A simple linear alternative to necrotic volume for predicting collapse in osteonecrosis of the femoral head.

objectiveThe clinical use of magnetic resonance imaging-based volumetric measurement for osteonecrosis of the femoral head (ONFH) is restricted by its complexity. This study aimed to identify a practical computed tomography-based imaging parameter as a reliable alternative to necrotic volume and to evaluate its ability to predict femoral head collapse. MATERIALS AND

methodsThis retrospective study included 125 hips from 90 patients with ONFH and initial collapse of < 3 mm. Four-dimensional ratios were examined for their association with necrotic volume using generalized estimating equation models. The parameter showing the strongest association was determined by comparing models with the Quasi-likelihood Information Criterion (QIC). Receiver operating characteristic curve analysis was then used to establish a cutoff value for predicting a necrotic volume of ≥ 30%, the threshold defined as severe in the Steinberg classification. This prognostic value of this cutoff for collapse (> 3 mm) was tested with a robust Cox proportional hazards model.

resultsThe coronal vertical diameter ratio (CVDR) showed the strongest association with necrotic volume, yielding the lowest QIC. A CVDR cutoff of 51% predicted a large necrotic volume (AUC 0.931). Hips with a CVDR ≥ 51% had a significantly higher risk of collapse compared with those with a CVDR < 51% (HR, 6.07; 95% CI, 3.25-11.34; P < 0.001). This predictive value was consistent across all Japanese Investigation Committee type subgroups.

conclusionThe CVDR represents a simple and reliable alternative to volumetric assessment. A cutoff of approximately 51% provides clinically useful risk stratification, and incorporating lesion location may further enhance predictive accuracy.