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J Bone Joint Surg Br. 2010 May;92(5):717-25. doi: 10.1302/0301-620X.92B5.23320.

Tribological performance of various CoCr microstructures in metal-on-metal bearings: the development of a more physiological protocol in vitro.

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1
Implant Development Centre, Smith and Nephew Orthopaedics, Aurora House, Spa Park, Harrison Way, Leamington Spa CV31 3HL, UK. amir.kamali@smithnephew.com

Abstract

Hip simulators have been used for ten years to determine the tribological performance of large-head metal-on-metal devices using traditional test conditions. However, the hip simulator protocols were originally developed to test metal-on-polyethylene devices. We have used patient activity data to develop a more physiologically relevant test protocol for metal-on-metal devices. This includes stop/start motion, a more appropriate walking frequency, and alternating kinetic and kinematic profiles. There has been considerable discussion about the effect of heat treatments on the wear of metal-on-metal cobalt chromium molybdenum (CoCrMo) devices. Clinical studies have shown a higher rate of wear, levels of metal ions and rates of failure for the heat-treated metal compared to the as-cast metal CoCrMo devices. However, hip simulator studies in vitro under traditional testing conditions have thus far not been able to demonstrate a difference between the wear performance of these implants. Using a physiologically relevant test protocol, we have shown that heat treatment of metal-on-metal CoCrMo devices adversely affects their wear performance and generates significantly higher wear rates and levels of metal ions than in as-cast metal implants.

PMID:
20436012
DOI:
10.1302/0301-620X.92B5.23320
[Indexed for MEDLINE]
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