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Scientific Article   |    
Rapid Polyethylene Failure of Unicondylar Tibial Components Sterilized with Gamma Irradiation in Air and Implanted After a Long Shelf Life
Thomas F. McGovern, MD; Deborah J. Ammeen, BS; John P. Collier, DE; Barbara H. Currier, MChE; Gerard A. Engh, MD
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Investigation performed at Anderson Orthopaedic Research Institute, Alexandria, Virginia

Thomas F. McGovern, MD
Deborah J. Ammeen, BS
Gerard A. Engh, MD
Anderson Orthopaedic Research Institute, 2501 Parker's Lane, Suite 200, Alexandria, VA 22306. E-mail address for T.F. McGovern, D.J. Ammeen, and G.A. Engh: ammeen@aori.org

John P. Collier, DE
Barbara H. Currier, MChE
Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

J Bone Joint Surg Am, 2002 Jun 01;84(6):901-906
5 Recommendations (Recommend) | 3 Comments | Saved by 3 Users Save Case

Abstract

Background: The mechanical toughness of polyethylene that has been sterilized by gamma irradiation in air decreases after a long shelf life. The purpose of the present study is to report the high failure rate after unicondylar knee replacements performed with polyethylene bearings that had been sterilized with gamma irradiation in air and implanted after a shelf life of =4.4 years.

Methods: Between December 1997 and January 2000, seventy-five unicondylar knee replacements were performed in sixty-two patients. All patients were followed both clinically and radiographically. A revision operation was offered when the patient had pain, swelling, and radiographic evidence of rapid polyethylene wear. The effect of aging of the polyethylene during storage was evaluated by dividing the knees into three groups on the basis of shelf life and comparing them with regard to the rate of revision and the observed wear of the polyethylene. Four retrieved components were examined for the presence of oxidation.

Results: At a mean of eighteen months after the arthroplasty, thirty knees had been revised and seven were scheduled for revision. The rate of polyethylene wear increased as the shelf life increased. There was a significant inverse linear correlation between the shelf life of the polyethylene and the time to revision (p < 0.01, r 2 = 0.64). All retrieved components had greater-than-expected wear with pitting and delamination of the surface. Seven components had fractured, and ten had both fractured and fragmented. Analysis of four components confirmed severe oxidation of the polyethylene.

Conclusion: The present study demonstrated early, severe wear of tibial polyethylene bearings that had been sterilized by gamma irradiation in air and stored for =4.4 years. This risk can be minimized by ensuring that implants have not been sterilized with gamma irradiation in air and stored for several years.

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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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    David R. Graham
    Posted on June 15, 2002
    Disaster strikes
    None

    Drs. McGovern et al are to be congratulated for their bravery in publishing this paper. Seventy-five index total knee arthroplasties were performed (in 62 patients). After a mean period of only eighteen months (range, seven to thirty months), fifty percent (thirty-seven of seventy- five) of the arthroplasties had failed due to polyethylene wear. This may rank as the worst results of any series of total knee arthroplasties reported in the orthopaedic literature - certainly in the past decade or more! I would suspect that the surgeon involved is now counting down: only 38 more revisions to go. Note that these were all arthroplasties performed by a master total knee surgeon.

    I do not believe that the explanation given (oxidation secondary to gamma irradiation in air) is a sufficient explanation for these results. Using the same prosthesis, the multicenter study by Lindstrad did not find that there was early wear and rapid failure of the tibial bearing, over a follow-up interval of one to six years.

    There is no question about the deleterious effects of gamma irradiation in air on polyethylene and little controversy about the cumulative effects over time. However, a polyethylene tibial bearing sitting on a shelf in a box or sitting on a shelf (the tibial plateau) in a patient continues to undergo oxidation. I am not aware that anyone has suggested that there is a protective effect of implanting gamma irradiated in air polyethylene into a patient. For many years, we all used polyethylene irradiated in air in our total hip and total knee arthroplasties. Virtually all of these components lasted longer than thirty months (some for 20 years or more).

    Unfortunately, I believe someone needs to delve more deeply into why this group of patients has such a high rate of failure. Recently we have seen numerous examples (from several orthopaedic suppliers) of "glitches" in the manufacturing process of total joint implants. Whether this is the case here, I do not know. All patients that received this prosthesis using implants manufactured during the time in question (a period of several years) need to be identified and evaluated, and this responsibility now lies with the manufacturer.

    Papers such as this are very important and valuable contributions. Most surgeons prefer to crow about their successes and hide their failures. The authors are to be applauded for their ethics in reporting this series of patients.

    Note that I just checked the Stryker Osteonics Howmedica web site and find that the Duracon unicompartmental knee is NOT shown. I suspect therefore that the sale and use of this prosthesis has been suspended until a complete explanation has been found for the dismal results reported in this paper.

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