Abstract
Summary Statement
Using current analysis/methodology, new implant technology is unlikely to demonstrate a large enough change in patient function to impact on the cost-effectiveness of the procedure.
Purpose
Cost effectiveness is an increasingly important metric in today's healthcare environment, and decisions surrounding which arthroplasty prosthesis to implant are not exempt from such health economic concerns. Quality adjusted life years (QALYs) are the typical assessment tool for this type of evaluation. Using this methodology, joint arthroplasty has been shown to be cost effective, however studies directly comparing the QALY achieved by differing prostheses are lacking.
Methods
Data was gathered in a single centre prospective double-blind randomised controlled trial comparing the outcome a modern implant, the Triathlon total knee replacement, with its traditionally designed predecessor the Kinemax, using the Short Form 6 dimensional (SF-6D) score and quality adjusted life year (QALY) methodology. The study cohort consisted of 64 patients that were randomised to a Triathlon and 60 randomised to a Kinemax.
Results
There was a significant improvement in the SF-6D score for both groups at one year compared with pre-operative scores (p<0.0001). The calculated overall life expectancy for the study cohort was 15.1 years, which resulted in an overall QALY gain of 2.144 (95% CI 1.752–2.507). The modern implant group demonstrated only a small improvement in the SF-6D score compared to the traditional design at one year (0.141 versus 0.143, p=0.94). This difference in health gain resulted in the modern implant costing £298 less per QALY at one year, however this saving diminished to less than £30 per year over the lifetime of the cohort.
Discussion
This study demonstrates that despite comparing 2nd and 4th generation design, modern implant technology does not influence the cost-effectiveness of TKA using the SF-6D and QALY methodology. As most implants demonstrate similar longevity, differences in patient function will likely carry the greatest influence on QALY. This type of analysis however assesses health status, and is not sensitive to joint specific function. Dramatic differences in patient outcome would be required to influence QALY score. Evolutionary design changes in implant technology are thus unlikely to influence QALY analysis following joint replacement, which has important implication for implant procurement.
