In an analysis of Medicare administrative data, we found similar rates of postoperative complications and LOS for patients who underwent primary TKA in top-ranked and non–top-ranked hospitals when compared with hospitals that were not eligible for the U.S. News & World Report rankings. Specifically, we found no evidence of lower postoperative complication rates, reduced readmission rates, or reduced hospital LOS in top-ranked hospitals. Alternatively, we found that top-ranked and non–top-ranked hospitals had lower costs for TKA than hospitals ineligible for the rankings. Our results are complex and warrant further discussion.
To our knowledge, this is the first study that evaluates outcomes and cost in “America's Best” orthopedic hospitals. While a number of prior studies have demonstrated that the reputations of top-ranked hospitals for cardiovascular diseases may be justified,4-8
it is far less certain what top rankings mean for other disciplines of medicine, including orthopedics. Despite a lack of evidence for improved outcomes, top-ranked programs in all disciplines heavily promote their top rankings for marketing purposes.31
There are 2 potential interpretations of our findings. First, it is possible that the U.S. News & World Report
rankings truly do not capture a group of hospitals with improved orthopedic quality when it comes to TKA. Second, it is possible that the U.S. News & World Report
rankings do capture a truly superior group of hospitals but that Medicare administrative data do not capture these improved outcomes. Thus, it is important to comment on the challenge of evaluating nationwide outcomes in the area of joint arthroplasty. More than 500,000 TKA procedures are performed annually in the United States at a cost of more than $8 billion.32,33
Despite the volume of procedures performed and the associated costs, our ability to assess outcomes (and quality) after joint arthroplasty remains relatively rudimentary when compared with other conditions, most notably cardiovascular disease. In particular, because mortality after elective TKA is uncommon and our ability to detect other outcomes (eg, DVT, PE, infection) reliably using administrative data is imperfect,10,21
physicians, payers, and patients are faced with a conundrum. Ideally we would have access to national TKA registries containing additional outcomes, including quality of life and functional status. Such registries are being developed but are not yet widely available.34,35
Thus, for the time being, we are left with administrative data that have clear value but notable limitations. Repeating our analyses with more detailed patient-level outcomes is a logical next step.
We also found that Medicare patients admitted to top-ranked hospitals resided in wealthier zip codes than patients admitted to non–top-ranked and ineligible hospitals, which is interesting and worth further study. It is possible that top-ranked hospitals attract wealthier patients because of the visibility provided by rankings such as those by U.S. News & World Report—an interesting possibility. It is also interesting to note that top-ranked hospitals had modestly lower rates of DVT and PE but higher rates of hemorrhage; this could be explained if top-ranked hospitals had higher use of pharmacologic thromboembolism prophylaxis.
Our findings with regard to TKA costs warrant brief mention. In particular, our finding that TKA costs were markedly higher in hospitals ineligible for the U.S. News & World Report
rankings than in top-ranked and non–top-ranked hospitals is somewhat surprising. Prior studies have found that academic medical centers—a group of hospitals disproportionately represented in the U.S. News & World Report
rankings—typically have higher costs when compared with other hospitals.36,37
However, at least some of the higher costs that have been observed in teaching hospitals seem to be related to the greater complexity of patient populations served by these hospitals.38
Thus, our finding of higher costs among the smaller hospitals that were ineligible for the U.S. News & World Report
rankings is somewhat puzzling and requires confirmation. It is also important to recognize that our estimates of cost were derived from Medicare cost-to-charge ratios, a method that, while commonly used in health services research, is well known to have important limitations.39
This study has several limitations. First, our analyses were limited to Medicare fee-for-service patients, given their routinely available hospital claims through the CMS; thus, our findings may not be generalizable to Medicare health maintenance organization or non-Medicare patients. Second, our analyses focused on in-hospital and short-term postoperative outcomes but did not examine other dimensions of TKA outcomes, such as longer-term functional status, pain reduction, and quality of life. Potential differences in these outcomes and their impact on long-term health care expenditures for TKA patients treated in different hospitals remain unknown. Third, our study shares the same limitations of administrative data-based analyses as previous studies. The ICD-9-CM codes in the claims data are relatively insensitive in identifying comorbidities and complications and sometimes may miscode the 2 types of diagnoses, which would lead to bias in our estimates of hospital quality and outcomes. However, there is no evidence that the issues of undercoding and miscoding of conditions are more substantial in either ranked or nonranked hospitals. Under the assumption that such coding issues are largely random across hospitals, our finding of cost difference between hospital groups tended to be a conservative estimate of the true difference, although the estimates of no difference in other outcomes may be a result of downward biases. Finally, our estimates of cost depend largely on the Medicare cost-to-charge ratios. However, previous comparative analyses of Medicare costing data reveal differences across hospitals in the reporting of both revenues and expenses and treatment of details such as charity care, bad debt, nonoperating income, and cash flow. Because of these limitations, it is possible that our analysis of hospital costs provides an inaccurate comparison across the 3 hospital categories. That said, cost-to-charge ratios are commonly used in comparison of hospital costs and remain well established and ubiquitous in outcomes research.