Prediction of fracture load at different skeletal sites by geometric properties of the cortical shell

Quantitative bone assessment today is primarily based on the analysis of bone mineral density (BMD). The geometric properties of bone, which are an important parameter for skeletal strength, are generally not considered in the routine clinical assessment of osteoporosis. This study combined the geometric properties and the BMD values determined by peripheral quantitative computed tomography (pQCT) at the distal radius and at the femoral neck to predict fracture loads of the radius, femur, and lumbar vertebrae of 20 cadavers. Generalized osteopenia reduced the fracture loads at all three sites (p < 0.001). The strength of the radius and the femoral neck could best be predicted by considering either the second moment of inertia and trabecular BMD (R = 0.93) or the moment of inertia and the cortical BMD (R = 0.91). The geometric properties at the distal radius were highly correlated with the fracture load at the same skeletal site (R = 0.89) and were also used to estimate the fracture risk at the lumbar vertebrae (R = 0.75) and at the femoral neck (R = 0.87). We conclude that both geometry and density contribute substantially to the strength of the skeleton. The screening for osteoporosis and the prediction of fracture risk can be improved, therefore, by an additional consideration of the geometric properties of the cortex.