The use of intravenous bisphosphonate therapy to treat vertebral fractures due to osteoporosis among boys with Duchenne muscular dystrophy

Abstract

The impact of intravenous bisphosphonate treatment to treat painful vertebral fractures in boys with DMD has not been documented. In this retrospective observational study of seven boys, 2 years of intravenous bisphosphonate therapy was associated with back pain improvement and stabilization or increases in the height ratios of fractured vertebrae. Boys with Duchenne muscular dystrophy (DMD) are at risk for vertebral fractures. We studied the impact of intravenous bisphosphonate therapy for the treatment of painful vertebral fractures in DMD. This was a retrospective observational study in seven boys with DMD (median 11.6 years, range 8.5 to 14.3) treated with intravenous pamidronate (9 mg/kg/year) or zoledronic acid (0.1 mg/kg/year) for painful vertebral fractures. At baseline, 27 vertebral fractures were evident in the seven boys. After 2 years of bisphosphonate therapy, 17 of the fractures had an increase in the most severely affected vertebral height ratio, 10 vertebrae stabilized, and none showed a decrease in height ratio. Back pain resolved completely (N = 3) or improved (N = 4). The median change in lumbar spine volumetric bone mineral density Z-score was 0.5 standard deviations (interquartile range, -0.3 to 1.7). Two boys had three incident vertebral fractures in previously normal vertebral bodies that developed over the observation period. There was a decline in the trabecular bone formation rate on trans-iliac bone biopsy but no evidence of osteomalacia. First-dose side effects included fever and malaise (N = 4), hypocalcemia (N = 2), and vomiting (N = 1); there were no side effects with subsequent infusions. Intravenous bisphosphonate therapy was associated with improvements in back pain and stabilization to improvement in vertebral height ratios of previously fractured vertebral bodies. At the same time, such therapy does not appear to completely prevent the development of new vertebral fractures in this context.