Do higher case volumes make us safer and more effective surgeons?

I’ve always held that “the surgeon is the method”, meaning that considering all of the variables that might affect the outcome of a given surgery for a given problem, the most important is the person making the decisions, carrying out the procedure, and analyzing the results = the surgeon. As surgeons we are engaged in the constant pursuit of learning to achieve better outcomes for our patients. We hope, as the saying goes, that experience is the great teacher and that practice makes us better at our art. But as we’ll see below, the number of repetitions is not the only thing that matters.

My friend JP Warner pointed to this article, Higher Surgeon Volume is Associated With a Lower Rate of Subsequent Revision Procedures After Total Shoulder Arthroplasty: A National Analysis, the authors of which assessed the association between increasing surgeon volume and decreasing rate of revision for anatomic (aTSA) and reverse (rTSA) shoulder arthroplasty using the Centers for Medicare and Medicaid Services (CMS) fee-for-service inpatient and outpatient claims data from 2015 through 2021. 

They found that in comparison to an arthroplasty case volume of <4 per year, an annual surgeon case volume of

 ≥ 10 aTSAs was associated with a 27% decreased odds of a revision within 2 years

≥ 29 aTSAs was associated with a 33% decreased odds of a revision within 2 years

An annual surgeon volume of ≥ 29 rTSAs was associated with a 26% decreased odds of a revision within 2 years.

The figure below shows the trend line for revisions as function of surgeon case volume.

There are several interesting observations to be made on this graph: 

(1) the downward trend appears to continue out to surgeons performing over 100 shoulder arthroplasties per year, No end in sight for the effect.

(2) the effect of case volume on revision rate appears relative continuous: there is no obvious inflection point after which the volume effect starts to level off, 

(3) there is wide scatter in the data, indicating that there are factors other than annual case volume that are driving a surgeon’s revision rate (some lower volume surgeons have lower revision rates than some higher volume surgeons).

So questions arise: 

(1) which is more important, the number of cases / year or the lifetime total number of cases (“how many do you do” vs “how many have you done”)?

(2) how does a patient learn a surgeon’s case volume? 

(3) how important should case volume be in a patient’s choice of surgeon (e.g. how far should the patient travel or how much more should they be willing to pay to be cared for by a higher volume surgeon)?  

(4) what factors account for the high variability shown in this chart (note especially the three surgeon outliers at the top with over twice the average revision rate even though they’re in the “high volume” category)? Should the patient be more concerned about the volume or the revision rate of their potential surgeon?

(5) if a large percentage of patients select their surgeon on volume, how do low volume surgeons become high volume surgeons? 

(6) is it experience (the number of cases) that is the determinant of revision rate?

In his books Noise a Flaw in Human Judgment and Thinking Fast and Slow Daniel Kahneman emphasized that experience does not automatically improve the outcome.  Over time, experienced surgeons may gain increased confidence but not necessarily increased competence, a phenomenon Kahneman calls the illusion of validity. Instead it is learning that leads to better outcomes. Learning, in turn, comes from quality, timely and accurate feedback. If a surgeon routinely takes and analyzes postoperative x-rays, she or he can learn how well the preoperative plan was executed – becoming smarter with each case. That’s pretty easy to do. What’s harder is to study each case that required revision to learn what went wrong – this is harder because the revision is delayed and memory fades. 

Each failure is a learning opportunity not to be passed up. Through the experience of studying the factors associated with each revision, the surgeon can reduce the risk of revisions in the future. There is safety in numbers, but its not the only thing that counts.

Dunlins Ocean Shores 2020

While there is safety in numbers, the peregrine falcon can usually cause an adverse event for one of them.