Comparison of isotropic and orthotropic material property assignments on femoral finite element models under two loading conditions

Abstract 

CT data has been widely used in the finite element modeling of bone. It can provide useful information on the geometrical topology and material properties of bone. Based on CT data, the assignment of bone material properties to finite element meshes is a fundamental step in the model generation. Most work done in this area has adopted isotropic assignment strategy due to its simplicity. However, bone material has been recognized as an orthotropic material. This work is aimed to investigate the effects of orthotropic material property assignment on femoral finite element model by comparing with isotropic material property assignment on the same model. There were 72 finite element models obtained from the frozen CT male dataset of visible human project. Based on the analysis results of the maximum equivalent Von Mises stress and the maximum nodal displacement, three parameters were defined to achieve this comparison. The results have shown that the differences between the two material property assignments are small under two loading conditions (double-leg standing and single-leg standing) investigated in this work.

Keywords: Finite element analysis, Femur, Material property assignment, CT numbers