Corrosion Testing and Surface Characterization Requirements for Intravascular Stents
This guidance addresses self-expanding and balloon expandable extracranial intravascular stents and their associated delivery systems used in coronary or peripheral arteries and saphenous vein grafts. It provides updates on specific aspects: pitting corrosion potential, galvanic corrosion, surface characterization, and nickel ion release testing.
Recommended Actions
- Develop test protocol for pitting corrosion testing according to ASTM F2129
- Assess need for galvanic corrosion testing based on material combinations
- Evaluate surface finishing process and determine if surface characterization is needed
- For nickel-rich alloys:
- Plan nickel ion release testing if required
- Develop risk assessment for nickel release
- Document justifications for:
- Sample selection and size
- Test duration
- Any deviations from recommended methods
- Establish acceptance criteria based on predicate devices or published guidelines
- Validate analytical methods for nickel ion release testing
- Consider implementing a testing flow following the provided flowchart in Appendix 1
Key Considerations
Non-clinical testing
- Pitting corrosion testing should be performed on as-manufactured stents after simulated use testing
- Test setup should meet ASTM G5-14 criteria
- Test worst-case device sizes in terms of corrosion susceptibility
- Use samples from multiple lots
- Galvanic corrosion testing may be replaced by justification if coupling potentials are small and surface ratios are low
Biocompatibility
- For nickel-rich alloys, quantify nickel ion release over minimum 30-60 days if corrosion resistance results don’t meet criteria
- Use buffered solution at physiologic temperature and pH
- Perform sampling at adequate intervals to capture initial bolus release
- Conduct validation testing of analytical instrumentation
- Perform risk assessment for nickel release considering toxicological risks
Safety
- Intravascular metallic stents should have polished, passive and clean surface
- Surface characterization required if:
- Other test results don’t meet acceptance criteria
- No final passivation step is used
- Non-standard surface finishing process is used
- Oxide layer should be less than 50nm and consist primarily of TiO2 for nitinol
Other considerations
- Test devices should be representative of final sterilized devices
- Consider manufacturing variations in sample selection
- Provide justification for sample sizes and selection criteria
Relevant Guidances
- Non-Clinical Testing and Labeling Requirements for Extracranial Intravascular Stents and Delivery Systems
- Technical Considerations for Nitinol-Containing Medical Devices
- Coronary, Peripheral, and Neurovascular Guidewires - Performance Testing and Documentation Requirements
- Use of ISO 10993-1 for Biological Evaluation and Testing of Medical Devices
Related references and norms
- ASTM F2129: Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Susceptibility of Small Implant Devices
- ASTM G5-14: Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements
Original guidance
This post is licensed under CC BY 4.0 by the author.