Volume versus Outcomes in Orthopaedic Surgery: A Proper Perspective is Paramount

Volume versus outcomes. How should the orthopaedic surgeon and the medical community at large react? This issue of The Journal contains an important article by Katz et al. dealing with the association between hospital and surgeon volume and outcomes of total hip surgery in the United States Medicare population1. It appears logical to assume that the more experience that a surgeon has with a particular procedure, the better the result and that a so-called learning curve may be associated with many surgical procedures. One can hardly argue with the goal of improving our care of patients by providing the best possible outcome. This is particularly true of high-volume procedures such as total hip replacements, which are performed at the rate of more than 200,000 per year2. The majority of both primary and revision total hip arthroplasties in patients in the Medicare population are performed by surgeons who carry out fewer than ten of these procedures per year. Higher surgeon and/or hospital volume has been associated with better outcomes in several areas, including cardiac surgery3,4; cancer surgery5; cataract surgery6; and medical management of various conditions, including myocardial infarction7. There have been similar reports involving orthopaedic procedures, including total knee8-11 and total hip12 arthroplasty. Kreder et al. noted significant differences in the case mix of low-volume providers compared with that of high-volume providers12. Surgeons and hospitals with a volume below the 40th percentile managed patients who had a more adverse risk profile in terms of age, comorbidity, and diagnosis. However, even after adjustment for this case mix there was a significant relationship between surgeons who averaged fewer than two hip replacements annually (which the authors defined as low-volume surgeons) and a worse outcome. Kreder et al. found that the patients managed by these low-volume surgeons tended to have higher mortality rates, more infections, higher rates of revision procedures, and more serious complications. Furthermore, they found that the duration of hospitalization was inversely related to surgeon volume and directly associated with hospital volume. When one looks at volume versus outcomes, there are several questions that should be considered: What do the data mean? What are their limitations? How should the data be used? What are the unanswered questions? Katz et al. analyzed Medicare claims data for more than 58,000 elective primary total hip replacements and almost 13,000 elective revision total hip replacements performed between July 1995 and June 19961. They assessed the relationship between surgeon and hospital volume and mortality, dislocation, deep infection, and pulmonary embolism occurring in the first three postoperative months. They found that patients treated with primary hip replacement in hospitals in which more than 100 of those procedures were performed per year had a lower risk of death than those operated on in hospitals in which ten or fewer were performed per year. The rate of dislocation was significantly lower for patients treated with primary hip replacement by surgeons who performed more than fifty of the procedures per year than it was for those operated on by surgeons who performed five or fewer per year. Patients treated with a revision hip replacement by surgeons who performed more than ten of those operations per year had lower mortality rates than those treated by surgeons who performed three or fewer such operations. We believe that it is important to carefully review the study limitations described by Katz et al., including the fact that analyses of Medicare claims are limited by the lack of key clinical information such as operative details, psychological and physical functional status, and pain. Furthermore, the complexity of the operative procedure, which is particularly important in the case of revisions, is not captured in the claims data. In addition, both Katz et al. and Kreder et al. identified key areas for additional research. Data such as these may be used as a reason to concentrate procedures or medical care in regional, high-volume centers in an attempt to reduce mortality and morbidity13,14; however, as Katz et al. pointed out, the trade-off between the comfort of having surgery at a community center and the better outcomes in larger, referral centers should be examined explicitly. Furthermore, since the Medicare data lack information on pain relief and physical as well as psychological function, the effects of procedure volume on pain relief and functional improvement as well as on the durability of the implant should be examined in order to provide a more complete picture of the influence of volume upon outcomes. A final question to be addressed is: “How good is good enough?” One can hardly argue with the contention that the results of total hip replacements are extremely good. Katz et al. reported that the overall mortality rate remains low, <2% for primary hip replacement, even in the lowest-volume centers. Furthermore, neither Kreder et al. nor Katz et al. identified a clear-cut point at which the complication rate changes dramatically; rather, there appears to be a continuum (that is, a linear relationship) between volume and outcome, making it difficult to identify a specific cutoff point. What is the orthopaedic surgeon to do with this information? The orthopaedist must take a proactive role and first of all be aware of the data and understand their limitations. In addition, more extensive research is necessary to refine and clarify the data before they can be used to justify changes in the delivery of total joint services in this country. The findings of this study should serve as a foundation for thoughtful dialogue about further improvement of the already remarkable success of total hip arthroplasty, and we must continue to pursue answers to the unanswered questions.