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This publication contains a finite element model for the analysis of bone core under consideration of bone tissue heterogeneity and tissue anisotropy. The model for bone tissue heterogeneity and anisotropy follows: Hammond, M.A., Wallace, J.M., Allen, M.R. and Siegmund, T., 2018. Incorporating tissue anisotropy and heterogeneity in finite element models of trabecular bone altered predicted local stress distributions. Biomechanics and Modeling in Mechanobiology, 17(2), pp.605-614. In this publication the finite element model, material set assignment and local orientations are provided. This dataset contains an inp file in the syntax of Abaqus/Standard software v2017. 

This publication contains a finite element model for the analysis of single bone trabeculae under consideration of bone tissue heterogeneity and tissue anisotropy. The model for bone tissue heterogeneity and anisotropy follows: Hammond, M.A., Wallace, J.M., Allen, M.R. and Siegmund, T., 2018. Incorporating tissue anisotropy and heterogeneity in finite element models of trabecular bone altered predicted local stress distributions. Biomechanics and Modeling in Mechanobiology, 17(2), pp.605-614. In this publication the finite element model, material set assignment and local orientations are provided. This dataset contains an inp file in the syntax of Abaqus/Standard software v2017. 

At the nanoscale bone is composed of aligned heterogeneously mineralized collagen fibrils. While raloxifene (Ral) and bisphosphonate (BP) treatment preserve bone mass, they also affect bone quality through changes in collagen hydration and mineral density/heterogeneity, respectively. It was hypothesized that the effects of pharmacological treatment on the tissue would alter linear microcracking in finite element (FE) models of trabeculae reflecting control (Ctrl), Ral and BP. A FE mesh of a single canine vertebral body trabecula was generated from a micro- CT scan using ScanIP. A custom MATLAB code imposed tissue property heterogeneity and a collagen fibril orientation parallel to the trabecular surface. Ctrl was heterogeneous (based on vBMD) in both modulus and strength, and BP was homogenous (+25% of Ctrl mean modulus and strength). Ctrl and BP models had identical microcracking toughness. Ral had increased microcracking toughness (+25%) and the same modulus and strength heterogeneity as Ctrl. Transverse deflections were applied to simulate bending of the trabeculae, microcrack formation and propagation was simulated with the imposed orientation using the extended FE method in Abaqus/Standard, and the energy dissipated by the microcrack was assessed. 

Trabecular bone is composed of organized mineralized collagen fibrils, which results in heterogeneous and anisotropic mechanical properties at the tissue level. Recently, biomechanical models computing stresses and strains in trabecular bone have indicated a significant effect of tissue heterogeneity on predicted stresses and strains. How-ever, the effect of the tissue-level mechanical anisotropy on the trabecular bone biomechanical response is unknown. Here, a computational method was established to automatically impose physiologically relevant orientation inherent in trabecular bone tissue on a trabecular bone microscale finite element model. Spatially varying tissue-level anisotropic elastic properties were then applied according to the bone mineral density and the local tissue orientation. The model was used to test the hypothesis that anisotropy in both homogeneous and heterogeneous models alters the predicted distribution of stress invariants. Linear elastic finite element computations were performed on a 3 mm cube model isolated from a microcomputed tomography scan of human trabecular bone from the distal femur. Hydrostatic stress and von Mises equivalent stress were recorded at every element, and the distributions of these values were analyzed. Anisotropy reduced the range of hydrostatic stress in both tension and compression more strongly than the associated increase in von Mises equivalent stress. The effect of anisotropy was independent of the spatial redistribution high compressive stresses due to tissue elastic heterogeneity. Tissue anisotropy and heterogeneity are likely important mechanisms to protect bone from failure and should be included for stress analyses in trabecular bone. 

At the nanoscale bone is composed of aligned mineralized collagen fibrils organized into packets along the surface of trabecular bone creating an anisotropic tissue microstructure. Newer packets at the trabecular surfaces are usually less mineralized than older bone in the interior of the trabeculae, which along with irregular mineral deposition within packets, forms a heterogeneous material across the span of a trabeculae. However, finite element (FE) models of bone typically use homogenous isotropic material properties, because it is challenging to build anisotropy and heterogeneity into a model in a way that is applicable to the complex geometries of trabecular bone. Both the material anisotropy and heterogeneity may influence the stress state of trabecular bone, and it is important to understand the implications of such differences for determining bone biomechanical failure. It was hypothesized that taking into consideration both the tissue anisotropy and heterogeneity of bone’s biomechanical properties would alter the expected failure locations by reducing tensile stress on near surface elements of an FE model of canine trabecular bone. The objective of this study was to test this hypothesis and to develop a method to apply anisotropic and heterogeneous material properties to a model automatically from micro-computed tomography (μCT) data.