A simplified scoring system for predicting total hip arthroplasty in hematologic cancer patients with osteonecrosis of the femoral head following allogeneic hematopoietic stem cell transplantation.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important treatment for patients with hematologic cancers. Osteonecrosis of the femoral head (ONFH) is a common complication following allo-HSCT, but factors that predict the need for surgery are unclear. In this retrospective study of ONFH patients after allo-HSCT at Peking University People's Hospital between 2009 and 2021, we aimed to describe the clinical features of ONFH after allo-HSCT and develop a simplified scoring system to identify patients at increased risk of requiring total hip arthroplasty (THA). Among 7707 allo-HSCT recipients, 164 (2.1%) developed ONFH, and 35 (21.3%) underwent THA. LASSO Cox regression identified ARCO stage (HR=2.679, 95% CI: 1.749-4.103, P<0.001) and limited hip mobility (HR=5.690, 95% CI: 2.548-12.708, P<0.001) as independent predictors for THA. A risk score (ARCO stages I- IV: 0, 20, 40, and 60 points, respectively; limited hip mobility: 35 points) stratified patients into low- (0-20 points), intermediate- (21-55 points), and high-risk (56-95 points) groups, which showed 1-year arthroplasty rates of 1.7%, 14.8%, and 52.9%, respectively (P<0.001). The scoring system showed excellent discrimination (bootstrap-corrected C-index=0.861), good calibration, and a positive net benefit in decision curve analysis. Inverse probability of treatment weighting sensitivity analysis yielded consistent estimates (ARCO: HR=2.439; limited hip mobility: HR=6.340). In conclusion, a two-variable scoring system incorporating ARCO stage and limited hip mobility was developed and internally validated to accurately predict the need for THA in patients with ONFH after allo-HSCT. The proposed risk score provides a practical tool for risk stratification and clinical decision-making.