Risk factors associated with prevalent vertebral fractures in Duchenne muscular dystrophy.

Patients with Duchenne muscular dystrophy (DMD) have a high fracture burden due to progressive myopathy and steroid-induced osteoporosis. This study in males with DMD showed that markers of systemic glucocorticoid exposure including shorter stature, greater bone age delay, and lower lumbar spine bone mineral density were associated with spine fragility. INTRODUCTION: Fragility  fractures are frequent in DMD. The purpose of this study was to identify clinical factors associated with prevalent vertebral fractures (VF) in boys, teens/young adults with Duchenne muscular dystrophy (DMD). METHODS: This was a cross-sectional study of males aged 4-25 years with DMD. VF were evaluated using the modified Genant semi-quantitative method on T4-L4 lateral spine radiographs. Areal bone mineral density (aBMD) was measured at the lumbar spine (LS) and used to estimate volumetric BMD (vBMD). Clinical factors were analyzed for their association with the Spinal Deformity Index (SDI, the sum of the Genant grades). RESULTS: Sixty participants were enrolled (mean age 11.5 years, range 5.4-19.5). Nineteen participants (32%) had a total of 67 VF; 23/67 VF (34%) were moderate or severe. Participants with VF were shorter (mean height Z-score ± standard deviation: - 3.1 ± 1.4 vs. - 1.8 ± 1.4, p = 0.001), had longer glucocorticoid exposure (mean duration 6.0 ± 3.3 vs. 3.9 ± 3.3 years, p = 0.027), greater bone age (BA) delay (mean BA to chronological age difference - 3.2 ± 3.4 vs. - 1.3 ± 1.2 years, p = 0.035), and lower LSaBMD Z-scores (mean - 3.0 ± 1.0 vs. - 2.2 ± 1.2, p = 0.023). There was no difference in LSvBMD Z-scores. Multivariable Poisson regression showed that every 0.1 mg/kg/day increment in average glucocorticoid daily dose was associated with a 1.4-fold SDI increase (95% confidence interval: 1.1-1.7, p = 0.013). Greater BA delay (p < 0.001), higher weight Z-score (p = 0.004), decreased height Z-score (p = 0.025), and lower LSvBMD Z-score (p = 0.025) were also associated with SDI increase. CONCLUSION: Readily measurable clinical variables were associated with prevalent VF in males with glucocorticoid-treated DMD. These variables may be useful to identify candidates for primary osteoporosis prevention after glucocorticoid initiation.

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.