, Volume 471, Issue 1, pp 102-108
Date: 16 Aug 2012

Long-term Survivorship and Failure Modes of Unicompartmental Knee Arthroplasty

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Abstract

Background

In a previously reported series of 51 patients with 62 cemented, fixed-bearing unicompartmental knee arthroplasties, we reported a 10-year, 98% survival rate with an average knee score of 92 points. The survivorship and modes of failure past 10 years are incompletely understood.

Questions/Purposes

At 15-year followup we sought to determine (1) the overall durability and survivorship of this design; (2) modes of failure; and (3) the progression of arthritis in the nonresurfaced compartments.

Methods

Nineteen knees in 16 patients were available for study with 34 patients lost to death and one lost to followup. At 15 years, we analyzed the Kaplan-Meier survivorship as well as durability with regard to radiographic loosening and knee scores, determined modes of failure, and assessed radiographs for degeneration in the nonresurfaced compartments.

Results

Fifteen-year survivorship was 93% and 20-year survivorship was 90%. Four of 62 knees were revised to total knee arthroplasty at a mean of 144 months. One knee was revised for patellofemoral and lateral compartment degeneration, one for lateral compartment degeneration, one for polyethylene disengagement and metallosis, and one for pain of unclear etiology. No patients had aseptic loosening or osteolysis. The mean knee score was 78 at latest followup. Arthritic progression in the nonresurfaced compartments was common although symptomatic in only two patients.

Conclusions

With this cemented, fixed-bearing design, the failure rates were low, there were no cases of failure secondary to wear or loosening, and the survivorship was similar to that reported for total knee arthroplasty.

Level of Evidence

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The institution of one or more of the authors (CJDV, RAB, JOG) has received, in any one year, funding from Zimmer (Warsaw, IN, USA), Smith & Nephew (Memphis, TN, USA), and Stryker (Kalamazoo, MI, USA). One of the authors (CJDV) certifies that he has or may receive payments or benefits, during the study period of an amount of less than $10,000 from Biomet (Warsaw, IN, USA), and less than $100,000 from Smith & Nephew. One of the authors (RAB) certifies that he certifies that he has or may receive payments or benefits, during the study period of an amount of $10,000–$100,000 from Medtronic (Memphis, TN, USA), more than $1,000,001 from Zimmer, less than $10,000 from Smith & Nephew, and less than $10,000 from DePuy (Warsaw, IN, USA). One of the authors (JOG) certifies that he certifies that he has or may receive payments or benefits, during the study period of an amount of less than $10,000 from Biomet and more than $1,000,001 from Zimmer.
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.
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 work was performed at Rush University Medical Center, Chicago, IL, USA.