Micromotion between the tibial tray and the polyethylene insert

This study quantifies the micromotion at the polyethylene insert tibial tray interface of four different designs of total knee components as a first step towards determining the role this interface plays in the generation of PE wear debris and subsequent failure of the implant. Evidence of backsurface wear was visible by eye on most PE inserts and easily found by profilometry on all inserts directly below the point of loading on the proximal surface. Design parameters were shown to have a significant effect on micromotion. The consistency of the data for each design testifies to the quality control efforts of the manufacturers. The uniformity of the data over a million cycles indicates that the differences seen are design-related and not evidence of changes due to loading. Prolonged testing is needed to assess the long term stability of insert fixation.