Abstract:
Osteoarthritis is the most common form of arthritis. It is a long term disease leading to degeneration of the knee joint and it causes stiffness, pain and swelling. The treatment includes replacement of the damaged knee joint with an implant (Total Knee Replacement). In a conventional knee replacement surgery, the damaged joints are replaced with materials such as metal and plastic, allowing for the natural motion of the knee. A new knee prosthesis has been designed recently and a prototype was built and tested under some simple loading conditions. The prosthesis is made up of a “femur plate” and a “tibia plate”, which are attached to either side of the femur and tibia. These plates are designed in such a way that they wrap around the lateral and medial sides of the distal femur and proximal tibia. The femur and tibia plates must be attached to the bone using fixators. The design of such fixators and their performance is the central issue of investigation in this project. There are various factors which could lead to the failure of fixators. This project addresses the issue of loosening of the fixators and the appropriate design of the fixators to prevent them from loosening. Following Wolf’s Law, the strain energy density in the vicinity of the fixators is used as a measure of strength of fixation. A higher strain energy density would suggest formation of bone and osteointegration whereas a lower strain energy density would indicate bone resorption and possible loosening. Three dimensional computational models of different peg designs were created using the SOLIDWORKS CAD software. The pegs used in this project were chosen to have three different shapes: circular, triangular and square. They were inserted into a bone model and imported into ABAQUS for computational Finite Element Analysis. The results of the computer simulations were used to evaluate the performance of each design. A bone remodelling process was simulated using Python scripting in conjunction with ABAQUS. This enabled the evaluation of the performance of each design over a period of time. The results suggest that a triangular peg encourages higher bone formation as compared to the other designs.