title: The Oxford unicompartmental knee fails at a high rate in a high-volume knee practice.
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.
  
  
  OBJECTIVE
  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.
authors.affiliation: St Louis Joint Replacement Institute, SSM DePaul Health Center, 12266 DePaul Drive, Suite 220, St Louis, MO, 63044, USA, kneecenter@yahoo.com.
authors.forename: William C
authors.initials: WC
authors.lastname: Schroer
authors.forename: C Lowry
authors.initials: CL
authors.lastname: Barnes
authors.forename: Paul
authors.initials: P
authors.lastname: Diesfeld
authors.forename: Angela
authors.initials: A
authors.lastname: LeMarr
authors.forename: Rachel
authors.initials: R
authors.lastname: Ingrassia
authors.forename: Diane J
authors.initials: DJ
authors.lastname: Morton
authors.forename: Mary
authors.initials: M
authors.lastname: Reedy
mesh_terms: D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000295:instrumentation*; D002983:Clinical Competence; D005260:Female; D061847:Hospitals, High-Volume; D006801:Humans; D053208:Kaplan-Meier Estimate; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D007720:Knee Prosthesis; D059032:Learning Curve; D008297:Male; D008875:Middle Aged; D008923:Missouri; D010149:Postoperative Pain / Q000209:etiology; D020959:Polyethylene; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D013997:Time Factors; D017211:Treatment Failure
chemical_list: D020959:Polyethylene
references.citation: J Bone Joint Surg Br. 2009 Jul;91(7):896-902
references.pmid: 19567853
references.citation: J Arthroplasty. 2008 Sep;23(6 Suppl 1):61-7
references.pmid: 18722304
references.citation: J Bone Joint Surg Br. 2011 Jun;93(6):777-81
references.pmid: 21586776
references.citation: J Arthroplasty. 2014 Jan;29(1):61-5
references.pmid: 23702268
references.citation: Knee. 2012 Aug;19(4):356-9
references.pmid: 21636281
references.citation: J Arthroplasty. 2011 Feb;26(2):192-7
references.pmid: 20667688
references.citation: Surg Technol Int. 2007;16:193-7
references.pmid: 17429788
references.citation: Knee. 2010 Jan;17(1):48-52
references.pmid: 19716706
references.citation: J Bone Joint Surg Br. 2010 Apr;92(4):508-12
references.pmid: 20357326
references.citation: Acta Orthop Belg. 2012 Apr;78(2):203-9
references.pmid: 22696991
references.citation: J Bone Joint Surg Br. 1998 Nov;80(6):983-9
references.pmid: 9853489
references.citation: Int Orthop. 2010 Dec;34(8):1137-43
references.pmid: 19838707
references.citation: J Bone Joint Surg Br. 2010 Dec;92(12):1628-31
references.pmid: 21119165
references.citation: J Bone Joint Surg Am. 2010 Sep 1;92(11):2102-9
references.pmid: 20810860
references.citation: J Arthroplasty. 2010 Aug;25(5):735-40
references.pmid: 19577895
references.citation: Clin Orthop Relat Res. 2011 Jan;469(1):174-9
references.pmid: 20706811
references.citation: Knee Surg Sports Traumatol Arthrosc. 2006 Jan;14(1):40-5
references.pmid: 15895294
references.citation: J Arthroplasty. 1995 Dec;10(6):722-31
references.pmid: 8749752
references.citation: J Bone Joint Surg Br. 2006 Jan;88(1):54-60
references.pmid: 16365121
references.citation: Clin Orthop Surg. 2011 Sep;3(3):178-83
references.pmid: 21909464
references.citation: Isr Med Assoc J. 2009 May;11(5):266-8
references.pmid: 19637502
references.citation: J Bone Joint Surg Am. 2013 Apr 17;95(8):702-9
references.pmid: 23595068
references.citation: J Bone Joint Surg Br. 2001 Jan;83(1):45-9
references.pmid: 11245537
references.citation: Orthopedics. 2007 May;30(5 Suppl):24-7
references.pmid: 17549862
references.citation: J Bone Joint Surg Br. 2011 Apr;93(4):470-5
references.pmid: 21464484