Predictive geometric factors in a standardized model of femoral neck fracture. Experimental study of cadaveric human femurs.

An experimental study was performed on 20 cadaveric human proximal femurs to investigate both the reproducibility of their mechanical behavior under uniaxial compression and the correlation of mechanical properties with geometric dimensions and bone density. These variables were assessed by radiography, physical measurement, and dual-energy X-ray absorptiometry (DEXA). The specimens were immobilized, loaded to the point of fracture, and analyzed with the help of a materials testing machine. The fractures invariably showed a similar pattern both in location (i.e. at the femoral neck) and in nature (i.e. "axial-shear" type according to the AO classification system). The mechanical properties of the tested proximal femurs correlated negatively with age (r = -0.39) and positively with sex (male femurs were stronger and correlated more closely than female femurs, P = 0.005). They showed a strong positive correlation with head diameter (r = 0.713, P = 0.0004), a moderate positive correlation with both neck axis length (r = 0.63) and neck diameter (r = 0.502), and a slight positive correlation with femoral neck-shaft angle (r = 0.326). All DEXA-based densitometry measures turned out to be powerful predictors of fracture force. The establishment of this solidly reproducible fracture model based on standardized loading conditions should have implications for future research on osteopenia/osteoporosis and preventive stabilization techniques.