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January/February 2011

Knee Bearings

The latest in a series of ASTM International standards developed for the characterization of mobile bearing knees prior to implementation has now been approved by ASTM International Committee F04 on Medical and Surgical Materials and Devices. The new standard, F2777, Test Method for Evaluating Knee Bearing (Tibial Insert) Endurance and Deformation Under High Flexion, is under the jurisdiction of Subcommittee F04.22 on Arthroplasty.

According to Leslie Gilbertson, L. Gilbertson Consulting LLC, and vice chairman, F04.22, F2777 and the three previously approved standards are designed to address the possible failure mechanisms of mobile knee systems, although in some instances they would also be used for fixed bearing knees.

“A group of orthopaedic company representatives was brought together under the Orthopedic Surgical Manufacturers Association to decide on the appropriate test methodologies based on their individual experiences,” says Gilbertson. The resulting test methods have now all become ASTM standards.

In addition to F2777, the other three standards in the series are:

  • F2722, Test Method for Evaluating Mobile Bearing Knee Tibial Baseplate Rotational Stops;
  • F2723, Test Method for Evaluating Mobile Bearing Knee Tibial Baseplate/Bearing Resistance to Dynamic Disassociation; and
  • F2724, Test Method for Evaluating Mobile Bearing Knee Dislocation.

“The concept of a mobile bearing knee system is that it can better approximate the complicated flexion, translation and interior exterior rotation of the natural knee,” says Gilbertson.

According to Gilbertson, primary users of F2777 and the other standards will be implant companies seeking to develop new mobile bearing knee systems and to compare them to other knee systems with no clinical histories. “Academics and surgeons may also be interested in running these tests to decide which knee performs best,” notes Gilbertson.

F04.22 invites all interested parties to take part in its activities and is particularly interested in the participation of orthopaedic companies and academic laboratories in upcoming round robin testing for F2777.


Technical Information: Leslie Gilbertson, L. Gilbertson Consulting LLC, Warsaw, Ind.

Phone: 574-377-0561

ASTM Staff: Daniel Schultz

Phone: 610-832-9716