California Medical Innovations Institute, 11107 Roselle st., San Diego, CA 92121, United States.
Cook Medical, Inc., Bloomington, IN, United States.
J Mech Behav Biomed Mater. 2018 Jan;77:176-186. doi: 10.1016/j.jmbbm.2017.08.031. Epub 2017 Aug 31.
In the present work, we propose the first structural constitutive model of the passive mechanical behavior of the swine colon that is validated against physiological inflation-extension tests, and accounts for residual strains. Sections from the spiral colon and the descending colon were considered to investigate potential regional variability. We found that the proposed constitutive model accurately captures the passive inflation-extension behavior of both regions of the swine colon (coefficient of determination R=0.94±0.02). The model revealed that the circumferential muscle layer does not provide significant mechanical support under passive conditions and the circumferential load is actually carried by the submucosa layer. The stress analysis permitted by the model showed that the colon tissue can distend up to 30% radially without significant increase in the wall stresses suggesting a highly compliant behavior of the tissue. This is in-line with the requirement for the tissue to easily accommodate variable quantities of fecal matter. The analysis also showed that the descending colon is significantly more compliant than the spiral colon, which is relevant to the storage function of the descending colon. Histological analysis showed that the swine colon possesses a four-layer structure similar to the human colon, where the longitudinal muscle layer is organized into bands called taeniae, a typical feature of the human colon. The model and the estimated parameters can be used in a Finite Element framework to conduct simulations with realistic geometry of the swine colon. The resulting computational model will provide a foundation for virtual assessment of safe and effective devices for the treatment of colonic diseases.
在本工作中，我们提出了第一个猪结肠被动力学行为的结构本构模型，该模型通过生理膨胀-拉伸测试进行了验证，并考虑了残余应变。螺旋结肠和降结肠的切片用于研究潜在的区域变异性。我们发现，所提出的本构模型准确地捕捉了猪结肠两个区域的被动膨胀-拉伸行为（决定系数 R=0.94±0.02）。该模型表明，在被动条件下，环形肌层不能提供显著的力学支撑，而环向载荷实际上由黏膜下层承担。该模型允许进行的应力分析表明，结肠组织可以在不显著增加壁面应力的情况下径向膨胀 30%，这表明组织具有高度顺应性。这符合组织需要轻松容纳可变数量粪便的要求。分析还表明，降结肠比螺旋结肠具有更高的顺应性，这与降结肠的储存功能有关。组织学分析表明，猪结肠具有类似于人类结肠的四层结构，其中纵行肌层组织成称为“结肠带”的带，这是人类结肠的一个典型特征。该模型和估计的参数可以在有限元框架中用于具有猪结肠真实几何形状的模拟。所得的计算模型将为虚拟评估治疗结肠疾病的安全有效的设备提供基础。
