, Volume 471, Issue 11, pp 3533-3539
Date: 02 Aug 2013

The Oxford Unicompartmental Knee Fails at a High Rate in a High-volume Knee Practice

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Abstract

Background

The Oxford knee is a unicompartmental implant featuring a mobile-bearing polyethylene component with excellent long-term survivorship results reported by the implant developers and early adopters. By contrast, other studies have reported higher revision rates in large academic practices and in national registries. Registry data have shown increased failure with this implant especially by lower-volume surgeons and institutions.

Questions/purposes

In the setting of a high-volume knee arthroplasty practice, we sought to determine (1) the failure rate of the Oxford unicompartmental knee implant using a failure definition for aseptic loosening that combined clinical features, plain radiographs, and scintigraphy, and (2) whether increased experience with this implant would decrease failure rate, if there is a learning curve effect.

Methods

Eighty-three Oxford knee prostheses were implanted between September 2005 and July 2008 by the principal investigator. Radiographic and clinical data were available for review for all cases. A failed knee was defined as having recurrent pain after an earlier period of recovery from surgery, progressive radiolucent lines compared with initial postoperative radiographs, and a bone scan showing an isolated area of uptake limited to the area of the replaced compartment.

Results

Eleven knees in this series failed (13%); Kaplan-Meier survivorship was 86.5% (95% CI, 78.0%–95.0%) at 5 years. Failure occurrences were distributed evenly over the course of the study period. No learning curve effect was identified.

Conclusions

Based on these findings, including a high failure rate of the Oxford knee implant and the absence of any discernible learning curve effect, the principal investigator no longer uses this implant.

Level of Evidence

Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

One of the authors (WCS), or a member of his or her immediate family, certifies that he has received or will receive payments or benefits, during the study period an amount less than USD 10,000 from Biomet, Inc, (Warsaw, IN, USA). One of the authors (CLB), or a member of his or her immediate family, certifies that he has received or will receive payments or benefits, during the study period, an amount less than USD 10,000 from Wright Medical (Arlington, TN, USA); an amount less than USD 10,000 from DJO/Conformis (Vista, CA, USA); and an amount less than USD 10,000 from J & J/Stryker (Kalamazoo, MI, USA).
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use.
Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.
This study was performed at the St Louis Joint Replacement Institute, St Louis, MO.
A comment to this article is available at http://dx.doi.org/10.1007/s11999-013-3251-9.