Association Between Sonographic Thigh Adjustment Ratio and Femoral-Neck Bone Mineral Density in Older Adults with Hip Fracture

Background and Objectives: Assessment of sarcopenia in older adults with acute hip fracture is challenging because standard imaging and functional tests are often impractical during the early post-fracture period. This exploratory study evaluated the cross-sectional association between the Sonographic Thigh Adjustment Ratio (STAR) and femoral-neck bone mineral density (BMD) in older adults with hip fracture; it was not designed to evaluate the diagnostic accuracy or prognostic performance of STAR. Materials and Methods: This prospective cross-sectional study included 35 patients aged ≥65 years admitted with hip fragility fractures. Sarcopenia was operationally classified using an ISarcoPRM-based approach combining low handgrip strength with low STAR values. Anterior thigh muscle thickness was assessed by ultrasound, and STAR was calculated by dividing muscle thickness by body mass index (BMI). Femoral-neck BMD and T-scores were measured using dual-energy X-ray absorptiometry. Associations between continuous STAR values and bone-density measurements were evaluated using correlation analyses. Results: Sarcopenia was operationally classified in 54.3% of patients, and 48.6% were classified in the exploratory lower-BMD group (femoral-neck T-score ≤ −2.0). STAR was positively correlated with femoral-neck BMD (r = 0.415, p = 0.013) and femoral-neck T-score (r = 0.356, p = 0.036). Because low STAR and low handgrip strength were components of the operational sarcopenia definition, between-group differences in these variables were not interpreted as independent validation of STAR. Conclusions: In this small exploratory cohort, STAR was associated with femoral-neck bone-density measurements. These cross-sectional findings do not establish diagnostic accuracy, screening performance, or prognostic value; such applications require validation against accepted reference standards in larger prospective studies.