Comparative Evaluation of Isotropic, Transversely Isotropic, and Orthotropic Material Properties in Human Femur Finite Element Analysis under Complex Loading Conditions

OpenAlex · İngilizce

The precision of Finite Element Analysis in skeletal biomechanics is heavily dependent on the accurate representation of bone’s material symmetry. This study aims to quantify the influence of isotropic, transversely isotropic, and orthotropic material models on the mechanical response of a detailed human femur model including cortical bone, trabecular networks, and marrow. A high-resolution 3D femur geometry was segmented and subjected to nine simulation scenarios. These scenarios combined three material symmetry assumptions-Isotropic, Transversely Isotropic, and Orthotropic-with three physiological loading modes: axial (1000 N), torsional (10,000 Nmm), and combined axial-torsional loading. Equivalent von Mises stress, total deformation, and equivalent strain (με) were evaluated using ANSYS Workbench software. While results were relatively consistent under axial loading (stress variations within 4-6%), significant discrepancies emerged under torsional and combined modes. For torsional loading, the isotropic model underestimated total deformation by 32% and equivalent strain by 43% compared to the orthotropic reference. Conversely, the transversely isotropic model predicted the highest structural compliance, overestimating deformation by 33% relative to the orthotropic case. In all combined loading states, the orthotropic model provided the most balanced representation of directional stiffness. The findings underscore that isotropic simplifications are particularly unreliable for predicting strain distributions and structural stability during rotational movements. Orthotropic material properties should be implemented to ensure clinical relevance in orthopedic simulations and fracture risk assessments.