Retrospective comparison of rates of aseptic loosening in fixed-bearing unicompartmental knee arthroplasty (UKA) implants

Abstract

Background: A prominent cause for failure and revision in unicompartmental knee arthroplasty (UKA) is aseptic implant loosening. This study compared the revision rates for aseptic loosening of a new UKA implant, Aesculap Univation X (B. Braun, Tuttlingen, Germany), versus a well-established standard design, Miller Galante (Zimmer, Warsaw, Indiana). Methods: Patient charts were retrospectively reviewed of medial UKAs performed using two different fixed-bearing UKA implants from different manufacturers between January 1, 2002, and November 6, 2020. Of 308 patients included in the study, 44 had the new implant (AUK) and 264 patients had a standard implant (ZUK). The revision rates for all-cause and aseptic loosening were compared. The Kaplan Meier curve for 5-year survival rate was calculated based on aseptic loosening as the cause of failure. Hazard ratios for failure were calculated with multivariable Cox regression analysis. Results: All-cause revision and revision from aseptic loosening were significantly higher for AUK versus ZUK (20% versus 5.30% and 18.18% versus 3.41%, respectively). The log-rank test showed significantly longer survival for ZUK versus AUK group (P<0.001). Multivariable Cox regression analysis found a hazard ratio of 21.62 (95% CI: 4.07, 114.72; P<0.001) for revision for the AUK versus ZUK group, controlling for sex, age, and body mass index. Conclusions: Among these patients, AUK had lower survivorship than the established implant, ZUK, due to significantly higher hazard of all-cause revision and revision from aseptic loosening. These findings suggest a need for caution with use of this new implant. Level of Evidence: Level III.