Effect of material property representation on stresses in endoprostheses

The present study sought to examine if, and to what extent, the representation of the elastic properties of material(s) in a model of an endoprosthesis per se or a construct that includes an endoprosthesis affects the stresses in the model, when the finite element analysis method is used to obtain these stresses. For this purpose, two models were examined. One was of an elastomeric metacarpophalangeal joint implant, with the material being assumed to have isotropic elastic properties in one case while it was represented as hyperelastic in the other. The model used in the second study case was that of a construct comprising the tibial component of a total knee replacement, the associated tibial insert, the resected bones, and the acrylic bone cement layer. In one analysis of this model, all the materials were taken to have isotropic elastic properties, while in the other analysis, the cortical bone was represented as transversely isotropic, with all other materials being considered to have isotropic elastic properties. The results show that, in both study cases considered, there is a strong effect of the representation of the elastic properties of material(s) on the stresses in the models.