Technical Considerations for Nitinol-Containing Medical Devices
This guidance outlines technical considerations for medical devices containing Nitinol, focusing on devices with at least one patient-contacting component made of Nitinol. It provides recommendations for non-clinical assessment of these devices, particularly addressing the unique properties of Nitinol compared to conventional metals.
Recommended Actions
- Determine device contact duration category (limited, prolonged, or permanent)
- Document material composition and manufacturing processes
- Characterize transformation temperatures of final finished form
- Conduct appropriate mechanical testing based on device design
- Perform corrosion testing following the recommended testing paradigm
- Complete biocompatibility assessment including nickel release risk assessment
- Develop appropriate labeling with required warnings
- Consider early engagement with FDA through Q-Submission process for specific feedback
- Prepare comprehensive test reports with appropriate justifications for test parameters
- Document any deviations from recommended testing with scientific rationale
Key Considerations
Non-clinical testing
- Mechanical testing should be performed under displacement control unless otherwise justified
- Testing should be conducted at clinically relevant temperatures
- Fatigue testing should be performed in liquid test solution rather than air
- For shape memory devices, cyclic shape memory testing at clinically relevant temperature range is recommended
- Computational stress/strain analyses should use appropriate material models for Nitinol
Labelling
- Warning statement required for prolonged and permanent contacting devices about Nitinol containing nickel and potential allergic reactions
- Patients should be counseled on device materials and potential allergies/hypersensitivity
Biocompatibility
- Follow ISO 10993-1 guidance for biocompatibility assessment
- Risk assessment comparing nickel release to Tolerable Intake (TI) value of 0.5 µg/kg/day for parenteral exposure
- Alternative TI may be derived for shorter exposure duration with appropriate justification
Safety
- Pitting corrosion testing per ASTM F2129 for prolonged exposure and permanent contacting devices
- Nickel ion release testing if corrosion resistance criteria not met
- Galvanic corrosion testing if Nitinol contacts dissimilar metals
Other considerations
- Material composition should be provided and conform to recognized standards
- Manufacturing process flow chart required, including thermal processes and surface processing steps
- Transformation temperatures of final finished form should be provided
- Surface processing effects on corrosion/nickel leach performance should be evaluated
Relevant Guidances
- Use of ISO 10993-1 for Biological Evaluation and Testing of Medical Devices
- Requests for Feedback and Meetings for Medical Device Submissions: The Q-Submission Program
- Recommended Format and Content for Non-Clinical Bench Performance Testing in Medical Device Premarket Submissions
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 F2063: Standard Specification for Wrought Nickel-Titanium Shape Memory Alloys for Medical Devices and Surgical Implants
- ASTM F2004: Standard Test Method for Transformation Temperature of Nickel-Titanium Alloys by Thermal Analysis
- ASTM F2082: Standard Test Method for Determination of Transformation Temperature of Nickel-Titanium Shape Memory Alloys by Bend and Free Recovery
- ASTM F3306: Standard Test Method for Ion Release Evaluation of Medical Implants
- ASTM F3044: Standard Test Method for Evaluating the Potential for Galvanic Corrosion for Medical Implants
- ISO 10993-1: Biological evaluation of medical devices - Part 1: Evaluation and testing within a risk management process
- ISO 10993-17: Biological evaluation of medical devices - Part 17: Establishment of allowable limits for leachable substances
Original guidance
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