3T-MRI-based age, sex and site-specific markers of musculoskeletal health in healthy children and young adults

Abstract

Objective: The aim of this study is to investigate the role of 3T-MRI in assessing musculoskeletal health in children and young people.

Design: Bone, muscle and bone marrow imaging was performed in 161 healthy participants with a median age of 15.0 years (range, 8.0, 30.0).

Methods: Detailed assessment of bone microarchitecture (constructive interference in the steady state (CISS) sequence, voxel size 0.2 × 0.2 × 0.4 mm3), bone geometry (T1-weighted turbo spin echo (TSE) sequence, voxel size 0.4 × 0.4 × 2 mm3) and bone marrow (1H-MRS, point resolved spectroscopy sequence (PRESS) (single voxel size 20 × 20 × 20 mm3) size and muscle adiposity (Dixon, voxel size 1.1 × 1.1 × 2 mm3).

Results: There was an inverse association of apparent bone volume/total volume (appBV/TV) with age (r = -0.5, P < 0.0005). Cortical area, endosteal and periosteal circumferences and muscle cross-sectional area showed a positive association to age (r > 0.49, P < 0.0001). In those over 17 years of age, these parameters were also higher in males than females (P < 0.05). This sex difference was also evident for appBV/TV and bone marrow adiposity (BMA) in the older participants (P < 0.05). AppBV/TV showed a negative correlation with BMA (r = -0.22, P = 0.01) which also showed an association with muscle adiposity (r = 0.24, P = 0.04). Cortical geometric parameters were highly correlated with muscle area (r > 0.57, P < 0.01).

Conclusions: In addition to providing deep insight into the normal relationships between bone, fat and muscle in young people, these novel data emphasize the role of MRI as a non-invasive method for performing a comprehensive and integrated assessment of musculoskeletal health in the growing skeleton.

Keywords: MRI; adiposity; bone; marrow; muscle.

Figure 1

Representative MRI and MRS analysis images. (A) Trabecular analysis; (B) cortical analysis, green and blue lines indicate endosteal and periosteal circumferences, respectively; (C) muscle analysis, ten manually drawn regions of interest around midthigh muscles; (D) MR image of the lumbar spine with the MRS voxel location (marked with a red square) placed in L3.

Figure 2

MRI-based musculoskeletal parameters for age and sex. Boxplots show the normative data of the MRI-based parameters and demonstrate the association of sex (white boxes for males and the grey for females) and age with these parameters. A significant sex difference within an age group is identified by ^*P < 0.05. ^**P < 0.01, ^***P < 0.001 Panels (A, B and C) show trabecular microarchitecture at proximal tibia, panels (D, E amd F) show trabecular microarchitecture at distal femur, panels (G to I) show cortical geometry parameters at femur, panels (J, K and L) show skeletal muscle parameters at femur and panel (M) shows marrow adiposity at lumbar vertebrae. AppBV/TV, apparent bone volume over total volume; appTbTh, apparent trabecular thickness; appTb N, apparent trabecular number; appTb Sp, apparent trabecular separation; MFF, mean fat fraction (muscle); muscle CSA, muscle cross-sectional area; RMA, residual muscle area; BMFF, bone marrow fat fraction.

Figure 3

Association between MRI-based musculoskeletal parameters and age. The scatter plots show MRI-based measures in males (white circles) and females (grey circles). Panels (A, B and C) show trabecular microarchitecture at proximal tibia, panels (D, E and F) show trabecular microarchitecture at distal femur, panels (G to I) show cortical geometry parameters at femur, panels (J, K and L) show skeletal muscle parameters at femur and panel (M) shows marrow adiposity at lumbar vertebrae. AppBV/TV, apparent bone volume over total volume; appTbTh, apparent trabecular thickness; appTb N, apparent trabecular number; appTb Sp, apparent trabecular separation; endos circ, endosteal circumference; perios circ, periosteal circumference; MFF, mean fat fraction (muscle); muscle CSA, muscle cross-sectional area; RMA, residual muscle area; BMFF, bone marrow fat fraction.

Figure 4

MRI-trabecular microarchitecture in tibia vs femur. AppBV/TV, apparent bone volume over total volume; appTbTh, apparent trabecular thickness; appTb N, apparent trabecular number; appTb Sp, apparent trabecular separation.