More Like this

1. MicroCT based FE model of single bone trabeculae with tissue heterogeneity and anisotropy

   https://doi.org/doi:10.4231/R7H41PP9  

   Siegmund, T ( June 2018 , Purdue University Research Repository)

   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. 

   more » « less
2. Incorporating tissue anisotropy and heterogeneity in finite element models of trabecular bone altered predicted local stress distributions

   https://doi.org/10.1007/s10237-017-0981-8  

   Hammond, Max A. ; Wallace, Joseph M. ; Allen, Matthew R. ; Siegmund, Thomas ( November 2017 , Biomechanics and Modeling in Mechanobiology)

   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. 

   more » « less
3. Anisotropy and Heterogeneity in Finite Element Models of Trabecular Bone Alters Expected Failure Outcomes

   Hammond, MA ; Wallace, JA ; Allen, MR ; Siegmund, T. ( March 2017 , Proccedings of the 2017 Annual Meeting of the Orthopedic Research Society)

   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. 

   more » « less
4. Biomechanical duality of fracture healing captured using virtual mechanical testing and validated in ovine bones

   https://doi.org/10.1038/s41598-022-06267-8  

   Inglis, Brendan ; Schwarzenberg, Peter ; Klein, Karina ; von Rechenberg, Brigitte ; Darwiche, Salim ; Dailey, Hannah L. ( February 2022 , Scientific Reports)

   Bone fractures commonly repair by forming a bridging structure called callus, which begins as soft tissue and gradually ossifies to restore rigidity to the bone. Virtual mechanical testing is a promising technique for image-based assessment of structural bone healing in both preclinical and clinical settings, but its accuracy depends on the validity of the material model used to assign tissue mechanical properties. The goal of this study was to develop a constitutive model for callus that captures the heterogeneity and biomechanical duality of the callus, which contains both soft tissue and woven bone. To achieve this, a large-scale optimization analysis was performed on 2363 variations of 3D finite element models derived from computed tomography (CT) scans of 33 osteotomized sheep under normal and delayed healing conditions. A piecewise material model was identified that produced high absolute agreement between virtual and physical tests by differentiating between soft and hard callus based on radiodensity. The results showed that the structural integrity of a healing long bone is conferred by an internal architecture of mineralized hard callus that is supported by interstitial soft tissue. These findings suggest that with appropriate material modeling, virtual mechanical testing is a reliable surrogate for physical biomechanical testing.

    

   more » « less
5. Computational analysis of tensile damage and failure of mineralized tissue assisted with experimental observations

   https://doi.org/10.1177/0954411919870650  

   Misra, Anil ; Sarikaya, Rizacan ( March 2020 , Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine)

   In this study, deformation and failure mechanisms of mineralized tissue (bone) were investigated both experimentally and computationally by performing diametral compression tests on millimetric disk specimens and conducting finite element analysis in which a granular micromechanics-based nonlinear user-defined material model is implemented. The force–displacement relationship obtained in the simulation agreed well with the experimental results. The simulation was also able to capture location of the failure initiation observed in the experiment, which is inside out from the hole along the loading axis. Furthermore, propagation of micro-sized cracks into failure was observed both in the experiment using simultaneous slow-motion microscopy imaging and in the simulation analyzing the local distortion and local volume change within the specimen. The anisotropy evolution was found to be significant around the hole along the loading axis by evaluating the anisotropy index computed using finite element results. In conclusion, this work revealed that the prediction capability of granular micromechanics-based user-defined nonlinear material model (UMAT) is promising considering the match between the results and observations from the physical experiment and finite element analysis such as force–displacement relationship and failure initiation/pattern. This work has also shown that the tensile damage and failure of mineralized tissues can be characterized using diametral compression (split tension) test. 

   more » « less