Department of Mechanical Engineering, Boston University, 110 Cummington Mall, Boston, MA, 02215, USA.
Biomech Model Mechanobiol. 2020 Apr;19(2):505-517. doi: 10.1007/s10237-019-01225-2. Epub 2019 Sep 10.
Quantitative computed tomography (QCT)-based finite element (FE) models of the vertebra are widely used in studying spine biomechanics and mechanobiology, but their accuracy has not been fully established. Although the models typically assign material properties based only on local bone mineral density (BMD), the mechanical behavior of trabecular bone also depends on fabric. The goal of this study was to determine the effect of incorporating measurements of fabric on the accuracy of FE predictions of vertebral deformation. Accuracy was assessed by using displacement fields measured via digital volume correlation-applied to time-lapse microcomputed tomography (μCT)-as the gold standard. Two QCT-based FE models were generated from human L1 vertebrae (n = 11): the entire vertebral body and a cuboid-shaped portion of the trabecular centrum [dimensions: (20-30) × (15-20) × (15-20) mm]. For axial compression boundary conditions, there was no difference (p = 0.40) in the accuracy of the FE-computed displacements for models using material properties based on local values of BMD versus those using material properties based on local values of fabric and volume fraction. However, when using BMD-based material properties, errors were higher for the vertebral-body models (8.4-50.1%) than cuboid models (1.5-19.6%), suggesting that these properties are inaccurate in the peripheral regions of the centrum. Errors also increased when assuming that the cuboid region experienced uniaxial loading during axial compression of the vertebra. These findings indicate that a BMD-based constitutive model is not sufficient for the peripheral region of the vertebral body when seeking accurate QCT-based FE modeling of the vertebra.
基于定量计算机断层扫描 (QCT) 的椎体有限元 (FE) 模型广泛应用于研究脊柱生物力学和力学生物学,但它们的准确性尚未得到充分证实。尽管这些模型通常仅根据局部骨密度 (BMD) 分配材料特性,但小梁骨的力学行为也取决于织构。本研究的目的是确定将织构测量值纳入到对椎体变形的 FE 预测的准确性的影响。通过使用数字体积相关技术(应用于时移微计算机断层扫描 (μCT))测量的位移场作为金标准来评估准确性。从人类 L1 椎体生成了两个基于 QCT 的 FE 模型(n = 11):整个椎体和小梁中心的长方体部分[尺寸:(20-30) × (15-20) × (15-20) mm]。对于轴向压缩边界条件,使用基于局部 BMD 值的材料特性的 FE 计算位移的准确性与使用基于局部织构和体积分数值的材料特性的 FE 计算位移的准确性之间没有差异(p = 0.40)。然而,当使用基于 BMD 的材料特性时,对于椎体模型(8.4-50.1%),误差高于长方体模型(1.5-19.6%),这表明这些特性在中心的外围区域不准确。当假设长方体区域在椎体轴向压缩过程中经历单轴加载时,误差也会增加。这些发现表明,当寻求对椎体进行基于 QCT 的准确 FE 建模时,基于 BMD 的本构模型不足以满足椎体体部外围区域的要求。
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