, Volume 470, Issue 7, pp 1860-1868
Date: 08 Feb 2012

Knee Wear Measured in Retrievals: A Polished Tray Reduces Insert Wear

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Topic
Knee

Abstract

Background

Polyethylene wear is often cited as the cause of failure of TKA. Rotating platform (RP) knees show notable surface damage on the rotating surface raising concerns about increased wear compared to fixed bearing inserts.

Questions/purposes

We therefore addressed the following questions: Is wear in RP inserts increased compared to that in fixed bearing inserts? Does the surface roughness of the tibial tray have a measurable impact on in vivo wear of modular knees? And does wear rate differ between posterior stabilized (PS) and cruciate retaining (CR) knees?

Methods

We compared wear in two series of retrieved knee devices: 94 RP mobile bearings with polished cobalt-chrome (CoCr) trays and 218 fixed bearings with both rough titanium (Ti) and polished CoCr trays. Minimum implantation time was 0.4 months (median, 36 months; range, 0.4–124 months) and 2 months (median, 72 months; range, 2–179 months) for the RP and fixed bearing series, respectively.

Results

Wear rate was lower for RP inserts than for fixed bearing inserts. Backside wear rate was lower for fixed bearing inserts mated to polished CoCr trays than for inserts from rough Ti trays. Inserts against polished trays (RP or fixed bearing) showed no increase in wear rate increase over time. Wear rate of PS knees was similar to that of CR knees.

Conclusions

We found mobile bearing knees have reduced wear rate compared to fixed bearings, likely due to the polished CoCr tibial tray surface. Fixed bearing inserts in polished CoCr trays wear less than their counterparts in rough Ti trays, and the wear rate of inserts from polished CoCr trays does not appear to increase with time.

One of the authors (DJB) certifies that he has or may receive payments or benefits, in any one year, an amount in excess of $100,000 from a commercial entity (DePuy Orthopaedics, Inc, a Johnson and Johnson company, Warsaw, IN, USA) related to this work; one of the authors (MBM) certifies that he has or may receive payments or benefits, in any one year, an amount in excess of $10,000 from a commercial entity (DePuy Orthopaedics, Inc) related to this work; one of the authors (JPC) is a consultant from a commercial entity (DePuy Orthopaedics, Inc) related to this work; the institution of two of the authors (MBM, JPC) has received funding from a commercial entity (DePuy Orthopaedics, Inc) related to this work.
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA approval status, of any drug or device before clinical use.
This work was performed at the Dartmouth Biomedical Engineering Center, Hanover, NH, USA.