Constructing anisotropic finite element model of bone from computed tomography (CT)

Abstract

Image-based finite element (FE) modeling of human bones has been increasingly applied as a useful tool in biomedical engineering. However, most existing image-based FE models assume isotropic mechanical properties for bones, although bones are typically anisotropic material. In this study, we attempted to construct anisotropic FE models from medical computed tomography (CT) scans by modifying the existing empirical relations of bone elasticity-density. The hypothesis adopted in the study is that bone anisotropy is generated by the variations of bone density and the proposed anisotropic relations should degenerate to the isotropic ones if bone density variation is taken zero. The effect of considering bone anisotropy in FE models was investigated by numerical studies. The obtained numerical results showed that the relative error in the finite element solutions produced respectively by the isotropic and anisotropic FE models can be as large as 50%. We concluded from this preliminary study that the consideration of anisotropy in bone FE models has a significant effect on the accuracy of bone behavior predicted by the FE models. However, well-designed bone tests have to be conducted to validate the anisotropic bone elasticity-density relation proposed in this study.

Bone Volume Fraction and Fabric Anisotropy Are Better Determinants of Trabecular Bone Stiffness Than Other Morphological Variables

“…(43) Finally, research now focuses on deriving fabric anisotropy tensors from conventional CT imaging, either via gradient-based methods or mapping of mCT information. (44)(45)(46)(47) Nevertheless, morphological variables are still combined into multiple linear models to predict the mechanical properties of cancellous bone, (14)(15)(16)(17)21,45) but never compared to a combination BV/TV-fabric anisotropy. In this study, a systematic analysis of the stiffness and morphology of 743 samples extracted from femur, radius, iliac crest, and vertebral body was performed to determine the relevant predictors of the bone elastic properties.…”

“…They predict stiffness and strength of bone as well as μFE, hence better than morphological parameters . Finally, research now focuses on deriving fabric anisotropy tensors from conventional CT imaging, either via gradient‐based methods or mapping of μCT information . Nevertheless, morphological variables are still combined into multiple linear models to predict the mechanical properties of cancellous bone, but never compared to a combination BV/TV–fabric anisotropy.…”

A method of reproducing complex, multi-object anatomical structures

“…Bone anisotropy in FE models was considered in numerical studies (Carnelli et al, 2010;Kazembakhshi and Luo, 2014). The inclusion of anisotropy in bone FE models is very important for obtaining accurate results of the numerical analysis of complex anatomical cases.…”

Anisotropy, Anatomical Region, and Additional Variables Influence Young's Modulus of Bone: A Systematic Review and Meta‐Analysis

“…[6][7][8] Ignoring anisotropy causes up to 50% of relative error by FEA. [4] Furthermore, the elasticity of bone can be measured by several in vitro or in vivo methods.…”

“…FEA is a numerical stress analysis technique that allows injury analysis, and presurgery simulation to model the behavior of implant fitting in bone. [ 2 , 3 , 4 ] During FEA, the examined region is divided into elements, with the proper material properties of each. [ 5 ] To recreate the appropriate virtual model, it is crucial to have precise material properties for each element.…”