Our analyses showed that, at an incremental cost of $18 300 per QALY gained, TKA is a highly cost-effective procedure for management of end-stage knee OA among Medicare-aged persons compared with non-operative management. This result is robust across a broad range of assumptions regarding both patient risk and hospital volume. For patients who choose to undergo TKA, hospital volume plays an important role: regardless of patient risk level, higher-volume centers consistently deliver better outcomes. But the additional survival benefits associated with high-volume centers provide limited cost-effectiveness benefits for high-risk patients deliberating between medium- and high-volume centers. Across all levels of patient risk and hospital volume, the cost-effectiveness of TKA lies well within the range of accepted cost-effectiveness for other musculoskeletal procedures, such as lumbar diskectomy36
and fusion of the spine for spondylolisthesis ().37
Cost-effectiveness of Selected Health Care Interventionsa
Several studies have evaluated the cost-effectiveness of TKA, but none to our knowledge have used data from nationally representative US cohorts and evaluated cost-effectiveness over the long term. One single-center study estimated the cost-effectiveness of TKA over 1 year to be $14 000 per QALY (inflated to 2006 US dollars) for all TKA recipients.10
A study conducted in Finland also reached favorable conclusions about the cost-effectiveness of TKA, though differences in method and setting make the study difficult to compare with ours.9
It is notable, however, that our general conclusions regarding cost-effectiveness of TKA are consistent with these prior findings.
For patients at highest risk, shifting from medium- to high-volume hospitals had a cost-effectiveness ratio of $135 700 per QALY. This comparatively unfavorable figure arises from the increased rates at which high-risk patients undergo TKA in high-volume centers, potentially distant from their places of residence, and the patients are then referred to costly inpatient rehabilitation centers. By contrast, low- and medium-risk patients who are shifted to hospitals with greater volume experience reduced costs and lower complication rates. Discharge to costly inpatient rehabilitation facilities is less common for these patients.
Our study had several limitations. We found no published literature on costs of TKA that provided estimates stratified by disease severity and patient risk. Thus, we used data from NHANES III29
to assist in building our cost estimates. Notably, the results of our sensitivity analyses suggest that TKA remains cost-effective under wide variations in costs and disease severity. We could not incorporate willingness to undergo TKA as a model input and did not consider the disutility of having surgery in an unfamiliar high-volume center vs a familiar low-volume center. We estimated the rate of TKA failure by using data on revisions of TKA. We acknowledge that revision may be an insensitive proxy for prosthesis failure because patients with a failed TKA may not be offered or may decline revision. Our sensitivity analyses showed that cost-effectiveness estimates were not sensitive to the proportion of persons with failed TKA who underwent revision. We also note that the QOL and annual cost associated with the no-TKA option did not account for continuing worsening of functional limitations related to end-stage knee OA. This assumption biased results against TKA, making the analysis more conservative.
For patients with symptomatic end-stage knee OA, TKA was very cost-effective. This finding applied even to the highest-risk patients. While having TKA in low-volume centers cost more and produced worse outcomes than having TKA in higher-volume centers, having TKA even in low-volume centers was cost-effective compared with no TKA for patients at all levels of risk for perioperative complications. On a societal level, it is more cost-effective for the population with end-stage knee OA to undergo TKA than to not have TKA, regardless of hospital TKA volume.
Clinicians, patients, and policy makers should consider the relative cost-effectiveness of TKA in making decisions about who should undergo TKA, where, and when. Cost-effectiveness analysis is useful in estimating the value of medical practices when randomized controlled trials are logistically or ethically difficult to implement. Lack of physician and patient equipoise regarding randomization would make the conduct of a trial of TKA difficult, and blinding would be nearly impossible. Cost-effectiveness analysis in this setting is particularly valuable in informing policy and practice.
Based on the data derived from TKA recipients of various risk groups, we showed that TKA is effective and cost-effective across all risk groups.40,41
Further analysis on the timing of TKA is necessary. While regionalization efforts to consolidate TKAs in high-volume centers are currently under consideration, our analysis showed that hospital volume above 25 TKA per year is sufficient to assure cost-effective delivery of TKA in the situations where there is a choice among different hospital settings. Even in the absence of such choice, TKA remains a cost-effective treatment compared with no TKA for patients with end-stage knee OA, regardless of setting and patient risk for complications and postoperative mortality.