A Comprehensive Evaluation of Thigh Mineral-Free Lean Mass Measures Using Dual Energy X-Ray Absorptiometry (DXA) in Young Children

This study aimed to (1) demonstrate the intra- and interrater reliability of quadriceps (QUADS) and hamstring (HAMS) mineral-free lean (MFL) mass measures using DXA scanning, (2) determine the association of total thigh MFL mass measures with MFL mass measures of the hamstrings and quadriceps combined and (3) analyze the association between total thigh MFL mass and total body MFL mass measures. A total of 80 young children (aged 5 to 11 yrs) participated and unique regions of interest were created using custom analysis software with manual tracing of the QUADS, HAMS, and total thigh MFL mass measures. Repeated-measure analysis of variance was used to determine if there were significant differences among the MFL measures while intraclass correlation coefficients (ICC), coefficients of variation (CV), and regression analysis were used to determine the intra- and interrater reliability and the explained variance in the association among MFL mass measures. The right interrater QUADS MFL mass was the only significant group mean difference, and ICCs between (≥0.961) and within (≥0.919) raters were high for all MFL measures with low variation across all MFL measures (≤6.13%). The explained variance was 92.5% and 96.3% for the between-investigator analyses of the right and left total thigh MFL mass measures, respectively. Furthermore, 97.5% of the variance in total body MFL mass was explained by the total thigh MFL mass. DXA MFL mass measures of the QUADS, HAMS and total thigh can be confidently used in young children and may provide an alternative to CT or MRI scanning when assessing changes in MFL cross-sectional area or volume measures due to disease progression, training and rehabilitative strategies.