Survivorship and Patient Outcomes of Conforming Bearings in Modern Primary Total Knee Arthroplasty: Mean 3.5 Year Follow-Up

Sohum K Patel; Leonard T Buller; Evan R Deckard; R Michael Meneghini

doi:10.1016/j.arth.2024.04.084

Survivorship and Patient Outcomes of Conforming Bearings in Modern Primary Total Knee Arthroplasty: Mean 3.5 Year Follow-Up

J Arthroplasty. 2024 May 9:S0883-5403(24)00435-2. doi: 10.1016/j.arth.2024.04.084. Online ahead of print.

Authors

Sohum K Patel¹, Leonard T Buller¹, Evan R Deckard², R Michael Meneghini³

Affiliations

¹ Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
² Indiana Joint Replacement Institute, Indianapolis, Indiana.
³ Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana; Indiana Joint Replacement Institute, Indianapolis, Indiana. Electronic address: rm_meneghini@yahoo.com.

PMID: 38734325
DOI: 10.1016/j.arth.2024.04.084

Abstract

Background: Conforming and congruent bearings in total knee arthroplasty (TKA) have rapidly increased due to the benefits of increased stability and the potential for replicating normal knee kinematics. However, limited data exist for these newly available bearings. This study evaluated revision-free survivorship and patient-reported outcome measures (PROMs) of a large granular database of primary TKAs using a single conforming bearing design.

Methods: A total of 1,306 consecutive primary TKAs performed using a single conforming bearing design (85% cemented and 15% cementless) were retrospectively reviewed. Kaplan-Meier (KM) survivorship estimates were calculated based on the latest clinical follow-up. The PROMs and minimal clinically important differences (MCIDs) were evaluated. A total of 93% of cases achieved minimum 1-year clinical follow-up (mean 3.5 years; range, 1 to 7), with a subset of 261 cases that achieved minimum 5-year follow-up (mean 5.8 years; range, 5 to 7).

Results: All-cause and aseptic KM survivorship estimates were 97.6 (95% CI [confidence interval], 97 to 99) and 98.1% (95% CI, 97 to 99) at 7.0 years. Revision-free survivorship did not differ by cemented or cementless fixation (98 versus 97%, P = 0.163). All PROM scores significantly improved from preoperative baseline (P < 0.001), and ≥ 86% of patients achieved MCIDs for Knee Society pain and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) total scores. A total of 89% of cases reported their knees to 'sometimes or always' feel normal. For cases with minimum 5-year PROMs, 93% were 'very satisfied' or 'satisfied.'

Conclusion: Conforming-bearing TKA demonstrated excellent survivorship up to 7.0 years. In addition, PROMs were comparable to other designs reported in the literature. While mid-term (mean 3.5-year) results are promising, long-term data are warranted on survivorship due to potential polyethylene wear in conforming bearings with more surface area in contact with articulating surfaces.

Keywords: conforming bearing; congruent bearing; patient reported outcomes; survivorship; total knee arthroplasty.