Diagnostic Value of Mid-Thigh and Mid-Calf Bone, Muscle, and Fat Mass in Osteosarcopenia: A Pilot Study

Osteosarcopenia is defined as the concomitant occurrence of osteoporosis and sarcopenia. Current lack of consensus on sarcopenia definitions, combined with the low sensitivity and specificity of screening methodologies, has resulted in varying prevalences of sarcopenia, and consequently osteosarcopenia diagnosis. Previous research indicates that mid-thigh is a potential surrogate region for the assessment of bone, muscle, and fat mass in a single, efficient and low-radiation dual x-ray absorptiometry (DXA) scan. We hypothesized that muscle and bone mass measurements in the mid-thigh region can be used to evaluate bone and muscle health and function. A retrospective study was conducted on community-dwelling older subjects (> 65 y.o., n = 260) who were at risk of falls and fractures. Mid-thigh and mid-calf bone, lean muscle, and fat masses, as well as their association with muscle function, falls, and fractures were compared against conventional measures (hip/spine bone, appendicular lean, and gynoid/android fat masses). Mid-thigh bone, lean, and fat masses showed strong correlation with conventional measures. Mid-thigh lean mass showed similar associations with grip strength, gait speed, and timed up and go (TUG) test as appendicular lean mass. Appendicular, mid-thigh and mid-calf lean masses corrected for body mass index (BMI) showed stronger associations than when corrected for height. None of the indices were associated with fractures; but fat mass was invariably associated with falls. Those with falls and fractures history had lower bone and muscle mass at mid-thigh. Mid-thigh is a potential new surrogate to study bone, muscle, and fat mass in older people, with comparable ability in predicting muscle performance and falls.