On incorporating osmotic prestretch/prestress in image-driven finite element simulations of cartilage
On incorporating osmotic prestretch/prestress in image-driven finite element simulations of cartilage
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DOI：
10.1016/j.jmbbm.2018.06.014
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发表时间：
2018-10-01
影响因子：
3.9
通讯作者：
Pierce, David M.
中科院分区：
文献类型：
--
作者：
Wang, Xiaogang;Eriksson, Thomas S. E.;Pierce, David M.
在体内进行的医学成像捕获了Donnan渗透载荷下的几何形状，即使在关节机械卸载的情况下也是如此。因此，基于此类软骨医学图像构建的患者特异性有限元（FE）模型代表渗透诱导的预拉伸/预应力状态。当将经典建模方法应用于患者特定的软骨模拟时，出现了理论上的不一致：体内成像几何（用于构建模型）不是一个卸载的，无应力的参考配置。此外，在拟合包括渗透膨胀在内的非线性本构模型（以获得材料参数）时，如果假设由渗透加载的软骨生成的实验数据从无应力参考配置开始，则拟合的应力-拉伸关系（参数）实际上将描述不同的行为。在本研究中，我们：(1)建立了一种实用的计算方法，将渗透诱导的预拉伸/预应力纳入软骨图像驱动模拟中；(2)研究在拟合包括渗透肿胀在内的纤维增强双相软骨本构模型和模拟软骨反应时，考虑预拉伸/预应力状态的影响。我们的结果强调了在解决感兴趣的边值问题之前，在成像配置中确定由渗透载荷诱导的软骨内预拉伸/预应力状态的重要性。通过我们新的本构模型和建模方法，我们的目标是提高基于fe的、患者特异性关节和软骨生物力学模拟的保真度。改进的模拟可以为医学研究人员提供通常在临床环境中无法获得的新信息，这些信息可能有助于更好地了解软骨疾病的病理生理学。
Medical imaging performed in vivo captures geometries under Donnan osmotic loading, even when the articulating joint is otherwise mechanically unloaded. Hence patient-specific finite element (FE) models constructed from such medical images of cartilage represent osmotically induced prestretched/prestressed states. When applying classical modeling approaches to patient-specific simulations of cartilage a theoretical inconsistency arises: the in-vivo imaged geometry (used to construct the model) is not an unloaded, stress-free reference configuration. Furthermore when fitting nonlinear constitutive models that include osmotic swelling (to obtain material parameters), if one assumes that experimental data-generated from osmotically loaded cartilage-begin from a stress-free reference configuration the fitted stress-stretch relationship (parameters) obtained will actually describe a different behavior. In this study we: (1) establish a practical computational method to include osmotically induced prestretch/prestress in image-driven simulations of cartilage; and (2) investigate the influence of considering the prestretched/prestressed state both when fitting fiber-reinforced, biphasic constitutive models of cartilage that include osmotic swelling and when simulating cartilage responses. Our results highlight the importance of determining the prestretched/prestressed state within cartilage induced by osmotic loading in the imaged configuration prior to solving boundary value problems of interest. With our new constitutive model and modeling methods, we aim to improve the fidelity of FE-based, patient-specific biomechanical simulations of joints and cartilage. Improved simulations can provide medical researchers with new information often unavailable in a clinical setting, information that may contribute to better insight into the pathophysiology of cartilage diseases.