Objective. To determine whether the load-carrying capacity of human proximal femora with simulated lytic defects can be predicted using QCT-derived simplified beam theory. Design. The predicted fracture load of simulated defects were calculated using new technique of QCT combined with engineering beam analysis. Patients. Simulated lytic defects were created using a surgical drill in the intertrochanteric region of twenty human cadaveric femora. QCT scans were conducted before and after creating defects on either AM (Anterior-Medial) or PL (Posterior-Lateral) regions. Results. A linear relation could be used to predict failure load from the proposed engineering analysis based on QCT scan. The coefficient of determination analysis of QCT-derived predicted load vs. the measured failure load was R2=0.73 (p<0.0001). Conclusions. The data suggest that three quarters of human femoral failure can be predicted in vivo, i.e. using QCT scan. Combined with information on the loads associated with the activities of daily living, these data may be used to prevent pathologic fractures of patients who had prior surgery of removing tumors on proximal femurs.