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Proper experimental design. Oversimplifying.
I came across what looked like an interesting paper but it has a major flaw, in that the authors have mixed mesh device makers. They are assuming that a lightweight mesh from one device maker is similar, except for weight, to a heavyweight mesh from another. It’s a shame because both device makers have light and heavyweight devices, probably from the same material, and similar knits. Beside that, it’s surprising that a referee did not catch this in review. Another sign that people are still over-simplifying these materials, despite the different knit patterns and shrinkage rates. The authors have boiled all of the potential differences down to g/m^2. The level of research expertise, as far as material characterization, could be improved dramatically.
It seems also that they were so focused on the comparison that they barely discussed the very large discomfort numbers, of 18.1 and 28.7%. Lightweight was “better” but still pretty bad. Heavyweight is terrible, at one year. Table 2 in their paper summarizes their data best. Pain numbers are also reported but I don’t really understand their reporting method.
90 g/m2, Bard™ Flatmesh, Davol
28 g/m2, ULTRAPRO™, Ethicon
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5960495/
“Chronic pain, discomfort, quality of life and impact on sex life after open inguinal hernia mesh repair: an expertise-based randomized clinical trial comparing lightweight and heavyweight mesh.”
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4 Replies
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I completely agree with the faults in the study. Without a doubt. However, one thing I’ve learned is that the quality of the study design can be dependent on the question being asked.
The study might make perfect sense if (and it’s a big “if”) the question is: How do the results of the most popular heavyweight mesh compare to the results of the most popular lightweight mesh? This way, you are controlling for the surgeons’ experience, and comfort with a particular product, with the assumption that they are unlikely to change products absent a very compelling reason.
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To be clear, I do research for a living, but not in the medical field.
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Yes, the design could have made sense, with more care taken to control the other variables. But as it stands, they have overlooked the knit pattern, and, possibly, other factors, like partially absorbable components that seem to be used in several Ultrapro products. Ultrapro is a brand name that Ethicon uses for many different devices. One more way that cause and effect are blurred, making it very difficult to determine which products are good, and which are bad. It’s not even clear which Ultrapro product that they are evaluating. I copied the Ultrapro product page link below.
One interesting fact, is that even though Bard offers a lightweight version of their “gold standard” mesh, they couldn’t find, apparently, enough surgeons that used it, even though they found enough that used the “heavy” mesh. It would have been very obvious that Bard Mesh and Bard Soft Mesh should be the subjects of the study, from the beginning. Makes me think that they compromised to Ultrapro lightweight, or vice versa to Bard heavy, when they couldn’t find the proper devices for a good study.
I do this type of work for a living so these things stand out to me when I see them. The concept is a good idea, poorly planned, but well-executed. Much talent and expertise was wasted to produce a nice paper that doesn’t really show anything, except for the collection of more general data showing that “mesh” causes significant pain and discomfort, even for open surgeries using the Lichtenstein method. That finding has value alone, I think.
https://www.ethicon.com/na/products/hernia-mesh-and-fixation/hernia-mesh/ultrapro-hernia-system
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The study design might make sense if the researchers chose the most popular heavy and light weight meshes (holding material and weave type constant). After all, you’ll get the best real world numbers by comparing the the most often used products that allow everything but weight to be held constant.
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