Of successful mammoth hunting and glenoid component failure - modeling causation

 

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 predict 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).

Revision for failed shoulder arthroplasty: one in six patients had a complication

Revision shoulder arthroplasty: a systematic review and comparison of North American vs. European outcomes and complications

These authors reviewed the published literature on revision arthroplasty. The indications for the index procedure and the revisions are shown below.

The most common revision indication overall was rotator cuff tear, deficiency, or arthropathy. The average time to revision was 4 years.

The complication rate for all revisions was 17%. There were a total of 465 complications, and of those, 74% lead to a reoperation.

Comment: These data require surgeons to examine their indications and technique for index arthroplasty, e.g. in the case of arthroplasty for fracture is it more appropriate to use a reverse total shoulder than a hemiarthroplasty, in the case of arthroplasty in the presence of a tenuous rotator cuff is it more appropriate to use a reverse total shoulder than an anatomic total shoulder? In cases of glenoid component failure, was the surgical technique good, was the failure secondary to cuff failure? When revising a failed arthroplasty, how can the risk of component loosening, fracture instability and infection be minimized?

Here's a related article

Analysis of 4063 complications of shoulder arthroplasty reported to the US Food and Drug Administration from 2012 to 2016

Most of the literature on shoulder arthroplasty failure comes from high-volume centers. These reports tend to exclude the experience of community orthopedic surgeons, who perform most of the shoulder joint replacements.

These authors analyzed the failure reports mandated by the US Food and Drug Administration for all hospitals. Each reported event from 2012 to 2016 was characterized by implant, failure mode, and year of surgery.

For the 1673 anatomic arthroplasties, the most common failure modes were glenoid component failure (20.4%), rotator cuff/subscapularis tear (15.4%), pain/stiffness (12.9%), dislocation/instability (11.8%), infection (9%), and humeral component loosening (5.1%). 

For anatomic shoulder arthroplasties, the failure modes have not appreciably changed over recent years

For the 2390 reverse arthroplasties, the most common failure modes were dislocation/instability (32%), infection (13.8%), glenosphere-baseplate dissociation (12.2%), failed/loosened baseplate (10.4%), humeral component dissociation/tray fracture (5.5%), difficulty inserting the baseplate (4.8%), and difficulty inserting the glenosphere (4.2%). 

For reverse shoulder arthroplasties, the failure modes have not appreciably changed over recent years

Although the percentage distribution among the different failure modes was relatively consistent over the years of this study, the percentage distribution of these failure modes differed substantially among different implant manufacturers.

The authors conclude that the Food and Drug Administration database reveals modes of shoulder arthroplasty failurethat are not emphasized in the published literature, such as rotator cuff tear, infection, and postoperative pain/stiffness for anatomic total shoulder arthroplasty and implant dissociation and baseplate failure for reverse shoulder arthroplasty. Knowledge of these failure modes may help inform surgical technique and implant design in ways that will lower the risk of implant failure in the future.

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To see a YouTube of our technique for total shoulder arthroplasty, click on this link.
To see a YouTube of our technique for a reverse total shoulder arthroplasty, click on this link.

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To see our new series of youtube videos on important shoulder surgeries and how they are done, click here.

Use the "Search" box to the right to find other topics of interest to you.

How you can support progress in shoulder surgery

You may be interested in some of our most visited web pages  arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

Shoulder joint replacement failure - a bigger problem than previously recognized.

Analysis of 4063 complications of shoulder arthroplasty reported to the US Food and Drug Administration from 2012 to 2016

Most of the literature on shoulder arthroplasty failure comes from high-volume centers. These reports tend to exclude the experience of community orthopedic surgeons, who perform most of the shoulder joint replacements.

These authors analyzed the failure reports mandated by the US Food and Drug Administration for all hospitals. Each reported event from 2012 to 2016 was characterized by implant, failure mode, and year of surgery.

For the 1673 anatomic arthroplasties, the most common failure modes were glenoid component failure (20.4%), rotator cuff/subscapularis tear (15.4%), pain/stiffness (12.9%), dislocation/instability (11.8%), infection (9%), and humeral component loosening (5.1%). 

For anatomic shoulder arthroplasties, the failure modes have not appreciably changed over recent years

For the 2390 reverse arthroplasties, the most common failure modes were dislocation/instability (32%), infection (13.8%), glenosphere-baseplate dissociation (12.2%), failed/loosened baseplate (10.4%), humeral component dissociation/tray fracture (5.5%), difficulty inserting the baseplate (4.8%), and difficulty inserting the glenosphere (4.2%). 

For reverse shoulder arthroplasties, the failure modes have not appreciably changed over recent years

Although the percentage distribution among the different failure modes was relatively consistent over the years of this study, the percentage distribution of these failure modes differed substantially among different implant manufacturers.

The authors conclude that the Food and Drug Administration database reveals modes of shoulder arthroplasty failurethat are not emphasized in the published literature, such as rotator cuff tear, infection, and postoperative pain/stiffness for anatomic total shoulder arthroplasty and implant dissociation and baseplate failure for reverse shoulder arthroplasty. Knowledge of these failure modes may help inform surgical technique and implant design in ways that will lower the risk of implant failure in the future.

Comment: In addition to the high numbers of failures reported to the FDA, the authors note that the rate of recall of new devices is also high, possibly due to unanticipated modes of failure that become evident only after periods of use. 

It is important to recognize that the device failures reported to the FDA under represents the number of actual arthroplasty device failures because there is no method for assuring that each device failure is reported.

The high rate of failure of new devices suggests caution before the adoption of new implants and instruments. Surgeons should recognize that 510(k) clearance requires only that the manufacturer demonstrate that the new device is "substantially equivalent" to a previously marketed device (even if the the previously marketed device has been recalled). This is in marked contrast to the rigorous premarket approval process the FDA requires for new drugs - the PMA process requires demonstration of both safety and efficacy.

We have a new set of shoulder youtubes about the shoulder, check them out at this link.

Be sure to visit "Ream and Run - the state of the art"  regarding this radically conservative approach to shoulder arthritis at this link and this link

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Use the "Search" box to the right to find other topics of interest to you.

How you can support progress in shoulder surgery

You may be interested in some of our most visited web pages   arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'