The Effect of Changing the Shape of Tibial Component on the Performance of Total Knee Replacement. (Dept. M ( Production ) )

Abstract

Stress shielding of the tibial component has remained one major cause of failure after total knee replacement surgery (TKR), which a relatively high stiffness of the prosthesis can cause most of the load to be transferred through the prosthesis rather than the bone. It leads to the resorption of the bone and a decrease in the bone strength and stiffness. The geometry of the tibial component has a strong effect on the bone compared to its material, so the present study investigates the optimum design of uncemented tibia tray to relieve the stress shielding by changing the dimensions of the metal tibial tray (shape optimization). The results of the optimization process for uncemented tibial component of TKR indicate a trend toward using a shorter cylindrical stem with a smaller diameter and longer metal tibial tray height to house the polymer insert compared with the initial design. This optimal shape model increases the maximum von-mises stress value five times the initial model on medial cancellous bone region. The maximum von-mises stress value of the optimal shape model is very close with that obtained using the natural bone with about 6.5% reduction in the maximum von-mises stress value on medial cancellous region. Also the maximum von-mises stress value of the optimal shape model is increased by 3% compared to the initial model on lateral cancellous bone region. Stress shielding is reduced related to increase stresses on medial and lateral regions. In addition, the maximum interface shear stress value on lateral region for the optimal shape model is decreased by 4% compared to the initial model. Aseptic loosening is decreased related to this reduction in shear stress on lateral side. This leads to reduce patient's pain and increases the implant life and stability.

Numerical Evaluation of a Porous Tibial-Knee Implant using Gyroid Structure

“…Aseptic loosening is due to micromotion between implant and bone and leads to implant instability. Also, stress concentrations appear at the stem tip and leads to severe patients' pain [18][19][20].…”