**Provider Volumes and Surgical Outcomes in Total Hip and Knee Replacement**

S. Rodriguez-Elizalde, R. Jenkinson, H. Kreder and J.M. Paterson *Division of Orthopaedic Surgery, Sunnybrook Health Sciences Centre, University of Toronto; and the Institute for Clinical Evaluative Sciences Canada* 

### **1. Introduction**

34 Recent Advances in Arthroplasty

Zhang, XW. & Thorlacius H. (2000) Inhibitory actions of ropivacaine on tumor necrosis

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factor-alpha-induced leukocyte adhesion and tissue accumulation in vivo. *Eur J* 

important role in up-regulating IL-1beta and IL-10. *Biochim Biophys Acta,* Vol.10,

There has been much discussion of the role of provider (both surgeon and hospital) surgical volumes and their effect on patient outcomes after total joint replacement (TJR)1-14. Common sense would suggest that individuals and institutions with greater experience should demonstrate reduced rates of complications and improved outcomes, however, in the setting of surgical outcomes, the question remains: does practice really make perfect? As medical costs continue to rise, institutions look for ways to optimize outcomes while decreasing complication rates and their associated financial and legal liabilities. There is ongoing debate as to whether the centralization of hospital resources to create large volume regional specialty centers and the sub-specialization of surgeons to increase their procedure volumes is an effective means of reducing cost and complications,2,5,7,12. Potential disadvantages of such centralization include increased wait times and travel distances for patients, and the possible closure of viable institutions. While most would likely agree that a volume exists below which procedure performance is suboptimal, where this threshold lies with respect to surgeon and institutional volumes in the field of hip and knee arthroplasty has yet to be defined.

Much of the literature on surgical volume-outcome associations comes from our colleagues in cardio-vascular, thoracic surgery and general surgery15. The early studies in this field were landmark in that they demonstrated a clear-cut reduction in mortality for procedures performed in specialized centers and by high volume surgeons15. In the past few decades, the frequency of total hip and knee arthroplasty has increased dramatically and these procedures are now considered among the most successful and reproducible medical procedures routinely performed 5,14,. Overall, complication rates are low and consequently demonstrating volume-outcome associations requires enormous sample sizes4,8.

Previous studies of the effect of provider volumes on the outcomes of hip and knee replacement have shown mixed results with respect to both surgeon volume and institutional volume1-14. Furthermore, difficulty arises when attempts are made to compare the results of studies across different institutions and countries due to the different methods used for defining procedure volumes, as well as for handling case complexity and patient comorbidities. This lack of consistency coupled with differences in health care delivery have contributed to inconsistent findings.

Below we review and comment on the key TJR volume-outcome studies from England and North America, where most TJR surgeries are performed. Results from the American and Canadian studies are summarized in Tables 1 and 2.

Provider Volumes and Surgical Outcomes in Total Hip and Knee Replacement 37

surgeons. Similar increased complication rates were found for low volume surgical centers (<25 TKA/year) when compared to high volume centers (>200/year). While this study demonstrated a clear trend toward better outcomes with higher volumes, no specific recommendations were given on what might constitute an acceptable minimum number of

Shortly thereafter, Katz's group used Medicare data from 1995-1997 to study rates of revision within 3 years of primary THA6. Hospitals were stratified into 4 volume groups: low (<25/year), medium (26-50/year and 51-100/year) and high (>100/year). Low volume surgeons were defined as those performing fewer than 12 primary THA/year. At the time of the study, 75% of all total hip replacements in the US were performed by surgeons doing less than 25/year, with centers performing over 100 cases a year accounting for only 10% of all hip replacements done. Comparing high volume surgeons (>12/year) in high volume hospitals (>100/year) to low volume surgeons (<12/year) and low volume centers (<25/year), the early failure rates were 3.3% vs 4.9%, or approximately a 50% increase in revision surgery. The highest rates of revisions for low volume surgeons were found within

SooHoo and Lieberman examined the effect of hospital volume on outcomes of total knee arthroplasty (TKA) in California from 1991-20018. They divided hospitals into three groups: low volume (bottom 40th percentile), intermediate volume (middle 40th percentile) and high volume (top 20th percentile). Interestingly, the lowest volume centers (which accounted for 40% of the hospitals examined) averaged only 13 (standard deviation (SD) 5) TKA/year. This is in stark contrast to the intermediate group (50, SD 15) and high volume group (145, SD 47). Outcome measures included complications within the first 90 days and 365 days postoperatively. Statistically significant higher complication rates were found for low-volume centers across the outcomes measured, including mortality, readmission for infection, pulmonary embolism and thromboembolism.. The largest difference between the low and high volume centers was for infection (1.13% versus 0.65%, respectively; p = 0.004). However, the overall postoperative complication rates remained relatively low, even among low-volume

centers, leading authors to question the rationale behind regionalization for TKA.

contrast to the early findings of Kreder et al1.

Hervey et al examined provider volumes and patient outcomes in an analysis of primary and revision TKAs3. Using the Healthcare Cost and Utilization Project Nationwide Inpatient Sample (HCUP-NIS), they were the first to create a national data set from multiple states and hospital settings in order to generate more comprehensive and robust estimates. Hospitals were divided by volume cutoffs into 4 groups: those performing <85, 85-149, 150- 250, and >250 TKA/year. Surgeons were stratified from lowest to highest volumes into 4 groups: those performing <15, 15-30, 30-59, and >60 procedures/year. Interestingly, surgeons performing 30 or fewer primary TKAs/year were responsible for nearly half the surgical volume of knee replacements in the US. Using multivariate regression analysis, higher volume surgeons and hospitals had lower mortality rates. Rates of other complications were elevated in the low volume groups, but did not differ statistically from those in the highest-volume groups. The other major finding was that low volume surgeons and centers tended to discharge patients later than their higher volume counterparts, in

Finally, Katz et al analyzed Medicare data on TKAs performed in Tennessee, Ohio, Illinois and North Carolina in 2000 to examine the effect of provider volume on patient function post-operatively7. Using a random sample of TKAs from various hospitals, patients were

procedures.

the first 18 months.
