Inhomogeneous, orthotropic material model for the cortical structure of long bones modelled on the basis of clinical CT or density data

For the simulation of stabilisation systems in femoral fractures with finite elements three factors are essential: (1) the geometry of the bone, (2) the loading of the acting muscle forces in combination with the body weight and (3) the inhomogeneously distributed orthotropic behaviour of the bone material must be known.This study will focus on the third condition.A technique is presented for transferring the density distributions gained from clinical computer tomographies to inhomogeneous, orthotropic material distributions suitable for finite element calculations.First, the algorithm for determining the orthotropy directions from the local variation of the density field is explained phenomenologically. Subsequently, a function for setting up the orthotropic elasticity matrices from the absolute CT field values is derived. Finally, the validation procedure for the cortical bone is presented in principle.