While surgeons and patients want to know how the surgery will work out for them in the long run, as pointed out in The challenge of long-term follow-up in orthopaedics: diminishing returns, long-term followup studies are both important and difficult.
The longer the period of followup:
(1) the percentage of the initial patient cohort that is lost to follow-up increases progressively with time after surgery (perhaps because the patients were dissatisfied and transferred their care to another surgeon, or because they had a revision that truncated the follow-up of their initial surgery, or because they could not afford to return for follow-up, or because they got tired of returning questionnaires, or because they became ill or expired).
(2) the procedures performed a while back become progressively less representative of what is being performed currently (the patient selection, surgical techniques, implants, and surgeons evolve progressively over time)
(3) the measures of patient comfort and function are inconsistent. over time.
(4) patients having complications and revisions have a tendency to get lost or omitted for one reason or another.
(5) the number of patients included in long-term followup studies is a very small (non-representative) sample of the total number of the patients originally having the procedure.
A recent study, Long-term clinical and radiographic outcomes of pegged vs. keeled glenoid components in total shoulder arthroplasty: A matched cohort study, provides a good illustrative example of these issues. It aimed to compare outcomes in over 600 patients having total shoulder arthroplasty by an individual surgeon using either keeled or pegged cemented glenoid components between the years 2001 and 2015. The rational for using one or the other type of component was not explained: "The choice of glenoid implant type was made intraoperatively."
A matching algorithm was employed to create a 1:2 cohort of patients receiving keeled (N=12) and pegged (N=24) cemented glenoid designs, respectively at an average of 9 years (range 5.0-17) years after surgery.
.
There were no significant differences in postoperative ranges of motion or in Simple Shoulder Test, ASES, VAS, or Lazarus scores.
Referring to #1 and 5 on the list above, the percentage of shoulders included in the analysis was very small as seen on this chart
It seems axiomatic that the longer the initial patient cohort is followed, the smaller the percentage of patients available for study (e.g. in this study, it is likely (A) that the percentage of patients with followup data at 2 years would be substantially greater than the 6% that were available at 9 years or 17 years and (B) the implants and techniques in use 2 years prior to the study are more likely to remain in current use in comparison to those used 9 or more years prior.
Diminishing returns. Which period of followup is most relevant?
How important is it today to compare the miles per gallon or service record of these two cars?
Today on my Zwift ride
I'm not saying that long-term studies are pointless, but it is essential to anticipate the challenges and limitations including those laid out here. These studies are time-consuming and expensive, so we need to be sure that we gain knowledge that is clinically useful today.
We want to avoid telling a student, resident or fellow to "look up my cases of X surgery and see what you find". Instead let's decide in advance what question we trying to answer and how many patients (N and %) and how long a period of followup do we need to answer the question? Sample size and power calculations seem critical.
Speaking of Long
Malheur
May 2025
You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link
Follow on twitter/X: https://x.com/RickMatsen
Follow on facebook: https://www.facebook.com/shoulder.arthritis
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/
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).
