Effects of Prosthesis Stem Materials on Stress Distribution of Total Hip Replacement

Bone loss and bone thickening phenomenon occurred due to different stiffness of the implant and femur. Implant with stiffer materials than the bone carries majority of the load and it transferred down along the implant till the distal tip of the stem. Both phenomenons contribute to stress shielding and loosening of the prosthesis stem. In this study, the stress distributions in intact femur and THR femur are established using finite element method. The THR femur model consists of cemented hip Ti6AI4V and CoCrMo prosthesis stem implanted inside the femur bone. Effects of different material properties of the prosthesis stem on the resulting stress distributions are investigated. Results shows that the largest discrepancy in stress values between intact and THR femur is predicted along the middle region at both lateral and medial planes. The distal region shows that the calculated stress for both THR femur experienced higher stress magnitude than that of intact femur. The higher stress in THR femur leads to bone thickening at the particular region. The corresponding stress magnitude saturates at 25 MPa for THR femur while intact femur is slightly lower at 22 MPa.