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Investigation reveals rationing of knee replacement is unjustified
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Because knee replacement is so cost-effective based on a recent cost analysis, rationing these procedures in the United Kingdom is unjustified, according to a presenter.
“If a threshold for rationing knee replacement based on cost-effectiveness was to be introduced, it would be so high that virtually no patient would be excluded, so there is no justification for rationing,” David W. Murray, MD, FRCS (Orth), of Nuffield Orthopaedic Centre in Oxford, United Kingdom, said.
“As far as the design is concerned, patellar resurfacing is cost-effective. Mobile bearings do not affect cost-effectiveness. All-polyethylene tibias are not cost-effective even in the elderly. Unicompartmental replacements are cost-effective,” Murray said.
The U.K. National Health Service (NHS) has limited funds and considers knee replacement to be a procedure of “limited value.” In some part of the NHS, thresholds are being used to restrict knee replacement and they are usually based on the Oxford Knee Score (OKS), but body mass index (BMI) is also used. The most commonly used threshold above which a knee replacement is not offered is an OKS of 26 points, according to Murray.
The decision whether to introduce a new procedure into the NHS is based, in part, on whether it is considered cost-effective. Procedures costing less than £20,000 to £30,000 per QALY (quality adjusted life year) are deemed to be cost-effective, he noted.
If a threshold is to be used to ration knee replacement, then the only fair way to determine the level for the threshold would be to base it on cost-effectiveness. Murray used data from a large, multicenter study to identify thresholds above which knee replacement was not cost-effective. This study included 2,131 knee replacements from 34 centers with a 10-year follow-up. A detailed analysis of cost and effectiveness was undertaken and, based on conservative assumptions, cost-effectiveness was determined.
The investigators found the cost of the knee replacement and 5 years subsequent care of £7,458 per patient with 1.33 QALYs gained. Overall, knee replacement cost £5,623 per QALY gained, which is considered highly cost-effective. The factor that influenced cost-effectiveness most was preoperative OKS. Other key factors were age, gender and American Society of Anesthesiologists grade.
Therefore, the best threshold would be based on preoperative OKS. As BMI did not influence cost-effectiveness, there is no justification to restrict knee replacement in patients with high BMI, according to Murray.
Knee replacements in patients with a preoperative OKS of <38 points were cost-effective using a <£20,000/QALY threshold, based on the results. Therefore, if knee replacement is to be rationed, an appropriate threshold would be a preoperative OKS of 38 points. This threshold would exclude about 3% of patients having a knee replacement. As so few patients would be excluded, rationing would not be justified due to the costs and bureaucracy involved, Murray noted.
A further analysis based on implant design was undertaken. In those results, patellar resurfacing was found to be cost-effective compared with not resurfacing. There was no difference in cost-effectiveness between mobile and fixed-bearing prostheses. – by Renee Blisard Buddle
- Reference:
- Murray D. Rationing of total knee replacement: A cost-effectiveness analysis. Presented at: Knee Society Specialty Day; March 23, 2013; Chicago.
- For more information:
- David W. Murray, MD, FRCS (Orth), can be reached at University of Oxford, Oxford OX3 7LD, United Kingdom; email; david.murray@ndorms.ox.ac.uk.
Disclosure: Murray receives royalties from Biomet and research support from Biomet, DePuy Synthes, Stryker and Zimmer.