ESPE Abstracts

Background: The pathophysiological mechanism of skeletal fragility in Duchenne Muscular Dystrophy (DMD) is unclear.

Objective: To compare trabecular bone microarchitecture, cortical geometry, muscle area and fat fraction (FF) at distal femur and vertebral bone marrow adiposity (BMA) between DMD and controls.

Method: Bone-muscle and muscle FF were assessed using 3T MRI and Dixon technique. BMA was assessed using 1H-MRS. Results expressed as median (range). Cortical parameters were adjusted for femur length, muscle area, and age.

Results: Sixteen boys with DMD, aged 11.7 years (8.8, 18.9) treated with 5.9 years (1.8, 10.5) of glucocorticoid (GC) were compared with 22 healthy boys, aged 12.6 years (8.1, 17.0). Of 16 boys, nine (56%) were non-ambulant for 2.1 years (1.1, 5.3). Three previously had intravenous bisphosphonate and two had testosterone therapy. Of the 16 boys, vertebral fractures (VF) were observed in 5/16(31.3%), non-VF in 6/16(37.5%) and both VF and non-VF in one (6.3%). Muscle area in DMD and controls was 3000 mm² (889, 12295) and 5400 mm² (33234, 10847), respectively [P=0.0004]. MuscleFF in DMD and controls was 52%(3.5, 93.1) and 1.5%(0.4, 4.9), respectively [P<0.0001]. Apparent trabecular bone volume/total volume (appBV/TV) in DMD and controls was 0.54(0.51, 0.62) and 0.56(0.51, 0.60), respectively [P=0.0027]. Apparent trabecular thickness (appTb.Th) in DMD and controls was 0.25 mm (0.23, 0.30) and 0.28 mm (0.25, 0.31), respectively [P<0.0001]. Trabecular appBV/TV (r=0.35, P=0.19) and appTB.Th (r=−0.29, P=0.32) were not associated with GC duration. Boys with DMD had significantly lower cortical thickness (β=−0.67, 95% CI:−0.95 to −0.39) and area (β=−83.2, 95% CI:−113.0 to −53.5). Cortical thickness (r=0.01, P=0.97) and area (r=0.1, P=0.26) were not associated with GC duration. BMA in DMD and controls was 49.6%(28.7, 78.9) and 21.1%(8.0, 52.3), respectively [P<0.0001]. BMA was not associated with muscleFF (r=−0.20, P=0.56), appBV/TV (r=0.58, P=0.07), appTb.Th (r=−0.16, P=0.65), cortical thickness (r=0.27, P=0.42), and area (r=0.59, P=0.07) in DMD. Similarly BMA was not associated with muscleFF (r=−0.03, P>0.99), appBV/TV (r=−0.70, P=0.15)], appTb.Th (r=−0.19, P=0.73), cortical thickness (r=0.22, P=0.61) and area (r=0.24, P=0.58)] in controls.

Conclusion: This first study using high-resolution MRI identified several abnormalities in trabecular microarchitecture and cortical geometry in DMD. The lack of a relationship of bone microarchitecture and geometry to the GC duration raises the possibility that these deficits may not be solely due to GC. The novel finding of increased marrow adiposity in DMD and its role in osteoporosis requires further exploration.