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Scientific Articles   |    
The Seven-Year Wear of Highly Cross-Linked Polyethylene in Total Hip ArthroplastyA Double-Blind, Randomized Controlled Trial Using Radiostereometric Analysis
Geraint E.R. Thomas, MA, MRCS1; David J. Simpson, PhD1; Shahid Mehmood, MRCS1; Adrian Taylor, FRCS(Orth)1; Peter McLardy-Smith, FRCS, MA1; Harinderjit Singh Gill, DPhil1; David W. Murray, MA, MD, FRCS(Orth)1; Siôn Glyn-Jones, MA, DPhil, FRCS(Orth)1
1 Biomedical Research Unit (G.E.R.T., D.J.S., S.M., H.S.G., D.W.M., S.G.-J.), Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), and the Nuffield Orthopaedic Centre (A.T., P.McL.-S., D.W.M., S.G.-J.), Headington, Oxford OX3 7LD, United Kingdom. E-mail address for S. Glyn-Jones: sion.glyn-jones@ndorms.ox.ac.uk
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Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from Zimmer, Inc. In addition, one or more of the authors or a member of his or her immediate family received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from commercial entities (Biomet, Corin, Wright Medical, and Zimmer).

Investigation performed at the Nuffield Orthopaedic Centre, Headington, Oxford, United Kingdom

Copyright © 2011 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2011 Apr 20;93(8):716-722. doi: 10.2106/JBJS.J.00287
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Abstract

Background: 

The use of highly cross-linked polyethylene is now commonplace in total hip arthroplasty. Hip simulator studies and short-term in vivo measurements have suggested that the wear rate of highly cross-linked polyethylene is significantly less than that of conventional ultra-high molecular weight polyethylene. However, long-term data to support its use are limited. The aim of this study was to compare the intermediate-term steady-state wear of highly cross-linked polyethylene compared with that of conventional ultra-high molecular weight polyethylene acetabular liners in a prospective, double-blind, randomized controlled trial with use of radiostereometric analysis.

Methods: 

Fifty-four patients were randomized to receive hip replacements with either conventional ultra-high molecular weight polyethylene acetabular liners (Zimmer) or highly cross-linked polyethylene liners (Longevity; Zimmer). All patients received a cemented, collarless, polished, tapered femoral component (CPT; Zimmer) and an uncemented acetabular component (Trilogy; Zimmer). Clinical outcomes were assessed and the three-dimensional penetration of the head into the socket was determined for a minimum of seven years. Linear regression was used to calculate the steady-state wear rate following the creep-dominated penetration seen during the first year.

Results: 

At a minimum of seven years postoperatively, the mean total femoral head penetration was significantly lower in the highly cross-linked polyethylene group (0.33 mm; 95% confidence interval [CI], ±0.10 mm) than it was in the ultra-high molecular weight polyethylene group (0.55 mm; 95% CI, ±0.10 mm) (p = 0.005). The mean steady-state wear rate of highly cross-linked polyethylene was 0.005 mm/yr (95% CI, ±0.015 mm/yr), compared with 0.037 mm/yr (95% CI, ±0.019 mm/yr) for conventional ultra-high molecular weight polyethylene (p = 0.007). No patient in the highly cross-linked polyethylene group had a wear rate above the osteolysis threshold of 0.1 mm/yr, compared with 9% of patients in the ultra-high molecular weight polyethylene group.

Conclusions: 

This study demonstrates that highly cross-linked polyethylene has a significantly lower steady-state wear rate compared with that of conventional ultra-high molecular weight polyethylene. Longer-term follow-up is required to determine if this will translate into improved clinical performance and longevity of these implants.

Level of Evidence: 

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

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    Accreditation Statement
    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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