Vertebral fractures and muscle function in glucocorticoid-treated individuals with Duchenne muscular dystrophy: a cohort study

Brief rationale: To investigate vertebral fracture and risk factors in DMD. MAIN RESULTS: Vertebral fractures were found in 42% of subjects with an increased risk associated with low TB BMD, early steroid exposure and low BMI. Significance of the paper: Bone health monitoring should start early, regardless of functional status. PURPOSE: To describe the prevalence of vertebral fractures (VFs) in Duchenne Muscular Dystrophy (DMD) and to establish the role of several risk factors, focusing on ambulatory status and functional motor scores (Performance Upper Limb, North Star Ambulatory Assessment) not previously assessed. METHODS: We recorded the number and site of fractures together with anthropometric, radiological (total body bone mineral density (TB BMD) Z-scores measured by Dual Energy X-ray Absorptiometry (DXA)), and functional scales. Logistic and linear regression analyses were conducted to identify factors associated with prevalent VFs and predictors of Spinal Deformity Index (SDI). RESULTS: Of the 149 individuals (7-26 years) studied, 62 (42%) had VFs. These were equally present in ambulant and non-ambulant individuals (41 vs 42%) and were not associated with functional scores. The TB BMD Z-score was a protective factor both in non-ambulant and ambulant subgroups. Lower TB BMD Z-scores were also predictive of a greater SDI. In the ambulant subgroup a lower BMI reduced the risk of VF. In the overall cohort, each one-year delay in starting glucocorticoids reduced the risk of VFs by 27% (p = 0.007), and each additional unit in TB BMD Z-score reduced the risk of VFs by 54% (p = 0.0007). CONCLUSION: Our results suggest that ambulatory status and functional scores alone may not be reliable predictors for developing VFs and confirm the association with known risk factors, such as early initiation of glucocorticoid therapy and low BMD Z-scores, highlighting the need to guarantee a careful surveillance of possible VFs from the time of glucocorticoid initiation.