Correlation of bone density and geometric parameters to the mechanical strength of the femoral neck

Abstract

Bone density in six different regions along the axis of the femoral neck was studied by single energy-quantitative CT (SE-QCT) and simple geometric parameters were measured in 42 proximal cadaveric femora. Mechanical testing of the proximal femur was performed simulating the peak load direction during the double support phase of gait. This load direction was maintained until femoral neck fracture occurred. The structural stiffness of the proximal femur was approximated by dividing the peak load by the deflection of the setup at peak load. Bone mineral density determined in the femoral head (r=0.74, p< 0.01), the femoral neck (r=0.51, p< 0.01) and the centre of the trochanteric area (r=0.30, p<0.05) significantly correlated with the mechanical strength of the femoral neck as found by statistical analysis (Pearson test). Considering geometric data, the best result was yielded by correlation of fracture load to the diameter of the femoral neck (r=0.53, p<0.01) and the collodiaphysis angle (CDA) (r=0.37, p<0.05). Bone stiffness was defined as the ratio of fracture load and amount of deformation of the proximal femur. The best correlation of density and stiffness were found in the femoral head (r=0.48, p<0.01) and the femoral neck (r=0.27, p<0.05). Statistical correlation could be improved by combining geometric parameters as lever arm (r=0.7714, p<0.01) and diameter of femoral neck (r=0.7557, p<0.01) with fracture pressure. In conclusion, the findings of this study contribute to the establishment of clinical guidelines for the identification and treatment of patients at high risk of a proximal femoral fracture.