FEM static analysis of knee endoprostheses implant systems for short and long stem lengths

The main aim of this work was evaluate the displacements and strains and stresses in components of knee endoprosthesis using Finite Element Method. The semi-constrained knee endoprosthesis with two stem length variants instrumented into femur and tibia bones was chosen for the analysis. The first step was preparation of two full knee endoprostheses geometrical models which were developed on a basis of a real model. To carry out an analysis it was necessary to develop a femur and tibia bone model. Next a grid for finiteelement method calculations was generated for the geometrical models. Subsequently it was necessary to specify and set the edge conditions to reflect appropriately the phenomena taking place in the real system. The system was loaded with axial force in range 500-2500N. Calculations were realized for endoprosthesis components made of Co-Cr-Ni-Mo alloy, Ti-6Al-4V alloy and UHMWPE. On a basis of obtained result, the highest values of reduced stress in both types of endoprostheses were observed in the stem of femoral part. Stress in bone didn’t exceed its compression strength. The biomechanical analysis may form the basis for improving the geometry of analyzed endoprostheses and optimising a selection of the mechanical properties of the material used to manufacture them.