Puértolas S, Peña E, Herrera A, Ibarz E, Gracia L
Department of Mechanical Engineering, University of Zaragoza, Zaragoza, Spain; Aragón Institute for Engineering Research, Zaragoza, Spain.
Department of Mechanical Engineering, University of Zaragoza, Zaragoza, Spain; Aragón Institute for Engineering Research, Zaragoza, Spain; CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Zaragoza, Spain.
J Mech Behav Biomed Mater. 2020 Feb;102:103507. doi: 10.1016/j.jmbbm.2019.103507. Epub 2019 Oct 24.
For colonic stents design, the interaction with colonic tissue is essential in order to characterize the appropriate radial stiffness which provides a minimum lumen for intestinal transit to be maintained. It is therefore important to develop suitable constitutive models allowing the mechanical behavior of the colon tissue to be characterized. The present work investigates the biomechanical behavior of colonic tissue by means of biaxial tests carried out on different parts of the colonic tract taken from several porcine specimens. Samples from the colonic tract were quasi-statically tensioned using a load-controlled protocol with different tension ratios between the circumferential and the axial directions. Fitting techniques were then used to adjust specific hyperelastic models accounting for the multilayered conformation of the colonic wall and the fiber-reinforced configuration of the corresponding tissues. It was found that the porcine colon changed from a more isotropic to a more anisotropic tissue and became progressively more flexible and compliant in circumferential direction depending on the position along the duct as it approaches the rectum. The best predictive capability of mechanical behavior corresponds to the Four Fiber Family model showing mean values of coefficient of determination R=0.97, and a normalized root mean square error of ε=0.0814 for proximal spiral samples, and R=0.89 , ε=0.1600 and R=0.94 , ε=0.1227 for distal spiral and descending colon samples, respectively. The other analyzed models provide good results for proximal spiral colon specimens, which have a lower degree of anisotropy. The analyzed models with the fitted elastic parameters can be used for more realistic and reliable FE simulations, providing the appropriate framework for the design of optimal devices for the treatment of colonic diseases.
对于结肠支架的设计，与结肠组织的相互作用至关重要，以便确定合适的径向刚度，从而为维持肠道运输提供最小管腔。因此，开发合适的本构模型来表征结肠组织的力学行为非常重要。本研究通过对取自多个猪标本的结肠不同部位进行双轴试验，研究结肠组织的生物力学行为。使用负载控制方案对结肠段样本进行准静态拉伸，在圆周方向和轴向方向之间采用不同的拉伸比。然后使用拟合技术来调整特定的超弹性模型，该模型考虑了结肠壁的多层结构以及相应组织的纤维增强结构。研究发现，猪结肠组织从各向同性更强转变为各向异性更强，并且随着接近直肠，沿管道的位置不同，其在圆周方向上逐渐变得更加柔韧且顺应性更强。力学行为的最佳预测能力对应于四纤维族模型，对于近端螺旋样本，决定系数R的平均值为0.97，归一化均方根误差ε为0.0814；对于远端螺旋和降结肠样本，R分别为0.89、ε为0.1600以及R为0.94、ε为0.1227。其他分析模型对于各向异性程度较低的近端螺旋结肠标本提供了良好的结果。具有拟合弹性参数的分析模型可用于更真实可靠的有限元模拟，为设计治疗结肠疾病的最佳装置提供合适的框架。
