JOA - 2026-05-26 - Journal Article
A Randomized Controlled Trial to Compare a Mobile Bearing Cementless and Cemented Unicompartmental Knee: Results of an Investigational Device Exemption Study in the United States.
Hamilton WG, Redfern RE, Klaassen MA, Berend KR, Lackey WG, Berend ME, Anseth SD, Emerson RH, Reitman RD, Masonis JL, Lombardi AV
Topics
Key Takeaway
Cementless mobile-bearing UKA achieved non-inferior 5-year survivorship (91.7%) versus cemented UKA (95.6%, P=0.24) with equivalent Knee Society scores and radiographic outcomes.
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Summary
This single-blind multicenter US IDE RCT compared cementless versus cemented mobile-bearing medial UKA using a 2:1 allocation ratio, with co-primary endpoints of survivorship, radiographic success, and Knee Society scores. Five-year Kaplan-Meier survivorship was 91.7% (cementless) versus 95.6% (cemented), P=0.24; radiographic success was 93.8% versus 97.4%, P=0.19. Knee Society clinical (95.5 vs 95.6) and functional (89.9 vs 89.8) scores at 2 years were statistically identical.
Key Limitation
Five-year follow-up is insufficient to evaluate the primary theoretical advantage of cementless fixation — superior long-term survivorship beyond 10 years when cement-bone interface degradation becomes clinically relevant.
Original Abstract
INTRODUCTION
Cementless implants have seen a resurgence in knee arthroplasty to improve long-term bone fixation. The purpose of this study was to report the results of the United States (US) Investigational Device Exemption (IDE) study comparing the mobile bearing cementless and cemented unicompartmental knee arthroplasty (UKA).
METHODS
A single-blind, multicenter, randomized controlled trial was performed to compare a medial cementless and cemented UKA implant. There were 378 patients allocated 2:1 to receive the cementless (n = 241) or cemented (n = 137) device between November 2013 and November 2018. The primary endpoints were identified to demonstrate non-inferiority of the cementless device in terms of survivorship, radiographic results, and Knee Society Clinical Assessment and Functional Scores.
RESULTS
There was no statistical difference in Kaplan-Meier two-year survivorship between the cementless (94.0%, 95% confidence interval (CI) 89.9 to 96.8) and cemented cohorts (97.5%, 95% CI 93.0 to 99.5, P = 0.19); similar survival persisted at five years (91.7%, 95% CI 86.4 to 95.0 versus 95.6%, 95% CI 88.4 to 98.4, P = 0.24). Examination of radiographic success revealed non-inferior performance of the cementless prosthesis (93.8 versus 97.4%, P = 0.19). Knee Society function (89.9 ± 13.0 versus 89.8 ± 14.0, P = 0.95) and clinical assessment (95.5 ± 8.5 versus 95.6 ± 6.9, P = 0.92) scores at two years demonstrated no differences between groups.
CONCLUSION
The cementless mobile bearing UKA demonstrated non-inferior clinical and radiographic outcomes compared to the cemented device in this US IDE study. Cementless fixation may be an attractive option for appropriately selected patients.