Finite Element Modelling of NiTi Shape Memory Alloy Abutment for an Osseointegration Trans-femoral Implant

Traditionally, prosthetic limb is interconnected to the residual limb via a “socket”. As the body weight upon the prosthesis is transferred through soft tissue to human skeleton, the muscles and skin could be traumatized. To overcome the problem, an osseointegration trans-femoral implant technique has been used to attach prosthetic limb to human skeleton directly. However, due to the malfunction of the prosthetic limb and accidentally loss balance of the prosthetic limb user, a significant impact load could over load the implanted bone. To protect the bone, a shape memory alloy (SMA) abutment was developed. Finite element (FE) method was used to investigate the mechanical performance of NiTi SMA abutments under both static and impact load conditions. In this study, a non-linear FE model was applied to simulate the large deformation of the abutment. The simulation in terms of the maximum stress involved and plastic deformation was used a) for safety and reliability assessment of the abutment, and b) as input for the further study of interfacial stress between femur and implant. A comparison of FE modelling was also made between NiTi SMA and other materials used in the clinical trials. The results reveal that NiTi SMA abutment can release much more impact load and reduce the over stress in the bone significantly.