Bone health measures in glucocorticoid-treated ambulatory boys with Duchenne muscular dystrophy

- We examined bone health measures in 292 glucocorticoid-treated ambulant boys with DMD.
- Bone health indices in ambulant boys with DMD worsened with declining motor function.
- Bone mineral content of the whole body by DXA may be a valuable measure in boys with DMD.
- Bone mineral density of the lumbar spine by DXA is subject to limitations in boys with DMD.
- Bone health evaluation in boys with DMD should include routine imaging for spine fractures.

Osteoporosis is a major problem in boys with Duchenne Muscular Dystrophy (DMD), attributable to muscle weakness and glucocorticoid therapy. Consensus regarding bone health assessment and management is lacking. Lumbar spine areal bone mineral density (defined as bone mass per area of bone) by dual-energy X-ray absorptiometry (DXA) is frequently the primary measure used, but has limitations for boys with DMD. We retrospectively studied 292 ambulant glucocorticoid-treated boys with DMD categorized by functional mobility score, FMS 1, 2 or 3. We assessed DXA whole body and lumbar spine areal bone mineral density and content Z-scores adjusted for age and height, lateral distal femur areal bone mineral density Z-scores, frequency of fractures, and osteoporosis by International Society for Clinical Densitometry 2013 criteria. Whole body and femoral DXA indices decreased, while spine fractures increased, with declining motor function. Lumbar spine areal bone mineral density Z-scores appeared to improve with declining motor function. Bone mineral content Z-scores were consistently lower than corresponding bone mineral density Z-scores. Our findings highlight the complexity of assessing bone health in boys with DMD. Bone health indices worsened with declining motor function in ambulant boys, but interpretation was affected by measure and skeletal site examined. Whole body bone mineral content may be a valuable measure in boys with DMD. Lumbar spine areal bone mineral density Z-score as an isolated measure could be misleading. Comprehensive management of osteoporosis in boys with DMD should include vertebral fracture assessment.