Psoas muscle area and frailty in elderly trauma patients

Severe trauma in patients aged ≥ 65 years is increasingly frequent. Frailty and sarcopenia are major prognostic factors, yet Total Psoas Area (TPA), an objective imaging biomarker of muscle mass, is usually measured at a single time point. We investigated the relationship between frailty, initial TPA, and its post-traumatic dynamics. observational retrospective cohort study of patient's ≥ 65 years with severe trauma and ≥ 2 CT scans from the from a level 1 trauma center (2018-2023). TPA was measured on axial L3 CT slices and indexed to height². Pre-trauma frailty was assessed using the Clinical Frailty Scale (CFS). Longitudinal TPA changes were analyzed with a multivariable GEE model, testing interactions between age and frailty. Among 76 patients, 56 were non-frail (CFS 1-3) and 20 frail (CFS ≥ 4). Initial TPA did not differ between groups. Longitudinal analysis revealed divergent trajectories: TPA decreased more sharply with age in frail patients (-17.7 mm²/m²/year) compared with non-frail (-1.1 mm²/m²/year). This significant age × frailty interaction indicates that, at younger ages, TPA is comparable or even higher in frail patients, whereas at older ages it becomes substantially lower. Time since trauma had only a modest effect on TPA evolution. In the multivariable Cox model, non-frailty and higher GCS at admission were independently associated with lower mortality, while age, ISS, ASA score, and antiplatelet therapy were not significant. TPA showed a borderline association without reaching statistical significance. The model demonstrated good discrimination (C-index 0.812). In elderly trauma patients, TPA dynamics are strongly influenced by frailty and age, rather than initial TPA alone. Early assessment of frailty and muscle mass can refine risk stratification and guide personalized rehabilitation and nutritional strategies.