Risk Factors Associated with Incident Vertebral Fractures in Steroid-treated Males with Duchenne Muscular Dystrophy

Purpose: Prevention of fractures is an unmet need in glucocorticoid (GC)-treated Duchenne muscular dystrophy. This study explored factors associated with incident vertebral fractures (VFs) to inform future fracture prevention efforts. Methods: VFs were evaluated prospectively at study baseline and 12 months on lateral spine radiographs in participants aged 4 to 25 years with Duchenne muscular dystrophy. Clinical factors were analyzed for their association with the change in Spinal Deformity Index (sum of the Genant-defined VF grades from T4 to L4) between baseline and 12 months. Results: Thirty-eight males were evaluated (mean +/- SD age at baseline 11.0 +/- 3.6 years; mean +/- SD GC duration at baseline 4.1 +/- 3.1 years; 74% ambulatory). Nine of 38 participants (24%) had 17 incident VFs, of which 3/17 VFs (18%) were moderate/severe. Participants with 12-month incident VF had lower mean +/- SD baseline lumbar spine areal bone mineral density Z-scores (-2.9 +/- 1.0 vs -1.9 +/- 1.1; P =.049) and lower total body less head areal bone mineral density Z-scores (-3.1 +/- 1.2 vs -1.6 +/- 1.7; P =.036). Multivariable linear regression showed that at least 1 VF at baseline (P <.001), a higher number of antecedent non-VF (P <.001), and greater bone age delay at baseline (P =.027) were significant predictors of an increase in the Spinal Deformity Index from baseline to 12 months. Conclusion: The observation that >= 1 prevalent VF and/or non-VF were the strongest predictors of incident VFs at 12 months supports the need for prevention of first fractures in this high-risk setting. Bone age delay, a marker of GC exposure, may assist in the prioritization of patients in efforts to prevent first fractures.