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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.

  1. Determine device contact duration category (limited, prolonged, or permanent)
  2. Document material composition and manufacturing processes
  3. Characterize transformation temperatures of final finished form
  4. Conduct appropriate mechanical testing based on device design
  5. Perform corrosion testing following the recommended testing paradigm
  6. Complete biocompatibility assessment including nickel release risk assessment
  7. Develop appropriate labeling with required warnings
  8. Consider early engagement with FDA through Q-Submission process for specific feedback
  9. Prepare comprehensive test reports with appropriate justifications for test parameters
  10. 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

  • 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

  • Technical Considerations for Nitinol-Containing Medical Devices
  • HTML / PDF
  • Issue date: 2021-07-09
  • Last changed date: 2021-08-09
  • Status: FINAL
  • Official FDA topics: Medical Devices, Animal & Veterinary, Animal Cell-Based Products, Premarket
  • ReguVirta summary file ID: e982859a37acfce7a97813c0e7109f9e
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