Three-dimensional finite element modelling of non-invasively assessed trabecular bone structures.

The three-dimensional microstructure of cancellous bone seems to be one of the key factors in the prediction of mechanical bone properties like bone strength or bone stiffness. In this paper trabecular bone structure was assessed nondestructively by means of high-resolution computed tomography (CT) with a spatial resolution of 250 microns. Mineralized bone was separated from bone marrow and muscle tissue with the help of a three-dimensional segmentation algorithm based on the analysis of directional derivatives. From the three-dimensional stack of CT slices a subvolume comparable in size (3.6 x 3.4 x 3.4 mm3) to standard histologic bone sections was selected. We refer to this subvolume as non-invasive bone biopsy. A new automated mesh generator was developed to create a three-dimensional finite element model of the non-invasive bone biopsy. Four-noded tetrahedron solid elements were used to guarantee a smooth surface representation. The aim of the presented work was to demonstrate the potential of high-resolution CT imaging in the prediction of the anisotropic material properties of cancellous bone. Preliminary results of the 3D finite element stress analysis are very promising. The predicted value of the apparent Young's modulus (564 MPa) is within the range reported for uniaxial compression testings of cancellous bone specimens.