The debate rages on regarding the clinical outcomes of unicompartmental knee arthroplasty (UKA), the long-term survivorship of which has been concerning. In the July 1, 2020 issue of The Journal, Kazarian et al. retrospectively analyze 253 primary medial UKAs (both fixed- and mobile-bearing designs) in terms of radiographic outliers, revision, and implant survival.
These operations were performed by a group of fairly experienced surgeons who averaged >14 UKAs per year, although a commonly used threshold for a “high-volume” UKA surgeon is >15 procedures per year. The cumulative revision rate of 14.2% over 8.7 years, the 5-year Kaplan-Meier survival rate of 88%, and the 10-year survival rate of 70% found by Kazarian et al. are disturbing. Using revision as an endpoint may be problematic because some surgeons are quick to revise a UKA when the radiographic evaluation of component placement is not perfect. Still, this study demonstrates that radiographically determined alignment and overhang “outliers” and “far outliers” had a significantly increased risk of implant failure, compared with patients with good alignment and overhang.
This study did not include UKAs that used computer-assisted methods, but it seems safe to conclude that computer-assisted component placement would be more reliable than “eyeballing,” especially among surgeons with less-experienced eyes. Based on this and other recent studies, I think a controlled trial comparing the functional outcomes and revision rates of UKAs performed with and without computer assistance is warranted.
Marc Swiontkowski, MD
Editor’s Note: Click here to read the JBJS Clinical Summary on Unicompartmental Knee Arthroplasty.