Sokolis Dimitrios P
Laboratory of Biomechanics, Center of Clinical, Experimental Surgery, and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
J Biomech. 2020 Aug 26;109:109940. doi: 10.1016/j.jbiomech.2020.109940. Epub 2020 Jul 9.
The human ureters have not been thoroughly explored from the biomechanics perspective, despite the wealth of such data for other soft-tissue types. This study was motivated by the need to use relevant biomechanical data from human ureters and microstructure-based material formulations for simulations of ureteral peristalsis and stenting. Our starting choice was the four-fiber family model that has proven its validity as a descriptor of the multiaxial response of cardiovascular tissues. The degree of model complexity, required for rigorous fits to passive quasi-static pressure-diameter-force data at several axial stretches, was systematically investigated. Ureteral segments from sixteen human autopsy subjects were evaluated. A diagonal and axial family model allowed equally-good fits as the full model for all age groups and ureteral regions; considerably better than those allowed by the phenomenological Fung-type model whose root-mean-square error of fitting was three-fold greater. This reduced model mimicked the structure seen in histologic sections, namely plentiful diagonal collagen fibers in the lamina propria and axial fibers in the muscle and adventitia. The paucity of elastin fibers and mixed muscle orientation justified the use of isotropic muscle-dominated matrix with small neo-Hookean parameter values. The significantly thicker lamina propria in the lower than the upper ureter of young subjects (312 ± 27 vs. 232 ± 26 μm; mean ± standard error) corroborated the significant regional differences in diagonal-fiber family parameter values. The significant muscle thickening with age (upper ureter: 373 ± 48 vs. 527 ± 67 μm; middle: 388 ± 29 vs. 575 ± 69 μm; lower: 440 ± 21 vs. 602 ± 71 μm) corroborated the significant age-related increase in axial-fiber family parameter values.
尽管有大量关于其他软组织类型的生物力学数据，但从生物力学角度对人体输尿管的研究尚未充分开展。本研究的动机是需要利用人体输尿管的相关生物力学数据和基于微观结构的材料配方来模拟输尿管蠕动和支架植入。我们最初选择的是四纤维族模型，该模型已证明其作为心血管组织多轴响应描述符的有效性。系统地研究了在几个轴向拉伸下对被动准静态压力 - 直径 - 力数据进行严格拟合所需的模型复杂度。对16名人体尸检受试者的输尿管段进行了评估。对于所有年龄组和输尿管区域，对角和轴向纤维族模型与完整模型的拟合效果相当；明显优于现象学冯氏模型，后者的拟合均方根误差大三倍。这种简化模型模仿了组织学切片中看到的结构，即在固有层中有大量对角胶原纤维，在肌肉和外膜中有轴向纤维。弹性纤维数量稀少且肌肉方向混合，这证明使用具有小neo-Hookean参数值的各向同性肌肉主导基质是合理的。年轻受试者下输尿管的固有层明显比上输尿管厚（312±27 vs. 232±26μm；平均值±标准误差），这证实了对角纤维族参数值存在显著的区域差异。随着年龄增长，肌肉显著增厚（上输尿管：373±48 vs. 527±67μm；中输尿管：388±29 vs. 575±69μm；下输尿管：440±21 vs. 602±71μm），这证实了轴向纤维族参数值随年龄显著增加。
