School of Biomedical Engineering, The University of Western Ontario, London, ON, Canada.
Roth|McFarlane Hand and Upper Limb Centre, St. Josephs Health Care, London, ON, Canada.
Ann Biomed Eng. 2019 Nov;47(11):2188-2198. doi: 10.1007/s10439-019-02312-2. Epub 2019 Jul 11.
Subject- and site-specific modeling techniques greatly improve finite element models (FEMs) derived from clinical-resolution CT data. A variety of density-modulus relationships are used in scapula FEMs, but the sensitivity to selection of relationships has yet to be experimentally evaluated. The objectives of this study were to compare quantitative-CT (QCT) derived FEMs mapped with different density-modulus relationships and material mapping strategies to experimentally loaded cadaveric scapular specimens. Six specimens were loaded within a micro-CT (33.5 μm isotropic voxels) using a custom-hexapod loading device. Digital volume correlation (DVC) was used to estimate full-field displacements by registering images in pre- and post-loaded states. Experimental loads were measured using a 6-DOF load cell. QCT-FEMs replicated the experimental setup using DVC-driven boundary conditions (BCs) and were mapped with one of fifteen density-modulus relationships using elemental or nodal material mapping strategies. Models were compared based on predicted QCT-FEM nodal reaction forces compared to experimental load cell measurements and linear regression of the full-field nodal displacements compared to the DVC full-field displacements. Comparing full-field displacements, linear regression showed slopes ranging from 0.86 to 1.06, r-squared values of 0.82-1.00, and max errors of 0.039 mm for all three Cartesian directions. Nearly identical linear regression results occurred for both elemental and nodal material mapping strategies. Comparing QCT-FEM to experimental reaction forces, errors ranged from - 46 to 965% for all specimens, with specimen-specific errors as low as 3%. This study utilized volumetric imaging combined with mechanical loading to derive full-field experimental measurements to evaluate various density-modulus relationships required for QCT-FEMs applied to whole-bone scapular loading. The results suggest that elemental and nodal material mapping strategies are both able to simultaneously replicate experimental full-field displacements and reactions forces dependent on the density-modulus relationship used.
基于体素的和基于部位的建模技术极大地改进了从临床分辨率 CT 数据中得出的有限元模型 (FEM)。在肩胛骨 FEM 中使用了各种密度-模量关系，但这些关系的选择对灵敏度的影响尚未通过实验进行评估。本研究的目的是比较不同密度-模量关系和材料映射策略映射的定量 CT (QCT) 衍生 FEM 与实验加载的尸体肩胛骨标本。六个标本在定制的六足加载装置内用微 CT（33.5 μm 各向同性体素）加载。数字体积相关 (DVC) 通过在加载前后的图像上注册来估计全场位移。使用 6-DOF 负载单元测量实验负载。QCT-FEM 使用 DVC 驱动的边界条件 (BC) 复制实验设置，并使用元素或节点材料映射策略之一对十五种密度-模量关系之一进行映射。通过将预测的 QCT-FEM 节点反作用力与实验负载单元测量值进行比较，以及将全场节点位移与 DVC 全场位移进行线性回归，对模型进行了比较。比较全场位移时，线性回归显示斜率范围从 0.86 到 1.06，r 平方值从 0.82 到 1.00，所有三个笛卡尔方向的最大误差为 0.039 毫米。元素和节点材料映射策略都产生了几乎相同的线性回归结果。将 QCT-FEM 与实验反作用力进行比较时，所有标本的误差范围从 -46 到 965%，特定标本的误差低至 3%。本研究利用体积成像结合机械加载来获得全场实验测量值，以评估应用于肩胛骨整体骨加载的 QCT-FEM 所需的各种密度-模量关系。结果表明，元素和节点材料映射策略都能够同时复制依赖于使用的密度-模量关系的实验全场位移和反作用力。
