Journal Published Online: 20 January 2011
Volume 8, Issue 2

Damage and Wear: An Important Distinction in Rotating Platform Knee Bearings

CODEN: JAIOAD

Abstract

Rotating platform mobile bearing knees are an appealing approach to the problems of tibial loosening and rotational malignment in fixed bearing knees. A potential disadvantage is the additional large articular surface that accommodates tibio-femoral rotation. Accurately assessing the tribological performance of this additional articular surface is important to understanding how mobile bearings perform in terms of generating polyethylene wear debris and associated osteolysis. A series of 76 retrieved Sigma Rotating Platform bearings were assessed for damage rating according to conventional protocol and through-thickness wear measurements were taken. The results show that the rotation surface of these bearings is very commonly subject to moderate and severe damage and that damage can occur early following implantation. The decrease of the through-thickness dimension is strongly correlated with time in vivo. The rotation surface damage rating shows a weak though statistically significant correlation to through-thickness wear. Three dimensional surface profilometry on the bearings illuminates phenomena that can explain the paradoxical observations that severely damaged bearings may not be worn and worn bearing areas are smoother and show less damage than unworn areas. This study finds that bearing damage is distinct from bearing wear and the two terms are not interchangeable in the context of assessing material loss from artificial knee bearings. While both processes are important in the tribology of knee devices, it is not accurate to use damage on ultrahigh molecular weight polyethylene as a proxy for wear.

Author Information

Currier, John
Dartmouth Biomedical Engineering Center, Thayer School of Engineering, Hanover, NH
Porter, Emily
Dartmouth Biomedical Engineering Center, Thayer School of Engineering, Hanover, NH
Mayor, Michael
Dartmouth Biomedical Engineering Center, Thayer School of Engineering, Hanover, NH
Collier, John
Dartmouth Biomedical Engineering Center, Thayer School of Engineering, Hanover, NH
Van Citters, Douglas
Dartmouth Biomedical Engineering Center, Thayer School of Engineering, Hanover, NH
Pages: 10
Price: $25.00
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Details
Stock #: JAI103164
ISSN: 1546-962X
DOI: 10.1520/JAI103164