New Guidance for UHMWPE Submissions

In the first of several possible material updates in 2016, FDA released draft guidance outlining new information companies must include when submitting devices with Ultra High Molecular Weight Polyethylene (UHMWPE) for approval.

FDA’s recently-released draft guidance, titled “Characterization of Ultrahigh Molecular Weight Polyethylene (UHMWPE) Used in Orthopedic Devices,” breaks UHMWPE materials into four groups: Conventional UHMWPE, Highly Crosslinked UHMWPE, Vitamin E Highly Crosslinked UHMWPE and Non-Conventional UHMWPE. Each offers individualized recommendations for what to include in submissions.

FDA provided a list of general information that should be included with any submission, regardless of UHMWPE type. That list includes:

  • Starting resin (e.g., GUR 1020, GUR 1050, HiMont 1900)
  • Concentration and identification of antioxidant or other additives (in weight percent and parts per million)
  • Resin consolidation method (e.g., ram extrusion, compression molding, etc.)
  • Radiation dose and type (e.g., gamma, electron beam, etc.)
  • Time and temperature of all post-consolidation thermal anneals (e.g., to reduce free radicals, relieve internal stresses, homogenize dopant concentration, etc.)
  • Compression ratio of all mechanical anneals
  • Terminal sterilization method

The draft document also provided the specific suggestions for information to include with each UHMWPE grouping.

For Conventional UHMWPE, FDA recommends including:

  • Tensile properties (e.g., yield strength, ultimate tensile strength, elongation at break) 
  • Impact resistance (either Charpy or Izod)
  • Density

For Highly Crosslinked UHMWPE/XLPE:

  • Comparison of the total absorbed radiation dose to the dose of a legally marketed device 263 with the same intended use
  • Percent crystallinity
  • Melting temperature
  • Biaxial mechanical properties (ultimate load, ultimate displacement, work to failure)
  • Post-accelerated aging oxidation index throughout the sample
  • Trans-vinylene index throughout the sample
  • Crosslink density
  • Fatigue resistance crack propagation testing (ΔKinception, Paris exponent, Paris 271 coefficient)
  • Free radical concentration

For Vitamin E, Highly Crosslinked UHMWPE/VEPE, submissions should include the information provided for Conventional UHMWPE and Highly Crosslinked UHMWPE, in addition to these specific requirements:

  • Stability of antioxidant in the material
  • Effect of antioxidant on the wear mechanism
  • Effect of antioxidant on material consolidation

For Non-Conventional UHMWPE, FDA did not provide specific recommendations.

Orthopaedic device companies can expect a greater focus on materials from FDA in the coming year. Two of FDA’s 2016 scientific priorities relate to materials: 1) modernize biocompatibility/biologic risk evaluation of device materials, and 2) advance methods to predict clinical performance of medical devices and their materials. Both priorities relate to improving methodologies and tools for material testing to ensure the quality and safety of the material, and ultimately the device.