The quest for ways to make shoulder arthroplasty safer for future patients continues through Shoulder Arthroplasty Research. Here are some things we know:
(1) most shoulder arthroplasties turn out well for the patient, thus our greatest opportunities to learn come from studying failures
(2) it is insufficient to focus on the type of failure (e.g. glenoid component loosening, rotator cuff failure); rather we need to hone in on what could have been done differently at the primary arthroplasty to lower the risk of component or cuff failure - this can be thought of as actionable intelligence.
(3) we want to avoid the assumption that technologies such as 3D CT based planning, patient specific instrumentation, robotics, virtual reality, augmented reality will lower failure risk until their effectiveness in vivo has been rigorously demonstrated
(4) our attention falls on the surgeon and the elements of care that are under her/his control
A recent article, The effect of surgeon volume on complications after total shoulder arthroplasty: a nation-wide assessment, provides some actionable intelligence. The authors retrospectively queried the Pearl Diver Mariner database for the years 2010 to 2022. Their analysis included 155,560 patients having primary anatomic total shoulder arthroplasty, excluding those younger than 40 years, those who underwent revision arthroplasty, cases of bilateral arthroplasty, and cases with a history of fracture, infection, or malignancy.
They included cases performed by surgeons with a minimum of 10 cases.
The 90th percentile for surgeon volume was determined to be 112 cases during the study period. Surgeons above the 90th percentile (n 340) operated on 68,531 patients, whereas surgeons below the 90th percentile (n 3038) operated on 87,029 patients. Surgeons in the high-volume group were significantly more likely to have completed a Shoulder and Elbow fellowship and less likely to have no fellowship training or fellowship training outside of Shoulder and Elbow or Sports Medicine.
Low-volume surgeons operated on patients with higher baseline comorbidities. Here's my summary of their data.
After adjusting for age, gender, CCI, obesity, and tobacco use, high-volume surgeons experienced lower rates of medical complications including renal failure, anemia, and urinary tract infection. All-cause readmission, reoperation at 90 days, and reoperation at 1 year were significantly lower among high-volume surgeons. Cases performed by high-volume surgeons exhibited lower rates of all complications including prosthetic joint infection and periprosthetic fracture. Here's my summary of their data. NB an odds ratio <1 means that cases operated by high volume surgeons had a lower rate of the complication than low volume surgeons.
Finally, the authors found that the proportion of shoulder arthroplaties performed by high volume surgeons has been decreasing with time.
Comment: This study appropriately puts the focus on the surgeon - the individual that decides which treatment is best suited for each patient, carries out the surgery, and manages the aftercare. In other words, the surgeon controls the modifiable variables for each patient. The surgeon is the method.
The authors characterize the surgeon in three dimensions: (1) case volume, (2) fellowship, and (3) the comorbidites of the patients the surgeon selects to have total shoulder arthroplasty. They then go on to compare complications for surgeons performing ≥ 112 arthroplasties to those performing < 112.
Thus the data available are ripe for a multivariable analysis (MVA) characterizing the relationship among these variables - individually or in combination - to the occurrence of medical and surgical complications. Without such an analysis we cannot know the relative importance of each of these dimensions.
Let's look at each of these characteristics:
Surgeon case volume: One of the big questions in orthopaedics is whether more is more, i.e do we continue to get a bit better with each case, or is there a threshold above which we are "good"? In this light it might be more informative to characterize surgeon case volume as the number of cases rather an whether they exceeded a threshold for qualification as "high volume"? This would get around the problem of having a surgeon performing 111 cases designated as "low volume" whereas if the surgeon had done one more case he/she would suddenly become "high volume". On reading this paper, a patient might ask "should I travel four hours to have an arthroplasty by a surgeon who has done 120 cases rather than sticking with my local surgeon who has done 110? Numbers may be better than categories. An MVA should be able to sort this out.
Fellowship: The additional year of specialized training afforded by fellowship exposes trainees to a greater case volume and breadth. High volume surgeons were more than twice as likely to have taken a shoulder fellowship; however, fewer than 30% of high volume surgeons took a shoulder fellowship. As a result we do not know from the data presented whether taking a shoulder fellowship results in a significantly greater arthroplasty practice volume or whether taking a shoulder fellowship reduces the surgeon's complication rate. An MVA should be able to sort this out.
Comorbidities: The patient population of high-volume surgeons was significantly healthier, i.e., comorbidities as reflected by the Charlson Comorbidity Index were lower in patients operated by higher volume surgeons (perhaps because experience teaches to think carefully before offereing elective surgery to patients who are ill or perhaps high volume surgeons operate in outpatient centers that exclude sick patients). The question is whether a shoulder fellowship or being a high volume surgeon enables safer surgery on patients with comorbidites. An MVA should be able to sort this out.
Complications: This article presents data on medical and surgical complications in terms of odds ratios, but does not present data on the rate of each complication. In an MVA it may be easier to characterize complications in terms of their rates.
Arthroplasty choice: The authors point out that "distinctions between anatomic and reverse shoulder arthroplasty were not made because of limitations associated with CPT coding". This is an important shortcoming of the analysis, because experienced (and perhaps fellowship-trained shoulder surgeons), may be better at deciding which patients are the best candidates for each procedure in terms of avoidance of medical and surgical complications.
Incremental value of each case: Numbers are not the only important thing. How much the surgeon learns from each case depends in large part on whether the sugeon conducts an After Action Report (AAR) after each case. An AAR is a structured process used to review the case to identify what happened, what went well, and what could be improved in future cases. We can assume that a 100 case surgeon who routinely conducts AARs will have better outcomes than a120 case surgeon who goes on to the next case without introspection. This is important because most shoulder arthroplasties are not operated on by high volume surgeons.
We can do a better job of helping our patients avoid problems.
Fresh Grizzly Bear Footprint
Devil's Gap, Alberta
Photo by Laura Matsen, M.D
8/23/2025
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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link).
The total shoulder arthroplasty (see this link).
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link)
Shoulder rehabilitation exercises (see this link).
