Radiographic Thigh Muscle Measurements Are a Reliable Predictor of Psoas Area and Sarcopenia

Background: Sarcopenia is associated with falls, fractures, postoperative complications such as periprosthetic joint infections and dislocations, and early mortality. Although cross-sectional imaging is currently used to diagnose sarcopenia, inexpensive and widely available screening tests are needed. The goal of this study was to investigate whether measurements of thigh muscles made on radiographs can predict psoas muscle area and the presence of sarcopenia as determined on computed tomography (CT) scans. Methods: A retrospective radiographic review was performed to measure thigh muscle area in the coronal and sagittal planes using the differential in soft-tissue attenuation. Psoas muscle area on CT at L3 and L4 served as the gold standard for the diagnosis of sarcopenia. The correlation between thigh muscle and psoas muscle areas was determined, and multivariable models were developed to identify predictors of psoas muscle area and sarcopenia. Results: Four hundred and fourteen patients (252 male, 162 female) were identified. Seventy-six (18.4%) of the patients had an L4 psoas muscle area below the sex-specific cutoff value for sarcopenia. Patients with sarcopenia on abdominal CT had significantly smaller thigh muscle measurements on all radiographic views. The mean and standard deviation of the thigh muscle measurements were determined for the entire cohort and for patients with sarcopenia, as well as for adults aged 18 to 40 years without sarcopenia to provide normative reference values. The intraclass correlation coefficients were >0.8 for all radiographic measurements. The anteroposterior-view measurement of thigh muscle width and lateral-view measurement of quadriceps height were identified as independent predictors of both psoas muscle area and sarcopenia. Conclusions: Measurements of thigh muscle size made on radiographs can predict both psoas muscle area and sarcopenia. These measurements are a reliable and readily available screening tool to aid in the diagnosis and treatment of sarcopenia in the orthopaedic population. Level of Evidence: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.