**3. The English experience**

Judge et al examined the effects of hospital surgical volumes and teaching center status on the outcomes of total joint replacement between 1997 and 2002 in the United Kingdom, looking at over 280,000 hip and 211,000 knee replacements11. They used National Health Service Hospital Episode Statistics and defined hospital volume groups of <51, 51-100, 101- 250, 251-500 and >500 procedures/year. They observed a decrease in patient mortality for both hip and knee replacement as volumes increased. Training institutions also had better THA outcomes, but no such effect was observed for TKA. Lower volume centers had longer lengths of stay.

This study demonstrated that overall, in contrast to the US, most arthroplasty surgery in England was being done in proportionally higher-volume centers. This was true for each of the six years studied. This finding is not surprising as it is easier to consolidate health care resources in a geographically smaller country. Further, over 80% of surgical services in the UK are publicly insured.

### **4. The Canadian experience**

Results from Canadian volume-outcome studies have been mixed. Compared to their southern neighbors, Canadians have a more centralized medical delivery system, with more limited access to surgeons. On average, Canadian surgeons perform higher volumes than their American counterparts, resulting in relatively greater average annual procedure volumes among both surgeons and institutions. For example, surgeons performing greater than 25 procedures a year in Canada account for nearly 75% of the THA and TKA surgical volume14 whereas in the US, only one third of arthroplasties are performed by those doing over 25 procedures a year6.

Kreder et al performed a study of THA using Ontario data from 199212. Surgeons and institutions were divided into 3 groups defined by the procedure volume distributions: <40th, 40-80th, and >80th percentile. The low surgeon volume group performed on average 9 THAs compared to the high volume group who performed on average over 27 THAs /year. Low volume centers performed <40 annual THAs compared to >80/year in the high volume groups. Though Kreder attempted to use the procedure volume cut-offs from his earlier Washington study1, Canadian provider volumes were such that the vast majority of Canadian surgeons would have been labeled high-volume (>10 procedures/year). The major finding of this study was that higher volume surgeons and centers discharged their patients much earlier (2.4 days earlier). No volume-outcome associations were found.

Kreder et al later looked at provider volume-outcome relations in Ontario TKAs from 1993- 1996 using similar methods to the above study10. Again, patients of lower-volume surgeons had longer lengths of stay in hospital. They also had double the risk of reoperation.

Finally, Paterson et al performed a more recent, larger study of Ontario patients including over 20,000 THA patients and 27,000 TKA patients14. In the 10 years since Kreder's previous analysis,12? hip replacement volumes had grown by 50%, and total knee replacement volumes by 100%. The number of arthroplasty surgeons during that time period also increased, but at a much slower rate, resulting in an increased volume of cases per individual surgeon.

In this study, low-volume hip surgeons performed an average of 2-25 cases per annum, compared to 2-35 cases per annum for low-volume knee surgeons. This contrasted to the highvolume groups which were greater than 60 cases per annum for hip and greater than 71 cases per annum for knee. Of note, extremely low volume surgeons (defined as those performing less than 2 procedures/year) and low volume centers (defined as those performing less than 10 procedures/year) were excluded from analysis. The results of this study corroborated those of Kreder's earlier work in that no consistent relationships were found between complication rates and hospital volumes for either TKA or THA. Surgeons in the lowest volume quartile demonstrated a 30% increased rate of complications for THA but no similar relationship was seen for TKAs. Surgeon volume was also related to increased risk of revision for THA but not for TKA. Again, patients of lower-volume surgeons had relatively longer lengths of stay in hospital, although no similar relation was observed with hospital volumes.

Overall, the Canadian experience with respect to TJR surgical volume-outcome relationships is mixed. The differences in adverse outcome as related to provider volumes is much less pronounced than in the US, with the most recent Canadian study showing essentially no relations for TKA and inconsistent findings for THA. The one consistent finding among the Canadian studies is that, adjusting for hospital volume, patients of higher-volume surgeons have relatively shorter lengths of hospital stay.
