Influence of bone-specific material properties on finite element modelling of the skull

The material properties of bone in the skull are known to be heterogeneous and orthotropic, although datasets detailing these properties on a species level are limited. Therefore, computational modelling frequently uses homogeneous, isotropic material properties to analyse stresses/strains in the skull. However, it is often unknown how the choice of bone/s from which the elastic modulus is measured, or the direction in which it is measured, influences predicted stresses/strains. This study integrated imaging and measured muscle properties to create a subject-specific finite element model of a rabbit (Oryctolagus cuniculus) skull, to investigate the influence of modelling the elastic modulus of bone through varying levels of complexity. The results demonstrate the importance of modelling orthotropic material properties, if known. Strain distribution was insensitive to whether the same isotropic elastic modulus was used for all bones in the skull versus modelling bone-specific isotropic elastic modulus. Strain distribution was also similar when using an isotropic elastic modulus based on measurement in different orthotropic directions, albeit with a slight difference when measured in the medio-lateral direction. This highlights that isotropic, homogeneous modelling of the skull is appropriate when analysing strain distribution, although alternative material modelling should be considered when strain magnitude is of particular interest.