Finite element analysis of trabecular bone structure: a comparison of image-based meshing techniques

In this study, we investigate if finite element (FE) analyses of human trab ecular bone architecture based on 168 mu m images can provide relevant info rmation about the bone mechanical characteristics. Three human trabecular b one samples, one taken from the femoral head, one from the iliac crest, and one from the lumbar spine, were imaged with micro-computed tomography (mic ro-CT) using a 28 mu m resolution. After reconstruction the resolution was coarsened to 165 mu m. First, all reconstructions were thresholded and dire ctly converted to FE-models built of hexahedral elements. For the coarser r esolutions of two samples, this resulted in a loss of trabecular connection s and a subsequent loss of stiffness. To reduce this effect, a tetrahedral element meshing based on the marching cubes algorithm, as well as a modifie d hexahedron meshing, which thresholds the image such that load carrying bo ne mass is preserved, were employed. For each sample elastic moduli and tis sue Von Mises stresses of the three different 168 mu m models were compared to those from the hexahedron 28 mu m model. For one sample the hexahedron meshing at 168 mu m produced excellent results. For the other two samples t he results obtained from the hexahedral models at 168 mu m resolution were poor. Considerably better results were attained for these samples when usin g the mass-compensated or tetrahedron meshing techniques. We conclude that the accuracy of the FE-models at 168 mu m strongly depends on the bone morp hology, in particular its trabecular thickness. A substantial loss of trabe cular connections during the hexahedron meshing process indicates that poor FE results will be obtained. In this case the tetrahedron or mass-compensa ted hexahedron meshing techniques can reduce the loss of connections and pr oduce better results than the plain hexahedron meshing techniques. (C) 1998 Elsevier Science Ltd. All rights reserved.