Shoulder Arthroplasty Failure Research in action

Most patients having primary arthroplasty do well, 

thus we learn most from studying the failures.

Publications of shoulder arthroplasty outcomes usually report the diagnostic categories associated with failure, such as glenoid component loosening, rotator cuff tear, infection, or instability. While such classifications are descriptively useful, they provide little insight into how failures might be prevented for future patients.

As Judea Pearl has emphasized in his must-read book

actionable knowledge is more likely to arise from asking the counterfactual question: “What might have been done differently that could have prevented this complication?” This principle underlies the Shoulder Arthroplasty Failure Research initiative, which seeks to move beyond descriptive epidemiology toward identification of surgeon-controlled, modifiable factors that govern arthroplasty failure.

A recent study exemplifies this approach: “Humeral and glenoid component malposition in patients requiring revision shoulder arthroplasty: a retrospective, cross-sectional study.” In this investigation, failure of a primary arthroplasty was defined as the occurrence of revision. The authors reviewed 234 revision shoulder arthroplasties performed at 3 institutions.

They reported demographic characteristics and frequencies of revision types following hemiarthroplasty, anatomic total shoulder arthroplasty (TSA), and reverse total shoulder arthroplasty (RSA)

While such descriptive information is important, it does not inform strategies for prevention of arthroplasty failure for patients having arthroplasty in the future. 

The study focused on some of the factors under the surgeon’s control, specifically the position of glenoid and humeral components. The findings were striking: glenoid malposition was identified in 51% of anatomic TSA revisions and 93% of RSA revisions. Humeral component malposition was also frequent, present in 57% of anatomic TSA, 62% of RSA, and 54% of hemiarthroplasty cases. These observations support the counterfactual inference that had the components been positioned appropriately, the likelihood of failure requiring revision may well have been substantially reduced. 

Here are a few examples from the article.

Placement of the RSA baseplate in superior tilt.

Superior placement of the RSA baseplate.

Superior placement of the humeral component in anatomic TSA

Inadequate humeral neck cut in hemiarthoplasty resulting in

superior-medial placement of the humeral component and overstuffing of the joint.

In that the surgeon is the method, each of these malpositions could have been avoided by better surgical technique.  The institutions conducting the revisions were usually not involved in the majority of the primary procedures and thus medical records for many of these patients could not be fully reviewed. As a result, the characteristics of the surgeon performing the primary arthroplasty that was revised (age, training, years in practice, arthroplasty experience, etc) were not available, but would be of great interest.

Comment: This is an imporant study in that it identifies actions that shoulder surgeons can take to reduce the risk of arthroplasty failure for their future patients. It provides a model of how clinically meaningful shoulder arthroplasty failure research can be conducted.

This is an uncommon bird, but well worth investigating.

Elegant Trogan

Madera Canyon, Tucson AZ

May, 2022

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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).