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Do modern total knee replacements offer better value for money? A health economic analysis |
Hamilton DF, Clement ND, Burnett R, Patton JT, Moran M, Howie CR, Simpson AH, Gaston P |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. CRD summary This study evaluated the cost-effectiveness of the new Triathlon implant, compared with the usual implant, for total knee arthroplasty. The authors concluded that different implants did not affect the cost-effectiveness of arthroplasty, and any new more expensive implant would have to be justified by substantial improvements in patient outcome. The authors' conclusions were reasonable, but methodological limitations make the results unreliable. Type of economic evaluation Study objective This study evaluated the cost-effectiveness of the new Triathlon implant, compared with the usual implant, for total knee arthroplasty. Interventions The new Triathlon implant, with a single radius of curvature, sided, femoral component, shorter posterior femoral condyles, and a thinner anterior femoral condyle, was compared with the Kinemax implant, a non-sided implant, with a multi-radius design. The standard hospital protocol was used for surgery and following care, for both interventions. Location/setting UK/in-patient and out-patient care. Methods Analytical approach:The economic evaluation was based on a small, ongoing, prospective, double-blind, randomised controlled trial of 212 patients. The perspective was not explicitly stated. Effectiveness data:The trial methods, including randomisation and inclusion criteria, were reported. Follow-up was 52 weeks after surgery, with outcomes evaluated at six weeks, six months, and one year. The primary outcome for this analysis was health-related quality-of-life, measured by the SF-6D. Only 60 of the 104 patients randomised to Kinemax were analysed, and 64 of the 104 randomised to Triathlon were analysed. Scottish life tables, based on the patient’s gender and age at time of surgery, for patients requiring the knee surgery, were used with the SF-6D scores to derive the measure of benefit. Monetary benefit and utility valuations:The utility values were from the trial participants, who completed the SF-6D. These scores were converted to utilities using the Brazier algorithm. The minimum clinically important difference in SF-6D utility score was estimated to be 0.03, based on a published study. Measure of benefit:The primary measure of benefit was quality-adjusted life-years (QALYs). The benefits were discounted at 5% per year. Cost data:Only the costs of the implants were included. They were reported in UK £, and they were estimated to be £3,000 for each device. Analysis of uncertainty:Differences between intervention outcomes were assessed for statistical significance, using t-tests for continuous variables, Χ² tests for dichotomous variables, or Fisher's exact tests for categorical variables with five or fewer categories. Statistical significance was set at a probability of less than 0.05. Results Patients in the Triathlon group had lower baseline scores, but this was not statistically significant. They had a utility score of 0.623, and patients in the Kinemax group had a utility score of 0.631, at baseline. For both groups, the utility scores showed statistically significant improvement at one year. At six weeks, patients with the Triathlon had a utility value of 0.719, while patients with the Kinemax had a utility of 0.670 (p=0.06). At six months and one year, there were no statistically significant differences between groups. Triathlon patients had a one year mean utility score of 0.766, a difference of 0.143 from baseline, while Kinemax patients had a mean score of 0.773, a difference of 0.141 from baseline. For Triathlon, the cost per QALY gained was £20,979 at one year, or £1,954 over a lifetime. For Kinemax, it was £21,277 at one year, or £1,982 over a lifetime. Authors' conclusions The authors concluded that different implants did not affect the cost-effectiveness of arthroplasty, and any new more expensive implant would have to be justified by substantial improvements in patient outcome. CRD commentary Interventions:Two implants were compared, and clearly described. There was no description of how these implants were chosen for comparison, nor whether there were other implants that could have been compared. It is therefore unclear whether all relevant comparators were analysed. Effectiveness/benefits:The utility scores were measured using the SF-6D, which appropriately assessed health-related quality of life. As acknowledged by the authors, it was not the standard instrument (EQ-5D) recommended in UK National Institute for Health and Care Excellence (NICE) guidance. They pointed out that the EQ-5D might be more sensitive to changes in health-related quality of life. They acknowledged that there was a small difference in baseline utilities between the two groups. In cost-effectiveness studies, a small difference can drive the cost-effectiveness results, and this may have occurred here. Costs:The costing perspective was not stated and was very limited; only the cost of the implants was assessed. As the authors stated that other studies had found that re-operation rates were crucial in determining the cost-effectiveness of implants. These costs were not included in the lifetime projection. No costs were included for surgery, and follow-up care; the authors assumed that these would be identical. These cost omissions do not seem justified and greatly limit the usefulness of the results. Analysis and results:The results were clearly reported, with statistical significance for all comparisons, but there were some limitations to the analysis. The results were not incremental cost-effectiveness ratios, comparing the two implants, and caution should be taken when interpreting them. The ratios appear to have been calculated by comparing the quality of life before to that after surgery, for each implant. As the authors noted, the analysis assumed that there were no future costs for either implant, and that re-operation rates were identical. The authors stated that the durability of implants was a key factor in other cost-effectiveness evaluations, but they did not include this in their own analysis. Concluding remarks:The authors' conclusions were reasonable, but methodological limitations make the results unreliable. Bibliographic details Hamilton DF, Clement ND, Burnett R, Patton JT, Moran M, Howie CR, Simpson AH, Gaston P. Do modern total knee replacements offer better value for money? A health economic analysis. International Orthopaedics 2013; 37(11): 2147-2152 Indexing Status Subject indexing assigned by NLM MeSH Aged; Arthroplasty, Replacement, Knee /economics /instrumentation /methods; Cost-Benefit Analysis; Disability Evaluation; Female; Health Care Costs /statistics & Humans; Knee Joint /physiology /surgery; Knee Prosthesis /economics; Life Expectancy; Male; Middle Aged; Osteoarthritis, Knee /surgery; Quality of Life; Quality-Adjusted Life Years; Randomized Controlled Trials as Topic; Treatment Outcome; numerical data AccessionNumber 22013027439 Date bibliographic record published 23/07/2013 Date abstract record published 13/08/2013 |
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