Parameter study for the finite element modelling of long bones with computed-tomography-imaging-based stiffness distribution

Abstract

Four radii of different horses were tested in three-point bending and in pure torsion. Detailed finite element (FE) models of these long bones were established by means of computed-tomography (CT) images and tests simulated for both load cases. For the allocation of the local isotropic material stiffness, individual exponential functions were applied whose factor and exponent were determined solely by fitting them to the measured torsional stiffness and bending stiffness of the entire bones. These stiffness functions referring directly to the CT number and having exponents between 1.5 and 2 were in good agreement with Young's moduli subsequently measured from small samples cut from the investigated bones. Based on a model with local orthotropic material definition, an additional parameter study was conducted to verify the sensitivities of the FE analysis results on single variations in the orthotropic elastic constants. This study revealed that the bending test simulations could be enhanced by substantial reduction in Young's moduli in the directions perpendicular to the bone axis; thus, orthotropic material definition is preferable for the FE analysis of long bones.