Discover Portal

Knee Replacement

NIHR Signal Partial knee replacement ‘could be first choice’ for suitable patients with osteoarthritis

Published on 2 October 2019

doi: 10.3310/signal-000824

Partial knee replacement surgery improves pain and function similarly to total knee replacement in people with osteoarthritis that affects only a single compartment of the knee. Partial knee replacement surgery is also cheaper.

In this NIHR-funded trial of 528 people with osteoarthritis affecting only one compartment of the knee, those who had partial knee replacement saw at least as much improvement as those who had a total joint replacement. Their care also cost about £900 less over five years, making partial knee replacement more cost-effective.

Partial knee replacement did not lead to a greater need for further surgery, a surprise finding which contrasted with previous evidence. However, the need for further surgery is uncommon and the study may not have been large enough to capture data on this.

Longer-term follow up of the trial is underway. However, the current results suggest that partial knee replacement could be offered more often to eligible patients as a first-line option, assuming that surgeons experienced with the technique are available.

Share your views on the research.

Why was this study needed?

Knee replacement is a common operation to treat severe knee osteoarthritis that has not been resolved by other treatments. More than 300,000 knee replacements were carried out in the UK between 2015 and 2017.

Some people have damage to the knee joint on only one side (uni-compartment osteoarthritis) which means they could consider either a partial or total knee replacement. There has been insufficient evidence about which operation works best for these people.

At present, fewer than 9% of knee replacements are partial. However, a recent study of registry data from England suggested that partial knee replacement could be more cost-effective than total knee replacement.

The current trial was intended to fill the gap in the evidence and inform practice.

What did this study do?

TOPKAT (Total Or Partial Knee Arthroplasty Trial) was a randomised controlled trial carried out at 27 sites across the UK, involving 68 surgeons and 528 patients.

The sites recruited people who were being considered for knee replacement, who had osteoarthritis of the medial compartment of the knee. This meant they would be suitable for either partial or total knee replacement. People were randomly assigned to one or other operation.

Amongst the 528 people randomised, 44 people had a knee replacement using the technique they had not been assigned to. This was either because of patient choice or surgeon decision once surgery was underway. For example, partial knee replacement was not possible if the arthritis was more widespread than expected.

Participants were followed up for five years and checked annually.

The results should be relevant to UK hospitals, assuming they have surgeons with sufficient expertise in partial knee replacement.

What did it find?

  • Both groups of patients had much-improved knee pain and function, assessed by the 48-point Oxford Knee Score. After five years, people who had total knee replacement had an 18 point improvement and people who had partial knee replacement had a 19 point improvement. A 5-point difference is considered clinically significant, so the two procedures were similar for this outcome.
  • The study’s cost-effectiveness analysis found that partial knee replacement was more effective in terms of quality of life, resulting in 0.24 additional quality-adjusted life-years (QALYs) over five years. It was also less expensive, with care costing £910 less over the five years of follow-up.
  • Average hospital stay was longer for those who underwent total knee replacement (4.3 days) than those who had partial knee replacement (3.2 days).
  • The proportion of people who had a re-operation was similar in both groups. Re-operation rates were 6% among the partial knee replacement group and 8% among the total knee replacement. In both groups, 4% of people needed a revision of their knee replacement.

What does current guidance say on this issue?

The guideline on osteoarthritis published by NICE in 2014 includes recommendations on referral for consideration of joint replacement. However, it does not include guidance on which type of joint replacement device or technique is recommended. This guideline is being updated, with the update due to be published in August 2021.

In addition, a NICE guideline on primary joint replacement of the hip, knee or shoulder is in development and is expected to be published in March 2020.

What are the implications?

The results of the study imply that partial knee replacement can be offered with confidence for people with single compartment disease considering knee replacement. Offering partial knee replacement as a first choice may be better value for the NHS as it reduces costs, mainly because of shorter hospital stays.

Questions remain about the revision and re-operation rate for partial knee replacement over the longer term, and results from the planned 10-year follow-up of this trial will be of interest.

Surgeons would need to be fully trained and experienced in partial knee replacement in order to be able to replicate the results of this study.

Citation and Funding

Beard D, Davies L, Cook J, et al. 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. Lancet 2019; 394(10200):746-56.

The study was funded by the NIHR Health Technology Assessment Programme (project number 08/14/08).

Bibliography

Evans J, Whitehouse M. Partial versus total knee replacement for knee osteoarthritis. Lancet 2019; 394(10200):712-3.

NICE. Joint replacement (primary): hip, knee and shoulder. GID-NG10084. London: National Institute for Health and Care Excellence; 2019.

NICE. Osteoarthritis: care and management. CG177. London: National Institute for Health and Care Excellence; 2014.

Why was this study needed?

Knee replacement is a common operation to treat severe knee osteoarthritis that has not been resolved by other treatments. More than 300,000 knee replacements were carried out in the UK between 2015 and 2017.

Some people have damage to the knee joint on only one side (uni-compartment osteoarthritis) which means they could consider either a partial or total knee replacement. There has been insufficient evidence about which operation works best for these people.

At present, fewer than 9% of knee replacements are partial. However, a recent study of registry data from England suggested that partial knee replacement could be more cost-effective than total knee replacement.

The current trial was intended to fill the gap in the evidence and inform practice.

What did this study do?

TOPKAT (Total Or Partial Knee Arthroplasty Trial) was a randomised controlled trial carried out at 27 sites across the UK, involving 68 surgeons and 528 patients.

The sites recruited people who were being considered for knee replacement, who had osteoarthritis of the medial compartment of the knee. This meant they would be suitable for either partial or total knee replacement. People were randomly assigned to one or other operation.

Amongst the 528 people randomised, 44 people had a knee replacement using the technique they had not been assigned to. This was either because of patient choice or surgeon decision once surgery was underway. For example, partial knee replacement was not possible if the arthritis was more widespread than expected.

Participants were followed up for five years and checked annually.

The results should be relevant to UK hospitals, assuming they have surgeons with sufficient expertise in partial knee replacement.

What did it find?

  • Both groups of patients had much-improved knee pain and function, assessed by the 48-point Oxford Knee Score. After five years, people who had total knee replacement had an 18 point improvement and people who had partial knee replacement had a 19 point improvement. A 5-point difference is considered clinically significant, so the two procedures were similar for this outcome.
  • The study’s cost-effectiveness analysis found that partial knee replacement was more effective in terms of quality of life, resulting in 0.24 additional quality-adjusted life-years (QALYs) over five years. It was also less expensive, with care costing £910 less over the five years of follow-up.
  • Average hospital stay was longer for those who underwent total knee replacement (4.3 days) than those who had partial knee replacement (3.2 days).
  • The proportion of people who had a re-operation was similar in both groups. Re-operation rates were 6% among the partial knee replacement group and 8% among the total knee replacement. In both groups, 4% of people needed a revision of their knee replacement.

What does current guidance say on this issue?

The guideline on osteoarthritis published by NICE in 2014 includes recommendations on referral for consideration of joint replacement. However, it does not include guidance on which type of joint replacement device or technique is recommended. This guideline is being updated, with the update due to be published in August 2021.

In addition, a NICE guideline on primary joint replacement of the hip, knee or shoulder is in development and is expected to be published in March 2020.

What are the implications?

The results of the study imply that partial knee replacement can be offered with confidence for people with single compartment disease considering knee replacement. Offering partial knee replacement as a first choice may be better value for the NHS as it reduces costs, mainly because of shorter hospital stays.

Questions remain about the revision and re-operation rate for partial knee replacement over the longer term, and results from the planned 10-year follow-up of this trial will be of interest.

Surgeons would need to be fully trained and experienced in partial knee replacement in order to be able to replicate the results of this study.

Citation and Funding

Beard D, Davies L, Cook J, et al. 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. Lancet 2019; 394(10200):746-56.

The study was funded by the NIHR Health Technology Assessment Programme (project number 08/14/08).

Bibliography

Evans J, Whitehouse M. Partial versus total knee replacement for knee osteoarthritis. Lancet 2019; 394(10200):712-3.

NICE. Joint replacement (primary): hip, knee and shoulder. GID-NG10084. London: National Institute for Health and Care Excellence; 2019.

NICE. Osteoarthritis: care and management. CG177. London: National Institute for Health and Care Excellence; 2014.

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

Published on 17 July 2019

Prof David J Beard, DPhil Loretta J Davies, MScJonathan A Cook, PhDProf Graeme MacLennan, MScProf Andrew Price, FRCSSeamus Kent, PhDet al.

The Lancet , 2019

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 ClinicalTrials.gov (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.

Revision is a later operation to replace the original knee implant with a new device, often as a result of device failure, infection, or persistent pain.

Re-operation refers to any later operation on the implanted knee, which could be a revision or other surgery.

Expert commentary

This is an important study which confirms that partial knee replacement has similar clinical outcomes, lower costs and similar complication rates when compared with total knee replacement.

The study design is robust, pragmatic and the results are reassuring to the surgical community. Contrary to current practice, partial replacement should be considered as a first choice of treatment when managing patients with single compartment knee arthritis.

Hemant Pandit, Professor of Orthopaedic Surgery, University of Leeds

The commentator declares no conflicting interests

Author commentary

The five-year results of this large multicentre prospectively randomised UK study clearly show the advantages of partial over total knee replacement: shorter length of stay, fewer complications and less expensive/more cost-effective.

Interestingly, contrary to registry data, the revision rates were the same in each group at 4%. Of the 10 partial knee replacement revisions, four involved a bearing dislocation, suggesting that the revision rate for fixed bearing partial replacement is lower than total replacement!

The findings suggest that partial replacements should be the surgical treatment of choice for medial compartment knee osteoarthritis. More surgeons need to be trained to do this procedure to improve patient experience and save the NHS money.

William Tice, Orthopaedic Surgeon, University Hospital Southampton NHS Foundation Trust

The commentator declares being an investigator for the TOPKAT study group in one of the participating hospitals