Clouthier Allison L, Hosseini Hadi S, Maquer Ghislain, Zysset Philippe K
Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, 3014 Bern, Switzerland.
Med Eng Phys. 2015 Jun;37(6):599-604. doi: 10.1016/j.medengphy.2015.03.007. Epub 2015 Apr 23.
Vertebral compression fractures are becoming increasingly common. Patient-specific nonlinear finite element (FE) models have shown promise in predicting yield strength and damage pattern but have not been experimentally validated for clinically relevant vertebral fractures, which involve loading through intervertebral discs with varying degrees of degeneration up to large compressive strains. Therefore, stepwise axial compression was applied in vitro on segments and performed in silico on their FE equivalents using a nonlocal damage-plastic model including densification at large compression for bone and a time-independent hyperelastic model for the disc. The ability of the nonlinear FE models to predict the failure pattern in large compression was evaluated for three boundary conditions: healthy and degenerated intervertebral discs and embedded endplates. Bone compaction and fracture patterns were predicted using the local volume change as an indicator and the best correspondence was obtained for the healthy intervertebral discs. These preliminary results show that nonlinear finite element models enable prediction of bone localisation and compaction. To the best of our knowledge, this is the first study to predict the collapse of osteoporotic vertebral bodies up to large compression using realistic loading via the intervertebral discs.
椎体压缩骨折正变得越来越常见。针对特定患者的非线性有限元（FE）模型在预测屈服强度和损伤模式方面已显示出前景，但尚未针对临床相关的椎体骨折进行实验验证，临床相关的椎体骨折涉及通过退变程度不同的椎间盘加载直至产生大的压缩应变。因此，在体外对节段施加逐步轴向压缩，并使用非局部损伤塑性模型在其有限元等效模型上进行计算机模拟，该模型包括骨在大压缩时的致密化以及椎间盘的与时间无关的超弹性模型。针对三种边界条件评估了非线性有限元模型预测大压缩时失效模式的能力：健康和退变的椎间盘以及嵌入的终板。使用局部体积变化作为指标预测骨压实和骨折模式，并且对于健康椎间盘获得了最佳的一致性。这些初步结果表明，非线性有限元模型能够预测骨的定位和压实。据我们所知，这是第一项通过椎间盘使用实际载荷预测骨质疏松椎体直至大压缩时塌陷的研究。
