Bone Abstracts

Background: Low total body BMD (TB-BMD) is an established risk factor for fractures in healthy children. However, bone strength depends not only on bone mass and density, but also on the structural geometry of bones. Hip structural analysis (HSA) is a technique applied on hip DXA scans to calculate several bone geometry parameters. The aim of our study was to evaluate other bone geometrical parameters that can constitute determinants of fracture risk. Specifically, we examined the association between femoral structural parameters including the geometry-derived femoral stress index (FSI) and risk of fracture in children.

Methods: We studied 1,851 children from the Generation R study, with whole body and hip scans measured using the same densitometer (GE-Lunar iDXA) at a mean age of 6.2 years. Hip DXA scans underwent HSA with derivation of FSI. This stress index considers both, bending and axial forces acting on the femoral neck and is adjusted for lean mass fraction. Fractures at any skeletal site were assessed using questionnaire reports obtained before a mean age of 9.8 years. Risk (odds) of fracture was estimated from logistic regression models adjusted for sex, age, weight and ethnicity.

Results: Fractures was observed in 251 children (13.7%). A significant increase in the odds of fracture was observed for every standard deviation (SD) decrease in TBLH-BMD (OR: 1.28 95%, CI 1.05–1.56; P=0.01). Similarly, an increase in the odds of fracture was observed for every reduction in one SD of femoral neck BMD (OR=1.23 95% CI 1.06–1.43; P=0.005) and narrow neck BMD (OR=1.26 95% CI 1.08–1.46; P=0.005). The FSI showed the strongest association with fracture, where every increment of one SD in the FSI resulted in 28% increased odds of fracture (OR: 1.28 95%CI 1.13–1.45; P=0.0001). After inclusion of both the FSI and each of the BMD variables in the multiple regression model, only the stress variable remained significantly associated with risk of fracture.

Conclusions: Femoral and total body BMD parameters are associated with fracture in children. The stress index which considers in addition to quantity, the distribution of bone in the region, constitutes a biomechanical assessment which captures fracture propensity of children.

Disclosure: TJB is founder of Beck Radiological Innovations, Inc. All other authors state that they have no conflicts of interest.