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Assessing the non-inferiority of prosthesis constructs used in total and unicondylar knee replacements using data from the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man: a benchmarking study
  1. Kevin C Deere1,
  2. Michael R Whitehouse1,2,
  3. Martyn Porter3,
  4. Ashley W Blom1,2,
  5. Adrian Sayers1,4
  1. 1 Musculoskeletal Research Unit, Translational Health Sciences, University of Bristol, Bristol, UK
  2. 2 National Institute for Health Research, Bristol Biomedical Research Centre, University Hospitals Bristol NHS Foundation Trust and University of Bristol, Bristol, UK
  3. 3 Centre for Hip Surgery, Wrightington Hospital, Wigan, UK
  4. 4 Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK
  1. Correspondence to Adrian Sayers; adrian.sayers{at}


Objectives To investigate the relative performance of knee replacement constructs compared with the best performing construct and illustrate the substantial variability in performance.

Design A non-inferiority study.

Setting England and Wales.

Participants All primary total and unicondylar knee replacements performed and registered in the National Joint Registry between 1 April 2003 and 31 December 2016.

Main outcome measures Kaplan-Meier failure function for knee replacement constructs. Failure difference between best performing construct (the benchmark) and other constructs.

Methods Using a non-inferiority analysis, the performance of knee replacement constructs by brand were compared with the best performing construct. Construct failure was estimated using the 1-Kaplan Meier method, that is, an estimate of net failure. The difference in failure between the contemporary benchmark construct and all other constructs were tested.

Results Of the 449 different knee replacement constructs used, only 27 had ≥500 procedures at risk at 10 years postprimary, 18 of which were classified as inferior to the benchmark by at least 20% relative risk of failure. Two of these 18 were unicondylar constructs that were inferior by at least 100% relative risk. In men, aged 55–75 years, 12 of 27 (44%) constructs were inferior by at least 20% to the benchmark at 7 years postprimary. In women, aged 55–75 years, 8 of 32 (25%) constructs were inferior at 7 years postprimary. Very few constructs were classified as non-inferior to the contemporary benchmark.

Conclusions There are few knee replacement constructs that can be shown to be non-inferior to a contemporary benchmark. Unicondylar knee constructs have, almost universally, at least 100% worse revision outcomes compared with the best performing total knee replacement. These results will help to inform patients, clinicians and commissioners when considering knee replacement surgery.

  • knee arthroplasty
  • non-inferiority
  • national joint registry
  • benchmarking
  • medical devices

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  • Contributors AS, MRW and AWB conceived the study. KD, AS and AWB designed the study. The data were extracted by Northgate (Hemel Hempstead, UK). KD and AS managed and analysed data. MRW, AS, MP and AWB reviewed the published work. All authors critically inputted into final design of the study, interpreted the data and cowrote the manuscript. AS is the guarantor and attests on behalf of the authors that the manuscript is a true and transparent reflection of the study without omissions.

  • Funding Posts of members of the research team are funded by a contract grant from the NJR for England, Wales, Northern Ireland and the Isle of Man. This study was also supported by the NIHR Biomedical Research Centre at the University Hospitals Bristol NHS Foundation Trust and the University of Bristol. AS is funded by a Medical Research Council Strategic Skills Fellowship MR/L01226X/1.

  • Disclaimer The sponsor of the study had no role in the study design, data collection, analysis, interpretation, or writing of the final report. KD and AS had full access to all of the data and AS had final responsibility for manuscript submission. The views expressed represent those of the authors and do not necessarily reflect those of the NHS, the National Institute for Health Research, the Department of Health, the National Joint Registry Steering Committee or Healthcare Quality Improvement Partnership, who do not vouch for how the information is presented.

  • Competing interests Submitted work as described in the funding statement; AWB and MRW are coapplicants on a grant from Stryker investigating the outcome of the triathlon total knee replacement; there are no other financial relationships with any organisations that might have an interest in the submitted work in the previous three years, and there are no other relationships or activities that could appear to have influenced the submitted work.

  • Ethics approval Pseudoanonymised analysis of NJR data are considered as secondary use of clinical registry data; under Health Research Authority guidance, this does not require formal ethical approval. However, all research projects are internally approved by the NJR. The full NJR privacy notice can be found at

  • Provenance and peer review Not commissioned; peer reviewed for ethical and funding approval prior to submission.

  • Data sharing statement Access to data is available from the NJR for England and Wales.

  • Patient consent for publication Not required.

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