Introduction I have been working with mobile-bearing implant designs for most of my orthopedic career. I continued my interest in mobile-bearing designs focusing on the location of the axis of rotation with cadaver studies on torque rotation. My colleagues and I patented a medial axis mobile-bearing knee but only 25 were implanted and the device was never commercialized. Currently, these are the only two primary mobile-bearing knee implants that have U.S. Food and Drug Administration approval.
Polyethylene wear in mobile-bearing design types.
Our challenge is to improve the wear potential and long-term function of total knees by resolving the kinematic conflict between low stress articulation and rotational freedom. Micromotion can occur between the polyethylene and baseplate in modular fixed-bearing designs. This backside wear may not be possible to eliminate as long as modular designs are used. As a result of wear, either backside or at the tibial femoral articulation, polyethylene debris is created. This debris is highly inflammatory and it is particularly reactive at the submicron size.