The goal of the Shoulder Arthroplasty Failure Research initiative is to reduce the risk of future patients having a surgical revision for failure of their shoulder arthroplasty.
It is apparent that this goal cannot be accomplished simply by classifying the failure (glenoid component failure, instability, infection, etc). Such a classification does not generate actionable intelligence that can be used to reduce the rate of failure. Rather we need to identify and seek to address the factors contributing to each type of failure.
In his "Book of Why"
Pearl has set out a compelling approach to the study of causation based on a model that identifies the factors that may affect the outcome of interest.
He gives the example of a mammoth hunt taking place 10,000 years ago. Here's my modification of the figure in his book.
Note that the design of the model does not attempt to indicate the relative importance of each of the factors on a given day, (1) because cumulative data (i.e. experience) from past hunts progressively modifies the weight attached to each factor and (2) because these factors vary from hunt to hunt (e.g. rain vs sunshine).
Note also that the items listed on the left are not under the hunters' control, but they do affect the chances of a successful hunt and may modify the hunter-controlled factors on the right (a bigger mammoth may indicate the need for more and more experienced hunters). In other words, this causal diagram helps the hunters imagine a plan for a hunt that has yet to take place.
Let's now do some time travel to today where we confront the fact that about one in ten shoulder arthroplasties requires a surgical revision. Published articles indicate that a leading indication for surgical revision is glenoid component failure Reducing the risk of future glenoid failures requires a causal model analogous to that for the mammoth hunt, which identifies factors that could contribute to revision for a failed glenoid component.
This causal model provides a framework enabling the investigating surgeon to (1) evaluate the role that each factor (both modifiable and non-modifiable) may have played in each case of glenoid component failure and (2) asses the counterfactual argument: "if this factor had not been present, would the chances of glenoid component failure have been reduced?" As in the case of the mammoth hunt, cumulative data from past failures progressively modifies the weight that can be attached to each factor.
The bad news is that there are a lot of factors to consider in each case (my current count is 25, but I'd appreciate the reader adding to the list). The good (?) news is that there are lots of cases of glenoid failure out there from which we can collect the data that will inform future practice.
While the opportunity to improve the chances of a successful mammoth hunt has passed
The opportunity to reduce the risk of patients having surgical revision for a failed glenoid component is clear and present.
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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).
