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.

Effects of age and sex on patient-reported outcomes following total knee arthroplasty with a rotating bearing tibial platform design: A single-surgeon practice registry study

“…While the clinical outcomes of younger females in this cohort were not markedly superior, the overall cohort reported good outcomes with the PS-RB implant. The baseline EQ-5D Index for this cohort was 0.52, which is lower than the population norm for a similar age group (65-74 years) in New Zealand (0.8), but comparable to what has previously been reported for arthroplasty preoperatively (0.53) (Bilbao et al, 2020) and preoperatively for an previous cohort from our group platform knee (0.57)* (Scholes et al, 2019). The baseline OKS of 22.3 was also similar to what has been reported for RB designs (Böhler et al, 2017;Jonas et al, 2015;Scholes et al, 2019).…”

“…The baseline EQ-5D Index for this cohort was 0.52, which is lower than the population norm for a similar age group (65-74 years) in New Zealand (0.8), but comparable to what has previously been reported for arthroplasty preoperatively (0.53) (Bilbao et al, 2020) and preoperatively for an previous cohort from our group platform knee (0.57)* (Scholes et al, 2019). The baseline OKS of 22.3 was also similar to what has been reported for RB designs (Böhler et al, 2017;Jonas et al, 2015;Scholes et al, 2019). At two years, postoperative OKS scores were 37.8 for this cohort, with 63.2% (CI 58-67) exceeding PASS.…”

“…At two years, postoperative OKS scores were 37.8 for this cohort, with 63.2% (CI 58-67) exceeding PASS. Scholes et al (Scholes et al, 2019) previously reported a postoperative OKS of 42 at 2.2 years, with 66% exceeding PASS.…”

“…All surgeries were performed by the senior author (JI) as previously described (Scholes et al, 2019) and as per the manufacturer's recommended technique. Imageless navigation (GPS, Exactech Inc, Florida USA) was used to align the femoral and tibial cuts in accordance with the manufacturer's instructions (Exactech Inc, Florida, USA), with restrictive kinematic alignment (Vanlommel et al, 2013) used to plan bone cuts on the femur to more closely resemble the orientation of the articular surface with compromise made on the tibial orientation for large tibial slopes.…”

Higher satisfaction after total knee arthroplasty using restricted inverse kinematic alignment compared to adjusted mechanical alignment

“…PASS is an absolute threshold proposed for symptomatic variables in osteoarthritis to determine the point beyond which patients consider themselves well and, as such, are satisfied with treatment. Recognized PASS thresholds are 37 for OKS [ 21 ] for OKS, and eight for VAS Satisfaction [ 3 ].…”