Differences in Trabecular Microarchitecture and Simplified Boundary Conditions Limit the Accuracy of Quantitative Computed Tomography-Based Finite Element Models of Vertebral Failure
Differences in Trabecular Microarchitecture and Simplified Boundary Conditions Limit the Accuracy of Quantitative Computed Tomography-Based Finite Element Models of Vertebral Failure
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DOI：
10.1115/1.4038609
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发表时间：
2018-02-01
影响因子：
1.7
通讯作者：
Morgan, Elise F.
中科院分区：
文献类型：
--
作者：
Hussein, Amira I.;Louzeiro, Daniel T.;Morgan, Elise F.
椎体骨折在老年人中很常见，但由于对所涉及的失效过程的不完全理解，降低其发生率的努力受到阻碍。本研究的目的是阐明腰椎的失效过程，并评估这些过程的定量计算机断层扫描（QCT）有限元（FE）模拟的准确性。在QCT扫描后，脊柱节段（n = 27）包括L1与相邻的椎间盘和相邻的T12和L2终板，以逐步的方式轴向压缩。在每个加载步骤进行微计算机断层扫描。使用数字体积相关（DVC）分析所得到的延时系列图像，以量化整个椎体的变形。虽然在椎骨之间观察到这些变形如何进展的一些多样性，但共同特征是在上级三分之一和同时在中横平面中逐渐发展的大应变，其方式与微观结构参数（如连接密度）的空间变化相关。有限元模拟的结果定性对应于测得的故障模式时，边界条件来自端板的DVC位移。然而，定量对应往往是穷人，特别是当边界条件被简化为均匀的压缩载荷。这些研究结果表明，骨小梁微观结构的变化是椎骨之间的故障模式的差异的原因之一，缺乏将这些变化纳入基于QCT的有限元模型和边界条件的过度简化限制了这些模型在模拟椎骨故障的准确性。
Vertebral fractures are common in the elderly, but efforts to reduce their incidence have been hampered by incomplete understanding of the failure processes that are involved. This study's goal was to elucidate failure processes in the lumbar vertebra and to assess the accuracy of quantitative computed tomography (QCT)-based finite element (FE) simulations of these processes. Following QCT scanning, spine segments (n = 27) consisting of L1 with adjacent intervertebral disks and neighboring endplates of T12 and L2 were compressed axially in a stepwise manner. A microcomputed tomography scan was performed at each loading step. The resulting time-lapse series of images was analyzed using digital volume correlation (DVC) to quantify deformations throughout the vertebral body. While some diversity among vertebrae was observed on how these deformations progressed, common features were large strains that developed progressively in the superior third and, concomitantly, in the midtransverse plane, in a manner that was associated with spatial variations in microstructural parameters such as connectivity density. Results of FE simulations corresponded qualitatively to the measured failure patterns when boundary conditions were derived from DVC displacements at the endplate. However, quantitative correspondence was often poor, particularly when boundary conditions were simplified to uniform compressive loading. These findings suggest that variations in trabecular microstructure are one cause of the differences in failure patterns among vertebrae and that both the lack of incorporation of these variations into QCT-based FE models and the oversimplification of boundary conditions limit the accuracy of these models in simulating vertebral failure.