Elsevier

Injury

Volume 45, Issue 12, December 2014, Pages 2035-2039
Injury

Biomechanical studies: Science (f)or common sense?

https://doi.org/10.1016/j.injury.2014.09.014Get rights and content

Abstract

Introduction

It is our impression that many biomechanical studies invest substantial resources studying the obvious: that more and larger metal is stronger. The purpose of this study is to evaluate if a subset of biomechanical studies comparing fixation constructs just document common sense.

Methods

Using a web-based survey, 274 orthopaedic surgeons and 81 medical students predicted the results of 11 biomechanical studies comparing fracture fixation constructs (selected based on the authors’ sense that the answer was obvious prior to performing the study). Sensitivity, specificity, and accuracy were calculated according to standard formulas. The agreement among the observers was calculated by using a multirater kappa, described by Siegel and Castellan.

Results

The accuracy of predicting outcomes was 80% or greater for 10 of 11 studies. Accuracy was not influenced by level of experience (i.e., time in practice and medical students vs. surgeons). There were substantial differences in accuracy between observers from different regions. The overall categorical rating of inter-observer reliability according to Landis and Koch was moderate (κ = 0.55; standard error (SE) = 0.01).

Conclusion

The results of a subset of biomechanical studies comparing fracture fixation constructs can be predicted prior to doing the study. As these studies are time and resource intensive, one criterion for proceeding with a biomechanical study should be that the answer is not simply a matter of common sense.

Introduction

It is our impression that many biomechanical studies [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22] invest substantial resources studying the obvious: that more and larger metal is stronger. Studies that evaluate “which construct is the strongest” distract from the more important question: “How strong is strong enough in physiological loading conditions?”.

The purpose of this study is to evaluate if some biomechanical studies comparing fixation constructs just document common sense. If so, there is a need for more careful use of resources in the lab and better collaboration with surgeons to enhance clinical relevance. This study tested our hypothesis that a subset of biomechanical studies comparing fracture fixation constructs can be predicted based on common sense and do not require formal testing. Specifically our primary hypothesis was that outcomes of some biomechanical studies comparing fracture fixation constructs are predictable with high accuracy. Our secondary hypotheses addressed inter-observer reliability and accuracy according to experience and other factors.

Section snippets

Methods

Between 2000 and 2012, we found 105 peer-reviewed biomechanical studies in peer-reviewed orthopaedic journals comparing two or more constructs in order to determine: “Which construct is the strongest?”. We excluded six studies of spine, skull, and facial fractures. From the remaining 99 studies, 12 had a good illustration of the constructs. Among those 12 studies, we selected 11 for which we thought the answer was obvious prior to performing the study [2], [7], [8], [9], [11], [12], [14], [15],

Results

Accuracy was 80% or greater for 10 of 11 studies that have been predicted by members of the SOVG (Table 1). The diagnostic performance characteristics for guessing the results of the study were as follows: sensitivity averaged 84%, ranging from 60% (for study 1) to 99% (for study 7); specificity 86%, ranging from 60% (for study 1) to 99% (for study 7), and accuracy averaged 86%, ranging from 60% (for study 1) to 99% (for study 7). Study 5 was predicted with the highest accuracy (accuracy 97%

Discussion

This study confirms our hypothesis that outcomes of a subset of biomechanical studies – comparing fixation constructs – are quite predictable as accuracy was at least 80% for all but one study. In addition, the secondary null hypothesis that the experience of observers has no influence on the accuracy of predicting outcomes was not rejected because medical students and experienced surgeons performed equally well. In other words, it seems that some comparative biomechanical studies just confirm

Conclusion

According to our findings, a subset of biomechanical studies comparing fracture fixation constructs can be predicted prior to doing the study. As these studies are time and resource intensive, one criterion for proceeding with a biomechanical study should be that the answer is not simply a matter of common sense.

Authors’ contributions

All authors have participated in a material way to at least three of the five elements below: Study design: JJM, JND, TGG, DR. Gathered data: JJM, TGG. Analyzed data: JJM, JND, DR. Initial draft: JJM, JND, DR. Ensured accuracy of data: JJM, JND, TGG, DR. Estimated effort: JJM 50%, JND 20%, TGG 10%, DR 20%.

Conflicts of interest

The authors declare that there are no conflicts of interest.

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    1

    The members of Science of Variation Group are listed in Appendix.

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