Polyethylene wear on the distal tibial insert surface in total knee arthroplasty

We studied polyethylene wear damage on articular (superior) and distal (inferior) surfaces of 27 tibial inserts after an average of 50 months in vivo. The damage scoring method overestimated the subtle damage on the inferior surface, but the average superior surface score was still four times the inferior surface score. Inferior surface damage correlated significantly only to implantation time and was highest for inserts having metal backings with holes. Wear damage occurs on the inferior surface of tibial inserts. In the absence of holes in the metal backing and large insert/tray relative motions, however, this wear appears insignificant.