Summary

A multicentre RCT of 528 patients with medial osteoarthritis of the knee found PKR to offer small benefits in outcome over TKR at 4 years; five year data will be presented.

Abstract

Introduction

Late stage knee osteoarthritis of the medial compartment can be treated using Total Knee Replacement (TKR) or Partial (or Unicompartmental) Replacement (PKR). There is high variation in treatment choice and insufficient evidence to guide selection with no large scale randomised trial. The cost efficacy implications for the healthcare provider are substantial. We present the results of the TOPKAT trial – the largest ever trial of TKR vs PKR, and which has the longest follow up – to five years.

Methods

TOPKAT is a pragmatic comparative effectiveness trial of TKR versus PKR which included an expertise component in the design to allow surgeons out of equipoise to contribute. Patients with medial compartment knee osteoarthritis were included from 27 sites and 63 surgeons. The Oxford Knee Score (OKS) at five years was the primary endpoint. Secondary outcomes included activity scores (UCLA), transition items, patient satisfaction and complications, (including re-operation, revision and composite ”failure” – defined by minimal OKS improvement and/or re-operation). The study was funded by the UK National Institute of Health Research.

Results

528 patients were randomised. Baseline variables between groups were well-balanced. A representative range of implants were used in the trial when compared to UK National Joint Registry data. At one year it was shown (and previously presented) that both operations had good early outcome and there was a small difference in OKS in favour of PKR (OKS diff 1.91; 95%CI 0.20, 3.62). There was little difference in re-operation and revision between groups at one year. At four years there continued to be a consistent direction of effect across all outcomes toward PKR – although differences remain small. (OKS: difference 1.78 (95%CI -0.23, 3.79); OKS APQ difference 5.52 (95%CI –1.34, 12.38); UCLA difference 0.21 (95%CI -0.13, 0.56); Satisfaction 83% (PKR) to 77% (TKR), and Transition [would you have the operation again?] 92% (PKR) and 84% (TKR).

Primary five year follow-up is almost complete (98% at the time of abstract writing, follow up closes in September 2018). The complete five year data will also be presented – this will be the first presentation at international conference of this largest randomised follow up of PKR versus TKR.

Trial registration: Current Controlled Trials ISRCTN03013488; ClinicalTrials.gov Identifier: NCT01352247