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FDA Finalizes Guidance for UHMWPE used in Orthopedic Devices

FDA released new guidance regarding the characterization of ultrahigh molecular weight polyethylene (UHMWPE) used in orthopedic devices. The guidance provides orthopedic manufacturers direction in determining the appropriate information and testing needed for regulatory submissions.

There are three main areas covered in FDA’s new guidance: Material Processing and Characterization, Biocompatibility and Shelf Life and Packaging. However, the guidance does not address device-specific functional testing, such as for impingement, wear or interconnection strength. Applicable tests of that nature will continue to be determined on a case-by-case basis. The guidance’s scope applies to four general categories of UHMWPE: conventional, non-conventional, highly crosslinked and antioxidant highly crosslinked, the latter of which extends the category beyond vitamin-E.

Material Processing and Characterization
For all material types and submission types, FDA recommends that manufacturers provide the following general technical information regarding the UHMWPE material:

  • Starting resin (e.g., GUR 1020, GUR 1050)
  • Resin consolidation method (e.g., ram extrusion, compression molding)
  • Terminal sterilization method

Depending on the type of UHMWPE used, different mechanical and chemical characterizations should be provided in accordance with FDA’s chart summary:

Property

 Conventional  

 HXLPE  

 AO- HXLPE  

  Non-Conventional  

 Relevant Standards

Tensile Properties X X X X ASTM F648, F2759
Crystallinity, Melting Temperature   X X X*  ASTM F2625, F2759  
Impact Resistance X X X X ASTM F648, F2565,   2759
Trans-vinylene index   X X X* ASTM F2381, F2625, F2759

Post-accelerated Aging;
Maximum Oxidation Index, and/or Mechanical Properties

  X X X* ASTM F2003, F2102, F2759
Density X X X X ASTM F648
Crosslink Density   X X X* N/A
Fatigue Resistance   X X X ASTM F2565, F2759
Free Radical Concentration   X X X* N/A
Morphology Testing     X X* ASTM F648
(Annex 2)

*Chart courtesy of FDA

Biocompatibility
FDA recommends that manufacturers determine the biocompatibility of all materials present in a device; therefore, it’s not a surprise that this is a subject of the guidance. Biocompatibility can be determined by either referencing an existing legally-marketed device with identical UHMWPE materials or by conducting new biocompatibility risk assessments.

There are existing resources to help with this process, including FDA’s guidance, “Use of International Standard ISO 109931, ‘Biological evaluation of medical devices – Part 1: Evaluation and testing within a risk management process’ ”(referred to as “CDRH’s 2016 Biocompatibility Guidance”), which identifies the type of biocompatibility assessments that should be considered and recommendations on how to conduct related tests.

Shelf Life and Packaging
In order to protect implantable devices containing UHMWPE materials, shelf-life and packaging testing must be conducted. Expiration dates must be tested to support package integrity for maintaining device sterility. Also, mechanical properties of UHMWPE that contain unstable free radicals may degrade if the product is exposed to air during shelf storage. Similarly, the shelf-life of UHMWPE that has been irradiated and packaged in an inert environment may be limited by substandard packaging. That being the case, FDA recommends that the stability of UHMWPE materials used in implantable devices be assessed throughout the duration of specified shelf life.

Specifically, FDA recommends that manufacturers follow methods described in the FDA-recognized series of consensus standards, ISO 11607-1: Packaging for terminally sterilized medical devices – Part 1: Requirements for materials, sterile barrier systems and packaging systems, and ISO 11607-2: Packaging for terminally sterilized medical devices – Part 2: Validation requirements for forming, sealing and assembly processes.

Before this document was released, the FDA guidance in place for UHMWPE characterizations dated back to March 1995. The industry has progressed significantly over the last 24 years and new guidance is a welcome resource for industry. The Advanced Medical Technology Association (AdvaMed) published its comments when the draft of this guidance was released in 2016, calling for recognition of ASTM F2759 and ASTM F2565 standards. Both are incorporated in FDA’s final guidance.

 

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