ASTM F2777 – Standard Test Method for Evaluating Knee Bearing (Tibial Insert) Endurance and Deformation Under High Flexion

This standard specifies a test method for determining the endurance properties and deformation, under specified laboratory conditions, of ultra-high molecular weight polyethylene (UHMWPE) tibial bearing components used in bicompartmental or tricompartmental knee prosthesis designs.  This test method is intended to simulate near posterior edge loading similar to the type of loading that would occur during high flexion motions such as squatting or kneeling.  Although the methodology described attempts to identify physiological orientations and loading conditions, the interpretation of results is limited to an in vitro comparison between knee prosthesis designs and their ability to resist deformation and fracture under stated test conditions.

  • Perform an A-P Draw Test per ASTM 1223 before and after the fatigue test.
  • Vertical Distraction measurements (when appropriate) are taken before and after the fatigue test.
  • Measure the posterior bearing tilt displacement before and after the fatigue test. Change in these displacements after testing may be useful as an indicator of damage.
  • The fatigue test consists of cycling between 2275 Ns and 275 Ns at 2 Hertz for 220,000 cycles or until the bearing component fractures or is no longer attached to the tibial component, which-ever occurs first.

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