Computational Simulation of a Femoral Nail Fracture

Abstract

Femoral nails are used to provide fixation for fractured long bones. These constructs simultaneously provide stability and union in nearly 10% of cases of premature failure. The goal of this investigation was to develop and test different models of the femur using cephalomedullary nail fixation. These models represent three different types of hip fractures (intracapsular, intertrochanteric, and subtrochanteric fractures). By testing the different fracture types, one can determine the fracture tolerance of the constructs from the resulting forces that occur due to the activities of daily living. Understanding the effects that the loads will have on the integrity of the nail-bone construct may help reduce the risks that could arise through its use. The computational simulations performed indicate that an undamaged femur can withstand the forces of 4.4× the body weight of the average adult male. A subtrochanteric femur fracture, however, can only withstand over 2.3× the same weight, nearly 50% lower than the normal femur. Regarding this lower amount, it is not impossible that an overloading scenario could occur. The data from the gait cycle show that, with a subtrochanteric fracture, the nail experiences stress that is just within the fatigue limit of the material. Given the collected data, subtrochanteric fractures are the most likely candidates for causing failures when comparing fracture types. In general, understanding the effects that different loads have on the integrity of the nail-bone construct may help reduce the risks that could arise through its use.