Some factors that affect the comparison between isotropic and orthotropic inhomogeneous finite element material models of femur

The objective of this study was to investigate whether there were significant differences between isotropic and orthotropic inhomogeneous material models of femur by taking into account the effects of some factors, such as comparative parameters, loading conditions and mesh refinement. Three femoral meshes of increasing refinement levels were assigned isotropic and orthotropic material properties. Then six different loading conditions were separately applied to each material model. Based on the analysis results of Von Mises stress and nodal displacement, eight regions of interest in femur were selected to compare the differences between isotropic and orthotropic material models. The results showed that marked differences for Von Mises stress (maximum 13.25%) and nodal displacement (maximum 15.04%) appeared in the regions where the maximum absolute Von Mises stress and the maximum absolute nodal displacement did not occur. It was observed that the comparison results were significantly different under different loading cases. The mesh refinement had a great influence on the comparison results, especially for the Von Mises stresses in the regions of the femoral neck. Therefore, it can be concluded that the differences between two material property assignments are significant, at least in some local regions.