Efficacy of a Second-Generation Rotating Bearing Tibial Platform in Total Knee Arthroplasty: A Prospective Observational Cohort Study with Registry Analysis.

Abstract

There is a lack of clinical outcomes reported for the rotating bearing knee (RBK) total knee arthroplasty (TKA), which is a second-generation rotating platform knee, with purported benefits over earlier versions. The purpose of the study was to report the complications, short-term (minimum 1 year) patient-reported outcomes and long-term (up to 15 years) procedure survival in a consecutive series of patients receiving a rotating platform TKA (RBK) from an independent clinic. A retrospective analysis of a single-surgeon, private/public practice, with prospectively collected data in a subset of patients were performed. A total of 1,130 procedures (primary, revision from unicompartmental knee arthroplasty (UKA) to TKA) were crossmatched with manufacturer records. Clinical outcomes (complications, reoperations) were summarized and linked to patient-reported outcome measures (Eq. 5D, KSS-function, Oxford knee score [OKS]). OKS results were classified using minimally clinical important difference (MCID) and patient acceptable symptom state (PASS). PROMs were summarized and regression models used to determine relationships between patient factors and outcomes in this cohort. Cumulative percent revision was reported by the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and compared between the senior author and national data using Kaplan-Meier survival analysis. We report a complication rate of 19.7% with the majority (> 60%) being thromboembolic events and complaints of stiffness. Significant improvements were observed in general health, knee pain, and function with > 89% exceeding the MCID for the OKS and > 65% exceeding the PASS for the OKS at an average follow-up of 3.2 years. We report a cumulative revision rate of 4.3% at 5 years and 4.8% at 14 years, with significantly lower revision rates in females and patients aged 55 to 64 years compared with AOANJRR data for fixed bearing designs. The RBK rotating platform TKA provides good functional outcomes, with relatively low revision and complications rates at up to 14 years follow-up. This design in conjunction with a gap balancing technique may be advantageous in certain patient subgroups.