This Article Full Text Full Text (PDF) CME: Take the activities for this article: Adult Knee Reconstruction Test 15: Summer 2007 (publication date August 15,... CME 2: April, May, June 2007 (publication date July 5, 2007; expiration dat... [Supplementary Material] Letters to the Editor: Submit a response Alert me when this article is cited Alert me when Letters to the Editor are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Reprints and Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Collier, M. B. Articles by Engh, G. A. Search for Related Content PubMed PubMed Citation Articles by Collier, M. B. Articles by Engh, G. A. Related Collections Adult Knee Social Bookmarking             What's this?

Factors Associated with the Loss of Thickness of Polyethylene Tibial Bearings After Knee Arthroplasty

¹ Anderson Orthopaedic Research Institute, P.O. Box 7088, Alexandria, VA 22307. E-mail address for all authors: research{at}aori.org

Investigation performed at the Anderson Orthopaedic Research Institute, Alexandria, Virginia

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. 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 a commercial entity (DePuy, a Johnson and Johnson Company). Also, a commercial entity (Inova Health System) paid or directed in any one year, or agreed to pay or direct, benefits in excess of $10,000 to a research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

Methods: We retrieved polyethylene tibial bearings from eighty-one unicondylar and eighty-nine total knee replacements that had been performed because of osteoarthritis with varus deformity from 1984 to 1998. All of the polyethylene bearings had been sterilized with gamma radiation in air. Polyethylene loss was quantified as the change in the minimum bearing thickness per years in vivo (the mean time in vivo [and standard deviation] was 8 ± 4 years). Multiple linear regression was used to assess whether polyethylene loss was associated with age, weight, gender, varus angle of the tibial component, postoperative hip-knee-ankle angle, initial thickness of the polyethylene, shelf age of the polyethylene, and either the type of polyethylene (for total knee replacements, which were of one posterior cruciate ligament-retaining design) or the manufacturer (for unicondylar knee replacements), and to determine the magnitude by which polyethylene loss would change if any of the significant risk factors were changed.

Results: The mean loss (and standard deviation) of polyethylene thickness in the medial compartment of total knee replacements (0.33 ± 0.28 mm/yr) and that in medial unicompartmental knee replacements (0.49 ± 0.40 mm/yr) were significantly (p < 0.05) associated with the same three variables: patient age, postoperative hip-knee-ankle angle, and shelf age of the polyethylene. A total knee bearing with a one-year increase in shelf age, a unicondylar knee bearing with a six-month increase in shelf age, a patient who was ten years younger at the time of operation, or a limb that was aligned in 5° more varus (less valgus) had similar effects on the loss of polyethylene thickness in the medial compartment; the coefficients of the linear regression equations indicated that any one of these changes would increase polyethylene loss by 0.11 to 0.14 mm/yr.

Conclusions: The wear-related loss of thickness in gamma-irradiated-in-air polyethylene bearings from unicondylar and total knee replacements implanted in osteoarthritic knees with varus deformity is influenced mainly by the shelf age of the polyethylene, the age of the patient, and the postoperative angulation of the knee in the coronal plane.

Clinical Relevance: Although polyethylene bearings have not been sterilized with gamma radiation in air since the end of the last decade, many arthroplasty patients have polyethylene bearings that were sterilized with use of this method. An understanding of the findings of this study may be of value as these patients return for follow-up care. Whether the study findings have relevance to bearings sterilized with other methods is unclear and will remain so for many years.

Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.

CiteULike    Connotea    Del.icio.us    Technorati    What's this?

This article has been cited by other articles:

				C. A. Deirmengian and J. H. Lonner What's New in Adult Reconstructive Knee Surgery J. Bone Joint Surg. Am., November 1, 2008; 90(11): 2556 - 2565. [Full Text] [PDF]

				A. K. Tsao, L. C. Jones, and D. G. Lewallen What patient and surgical factors contribute to implant wear and osteolysis in total joint arthroplasty? J. Am. Acad. Ortho. Surg., July 1, 2008; 16(suppl_1): S7 - S13. [Abstract] [Full Text] [PDF]

Stanford University Libraries' HighWire Press (TM) assists in the publication of JBJS Online.
Copyright © 2007 by The Journal of Bone and Joint Surgery, Inc. Online ISSN: 1535-1386.
The Journal of Bone and Joint Surgery®, JBJS®, JB&JS®, and eJBJS® are registered in the U.S. Patent and Trademark Office.