Relationship between CT-derived Muscle Parameters and Bone Attenuation in the Indian Population: A Retrospective Observational Study

Introduction: Psoas muscle area and attenuation provide a practical, reproducible marker for overall skeletal muscle health and can be readily measured on routine abdominal Computed Tomography (CT). CT-derived femoral neck and lumbar vertebral attenuation have been proven as quantitative, reproducible imaging biomarkers of bone quality, which help in the detection and screening of osteoporosis. Thus, the combined assessment of CT-derived muscle parameters and bone attenuation may assist radiologists and clinicians in characterising the musclebone unit, and improving risk stratification for fractures, frailty, and adverse clinical outcomes. Aim: To measure the psoas muscle area and attenuation, femoral neck attenuation, and lumbar vertebral attenuation across various age groups on plain CT abdomen scans and to assess the correlation between these parameters, age, and gender in the Indian population. Materials and Methods: This retrospective observational study was conducted in the Radiology Department at Madha Medical College and Research Institute, Chennai, Tamil Nadu, India from January 2025 to June 2025. Analysis was done from July 2025 to August 2025. The study included consecutive CT abdomen studies of 796 patients (467 males and 329 females) in the age range of 11-90 years. The variables that were measured included the psoas area, psoas attenuation, Hounsfield Unit Average Calculation (HUAC), vertebral attenuation, and femoral neck attenuation. The association between age and outcome variables was assessed by Pearson’s correlation coefficient at a 95% confidence interval. Results: The overall mean age was 43.8±16.176 years. All the variables showed a decrease with increasing age, with a statistically significant decline (p-value <0.01) noted in the psoas muscle area and attenuation, femoral neck attenuation, and vertebral attenuation (particularly L3 and L4 vertebrae). Males exhibited significantly higher attenuation values at all vertebral levels (L1-L4), with a mean lumbar HU of 192.88±49.43 compared to 169.09±61.69 in females (p-value <0.001). Males showed a significantly larger psoas cross-sectional area (8.41±2.75 cm²) compared to females (4.32±1.42 cm², p-value <0.001). The strongest correlation was found between the lumbar attenuation and the femur attenuation (r=0.690) and between the psoas attenuation and the HUAC (r=0.668). Weak correlation was found between the psoas area and the HUAC (r=0.095), all statistically significant (p-value <0.01). Conclusion: The muscle and bone parameters measured on CT in the present study showed good correlation and these simple measurements on CT scans can be used in the future as prognostic indicators for osteosarcopenia, which may significantly assist in the treatment plan and prognostication of patients, especially in areas where Dual-energy X-Ray Absorptiometry (DXA) scan is unavailable.