The pathophysiological mechanism of increased fractures in young adults with type 1 diabetes mellitus (T1DM) is unclear. We conducted a case-control study of trabecular bone microarchitecture and vertebral marrow adiposity in young women with T1DM. Thirty women with T1DM with a median age (range) age of 22.0 years (16.9, 36.1) attending one outpatient clinic with a median age at diagnosis of 9.7 years (0.46, 14.8) were compared with 28 age-matched healthy women who acted as controls. Measurements included MRI-based assessment of proximal tibial bone volume/total volume (appBV/TV), trabecular separation (appTb.Sp), vertebral bone marrow adiposity (BMA), and abdominal adipose tissue and biochemical markers of GH/IGF-1 axis (IGF-1, IGFBP3, ALS) and bone turnover. Median appBV/TV in cases and controls was 0.3 (0.22, 0.37) and 0.33 (0.26, 0.4), respectively (p ¼ 0.018) and median appTb.Sp in T1DM was 2.59 (2.24, 3.38) and 2.32 (2.03, 2.97), respectively (p ¼ 0.012). The median appBV/TV was 0.28 (0.22, 0.33) in those cases with retinopathy (n ¼ 15) compared with 0.33 (0.25, 0.37) in those without retinopathy (p ¼ 0.02). Although median visceral adipose tissue in cases was higher than in controls at 5733 mm 3 (2030,11,144) and 3460 mm 3 (1808, 6832), respectively (p ¼ 0.012), there was no difference in median BMA, which was 31.1% (9.9, 59.9) and 26.3% (8.5, 49.8) in cases and controls, respectively (p ¼ 0.2). Serum IGF-1 and ALS were also lower in cases, and the latter showed an inverse association to appTbSp (r ¼ -0.30, p ¼ 0.04). Detailed MRI studies in young women with childhood-onset T1DM have shown clear deficits in trabecular microarchitecture of the tibia. Underlying pathophysiological mechanisms may include a microvasculopathy.

Irrespective of the presence of an underlying metabolic condition, young women display a negative relationship between MRI-measured BMA and DXA-based assessment of BMD. Furthermore, an association between BMA and visceral adiposity supports the notion of a common origin of these two fat depots.

Objective: 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 yrs (range, 8.0, 30.0). Methods: Detailed assessment of bone microarchitecture (CISS sequence, voxel size 0.2x0.2x0.4mm3), bone geometry (TSE sequence, voxel size 0.4x0.4x2mm3) and bone marrow (1H-MRS, PRESS sequence, single voxel size 20x20x20mm3), size and muscle adiposity (Dixon, voxel size 1.1x1.1x2mm3). 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 yrs 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.

Methods Background & Objective Conclusion High-resolution magnetic resonance imaging (hrMRI) can assess trabecular bone microarchitecture but the number of image slices required for reliable assessment is unclear. Our aim is to determine the number of images that needs to be processed to yield representative estimates of trabecular bone microarchitecture.

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