The clinical and cost-effectiveness of total versus partial knee replacement in patients with medial compartment osteoarthritis (TOPKAT): 5-year outcomes of a randomised controlled trial

TOPKAT Study Group

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BACKGROUND: Late-stage isolated medial knee osteoarthritis can be treated with total knee replacement (TKR) or partial knee replacement (PKR). There is high variation in treatment choice and little robust evidence to guide selection. The Total or Partial Knee Arthroplasty Trial (TOPKAT) therefore aims to assess the clinical effectiveness and cost-effectiveness of TKR versus PKR in patients with medial compartment osteoarthritis of the knee, and this represents an analysis of the main endpoints at 5 years.

METHODS: Our multicentre, pragmatic randomised controlled trial was done at 27 UK sites. We used a combined expertise-based and equipoise-based approach, in which patients with isolated osteoarthritis of the medial compartment of the knee and who satisfied general requirements for a medial PKR were randomly assigned (1:1) to receive PKR or TKR by surgeons who were either expert in and willing to perform both surgeries or by a surgeon with particular expertise in the allocated procedure. The primary endpoint was the Oxford Knee Score (OKS) 5 years after randomisation in all patients assigned to groups. Health-care costs (in UK 2017 prices) and cost-effectiveness were also assessed. This trial is registered with ISRCTN (ISRCTN03013488) and (NCT01352247).

FINDINGS: Between Jan 18, 2010, and Sept 30, 2013, we assessed 962 patients for their eligibility, of whom 431 (45%) patients were excluded (121 [13%] patients did not meet the inclusion criteria and 310 [32%] patients declined to participate) and 528 (55%) patients were randomly assigned to groups. 94% of participants responded to the follow-up survey 5 years after their operation. At the 5-year follow-up, we found no difference in OKS between groups (mean difference 1·04, 95% CI -0·42 to 2·50; p=0·159). In our within-trial cost-effectiveness analysis, we found that PKR was more effective (0·240 additional quality-adjusted life-years, 95% CI 0·046 to 0·434) and less expensive (-£910, 95% CI -1503 to -317) than TKR during the 5 years of follow-up. This finding was a result of slightly better outcomes, lower costs of surgery, and lower follow-up health-care costs with PKR than TKR.

INTERPRETATION: Both TKR and PKR are effective, offer similar clinical outcomes, and result in a similar incidence of re-operations and complications. Based on our clinical findings, and results regarding the lower costs and better cost-effectiveness with PKR during the 5-year study period, we suggest that PKR should be considered the first choice for patients with late-stage isolated medial compartment osteoarthritis.

FUNDING: National Institute for Health Research Health Technology Assessment Programme.

Original languageEnglish
Pages (from-to)746-756
Number of pages11
JournalThe Lancet
Issue number10200
Early online date17 Jul 2019
Publication statusPublished - 31 Aug 2019

Bibliographical note

Funding from the National Institute for Health Research Health Technology Assessment Programme.

The views and opinions expressed are those of the authors and do not necessarily reflect those of the Health Technology Assessment (HTA) Programme, the UK National Institute of Health Research (NIHR), National Health Service or Department of Health. The TOPKAT study is funded by the NIHR HTA Programme (number HTA 08/14/08), sponsored by the University of Oxford, and supported by Oxford Surgical Intervention Trials Unit (SITU; supported by Oxford NIHR Biomedical Research Centre) in the Royal College of Surgeons Surgical Trials Initiative. Study management was divided between the SITU (Oxford) and the Aberdeen trials centre, the Centre for Healthcare Randomised Trials. JAC held a Medical Research Council Methodology Fellowship (G1002292) for part of the study. The Health Services Research Unit is core funded by the chief scientist office of the Scottish Government Health and Social Care Directorates. We would like to thank the principal investigators and their teams at each of the TOPKAT sites.

The data collected for the study, including individual participant data and a data dictionary defining each field in the set, will be made available to researchers on request to the study team and with appropriate reason when accompanied by a peer-reviewed protocol, with publication and on agreement of the Trial Steering Committee. The shared data will be deidentified participant data. Data will be shared with investigator support, after approval of a proposal, with a signed data access agreement. The study protocol, statistical analysis plan, and informed consent form are available online.




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