Bone Abstracts

Objectives: The objective of this study is to characterize patterns of bone morphology in children with osteogenesis imperfecta (OI), using measurements of the second metacarpal. A secondary objective is to look for impact of bisphosphonate treatment on bone morphology in this population.

Methods: This is an IRB-approved retrospective review of 82 de-identified bone age films (AP hand/wrist) for 42 children with OI (17M, 25F). Measurements (Sectra IDS 7 PACS) included metacarpal length, width, and cortical thickness. Robustness (total area/length) and relative cortical area (RCA, cortical area/total area) were calculated to analyze metacarpal size and strength. Charts were reviewed to determine if they received bisphosphonate treatment within two years prior to the hand x-ray. Measurements were compared to 54 hand radiographs from 28 healthy controls (14M, 14F). Control ages ranged from 3 to 14. Non-parametric Kruskal-Wallis tests were used to compare differences in bone characteristics between study groups (P<0.05).

Results: Twenty-six untreated people with OI (7M, 19F) were included and typed as follows: type 1: 13; type 3: 4; type 4: 6; type V: 1; type 8: 1; type 9: 1. Ages ranged from 5 months to 14 years. 16 individuals treated with bisphosphonates (10M, 6F) were included and typed as follows: type 1: 3; type 3: 6; type 4: 4; type 5: 1; type 9: 1; unknown recessive: 1. Ages ranged from 2 to 14 years. All individuals with OI displayed decreased robustness, metacarpal width and length, and cortical thickness compared to the control group (P<.0.001). There were no significant differences between treated and untreated OI groups. Control males displayed higher robustness, width, length, and cortical thickness to females (P<.0.001). No sexual dimorphism was observed within OI groups.

Conclusion: People with OI had decreased robustness compared to controls, suggesting that OI bones are slender. Slender bones are structurally weaker compared to wider, more robust bones. Decreased cortical thickness has been found to correlate with decreased bone strength. These factors contribute to bone fragility of the OI population. Biological differences in the control populations are sex-specific, while no sexual dimorphism was noted for individuals with OI. Therefore, OI genotype trumps sex.

Disclosure: OI Foundation - Grants/Research Support, Advisory Board or Panel. EDS - Advisory Board or Panel. Biomarin - Consultant, Speaker’s Bureau, Advisory Board or Panel. Alexion - Speaker’s Bureau. Ascendis - Advisory Board or Panel.