The Oxford Unicompartmental Knee Fails at a High Rate in a High-volume Knee Practice
- First Online:
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.
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.
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.
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.
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.
- 19.New Zealand Orthopaedic Association. The New Zealand Joint Registry. Thirteen year report: January 1999–December 2012. Available at: www.nzoa.org.nz/nz-joint-registry. Accessed July 3, 2013.
- 20.Pandit H, Jenkins C, Barker K, Dodd CA, Murray DW. The Oxford medial unicompartmental knee replacement using a minimally-invasive approach. J Bone Joint Surg Br. 2006;88:54–60.Google Scholar
- 26.Schroer WC, Stormont DM, Pietrzak WS. Seven-year survivorship and functional outcomes of the high-flexion Vanguard complete knee system. J Arthroplasty. 2013 May 20. pii: S0883-5403(13)00311-2 [Epub ahead of print].Google Scholar