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Journal of Bone and Joint Surgery - British Volume, Vol 91-B, Issue 9,
1134-1141.
doi: 10.1302/0301-620X.91B9.22306 Copyright © 2009 by British Editorial Society of Bone and Joint Surgery Ceramic-on-metal bearings in total hip replacementWHOLE BLOOD METAL ION LEVELS AND ANALYSIS OF RETRIEVED COMPONENTSG. H. Isaac, PhD, Visiting Professor, Distinguished Hip Fellow1; C. Brockett, PhD, Research Fellow2; A. Breckon, MSc, Research Assistant3; D. van der Jagt, FCS(SA)Orth, Orthopaedic Surgeon4; S. Williams, PhD, Academic Research Fellow2; C. Hardaker, MSc, Research and Test Manager1; J. Fisher, DEng, Professor of Mechanical Engineering2; and A. Schepers, FCS(SA)Ortho, Orthopaedic Surgeon4
1 DePuy International Ltd., Number 1 White Rose Office Park, Leeds LS11 0BG, UK. Correspondence should be sent to Professor G. H. Isaac; e-mail: gisaac{at}its.jnj.com
This study reports on ceramic-on-metal (CoM) bearings in total hip replacement. Whole blood metal ion levels were measured. The median increase in chromium and cobalt at 12 months was 0.08 µg/1 and 0.22 µg/1, respectively, in CoM bearings. Comparable values for metal-on-metal (MoM) were 0.48 µg/1 and 0.32 µg/1. The chromium levels were significantly lower in CoM than in MoM bearings (p = 0.02). The cobalt levels were lower, but the difference was not significant. Examination of two explanted ceramic heads revealed areas of thin metal transfer. CoM bearings (one explanted head and acetabular component, one explanted head and new acetabular component, and three new heads and acetabular components) were tested in a hip joint simulator. The explanted head and acetabular component had higher bedding-in. However, after one million cycles all the wear rates were the same and an order of magnitude less than that reported for MoM bearings. There were four outliers in each clinical group, primarily related to component malposition.
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