Bone microstructural and strength changes over 1 year in children with osteogenesis imperfecta are comparable to age- and sex-matched healthy controls

Introduction Osteogenesis imperfecta (OI) is characterized by bone fragility with frequent fractures, especially in children. Some studies have used peripheral-QCT (pQCT) to examine bone density in children with OI and one cross-sectional study used HR-pQCT in 9 children with OI. Materials and Methods We compared bone density, microstructure, and strength changes over 1 yr at the metaphysis and diaphysis of the radius and tibia, as well as lumbar spine (LS) bone mass and area, in 20 children with OI under bisphosphonate treatment and 20 age- and sex-matched controls. For the double-stack metaphyseal scans, we developed an algorithm to correct stack misalignment. For the LS, we used DXA. Results At the tibial metaphysis, children with OI had lower baseline total and trabecular volumetric BMD (vBMD), trabecular and cortical microstructure, and strength. At the radial metaphysis, baseline trabecular microstructure and strength were lower in children with OI. At the tibial and radial diaphysis, children with OI had lower bone area and strength. At the tibial and radial metaphysis, 1-yr increases in most measurements were similar for both groups. Cortical vBMD and trabecular separation (radius) only increased in the OI group. Trabecular vBMD, volume fraction (tibia), number (tibia), and total vBMD (radius) only increased in the control group. At the tibia and radius diaphysis, cortical vBMD increased in the OI group. Tibial Ct.Po decreased in children with OI. At the LS, the OI group had lower bone mass, density, and area, but similar longitudinal changes. Discussion In summary, baseline trabecular bone density, trabecular and cortical microstructure, and strength were lower in metaphyseal regions of children with OI. At diaphysis, children with OI had lower bone area and strength. While longitudinal changes over 1 yr were generally comparable, certain outcomes demonstrated differences. These data are essential for powering future clinical trials.