Recent studies have documented improved outcomes by high-volume providers at high-volume hospitals1-3. In the report "Factors Predicting Complication Rates Following Total Knee Replacement," the authors examine not only the relationship between outcome and hospital volume but also the potentially important role of a variety of patient and hospital characteristics. Using a statewide database, the authors performed a regression analysis to examine patient-based predictors (comorbidity index, age, race, gender, ethnicity, and insurance status) and hospital-based predictors (surgical volume, teaching status, and hospital size). These independent variables were evaluated with the dependent variables (mortality, readmission due to infection, and readmission due to pulmonary embolus) in the first ninety days after discharge. Following the evaluation of 222,684 patients, the authors noted 1176 deaths (0.53%) 1586 infections (0.71%), and 914 pulmonary emboli (0.41%).
The majority of patients (58%) were treated at high-volume hospitals. The final regression model showed the most consistent associations with complications to be increasing age, increasing comorbidity index, and decreased hospital volume. The effect of age and comorbidity index on the probability of adverse outcome following total knee arthroplasty was similar to or greater than the effect of hospital volume.
The data presented here has policy-related implications. The results of this study indicate that the regionalization of total knee arthroplasty to high-volume centers may decrease mortality following total knee arthroplasty. However, the authors have also documented that hospital volume is not the only important variable that affects outcome. It is not surprising that elderly patients with multiple comorbidities have the highest mortality and complication rates. Therefore the relation between hospital volume and outcome as reported in this paper is most germane to clinical practice.
The major strength of this study is the large number of patients studied and the multiple variables analyzed. The major limitation of this study is the lack of an analysis of provider volume and outcome. Further limitations of this study include the short-term end point (ninety days) and the lack of functional evaluation for the patients studied. Information concerning the necessity of early revision (less than five years after operation) performed at low-volume versus high-volume centers would also be helpful. Early failure requiring revision has been documented in one large revision series4, while another has noted an association between low hospital volume and an increased rate of early revision arthroplasty3.
With regard to the importance of comorbid conditions, it would have been helpful to specifically analyze where patients with the most severe comorbidities were undergoing surgery. Low-volume centers tend to market the fact that they have low complication rates, yet they refer most of their difficult cases to high-volume centers. Therefore, it would be important to compare the success of high-volume centers versus low-volume centers with regard to the management of patients with severe comorbidity.
In conclusion, the authors of this paper have once again shown that volume improves outcomes, and they intimate that regionalization of total knee arthroplasty may be in the best interest of patients. While regionalization may be a laudable goal, we are currently entering an era of explosive growth in joint replacement as the baby-boomer generation reaches maturity. Clearly, high-volume centers cannot handle all of the surgery that will be needed. Therefore, an understanding of the processes that are successful at these high-volume centers seems to be the short-term key to success. I agree with the authors that it would be beneficial to focus on identifying and disseminating the practices that lead to lower complication rates at high-volume hospitals.
*The author did not receive grants or outside funding in support of his research for or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.
1. Hervey SL, Purves HR, Guller U, Toth AP, Vail TP, Pietrobon R. Provider volume of total knee arthroplasties and patient outcomes in the HCUP-nationwide inpatient sample. J Bone Joint Surg Am. 2003;85:1775-83.
2. Katz NJ, Barrett J, Mahomed NN, Baron JA, Wright RJ, Losina E. Association between hospital and surgeon procedure volume and the outcomes of total knee replacement. J Bone Joint Surg Am. 2004;86:1909-16.
3. Kreder HJ, Grosso P, Williams JI, Jaglal S, Axcell T, Wal EK, Stephen DJ. Provider volume and other predictors of outcome after total knee arthroplasty: a population study in Ontario. Can J Surg. 2003;46:15-22.
4. Fehring TK, Odum S, Griffin WL, Mason JB, Nadaud M. Early failures in total knee arthroplasty. Clin Orthop Relat Res. 2001;392:315-8.