Bernini Martina, Colombo Monika, Dunlop Craig, Hellmuth Rudolf, Chiastra Claudio, Ronan William, Vaughan Ted J
Biomechanics Research Centre (BioMEC), School of Engineering, College of Science and Engineering, National University of Ireland, Galway, Ireland; Vascular Flow Technologies, Dundee, UK.
Laboratory of Biological Structure Mechanics (LaBS), Dept. Chem., Materials and Chem. Eng. "Giulio Natta", Politecnico di Milano, Italy; Institute for Chemical and Bioengineering, ETH, Zurich, Switzerland.
J Mech Behav Biomed Mater. 2022 Aug;132:105259. doi: 10.1016/j.jmbbm.2022.105259. Epub 2022 May 5.
Despite being commonly employed to treat peripheral artery disease, self-expanding Nitinol stents are still associated with relatively high incidence of failure in the mid- and long-term due to in-stent restenosis or fatigue fracture. The practice of stent oversizing is necessary to obtain suitable lumen gain and apposition to the vessel wall, though it is regarded as a potential cause of negative clinical outcomes when mis-sizing occurs. The objective of this study was to develop a computational model to provide a better understanding of the structural effects of stent sizing in a patient-specific scenario, considering oversizing ratio OS, defined as the stent nominal diameter to the average vessel diameter, between 1.0 and 1.8. It was found that OS < 1.2 resulted in problematic short-term outcomes, with poor lumen gain and significant strut malapposition. Oversizing ratios that were in the range 1.2 ≤ OS ≤ 1.4 provided the optimum biomechanical performance following implantation, with improved lumen gain, reduced incomplete stent apposition and favourable predicted long-term fatigue performance. Excessive oversizing, OS > 1.4, did not provide any further benefit in outcomes, showing limited increases in lumen gain and unfavourable long-term performance, with higher mean strain values predicted from the fatigue analysis. Therefore, our findings predict that the optimal oversizing ratio for self-expanding Nitinol stents is in the range of 1.2 ≤ OS ≤ 1.4, which is similar to clinical observations, with this study providing detailed insight into the biomechanical basis for this.
尽管自膨胀镍钛诺支架常用于治疗外周动脉疾病，但由于支架内再狭窄或疲劳骨折，其在中长期的失败发生率仍然相对较高。支架尺寸过大的做法对于获得合适的管腔增益以及与血管壁的贴合是必要的，不过当尺寸错误时，它被视为负面临床结果的一个潜在原因。本研究的目的是开发一个计算模型，以更好地理解在特定患者情况下支架尺寸的结构效应，考虑尺寸过大比率OS（定义为支架标称直径与平均血管直径之比）在1.0至1.8之间。研究发现，OS < 1.2会导致短期结果出现问题，管腔增益不佳且支柱贴合不良。1.2≤OS≤1.4范围内的尺寸过大比率在植入后提供了最佳的生物力学性能，管腔增益得到改善，支架不完全贴合减少，并且预测的长期疲劳性能良好。过度尺寸过大，即OS > 1.4，在结果方面没有提供任何进一步的益处，管腔增益增加有限且长期性能不佳，疲劳分析预测的平均应变值更高。因此，我们的研究结果预测，自膨胀镍钛诺支架的最佳尺寸过大比率在1.2≤OS≤1.4范围内，这与临床观察结果相似，本研究为此提供了对生物力学基础的详细见解。
