Predicting failure load of the femur with simulated osteolytic defects using noninvasive imaging technique in a simplified load case.

Currently, there is no proven sensitive or specific method for predicting pathological fracture of the femur. The clinical management of lytic femoral metastases is based on geometric measurement of the bone, of the defect, or both. However, the mechanical behavior of a structure depends on both its material and geometric properties. Our hypothesis is that a change in bone structural properties as the result of tumor induced osteolysis determines the fracture risk in bones with skeletal metastases. We developed a method of QCT (Quantitative Computed Tomography) combined with engineering beam analysis as a noninvasive tool for measuring the material and geometric properties of the femur with simulated lytic defects in the intertrochanteric region. In this ex-vivo study we prove that engineering beam structural analysis applied to serial transaxial QCT scans through human femora with simulated lytic defects at the proximal femur predicts the load at failure and location of fracture better than current clinical guidelines. Structural rigidity measured by QCT in this study may be used to predict the load carrying capacity of femurs with metastatic defects and, furthermore, may be used when the tumor has weakened the bone sufficiently such that pathological fracture is imminent and prophylactic stabilization is necessary.