Endocrine Abstracts

Background: Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disorder associated with osteoporosis and increased fracture risk. Dual-energy X-ray absorptiometry (DXA) is the gold standard for assessing bone density but can be limited in DMD by scoliosis and positioning challenges. The Bone Health Index (BHI), derived from automated analysis of hand radiographs using BoneXpert, may offer a practical alternative by estimating cortical geometry from the metacarpals. To date, no longitudinal data on BHI in DMD have been reported.

Methods: We conducted a retrospective longitudinal study of 34 boys with DMD who underwent same-day DXA scans and left-hand radiographs at two timepoints. DXA outcomes included lumbar spine bone mineral apparent density (LS-BMAD) Z-scores and total body less head bone mineral content adjusted for bone area (TBLH-BMC) Z-scores. Results are reported as median (range); P < 0.05 was considered significant.

Results: At baseline, BHI Z-scores correlated positively with TBLH-BMC (r = 0.65, P < 0.0001) and LS-BMAD Z-scores (r = 0.46, P < 0.05). At baseline, median age was 10.0 years (4.6 to 17.2); 79% were ambulant. All were on glucocorticoids (33 on daily regimens), with 12% on bisphosphonates. At follow-up (median age 13.6 years), ambulation declined to 47%, all remained on glucocorticoids (32 daily), and 56% were on bisphosphonates. Median BHI Z-scores declined from –1.5 (–3.6 to +0.9) to –2.3 (–5.5 to +0.6) (P < 0.001), and TBLH-BMC Z-scores decreased from –1.5 (–2.3 to +1.4) to –1.8 (–3.2 to –0.8) (P < 0.001). In contrast, LS-BMAD Z-scores increased from –1.3 (–3.0 to +2.7) to –0.8 (–3.5 to +4.3) (P = 0.038), driven by improvement in the subgroup (n = 16) who commenced bisphosphonates post-baseline (P = 0.002). No change was seen in those already on or never on bisphosphonates.

Conclusion: BHI Z-scores deteriorated over time in boys with DMD, mirroring changes in TBLH-BMC Z-scores and reflecting disease progression and loss of ambulation. Unlike LS-BMAD, BHI did not improve with bisphosphonate therapy, but may be useful for tracking bone health prior to treatment initiation. Further research is needed to evaluate the utility of BHI Z-scores to predict fractures in DMD.