“This article was published in Journal of Shoulder and Elbow Surgery, Vol 27, William J. Mallon, MD, Einstein, 3 Dimensions, and Chainsaws, 577-578, © Journal of Shoulder and Elbow Surgery Board of Trustees (2018).” The publisher and author have kindly allowed us to reproduce it in its entirety here.
Einstein, 3 Dimensions, and Chainsaws (link)
by William J. Mallon, MD Editor-in-Chief Journal of Shoulder and Elbow Surgery Hilton Head Island, SC, USA
Einstein, 3 Dimensions, and Chainsaws (link)
by William J. Mallon, MD Editor-in-Chief Journal of Shoulder and Elbow Surgery Hilton Head Island, SC, USA
I have little patience with scientists who take a board of wood, look for its thinnest parts, and then drill holes where drilling is easy.—Albert Einstein
Although I eventually attended medical school, my own academic training was in mathematics and physics in college, with research done my senior year in general relativity and tensor analysis, which often involves studying motions in 4 dimensions, and learning about many of the teachings of Albert Einstein.
This was good training for my position as editor-in-chief of the Journal of Shoulder and Elbow Surgery over the last year, because of the proliferation of articles we now receive that do 3-dimensional (3D) studies, usually via computed tomography (CT) scans. Many of these articles analyze the anatomy of the shoulder or elbow, comparing that analysis when done using 2-dimensional (2D) CT scans versus 3D CT scans. Invariably, the 3D analysis is shown to be superior al- though often by very fine margins.
My standard response, when I initially read these sub- missions, is something like “No s—.” Just as Einstein’s 4-dimensional space-time improved upon Newton’s 3D analysis of motion, providing better precision, so we would expect 3 dimensions to show us things about shoulder anatomy that 2 dimensions may miss.
However, we live in Newton’s world, for the most part, and not Einstein’s. Einstein’s 4 dimensions are only necessary at the very small, at the atomic level; the very large, such as black holes; or the very fast, at speeds approaching the speed of light. On planet Earth, Newton’s laws suffice almost in- variably for us to obtain adequate precision in our measurements.
And it seems to me that 2 dimensions likely also suffice in preoperative planning of shoulder anatomy, with rare exception. The old bromide about orthopedic surgeons “Measure with a micrometer, mark it with a piece of chalk, and cut it with a chainsaw” is humorous, but the reason is that, like all humor, there is an element of truth to it.
Many of the 3D studies we receive show differences between 2 dimensions and 3 dimensions of only a few degrees, often as small as 1°-2°, and some of the studies of the glenoid have only shown this difference in certain planes, such as the superior or inferior portions. Does that make a clinical difference in our surgery or how we treat patients? I think it usually does not. During surgery, can we even tell the difference between a glenoid that is retroverted 11° versus one that is retroverted 9°? If we can, how accurate is the cut we make or planing of the glenoid? Can we actually get that accurate to within 1°-2°?
Furthermore, does using 3D analysis in preference to 2D make any difference in outcomes, even if the surgery can be done as accurately as the 3D analysis asks of you? If it does, I have not seen those articles yet, because clinical outcome studies using 3D radiographic analysis have not yet been done.
We also live in a medical world that is now emphasizing cost containment, and this is not just in the United States but worldwide. What about the costs of doing these 3D analyses? How much does the software cost? This is rarely mentioned, although one recent article noted that it was very expensive. While the cost may not be much when amortized over many clinical studies, there is still a cost element that should be studied, and for our journal, it has not been.
Finally, in this world of cost containment, we often use the value equation, in which Value = Outcome/cost. So, we do not have studies showing that 3D analysis provides superior clinical outcomes to 2D, and the cost is rarely mentioned, yet when it is, it is more costly. As such, we have no information about what this analysis does to the value equation, although given the increased costs, it likely decreases the value. We really do not know because none of the studies submitted have yet mentioned this.
So why are these studies done? I think it is because of Einstein’s admonition that these are relatively easy studies to do, so the authors have been drilling holes in boards simply because they have a drill (3D software) and drilling is easy.
What are we to do about this? As editor, I have to make decisions about which papers we will review, and which we will not, and eventually make decisions about which of those we review will be accepted. I am going to say “stop” at this point on 3D studies unless they provide us with more information than simply showing that 3D CT scans are more accurate in defining anatomy than 2D. If I am wrong that 2 dimensions suffice in preoperative planning of shoulder anatomy, prove it to us.
Here is my new policy on 3D studies of shoulder or elbow anatomy: Submit them all you like, but be forewarned that the studies are now required to provide cost information and outcome information, comparing 3D and 2D analysis using clinical outcomes. If they do not contain this information, they will not be reviewed.
Comment: In this editorial, the author has asked the critical question about new technology, "Does that make a clinical difference in our surgery or how we treat patients?" We live at a time when it is easy to make more measurements, but these measurements may cost more in terms of time, money and radiation exposure. In our practice, we find that for almost all cases we can gather the information needed for the management of a shoulder with glenohumeral arthritis from a standardized axillary view as shown below (see this link).
As suggested in the editorial, the burden of proof would seem to fall on those advocating more complex, more costly methods of assessment of glenohumeral pathoanatomy: do they lead to better patient outcomes?
As suggested in the editorial, the burden of proof would seem to fall on those advocating more complex, more costly methods of assessment of glenohumeral pathoanatomy: do they lead to better patient outcomes?
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We have a new set of shoulder youtubes about the shoulder, check them out at this link.
We have a new set of shoulder youtubes about the shoulder, check them out at this link.
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