Division of Applied Mechanics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, USA.
Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA.
J Mech Behav Biomed Mater. 2018 Jun;82:338-344. doi: 10.1016/j.jmbbm.2018.04.004. Epub 2018 Apr 4.
In vitro durability tests of cardiovascular devices are often used to evaluate the potential for fretting damage during clinical use. Evaluation of fretting damage is important because severe fretting can concentrate stress and lead to the loss of structural integrity. Most international standards call for the use of phosphate buffered saline (PBS) for such tests although there has been little evidence to date that the use of PBS is appropriate in terms of predicting the amount of fretting damage that would occur in vivo. In order to determine an appropriate test media for in vitro durability tests where fretting damage is being evaluated, we utilized an in vitro test that is relevant to cardiovascular devices both in terms of dimensions and materials (nitinol, cobalt-chromium, and stainless steel) to characterize fretting damage in PBS, deionized water (DIW), and heparinized porcine blood. Overall, tests conducted in blood were found to have increased levels of fretting damage over tests in DIW or PBS, although the magnitude of this difference was smaller than the variability for each test media. Tests conducted in DIW and PBS led to mostly similar amounts of fretting damage with the exception of one material combination where DIW had greatly reduced damage compared to PBS and blood. Differences in fretting damage among materials were also observed with nitinol having less fretting damage than stainless steel or cobalt-chromium. In general, evaluating fretting damage in PBS or DIW may be appropriate although caution should be used when selecting test media and interpreting results given some of the differences observed across different materials.
心血管设备的体外耐久性测试通常用于评估临床使用过程中微动损伤的潜在风险。评估微动损伤很重要，因为严重的微动会集中应力，导致结构完整性丧失。大多数国际标准都要求使用磷酸盐缓冲盐水 (PBS) 进行此类测试，尽管迄今为止几乎没有证据表明 PBS 的使用适合预测体内会发生多少微动损伤。为了确定正在评估微动损伤的体外耐久性测试的适当测试介质，我们利用与心血管设备在尺寸和材料（镍钛诺、钴铬和不锈钢）方面都相关的体外测试来表征 PBS、去离子水 (DIW) 和肝素化猪血液中的微动损伤。总体而言，与 DIW 或 PBS 中的测试相比，血液中的测试发现微动损伤程度更高，尽管这种差异的幅度小于每种测试介质的变异性。DIW 和 PBS 中的测试导致的微动损伤程度大多相似，但有一种材料组合除外，与 PBS 和血液相比，DIW 大大降低了损伤程度。不同材料之间也观察到微动损伤的差异，镍钛诺的微动损伤比不锈钢或钴铬少。一般来说，评估 PBS 或 DIW 中的微动损伤可能是合适的，但是在选择测试介质和解释结果时应该谨慎，因为在不同材料之间观察到了一些差异。
