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Scientific Articles   |    
The In Vivo Linear and Volumetric Wear of Hip Resurfacing Implants Revised for Pseudotumor
Siôn Glyn-Jones, MA, DPhil, FRCS(Orth)1; Anne Roques, PhD2; Adrian Taylor, FRCS(Orth)3; Young-Min Kwon, FRACS4; Peter McLardy-Smith, MA, FRCS3; Harinderjit S. Gill, DPhil1; William Walter, FRACS, FAOrthA, PhD5; Mike Tuke, PhD2; David Murray, MA, MD, FRCS1
1 Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Windmill Lane, Headington, Oxford OX3 7LD, United Kingdom. E-mail address: sion.glyn-jones@ndorms.ox.ac.uk
2 Finsbury Orthopaedics, 13 Mole Business Park, Randalls Road, Leatherhead, Surrey KT22 7BA, United Kingdom
3 Nuffield Orthopaedic Centre, Windmill Lane, Headington, Oxford OX3 7LD, United Kingdom
4 Department of Orthopaedic Surgery, Adult Reconstructive Surgery Unit, Harvard Medical School, Massachusetts General Hospital, 55 Fruit Street, GRJ 1126, Boston, MA 02116
5 Sydney Hip and Knee Surgeons, Mater Clinic Building, Suite 1.08, 3-9 Gillies Street, Wollstonecraft NSW 2065, Australia
View Disclosures and Other Information
Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

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Investigation performed at Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
A commentary by James A. Keeney, MD, is linked to the online version of this article at jbjs.org.

Copyright © 2011 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2011 Dec 07;93(23):2180-2188. doi: 10.2106/JBJS.J.01206
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Abstract

Background: 

Metal-on-metal arthroplasty-related pseudotumors can cause severe local destruction of bone and soft tissues. The cause of pseudotumors is unknown, although some authors have implicated metal wear debris. The aim of this study was to measure the location and magnitude of wear on resurfacing devices that were retrieved during revision procedures for pseudotumor (the pseudotumor group) and for other reasons (the control group).

Methods: 

We examined thirty-six hip-resurfacing implants, which were divided into two groups: eighteen implants from patients with a diagnosis of pseudotumor and eighteen control implants. Implant orientation and patient demographics were recorded. Three-dimensional, contactless metrology was used to scan the surface of the femoral and acetabular components to a resolution of 20 nm. Linear and volumetric wear were measured, and the components were examined for evidence of edge wear.

Results: 

There was three times more total linear wear and over six times more total volumetric wear of the femoral and acetabular components in the pseudotumor group as compared with that in the control group. The mean linear wear rate and standard deviation of the femoral components in the pseudotumor group (8.4 ± 8.7 μm/yr) were significantly greater than those in the control group (2.9 ± 3.9 μm/yr; p = 0.01). The mean volumetric wear rate of the femoral components was also significantly greater in the pseudotumor group (3.3 ± 5.7 mm3/yr) than it was in the control group (0.8 ± 1.2 mm3/yr; p = 0.009). Seventeen of eighteen subjects in the pseudotumor group had edge wear, compared with six of eighteen in the control group (p < 0.001).

Conclusions: 

Implants that were retrieved because of pseudotumor had a significantly higher wear rate and prevalence of edge wear than the control implants did. There was a strong association between pseudotumor and the high levels of wear debris that are generated during edge-loading. However, not all patients with high wear developed pseudotumors, and not all pseudotumors had high wear; therefore, other factors are most likely involved in the cause of pseudotumors.

Level of Evidence: 

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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