ESPE Abstracts

Introduction: Osteoporosis is medical condition commonly associated with immobilization in children, which can lead to a vicious cycle of disability, worsening osteoporosis, and recurrent fractures. Currently, bisphosphonates are widely used as a standard therapy in children with osteoporosis, but there are limited data on efficacy according to its dosage and duration. We aimed to evaluate efficacy of bisphosphonate treatment according to the dosage and duration in pediatric patients with osteoporosis due to immobilization.

Method: We reviewed medical records of pediatric patients who were diagnosed with osteoporosis due to immobilization rated as Gross Motor Function Classification System (GMFCS) grade V, and who received bisphosphonate therapy with regular check-up for at least 1 year. The dosage and duration of the treatment, biochemical laboratory measurements, data of bone densitometry, and the occurrence of side effects were collected.

Results: Subjects were 21 children. The average duration of bisphosphonate treatment was 2.0 ± 0.9 years, and mean cumulative dose per body weight of bisphosphonate was 7.7 ± 2.5 (mg/kg/year). After the treatment, mean lumbar spine bone mineral contents (BMC) significantly increased from 14.20 ± 8.58 (g) to 19.38 ± 9.89 (g) (P<0.05), lumbar spine bone mineral density (BMD) significantly increased from 0.40 ± 0.14 (g/cm2) to 0.49 ± 0.14 (g/cm2) (P<0.05), and height-adjusted lumbar spine BMD Z-score also showed improvement from -2.66 ± 1.66 to -1.66 ± 1.38 with statistical significance (P<0.05). The cumulative dose and the duration of treatment were not related to its efficacy, but increasing average dose per body weight in each cycle (mg/kg/cycle) showed significant effects on increasing change in height-adjusted lumbar spine BMD z-score (regression coefficient β = 1.065, P<0.05).

Discussion: BMC, BMD, and height-adjusted BMD z-score significantly increased after bisphosphonate treatment in pediatric patient with osteoporosis due to immobilization. Independent of cumulative dosage and duration, the efficacy of bisphosphonate treatment increased significantly as average dose per body weight in each cycle increased. Further studies with sufficient number of subjects and long term follow-up observation are needed.