In-Vitro Study of Backside Wear Mechanism on Mobile Knee Bearing Components

Backside wear in the form of scratching and pitting observed on a series of mobile bearing rotating platform knee retrievals (n = 100) appears to be indicative of third body wear. The appearance of scratching and pitting on the backside does not correlate with duration in vivo or with linear backside wear measurements, but there is a weak correlation with fixation method indicating that some of the third body debris may be bone cement. Tribological tests representing rotation and fretting in the knee were run with bone cement, bone chips, and metal porous coating beads placed as third bodies in the contact. Results with bone cement show scratches similar to those found on retrievals.