Current practices in corrosion, surface characterization, and nickel leach testing of cardiovascular metallic implants

Abstract

In an effort to better understand current test practices and improve nonclinical testing of cardiovascular metallic implants, the Food and Drug Administration (FDA) held a public workshop on Cardiovascular Metallic Implants: corrosion, surface characterization, and nickel leaching. The following topics were discussed: (1) methods used for corrosion assessments, surface characterization techniques, and nickel leach testing of metallic cardiovascular implant devices, (2) the limitations of each of these in vitro tests in predicting in vivo performance, (3) the need, utility, and circumstances when each test should be considered, and (4) the potential testing paradigms, including acceptance criteria for each test. In addition to the above topics, best practices for these various tests were discussed, and knowledge gaps were identified. Prior to the workshop, discussants had the option to provide feedback and information on issues relating to each of the topics via a voluntary preworkshop assignment. During the workshop, the pooled responses were presented and a panel of experts discussed the results. This article summarizes the proceedings of this workshop and background information provided by workshop participants.

On the High Sensitivity of Corrosion Resistance of NiTi Stents with Respect to Inclusions: An Experimental Evidence

“…Corrosion Susceptibility of All Samples. Corrosion susceptibility assessments (F2129-17 19 ) were repeated on the eight specimens of Stents A and B, respectively. The above results demonstrated a clear dependence between the inclusion density and corrosion resistance in the model stents.…”

“…Several points are also worth mentioning: (a) compared to Tubes A and B, Stents A and B seemed to present a slight reduction of inclusion fractions, but the differences were in the magnitude of measurement error; (b) the inclusions could be present as a single type (oxides or carbides) or mixed types; and (c) in the samples with mixed inclusions, the ratios between oxide and carbide were also different from one another. Figure 4b summarizes the results of F2129 19 assessments of all of the stent samples. The standard deviations of the measurements of the stent samples were close to the ASTM (the first two columns) studies.…”

Extracellular Matrix Bioscaffolds as Immunomodulatory Biomaterials

“…Metals and alloys have long been used for orthopedic implants and dental implants, but are typically subject to corrosion, leaching, and adverse immune responses to wear debris. [36][37][38][39][40] Silicone rubber and natural rubber have been used for breast implant and ocular lens applications, among others, but are associated with oil adhesions and other complications associated with the FBR, including capsular contraction that may eventually necessitate the need for explants. [41][42][43][44] Drugeluting and other porous materials and sensor-based strategies to direct tissue repair are eventually ineffective if they fail to address the FBR, as the fibrous capsule that will inevitably surround the material will inhibit diffusion or controlled release of drug or sensor-related signals.…”

The effect of fatigue on the corrosion resistance of common medical alloys

“…This can present logistical, time, and sample size constraints for completion of a corrosion study. These challenges were highlighted at the 2012 FDA Corrosion Workshop and test results submitted by attendees did not show that fatigue loading prior to ASTM F2129 testing was more conservative than corrosion testing of as manufactured components . This work aims to test the hypothesis that fatigue testing reduces the pitting corrosion resistance via damage to the oxide layer.…”