Scientific Article   |    
Provider Volume of Total Knee Arthroplasties and Patient Outcomes in the HCUP-Nationwide Inpatient Sample
Sheleika L. Hervey, MD; Harriett R. Purves, MPH; Ulrich Guller, MD; Alison P. Toth, MD; Thomas P. Vail, MD; Ricardo Pietrobon, MD
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Investigation performed at the Center for Excellence in Surgical Outcomes, Department of Surgery, Division of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina

Sheleika L. Hervey, MD
Harriett R. Purves, MPH
Ulrich Guller, MD
Alison P. Toth, MD
Thomas P. Vail, MD
Ricardo Pietrobon, MD
Center for Excellence in Surgical Outcomes, Department of Surgery, Division of Orthopaedic Surgery, Duke University Medical Center, Box 3094, Durham, NC 27710. E-mail address for R. Pietrobon: rpietro@duke.edu

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from the National Institute of General Medical Sciences (Grant T35-GM08579) and Bristol-Meyers Squibb Company-NMF Fellowship Program in Academic Medicine. They 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 authors are affiliated or associated.

J Bone Joint Surg Am, 2003 Sep 01;85(9):1775-1783
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Background: The relationship between volume and outcome of total knee arthroplasties has never been evaluated in a nationally representative sample, to our knowledge. We hypothesized that surgeons and hospitals with higher patient volumes would have better outcomes, as defined by lower mortality rates, shorter hospital stays, and lower postoperative complication rates.

Methods: The 1997 Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample, Release 6, provided discharge abstracts of patients undergoing total knee arthroplasty from a national stratified probability sample. Logistic and multiple regression models were used to estimate the adjusted association of surgeon or hospital volume with rates of in-hospital mortality, pulmonary thromboembolism, deep venous thrombosis in the lower extremity, and postoperative wound infection as well as length of hospital stay. Estimates were calculated for a target population of 277,550 patients. Models were adjusted for comorbidity, age, gender, race, household income, and procedure (primary or revision arthroplasty).

Results: The patients were mostly white (70.2%) and female (62.7%), with a mean age of 68.9 years. The overall in-hospital mortality rate for the target population was 0.2%, and the average length of stay was 4.6 days for the primary total knee arthroplasties and 4.9 days for the revision procedures. Surgeon volumes of at least fifteen procedures per year and hospital volumes of at least eighty-five per year were significantly and linearly associated with lower mortality rates (odds ratio = 0.56 [0.24 to 1.31] for surgeon volume of = 60). No other association demonstrated a significant and directionally consistent linear trend for improved outcomes.

Conclusion: Patients treated by providers with lower caseload volumes had higher rates of mortality following total knee arthroplasty in 1997. Proposing volume standards could decrease patient mortality following this procedure.

Level of Evidence: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

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    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Ricardo Pietrobon
    Posted on October 24, 2003
    Dr. Pietrobon responds to Dr Feinstein
    Duke University Medical Center

    We thank Dr. Feinstein for his comments on our manuscript. Dr. Feinstein raises concerns regarding the generalizabilitiy of our findings to orthopedic surgeons who have extensive expertise but who may be regarded as low volume providers. These concerns are legitimate.

    Our investigation was based solely on one year of Nationwide Inpatient Sample data (1997), and his point thus represents a limitation of our study as it might wrongly classify orthopedic surgeons who have changed the volume of their surgical activities over time. Thus, orthopedic surgeons that decreased their case load over time and were in the low volume category in our study may have better outcomes than other low volume providers. Similarly, low volume orthopedic surgeons who suddenly increased their case load and were classified in the high volume subset in our analysis might have worse outcomes than other high volume providers.

    To overcome this limitation a combined analysis based on several years (or even decades) would be necessary. Nonetheless, this drawback biases our findings towards the null hypothesis and thus the real differences between low and high volume providers might be even higher than the ones reported in our study.

    Peter A. Feinstein
    Posted on October 02, 2003
    Provider Volume of Total Knee Arthroplasties and Patient Outcomes HCUP-Nationwide Inp.Sample
    Wilkes-Barre General Hospital

    To the Editor:

    The authors of this study found that doctors who perform joint replacement surgery more frequently apparently have fewer complications (excluding complications associated with DVT).They recommend that consideration be given to adopting a system in which a certain number of joint replacements are required to have been performed by an individual or a hospital to qualify to do that type of surgery.

    The problem with this article and its conclusion is that it does not take into account whether an individual practices in a rural or metropolitan area, and to what extent the potential number of joint replacement patients exist.

    I perform approximately 20 hip and knee replacements a year. According to the article, I would be less “competent” than someone doing a much higher number. However,I have been doing joint replacements for approximately 25 years and have prformed well over a 1,000 of these operations. My experience is extensive, and my record over the past 5-10 years is excellent in terms of absence of complications and happy patients.

    I believe that I service my community extremely well in this regard. If the conclusions of this article were followed, my patients would have to travel anywhere from an hour and half to two and half hours to have a joint replacement done.

    There are other orthopedic surgeons in my community who are in a similar situation and who provide excellent and quite competent care to our patients. I am certain that the statistics at my community hospital compare favorably to hospitals that have higher volumes. In fact, my hospital has been recognized as one of the 100 outstanding orthopedic hospitals in the country for just that reason.

    I would, therefore, respectfully submit that the conclusions of this article do not reflect conditions in individual communities. They present a great danger to our ability to provide care to our patients by implying that very qualified and experienced orthopedic surgeons should not be doing this type of surgery.

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