity of HO. No significant risk factor for HO was identified other than the surgical approach. In our study, the incidence of HO after THA in patients undergoing DAA without an orthopaedic table was higher than in patients undergoing a posterior approach after 6 months of follow-up. This result is closely related to the surgical trauma. It suggests that the minimally invasive feature of a surgical approach cannot be dissociated from the overall conditions in which it is performed.