Orthotropic Properties of Trabecular Bone Determined by Adaptation Models

Bone adaptation algorithms that predict the relationship between bone loads and density assume that bone is effectively isotropic. The isotropic assumption cannot explain bone anisotropy and directionality, which are evident from the trabecular architecture. We have modeled the trabecular bone in the proximal femur as effectively orthotropic. Instead of determining the density distribution, we used the local material directions and effective moduli as the variables determined by an adaptation algorithm. The algorithm proposed determines the local material directions and the elastic moduli in material directions, for each element of a 2D model of the proximal femur. Since the directions of the trabeculae correspond to material axes, this approach can explain the trabecular morphology and take bone anisotropy into account in modeling bone adaptation.