Opportunistic lumbar vertebral CT attenuation is associated with intertrochanteric femur fracture occurrence and fracture instability in older adults.

OBJECTIVE: To evaluate the association between opportunistic lumbar vertebral computed tomography attenuation measurements and both intertrochanteric femur fracture occurrence and fracture instability in elderly patients presenting after low-energy trauma. MATERIALS AND METHODS: This retrospective study included 340 patients aged ≥ 65 years who underwent CT evaluation after low-energy trauma between January and December 2025. The study cohort consisted of 169 patients with intertrochanteric femur fractures and 171 consecutive patients without fracture. Mean Hounsfield unit (HU) was calculated from L1 to L3, and the mean value was recorded as Mean-HU. Fractures were classified according to the AO/OTA system and categorized as stable or unstable. Multivariable logistic regression and receiver operating characteristic analyses were performed, with bootstrap internal validation. As fracture status was already known at HU measurement, the design evaluates association with prevalent fracture rather than prospective prediction. RESULTS: Mean-HU was lower in patients with fractures than in those without (66.67 ± 32.33 vs 90.20 ± 42.32, p < 0.001) and in unstable versus stable fractures (61.77 ± 33.02 vs 76.56 ± 28.69, p = 0.005). Each 10-HU decrease in Mean-HU was independently associated with fracture occurrence (OR, 1.20; 95% CI, 1.11-1.29, p < 0.001) and instability (OR, 1.13; 95% CI, 1.01-1.28, p = 0.039). Mean-HU showed moderate discrimination for fracture occurrence (AUC, 0.663), which improved with addition of sex and BMI (AUC, 0.725; DeLong p = 0.005). Discrimination for instability was modest (AUC, 0.627). CONCLUSION: Opportunistic lumbar vertebral HU was independently associated with intertrochanteric fracture occurrence and instability in elderly patients with low-energy trauma. However, its discriminatory performance was modest, particularly for instability, and its clinical utility requires prospective validation.