Full-Body Radiographic Imaging-Based Thigh Muscle Measurement for Sarcopenia

STUDY DESIGN: Multicenter retrospective cohort study of prospectively collected data. OBJECTIVE: Evaluate the impact of EOS-derived thigh muscle measurements as indicators of sarcopenia and their effect on compensatory mechanisms in adult spinal deformity (ASD) patients. SUMMARY OF BACKGROUND DATA: ASD patients frequently present with sarcopenia, the progressive loss of muscle strength and mass associated with worse postoperative outcomes. Routine EOS full-body radiographs allow opportunistic thigh muscle measurement without added cost or radiation. This study evaluated EOS-derived thigh and quadriceps thickness against clinical indicators of sarcopenia and their impact on compensatory mechanisms in ASD. METHODS: We retrospectively analyzed prospectively collected data from 24 U.S. and Canadian spine centers(2019-2024). Sarcopenia was defined using validated sex-specific EOS cutoffs. Patients were classified as sarcopenic only when both AP thigh and LAT quadriceps measurements fell below threshold. Clinical frailty scores, grip strength, 3-meter timed up and go(TUG), and epigenetic age were compared between sarcopenic(SARCO) and non-sarcopenic(NON-SARCO) patients. Multivariate regressions assessed associations between thigh measurements, sarcopenia status, and compensatory radiographic parameters. RESULTS: Among 540 ASD patients (mean age 60, 71% female), 61 (11.3%) were SARCO. SARCO patients had lower BMI(23.6 vs. 27.3 kg/m²), higher clinical frailty scores (3.4 vs. 3.0), and slower TUG (12.2 vs. 10.5s) (all P