Effect of Oral Direct Factor Xa Inhibitors on the Prevalence of Hip Heterotopic Ossification Following Arthroplasty for Acute Femoral Neck Fracture: A Propensity Score-matched Cohort Study.

BACKGROUND

Heterotopic ossification (HO) is a common complication following hip arthroplasty that can limit hip range of motion. Oral direct factor Xa (FXa) inhibitors are commonly used anticoagulants after arthroplasty; however, they have a high risk of local bleeding and hematoma formation, which are significant triggers for HO formation. To our knowledge, there is no evidence regarding whether FXa inhibitors use will increase HO incidence following hip arthroplasty.

METHODS

In this retrospective propensity score-matched cohort study conducted at a national orthopaedic center in Shanghai (2019-2023), 944 patients undergoing hip arthroplasty for acute femoral neck fracture were evaluated. After exclusions and 1:1 matching (sex, age, body mass index, injury side, nonsteroidal anti-inflammatory drugs use), 362 patients were included in each group (FXa inhibitors vs. no FXa inhibitors). All patients received low-molecular-weight heparin during hospitalization and no other anticoagulants.

RESULTS

In the propensity score-matched population, the incidence of HO was 29.2% in the FXa inhibitors group and 15.7% in the no-FXa inhibitors group (7.7% and 2.4% for clinically important HO, respectively). Logistic regression analyses revealed that FXa inhibitors usage was significantly associated with a higher rate of HO (odds ratio, 2.22; 95% confidence interval, 1.55 to 3.20; P < 0.001) compared to no usage. Additionally, FXa inhibitors use was also linked to an increased risk of clinically significant HO (odds ratio, 3.29; 95% confidence interval, 1.59 to 7.48; P = 0.002). None of the baseline covariates demonstrated a significant influence on the association between FXa inhibitors use and HO incidence (P > 0.05 for all). Sensitivity analyses further corroborated these results.

CONCLUSIONS

Direct FXa inhibitors use may be a new risk factor of HO development following hip arthroplasty for acute femoral neck fracture.

LEVEL OF EVIDENCE: Therapeutic Level II.