Validation of Anthropometric Muscle Cross-Sectional Area Equation after Spinal Cord Injury

The purposes of this study were to cross-validate a previously derived anthropometric estimation equation specific to the spinal cord injury population and determine the ratios of absolute skeletal muscle cross-sectional area (CSA) for the quadriceps, hamstrings, and adductor muscle groups based on magnetic resonance imaging. The validation cohort consisted of eleven men with chronic (>1 yr. post injury) spinal cord injury (SCI). Ten individuals were classified as AIS A or B and one participant was classified as an AIS C. Significant correlations were found between the anthropometrically predicted CSAs and MRI-derived CSAs for the whole muscle including bone and intramuscular fat (r²=0.72, SEE=10.6 cm², P<0.001), absolute muscle excluding bone and intramuscular fat (r²=0.60, SEE=10.1 cm², P=0.005), and absolute quadriceps muscle (r²=0.67, SEE=5.5 cm², P=0.002). The quadriceps, hamstrings and the adductor muscle groups represented 52±5%, 23±6%, and 20±4%, respectively, of the absolute muscle CSA. Our results suggest that the utilization of a previously developed anthropometric equation is applicable to a different validation cohort with SCI. The equation has the ability to predict whole muscle CSA, absolute muscle CSA excluding bone and intramuscular fat, and absolute muscle CSA of the quadriceps in individuals with chronic SCI.