Optimum design of a biodegradable implant for femoral shaft fracture fixation using finite element method

Recent developments in biodegradable implant technology have expanded its use in several medical fields, such as orthopedics, cardiology, dentistry, and tissue engineering. Degradable bone-fixing implants, consisting of plates and screws, provide the advantage of completely degrading after efficaciously supporting the broken bone and can accelerate healing through nutrient release while maintaining mechanical stability. Magnesium alloys are considered promising options for bone implants owing to their natural degradability, biocompatibility, and potential to reduce long-term complications, but challenges such as rapid corrosion rate and lower mechanical strength compared to non-biodegradable materials may reduce structural strength before the broken bone completely heals. This article mainly concentrates on the design of a biodegradable implant plate for a femoral shaft fracture in the walking cycle, considering the plate's dimension, number of screws, biodegradation rate, and sufficient mechanical stability. Using the results of the numerical analyses, the safe zone of the implant plate design is determined based on the implant plate stress and the total displacement of the femur bone. Then, the appropriate number of screws and optimum topology of the plate are determined. The outcomes indicate that lengthening the implant plate significantly reduces stress and bone displacement. Reducing screw numbers increases stress and displacement, so fewer screws can be used for strong bones, while weaker bones require more screws for support, and topology optimization helps maintain satisfactory outcomes with minimal material use. This research lays the foundation for future studies that simultaneously consider implant material degradation and bone fracture healing.