Intravenous Bisphosphonate Therapy of Young Children With Osteogenesis Imperfecta: Skeletal Findings During Follow Up Throughout the Growing Years

Abstract

Cyclical intravenous bisphosphonate therapy is widely used to treat children with osteogenesis imperfecta (OI), but little is known about long-term treatment outcomes. We therefore reviewed 37 children with OI (OI type I, n = 1; OI type III, n = 14; and OI type IV, n = 22) who started intravenous bisphosphonate therapy before 5 years of age (median 2.2 years; range, 0.1 to 4.8 years), and who had a subsequent follow-up period of at least 10 years (median 14.8 years; range, 10.7 to 18.2 years), during which they had received intravenous bisphosphonate treatment (pamidronate or zoledronic acid) for at least 6 years. During the observation period, the mean lumbar spine areal bone mineral density Z-score increased from -6.6 (SD 3.1) to -3.0 (SD 1.8), and weight Z-score increased from -2.3 (SD 1.5) to -1.7 (SD 1.7) (p < 0.001 and p = 0.008). At the time of the last assessment, patients with OI type IV had significantly higher height Z-scores than a control group of patients matched for age, gender, and OI type who had not received bisphosphonates. Patients had a median of six femur fractures (range, 0 to 18) and five tibia fractures (range, 0 to 17) during the follow-up period. At baseline, 35% of vertebra were affected by compression fractures, whereas only 6% of vertebra appeared compressed at the last evaluation (p < 0.001), indicating vertebral reshaping during growth. Spinal fusion surgery was performed in 16 patients (43%). Among the 21 patients who did not have spinal fusion surgery, 13 had scoliosis with a curvature ranging from 10 to 56 degrees. In conclusion, long-term intravenous bisphosphonate therapy was associated with higher Z-scores for lumbar spine areal bone mineral density and vertebral reshaping, but long-bone fracture rates were still high and the majority of patients developed scoliosis.