Bone Abstracts

Background: Fracture incidence rate and growth according to different glucocorticoid (GC) regimen in Duchenne Muscular Dystrophy (DMD) is currently unknown.

Objective: To determine the extent of skeletal morbidity and the influence of GC regimen on fracture incidence rate and growth in a contemporary cohort of DMD in the UK.

Method: Clinical details of 832 boys with DMD in the North Star database (2006–2015) from 23 centres were analysed. Fracture incidence rate per 10,000 person years were determined for the group and according to GC regimen. Adjusted models using linear regression was used to evaluate factors associated with change in height standard deviation score (SDS).

Results: A total of 62 vertebral fracture (VF) episodes were observed in 52/832 (6%) and 118 non-VF episodes were observed in 112/832 (13.5%) boys. Median age at first VF and non-VF were 12 years (95% CI 10.5, 13.5) and 10.9 years (95% CI 10.3, 11.9), respectively. Kaplan-Meier analysis showed that 50% probability of first fracture was observed after 7.4 years (95% CI 6.3, 8.4) of GC therapy. Among the correlates of first incident fracture, ambulant status was associated with statistically significant increase in first fracture risk (Hazard ratio 2.5; 95% CI 1.1; 5.6, P=0.03). Over the follow-up period, fracture incidence rate was 682/10,000 (95% CI 580,780) person-years. Fracture incident rate was 254/10,000 (95% CI 29,887) person-years in GC naïve boys. The highest fracture incident rate was observed in those treated with daily Deflazacort 1367/10,000 (95% CI 796, 2188) person-years. Using adjusted multiple regression models (age, height SDS baseline, duration of follow-up), change in height SDS was −0.7 S.D. (95% CI −1.2, −0.2, P=0.01) lower in those treated with daily Deflazacort compared with GC naïve boys, whereas there were no statistical differences in the other GC regimen.

Conclusion: In the largest cohort of boys with DMD to date with longitudinal fracture data, there is an overall 4.2 fold increase in fracture incident rate compared with healthy UK boys (1). Our study showed for the time time that fracture incident rate and growth failure is highest in those treated with daily Deflazacort.

Disclosure: The authors declared no competing interests.

Reference
1. Cooper, C. Dennison, E. M. Leufkens, H. G. Bishop, N. and van Staa, T. P. Epidemiology of Childhood Fractures in Britain: A Study Using the General Practice Research Database. J Bone Miner Res, 2004;19: 1976–1981.