Evaluation of the Muscle-Bone Relationship in Children Using Magnetic Resonance Imaging

Abstract

PURPOSE: To examine the relationship between muscle mass in the midthigh and bone structure in the femur in 8 to 12 year-old children. METHODS: Twenty children (8 boys and 12 girls) 8 to 12 years of age and within the 10th and 90thage-based percentiles for height and weight participated in the study. Pubertal development was assessed by Tanner staging. Height and weight were determined using standard procedures. Magnetic resonance imaging (GE, 1.5 T) was used to determine muscle mass, cortical bone volume, cross-sectional moment of inertia (CSMI), section modulus (Z) and polar moment of inertia (J) at the level of the middle third of the femur (TR = 750, TE = 14, FOV = 16, 1 cm thick separated by 0.5 cm, 512x512 imaging matrix) and trabecular bone microarchitecture in the lateral half of the distal femur (TR = 30, TE = 4.5, FOV = 9 cm, 0.7 cm thick, 512 × 512 imaging matrix). RESULTS: Children were prepubertal (Tanner stage I; n = 18) or early pubertal (Tanner stage II; n = 2) and not different from the 50th percentile for height (48 ±21 %) and weight (48 ± 24 %). Midthigh muscle mass was strongly related to midfemur cortical bone volume, CSMI, J and Z (r = 0.91, 0.87, 0.88 and 0.89, respectively, P < 0.05). Midthigh muscle mass was not related to apparent trabecular number or separation in the distal femur (P > 0.05), however, it was moderately related to apparent trabecular bone volume and trabecular thickness (appTb.Th; r = 0.58 and 0.80, respectively, P < 0.05). When height and weight were taken into account, midfemur cortical bone volume, CSMI, J and Z and distal femur appTb.Th were still related to midthigh muscle mass (partial r = 0.68, 0.58, 0.59, 0.63 and 0.65, respectively, P < 0.05). CONCLUSION: Midthigh muscle mass is related to cortical and trabecular bone structure in the femur of children, however, the relationship to cortical bone structure is stronger. Supported by the National Osteoporosis Foundation.