Study on the Effects of Femoral Muscle Forces on Performance of Internal Fixation Devices Utilizing a Simulation Based Approach

Fractures of the distal femur are severe traumatic injuries that are treated with the utilization of internal fixation devices. Current preclinical device designs have primarily been investigated without observance of femoral muscle group effects — in addition to joint hip reaction forces — and irregular geometry of the human femora. This has led to a need to optimize the performance and fit of internal fixation devices to produce maximal reliability and structural integrity. The present study utilizes a systematic design approach that employs computer-aided modeling, robust design methodology, finite element methods, and optimization processes for a femoral locking plate system. In doing so, a computer-aided model was constructed to illustrate a distal femoral fracture fixation system. Femoral muscle force directions and magnitudes associated with a normal walking gait cycle were inputted into the system to simulate realistic loading conditions. In conjunction with finite element methods, the model was used to assess stress and strain distributions along the femur, femoral plate, and screws. Subsequently, optimization processes were then employed to assess the effects of varying device geometric parameters and bone topology on the bone-implant stress distributions and overall device design. The proposed simulation-based optimization process was able to yield a more accurate representation of the biomechanics within the bone-implant interaction by taking into consideration the substantial effects of femoral muscle groups. In doing so, a robust device design is developed which improves overall performance via minimizing weight and maximizing overall factor of safety.