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Letter to the Editor

The Science of Variation Group recently published an article about the (common)sense on biomechanical studies which was published in Injury recently. Zadpoor and Valstar commented on this in their letter to the editor. You can find their response below:

Letter to the Editor

Available online 15 April 2015

In Press, Accepted Manuscript — Note to users

The sense of biomechanical studies in orthopaedics: a discussion on a recent study published in Injury

We read the study by Mellema et al. [1] with interest. The study seems to conclude that at least some of the biomechanical studies comparing alternative reconstruction techniques may be superfluous, as the result of those studies could be predicted without performing the study and merely based on common sense. If correct, this conclusion could have important implications for at least specific types of orthopedic research. Most importantly, one could ask ‘is it not better to spend such scarce resources as research budget and time on other types of studies?’ We think this is a fair question to ask and an important one to answer.

The study uses a survey to see whether “274 orthopaedic surgeons and 81 medical students” could predict “the results of 11 biomechanical studies comparing fracture fixation constructs” [1]. Obviously, one has to assume that those individuals did not have any pre-knowledge of the results of those 11 studies that were published between 2002 and 2012. That is probably the most important assumption of the study by Mellema et al. [1]. We cannot help but question the validity of that assumption. Is it really safe to assume that orthopaedic surgeons and medical students are not informed about the results of the studies that have direct consequences for their practice and are published as long as a decade ago? If that is safe to assume, we might have a bigger issue to worry about than whether the results of biomechanical studies could be predicted merely based on common sense. If there are no mechanisms through which the practitioners of some of the most developed countries in the world are informed about the results of the studies published as long as a decade ago, why do orthopaedic and biomechanical journals publish any studies at all? Is that not an even bigger waste of our scarce resources?

If, indeed, a significant part of the published information finds its way to clinical practice, is the study by Mellema et al. [1] not built on a shaky foundation? After all, the surgeons and students participating in the survey may have already seen or have been indirectly informed about the findings of those studies in courses, workshops, and conferences or through consultation with their colleagues doing biomechanical research. That possibility cannot be ruled out particularly given the fact that it is hard to think of many areas of biomechanical research that have more applicability in the day-to-day practice of surgeons than comparative study of reconstruction techniques. We performed a simple citation analysis of the 11 studies and found that they were in total 446 times cited (Google Scholar, average citation per study: 40). If the citation number is any indication of readership, it is clear that those 11 studies have been actually enjoying quite a wide readership as compared to many other biomechanical studies.

Another point is the search methodology for finding the studies and the inclusion criterion for the 11 studies that were used in the survey. It is not clear to us how the authors searched the literature and “found 105 peer-reviewed biomechanical studies in peer-reviewed orthopaedic journals comparing two or more constructs” [1]. The purpose of the study comes quite close to what is normally expected from the systematic reviews of the literature. There are standard protocols for performing systematic reviews (e.g. PRISMA) that we think should have been at least partially followed in the study by Mellema et al. [1] to make sure the applied methodology is clear and the results of the study are reproducible. At the very least, we think the search terms used when finding the studies and the methodology used to narrow down the search results should have been clearly presented in the paper. Even more important is the fact that the authors only included the studies that had good illustration of the constructs and for which they “thought the answer was obvious prior to performing the study” [1]. As the authors acknowledge to some extent in the discussion of the study, this could bias the results of the study. Given all those limitations and even if the methodology applied in the study is solid and the results are reproducible, the study shows little more than that the orthopedic surgeons and medical students could predict the outcome of less than 10% of the studies that compared alternative constructs, and let us do not forget that those studies were already available in the open literature for up to a decade.

Finally, we would like to point out that finding the strongest reconstruction technique might not be the only aim of biomechanical studies that compare alternative reconstructions. Even if we already know that a specific reconstruction is stronger than another, quantitative comparison between both reconstructions could be still quite useful. Let us assume that, as a rule of thumb, any construction using “more and larger metal is stronger”. Should not we try to estimate how much stronger? Since using specific reconstruction techniques and implant sizes is associated with increased surgical time and infection risk, biomechanical stability is not the only criterion when deciding which implant or reconstruction technique should be used in a surgery. The surgeon needs to balance the risks and advantages of alternative reconstruction techniques as quantitatively as possible and make an informed decision. Quantitative comparison between the biomechanical stability of alternative reconstruction techniques may therefore help the surgeon to better evaluate the advantage of using “more and larger metal” and see whether the added value of the increased biomechanical stability outweighs any potential increase in operation time and risk of infection.

Because of all above-mentioned reasons, we think care should be exercised when interpreting the results of the study by Mellema et al. [1]. We would have been less concerned about the implications of that study, if it was published as an opinion piece or other types of non-research articles. Given the fact that the study is published as an original research paper, the conclusions of the study could potentially be used to justify bypassing methodologically sound approaches for comparison of surgical techniques and resorting to “common sense”. We are not sure whether that would be the best option considering patient safety.

Conflict of interest


Conflict of interest statement

Authors do not have any financial and personal relationships with other people or organisations that could inappropriately influence (bias) their work.


Corresponding author.

Copyright © 2015 Published by Elsevier Ltd.

Letter to the Editor

The sense of biomechanical studies in orthopaedics: a discussion on a recent study published in Injury

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