Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology, Limassol, 3036 Cyprus.
J Mech Behav Biomed Mater. 2013 Apr;20:227-36. doi: 10.1016/j.jmbbm.2012.11.006. Epub 2012 Dec 13.
Preliminary studies have revealed that some stents undergo corrosion and fatigue-induced fracture in vivo, with significant release of metallic ions into surrounding tissues. A direct link between corrosion and in-stent restenosis has not been clearly established; nonetheless in vitro studies have shown that relatively high concentrations of heavy metal ions can stimulate both inflammatory and fibrotic reactions, which are the main steps in the process of restenosis. To isolate the mechanical effects from the local biochemical effects, accelerated biomechanical testing was performed on single and overlapping Nickel-Titanium (NiTi) stents subjected to various degrees of curvature. Post testing, stents were evaluated using Scanning Electron Microscopy (SEM) to identify the type of surface alterations. Fretting wear was observed in overlapping cases, in both straight and curved configurations. Stent strut fractures occurred in the presence of geometric curvature. Fretting wear and fatigue fractures observed on stents following mechanical simulation were similar to those from previously reported human stent explants. It has been shown that biomechanical factors such as arterial curvature combined with stent overlapping enhance the incidence and degree of wear and fatigue fracture when compared to single stents in a straight tube configuration.
初步研究表明，一些支架在体内会发生腐蚀和疲劳引起的断裂，大量金属离子会释放到周围组织中。腐蚀与支架内再狭窄之间并没有明确的直接联系；然而，体外研究表明，相对较高浓度的重金属离子可以刺激炎症和纤维化反应，这是再狭窄过程中的主要步骤。为了将机械效应与局部生化效应隔离开来，对不同程度弯曲的单个和重叠的镍钛（NiTi）支架进行了加速生物力学测试。测试后，使用扫描电子显微镜（SEM）对支架进行评估，以确定表面改变的类型。在重叠的情况下，无论是直线还是曲线配置，都观察到微动磨损。在存在几何曲率的情况下，支架支柱发生了断裂。在机械模拟后观察到的支架上的微动磨损和疲劳断裂与先前报告的人类支架样本中的断裂相似。研究表明，与直线管配置中的单个支架相比，动脉弯曲与支架重叠等生物力学因素会增加磨损和疲劳断裂的发生率和程度。
