Today's News

Saturday, March 13, 2004

Reducing backside damage in TKR

By Jeannie Glickson

Backside damage of the polyethylene tibial inserts in total knee replacement can contribute to implant failure due to wear particle-induced osteolysis. Researchers for Poster Exhibit P104 were able to characterize backside damage on retrieved tibial inserts and identify the tribological factors involved.

Researchers performed a quantitative analysis on 53 retrieved tibial inserts. Three types of inserts were analyzed:

The retrieved tibial trays had no screw holes and the inserts were sterilized by either "gamma-in-air," gas plasma or ethylene oxide. Investigators applied a scoring system based on the percentage of surface area containing burnishing, grooving, indentations, stippling, deformation, delamination, pitting and cracking. Scanning electron microscopy and surface profilometry were used to characterize the damage features.

Researchers observed backside damage on all retrieved tibial inserts with no strong influence of sterilization technique. Significant observations included:

Based on their observations, researchers concluded that backside damage is caused by fretting from micromotion between the insert and the tray, and the roughness of the tray surface will influence the damage features. However, the overall damage score suggested that the partial peripheral capture mechanism was more effective than the surface finish in reducing backside damage. Thus, using inserts with improved locking mechanisms and unpolished tibial trays could reduce backside damage in total knee replacements.

The research team included Jan Mels B. Brandt, MD; Chris Haydon; Richard W. McCalden, MD; Robert Barry Bourne, MD; Steven J. MacDonald, MD, and Cecil H. Rorabeck, MD, all of London, Ontario, Canada, and John B. Medley, PhD, of Waterloo, Ontario, Canada.

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Last modified 01/March/2004