**5. Discussion**

38 Recent Advances in Arthroplasty

sent questionnaires capturing both self-reported WOMAC scores and surgery satisfaction scores. Poor WOMAC functional status scores (< 60) were noted to be more frequent among patients of surgeons who performed fewer than 12 TKA/year (20%), and centers performing fewer than 10 TKA/year (19%), as compared to their higher-volume counterparts (12% and 10% amongst high-volume surgeons and hospitals, respectively). These findings were

Overall, the American experience is quite unique in that across the country there is a virtual myriad of low volume centers that coexist with some of the largest and highest volume centers in the world. The current body of data indicates that despite increasing volume trends for THA and TKA, the majority of these procedures in the United States are still being performed by surgeons who perform fewer than 30/year and centers performing fewer than 100/year. Several studies have demonstrated increased complications rates, including increased risk of infection, revision, and mortality among low-volume surgeons and centers. In particular, it is evident that very low provider volumes (fewer than 10/year) are more frequently associated with increased morbidity and mortality. However, consensus on a minimum individual or institutional volume threshold for optimal patient outcomes has not been reached. The data are less conclusive with respect to the relationship between provider volumes and length of hospital stay, with early studies showing shorter stays in low-volume centers and subsequent studies the reverse. Little has been published on the financial costs of care in high versus low-

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

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

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

consistent across the country, even after adjusting for medical comorbidities and age.

volume centers. Further such studies are needed.

**3. The English experience** 

lengths of stay.

UK are publicly insured.

over 25 procedures a year6.

**4. The Canadian experience** 

In summary, while the literature suggests that lower surgeon and hospital procedure volumes are associated with poorer short-term patient outcomes after TJR,1-3,6,7*,*8,10,12,14 this relationship appears to exist only when provider volumes are extremely low. The data among moderate and high volume providers is otherwise inconsistent with no clear relationship between surgeon or center experience and patient outcomes. Shorter hospital stays have also been observed among high volume surgeons and to a lesser extent among high volume centers1,10,12,14.

Provider Volumes and Surgical Outcomes in Total Hip and Knee Replacement 41

Categories

3 groups: low <40 %ile, medium 40- 80 %ile and high

Surgeon volume: Low: 1-3/yr Medium: 4-10/yr High: >10/yr Hospital volume:

Created 4 volume groups for surgeon and hospital volume

Hospital volume:

to attain approximately equal percentages in each category Surgeon volume: <15/yr, 15-29/yr, 30-59/yr and >60/yr

1-5/yr 6-10/yr 11-25/yr 26-50/yr >50/yr

>80 %ile Surgeons: Low: <2/yr Medium: 2-10/yr High: >10/yr Hospitals: Low: <16/yr Medium: 16- 65/yr High: >65/yr

Results

Low volume surgeons experienced higher rates of mortality, infection, revision operations and serious complications during initial hospital

High volume surgeons demonstrates shorter length of hospital stay High volume centers had longer average length of hospital stay Average cost per procedure higher in low

volume centers

identified

mortality

risk

outcome

Higher surgeon and hospital volumes associated with lower

Surgeons performing <15/yr category associated with

increased DVT risk and post-operative infection

No other relationship between volume and

Higher hospital volume associated with lower rates of mortality and dislocation following primary THA

Higher surgeon volume associated with lower rate of dislocation and deep hip infection Similar results for revision THA Steady trend toward better outcome associated with higher volume but no discrete volume thresholds

stay

Author Year Databases Methods Volume

Examined 7936 primary THA between 1988-1991

Examined 58,521 primary THA and 12,956 revision THA between July 1995-June 1996

Examined 50,874 primary TKA and 4636 revision TKA performed in

1997

Kreder et al1

Katz et al2

Hervey et

al3

1997 CHARS

2007 Medicare

2003 Healthcare Cost and Utilization Project Nationwide Inpatient Sample

claims data

computerized data set of Washington State Health Department

These findings raise several points for consideration. The fact that extremely low provider volumes are associated with higher complication rates supports the notion of some minimum number of procedures that surgeons and surgical centers should perform in order to optimize outcomes. However, exactly where this threshold lies is difficult to determine from published reports. The fact that Canadian studies, where individual surgeons and centers perform relatively more procedures on average, generally fail to demonstrate a link between provider volumes and adverse outcomes suggests that few Canadian providers fall below this unidentified threshold. The association between surgeon procedure volume and decreased length of hospital stay (even after adjustment for hospital volume) does seem to be a reproducible finding and may be associated with lower costs for acute hospital care. It has been hypothesized that high volume surgeons and centers have more streamlined post-operative protocols and better access to rehabilitation and other ancillary services that could act to facilitate more rapid discharge1. Further research is needed to demonstrate whether there is a cost benefit to performing joint replacements in higher volume settings.

There is a global trend toward increasing surgeon and center procedure volumes in an effort to accommodate the fast-growing needs of an aging population. This increasing demand for joint replacement surgery has lead to the introduction of practice standards and protocols for everything from intake assessments, pre-operative work-up, surgical techniques, postoperative pain management and rehabilitation, which serve to streamline the care process and have contributed to significantly lower complication rates than seen in the previous two decades. The fact that complication rates are so low makes it harder to detect significant differences in outcomes related to provider volumes and also raises the question of whether small statistical differences in complication rates are of sufficient clinical importance to warrant the closure of low-volume centers in favor of high-volume regionalized centers of excellence. While small differences in outcomes, such as mortality, are likely to be important to patients, these must be weighted against potentially competing priorities such as access to service, inconvenience, and quality of life.

Other factors that may be contributing to heterogeneity among volume-outcome study findings are differences in the data used and patients studied. Most American studies have used Medicare data. In the US, Medicare covers selected patients (including those aged 65 years). This contrasts the Canadian and British public health insurance systems, which are universal. Consequently, it is likely that US Medicare patients undergoing TJR are, on average, older than Canadian and British TJR recipients. Furthermore, the US studies' reliance on Medicare data means that many private, high-volume clinics are excluded. When such centers are included, Medicare patients typically comprise a small percentage of total clinic and surgeon volumes. Thus, relative to Canadian and British studies, the American studies may be biased toward poorer outcomes, making volume-outcome relationships potentially easier to detect.

In summary, the relationship between TJR provider volumes and patient outcomes is complex. Based on intuition, it seems logical that surgeons and institutions that perform few procedures should have higher rates of complications, given the lack of familiarity, practice and available resources, such as rehabilitation and other ancillary services. US studies support this notion. However, there is no consensus regarding the number of procedures below which adverse patient outcomes (and possibly increased costs) would justify a change in policy. Further research and debate are needed to determine whether such a threshold exists and if so, where it lies.

These findings raise several points for consideration. The fact that extremely low provider volumes are associated with higher complication rates supports the notion of some minimum number of procedures that surgeons and surgical centers should perform in order to optimize outcomes. However, exactly where this threshold lies is difficult to determine from published reports. The fact that Canadian studies, where individual surgeons and centers perform relatively more procedures on average, generally fail to demonstrate a link between provider volumes and adverse outcomes suggests that few Canadian providers fall below this unidentified threshold. The association between surgeon procedure volume and decreased length of hospital stay (even after adjustment for hospital volume) does seem to be a reproducible finding and may be associated with lower costs for acute hospital care. It has been hypothesized that high volume surgeons and centers have more streamlined post-operative protocols and better access to rehabilitation and other ancillary services that could act to facilitate more rapid discharge1. Further research is needed to demonstrate whether there is a cost benefit to

There is a global trend toward increasing surgeon and center procedure volumes in an effort to accommodate the fast-growing needs of an aging population. This increasing demand for joint replacement surgery has lead to the introduction of practice standards and protocols for everything from intake assessments, pre-operative work-up, surgical techniques, postoperative pain management and rehabilitation, which serve to streamline the care process and have contributed to significantly lower complication rates than seen in the previous two decades. The fact that complication rates are so low makes it harder to detect significant differences in outcomes related to provider volumes and also raises the question of whether small statistical differences in complication rates are of sufficient clinical importance to warrant the closure of low-volume centers in favor of high-volume regionalized centers of excellence. While small differences in outcomes, such as mortality, are likely to be important to patients, these must be weighted against potentially competing priorities such as access to

Other factors that may be contributing to heterogeneity among volume-outcome study findings are differences in the data used and patients studied. Most American studies have used Medicare data. In the US, Medicare covers selected patients (including those aged 65 years). This contrasts the Canadian and British public health insurance systems, which are universal. Consequently, it is likely that US Medicare patients undergoing TJR are, on average, older than Canadian and British TJR recipients. Furthermore, the US studies' reliance on Medicare data means that many private, high-volume clinics are excluded. When such centers are included, Medicare patients typically comprise a small percentage of total clinic and surgeon volumes. Thus, relative to Canadian and British studies, the American studies may be biased toward poorer outcomes, making volume-outcome

In summary, the relationship between TJR provider volumes and patient outcomes is complex. Based on intuition, it seems logical that surgeons and institutions that perform few procedures should have higher rates of complications, given the lack of familiarity, practice and available resources, such as rehabilitation and other ancillary services. US studies support this notion. However, there is no consensus regarding the number of procedures below which adverse patient outcomes (and possibly increased costs) would justify a change in policy. Further research and debate are needed to determine whether such a

performing joint replacements in higher volume settings.

service, inconvenience, and quality of life.

relationships potentially easier to detect.

threshold exists and if so, where it lies.


Provider Volumes and Surgical Outcomes in Total Hip and Knee Replacement 43

Hospital volume: Low (<40%ile):

Intermediate (40- 80%ile): 50/yr High (>80%ile):

Categories

Volumes stratified based on percentiles into 3 categories –

low (<40%ile), medium (40- 80%ile) and high (>80%ile) Surgeon volume: Low: <9/yr Medium: 9- 27/yr High: >27/yr

Hospital volume: Low: <42/yr Medium: 42- 107/yr High: >107/yr

Volumes stratified based on percentiles into 3

13/yr

145/yr

Examined 3645 patient with elective THA in Ontario in 1992

Examined 14,352 patients with elective TKA between 1993-1996

Examined discharge data for 222,684 primary TKA between 1991-

2001

Table 1. Summary of American TJR Volume-Outcome Studies

Author Year Databases Methods Volume

SooHoo et al8

Kreder et al12

Kreder et al10

2006 California's Office of Statewide Health Planning and Development records

1998 Canadian

Institute for Health Information (CIHI) Hospital Discharge Abstracts and Ontario Health Insurance Plan (OHIP) Physician Service Claims

2003 CIHI Hospital Discharge Abstracts and Ontario Health Insurance Plan

No difference in pain or level of satisfaction

Low volume hospitals had higher mortality in 90 days post discharge and higher 90-day readmission rate for infection, pulmonary embolism and thrombophlebitis

Results

No difference in complication rate between low and high volume categories Patients of high volume surgeons had shorter length of hospital stay with lowest volume group averaging 2.4 days longer in hospital than highest volume

group

Hospital volume not related to length of stay

No effect of provider volume on infection or

Low volume groups (both surgeon and center) had longer

mortality


Examined 78,745 primary TKA performed between January and August 2000

Examined 76,627 primary THR between July 1995 and June

Examined functional status of 932 patients who underwent primary TKA

1996

Katz et al5

Losina et al6

Katz et al7

2004 Medicare

2003 Medicare

2006 Medicare

claims data

claims data

claims data

<85/yr, 85-149/yr 150-249/yr and >250/yr No clear

definition of low versus high volume

Surgeon volume: 1-12/yr, 13-25/yr, 26-50/yr and >50/yr

Highest volume centers had lower risk of pneumonia, dealth, PE acute MI and infection when compared to lowest volume centers Highest volume surgeons compared to lowest volume surgeons had lower risks of pneumonia and any adverse outcome

Only looked at rate of early failure requiring revision surgery Patients of low volume surgeons more likely to need revision THA compared to high volume surgeons Strongest association within first 18 months suggesting technical cause as mechanism of

early failure

failure rates

centers

motion

independently associated with lower

Higher hospital volume

Patients of low volume surgeons and centers were 2X as likely to report poor functional score compared to high volume surgeons and

Lowest volume group 2X as likely to have decreased range of

Hospital volume: 1-25/yr, 26- 100/yr, 101- 200/yr and >200/yr No clear

definition of low versus high volume

Surgeon volume: Low: <12/yr Hospital volume:

Surgeon volume: Low: <6/yr Hospital volume: Low: <25/yr

1-25/yr 26-50/yr 51-100/yr >100/yr


Table 1. Summary of American TJR Volume-Outcome Studies


Provider Volumes and Surgical Outcomes in Total Hip and Knee Replacement 45

Gawande, A. (2003). Complications: a surgeon's notes on an imperfect science. Metropolitan

Hagen, T.P., Vaughan-Sarrazin, M., & Cram, P. (2010). Relation between hospital

older:retrospective analysis of US Medicare data. *Br Medical J*. Pp. 340:c165. Hervey, S.I., Purves, H.R., Guller, U., Toth, A.P., Vail, T.P., & Pietrobon, R. (2003). Provider

Judge, A., Chard, J., Learmonth, I., & Dieppe, P. (2006). The effects of surgical volumes and

Katz, J.N., Losina, E., Barrett, J., Phillips, C.B., Mahomed, N.N., Lew, R., Guadagnoli, E.,

Katz, J.N., Barrett, J., Mahomed, N.N., Baron, J.A., Wright, J., & Losina, E. (2004). Association

Katz, J.N., Mahomed, N.N., Baron, J.A., Barrett, J.A., Fossel, A.H., Creel, A.H., Wright, J.,

Kreder, H.J., Deyo, R.A., Koepsell T., Swiontkowski, M.F., & Kreuter, W. (1997).

Kreder, H.J., Williams, J.I., Jaglal, S., Hu, R., Axcell, T., & Stephen, D. (1998). Are

Kreder, H.J., Grosso, P., Williams, J., Jangial, S., Axcell, T., Wai, E.K., & Stephen, D.J.G.

Mahomed, N.N., Barrett, J.A., Katz, J.N., Phillips, C.B., Losina, E., Lew, R.A., Guadagnoli, E.,

Patterson, J.M., Williams, J.I., Kreder, H.J., Mahomed, N.N., Gunraj, N., Wang, X., &

SooHoo, N.F., Zingmond, D.S., Lieberman, J.R., & Ko, C.Y. (2006). Primary Total Knee Arthroplasty in California 1991 to 2001. *J of Arthroplasty*. Pp. 21(2):199-205.

arthroplasty: a population study in Ontario. *Can J Surg*. Pp. 46(1):15-21. Losina, E., Barrett, J., Mahomed, N.N., Baron, J.A., & Katz, J.N. (2004). Early Failures of Total

Hip Replacement. *Arthritis and Rheumatism*. Pp. 50(4):1338-43.

replacement in Ontario. *Can J Surg*. Pp. 53(3):175-83.

Nationwide Inpatient Sample. *J Bone Joint Surg Am*. Pp. 85:1775-83.

States Medicare Population. *J Bone Joint Surg Am.* Pp 83:1622-29.

Hospital Episode Statistics for England. *J of Public Health*..

Replacement. *J Bone Joint Surg Am*. Pp. 86:1909-16.

*Rheumatism*.Pp. 56(2):568-574.

*J Bone Joint Surg Am.* Pp 79:485-94.

*Joint Surg Am*. Pp. 85:27-32.

41(6):431-7.

orthopaedic specialization and outcomes in patients aged 65 and

Volume of Total Knee Arthroplasties and Patient Outcomes in the HCUP-

training centre status on outcomes following total joint replacement: analysis of the

Harris, W.H., Poss, R., & Baron, J.A. (2001). Association Between Hospital and Surgeon Procedure Volume and Outcomes of Total Hip Replacement in the United

Between Hospital and Surgeon Procedure Volume and the Outcomes of Total Knee

Wright, E.A., & Losine, E. (2007). Association of Hospital and Surgeon Procedure Volume With Patient-Centered Outcomes of Total Knee Replacement in a Population-Based Cohort of Patients Age 65 Years and Older. *Arthritis and* 

Relationship between the Volume of Total Hip Replacement Performed by Providers and the Rates of Postoperative Complications in the State of Washington.

Complication Rates for Elective Primary Total Hip Arthroplasty in Ontario Related to Surgeon and Hospital Volumes? A Preliminary Investigation. *Can J Surg*. Pp.

(2003). Provider volume and other predictors of outcome after total knee

Harris, W.H., Poss, R. & Baron, J.A. (2003). Rates and Outcomes of Primary and Revision Total Hip Replacement in the United States Medicare Population. *J Bone* 

Laupacis, A. (2010). Provider volumes and early outcomes of primary total joint

**6. References** 

Books.


Table 2. Summary of Canadian TJR Volume-Outcome Studies
