STP1531: Wear Rate in a Series of Retrieved RP Knee Bearings

    Currier, John H.
    Thayer School of Engineering, Dartmouth College, Hanover, NH

    Mayor, Michael B.
    Thayer School of Engineering, Dartmouth College, Hanover, NH

    Collier, John P.
    Thayer School of Engineering, Dartmouth College, Hanover, NH

    Currier, Barbara H.
    Thayer School of Engineering, Dartmouth College, Hanover, NH

    Van Citters, Douglas W.
    Thayer School of Engineering, Dartmouth College, Hanover, NH

    Pages: 13    Published: Feb 2011


    Abstract

    Rotating platform mobile bearing knees are an appealing approach to the problems of tibial loosening and rotational mal-alignment that are of concern with fixed bearing knees. A potential disadvantage of rotating platform (RP) bearings is ultra-high molecular weight polyethylene (UHMWPE) wear debris from the large additional backside articular surface that accommodates tibio-femoral rotation. The investigation of a series of 76 rotating platform knees (Sigma® RP, DePuy/J&J, Warsaw, IN) indicates that UHMWPE bearing wear, as measured by change in through-thickness dimension, increases monotonically with time in vivo. Total wear penetration rate is 0.023 mm/year and shows a decreasing trend, though this trend is not statistically significant. The current study results are consistent with the decreasing wear rate previously reported in a series of LCS® RP (DePuy/J&J, Warsaw, IN) knee. This decreasing wear rate stands in contrast to an increasing backside-only wear rate reported in fixed bearing knees. An important contribution of the current study is that it provides a conservative measurement of total wear penetration and penetration rate in one mobile bearing design over time out to >8 years.

    Keywords:

    knee wear, UHMWPE wear, mobile bearing knees, backside wear


    Paper ID: STP153120120013

    Committee/Subcommittee: F04.22

    DOI: 10.1520/STP153120120013


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