title: Tribological performance of various CoCr microstructures in metal-on-metal bearings: the development of a more physiological protocol in vitro.
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.
authors.affiliation: Implant Development Centre, Smith and Nephew Orthopaedics, Aurora House, Spa Park, Harrison Way, Leamington Spa CV31 3HL, UK. amir.kamali@smithnephew.com
authors.forename: A
authors.initials: A
authors.lastname: Kamali
authors.forename: A
authors.initials: A
authors.lastname: Hussain
authors.forename: C
authors.initials: C
authors.lastname: Li
authors.forename: J
authors.initials: J
authors.lastname: Pamu
authors.forename: J
authors.initials: J
authors.lastname: Daniel
authors.forename: H
authors.initials: H
authors.lastname: Ziaee
authors.forename: J
authors.initials: J
authors.lastname: Daniel
authors.forename: D J W
authors.initials: DJ
authors.lastname: McMinn
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects; D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D002858:Chromium Alloys / Q000737:chemistry*; D003430:Cross-Sectional Studies; D006622:Hip Prosthesis; D006358:Hot Temperature; D006801:Humans; D054327:Lubricants / Q000737:chemistry; D008297:Male; D008422:Materials Testing / Q000379:methods*; D008669:Metallurgy / Q000379:methods; D008875:Middle Aged; D008954:Models, Biological; D010014:Osteolysis / Q000209:etiology; D020959:Polyethylene; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013499:Surface Properties; D016138:Walking / Q000502:physiology / Q000706:statistics & numerical data
chemical_list: D001672:Biocompatible Materials; D002858:Chromium Alloys; D054327:Lubricants; D020959:Polyethylene