Bone Abstracts

The incidence of distal forearm fractures in children is increasing, and peaks during the adolescent growth spurt. Advances in bone imaging have allowed us and other groups to obtain non-invasive ‘virtual bone biopsy’ data in growing children using high resolution peripheral quantitative computed tomography (HRpQCT). We studied changes in bone structure at the distal radius in individuals ranging from age 6 to till 21 years using HRpQCT. Transient regional deficits in cortical strength due to increased cortical porosity were observed during the pubertal growth spurt, mirroring the peak incidence of forearm fractures. In males during this period of rapid growth, we observed that a rise in serum osteocalcin (OCN) was associated with increasing serum testosterone (T), which in turn correlated with increasing periosteal circumference. This supports the evidence for a novel bone-testis axis, where OCN may further stimulate testicular testosterone production, which, in turn, contributes to an increase in bone size. Serum sclerostin (S) levels were found to be higher in boys compared to girls, and declined in both sexes after puberty. In both males and females, serum sclerostin levels were inversely related to cortical porosity, suggesting that changes in sclerostin production may play a role in defining cortical structure. We then went on to perform a fracture case-control study to directly compare bone structure in children aged 8–14 years with and without a distal forearm fracture. We found that in children with a distal forearm fracture due to mild trauma, there was cortical thinning and deficits in trabecular microstructure not only at the distal radius, but also at the tibia. No such differences were found between cases and controls in children who fractured due to moderate trauma, indicating that fractures caused by mild trauma are due to underlying skeletal deficits. Our population-based cohort studies indicate that a distal forearm fracture in boys, but not girls, is associated with an increased risk for fragility fractures as older adults. Further work needs to be done to clarify these sex-differences, and to show if lifestyle and nutritional interventions will prevent these deficits in bone quality.