THE VALUE OF TOTAL KNEE REPLACEMENT REVISITED: A COMPARATIVE ANALYSIS OF THE IMPACT OF INCREASED PROCEDURE RATES ON HEALTH OUTCOMES AND COSTS USING DATA FROM THE OSTEOARTHRITIS INITIATIVE

Purpose:

   Total knee replacement (TKR) utilization in the U.S. has more than doubled since the year 2000, however, the benefit of TKR has not been evaluated in randomized trials to date. We assessed the cost-effectiveness of TKR in knee osteoarthritis patients when performed at current rates and at rates before the procedure’s post-millennial increase.

Method:

   We estimated the effect of TKR vs no TKR on quality of life in knee osteoarthritis patients assessed by longitudinally collected 12-item Short Form Health Surveys in the Osteoarthritis Initiative (OAI, n=1,281) and the Multicenter Osteoarthritis Study (MOST, n=1,188). Both studies are nationwide population-based cohort studies including patients aged 45 to 79, started in 2003-2004. Using multivariable Cox-regression of primary TKR and mortality data from the OAI, and age-specific TKR revision data from the United Kingdom’s National Joint Registry, we developed the Knee OSteoarthritis MicrOSimulation (KOSMOS) model. Cost inputs (2012 USD), including procedure and medication costs, were estimated from a U.S. health-system perspective. The KOSMOS model was used to estimate lifetime costs and quality-adjusted life years (QALYs) for patients aged 45, 60, and 75 in scenarios of current TKR practice and at a 65% lower rate, as observed before the year 2000. We bootstrapped the survival and quality of life estimates to address parameter uncertainty. Lastly, we conducted a meta-analysis of uncontrolled before-after studies, and substituted the TKR effectiveness estimate with the literature-based effect in a sensitivity analysis.

Result:

   TKR practice as currently implemented in the U.S. increased QALYs, as compared with premillennial rates, by 0.019 (95% CI -0.098-0.142), 0.013 (95% CI -0.121-0.145), and 0.004 (95% CI -0.084-0.104) for patients aged 45, 60, and 75, respectively. Lifetime costs rose by $3730 (95% CI 2,257-6,240), $4,023 (95% CI 2,300-6,859), and $3,412 (95% CI 1,708-6,453), resulting in incremental cost-effectiveness ratios of $194,379, $313,561, and $784,365 per QALY. Incremental cost-effectiveness improved tremendously in the scenario analysis, when the effect on quality of life with TKR was derived from before-after studies. 

Conclusion:

   TKR at current procedure rates seems not to be cost-effective as compared to practice pattern in the near past, considering a cost-effectiveness threshold of $100,000-150,000. However our results were sensitive to the effect of TKR on quality of life. Randomized trials should be conducted to elucidate the true effect of TKR.