Characterizing fretting damage in different test media for cardiovascular device durability testing

Abstract

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.

Influence of fatigue stress on the radial strength of polymeric braided vascular stents

“…For commercially available Stainless Steel, Cobalt–Chromium, and Nitinol stents, localized crack, fretting wear, and fatigue‐induced fractures were found on their struts surfaces after exposure to radial pulsatile and axial fatigue testing . 10,30,31 Furthermore, for the metallic braided stents, the fretting due to the motion between metallic wires causes the material wear which affects the stents performances and structural integrity 31 . This seems to be limited here with polymeric stents.…”

Corrosion behavior of TiN and TiCN coatings synthesized by PVD on the spark plasma sintered NiTi substrate

“…Up to now, NiTi alloy has been utilized in the cardiovascular, orthopedics, and orthodontics fields as non-vascular and vascular stenting, fixation plates for bone fractures and nails. Hence, NiTi alloy is known as one of the bioinert materials that not only shows weak osteoinductive characteristics when used in living organisms but also corrosion and wear easily occur between them under the influence of physiological environment and human load [24][25][26][27][28]. In addition, the high content of nickel in the alloy is of high concern due to its biocompatibility, since the release of nickel is a potential risk that can cause allergic and toxic reactions [29,30].…”

The effect of nanoparticles of cobalt–chromium on human aortic endothelial cells in vitro

“…This indicates that corrosion of CoCr stents does occur in vivo. In addition, surface deterioration of CoCr alloy was also found in vitro in presence of various factors which can simulate the peri‐implant environment (Kapnisis et al, 2014; Weaver et al, 2018; Xu et al, 2019).…”