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Shoulder crane: a new paradigm
  1. C Niek Van Dijk
  1. Correspondence to Professor C Niek Van Dijk, Orthopaedic Department, Academic Medical Center Amsterdam, Amsterdam 1105AZ, The Netherlands; C.NiekvanDijk{at}

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On books, articles and a scientific fairy tale

In modern science, books and journals play different roles. Scientific books are an important and popular source of information. They are used for reference, providing an overview and background information on a particular subject. A book is a detailed exploration running into many pages on a particular subject. Scholarly journals contain original research, and conclusions are based on data. They are periodical, whereas books are usually not.

Let’s take an example: you are interested in sports injuries of the foot and ankle. A book such as Sports Injuries of Foot and Ankle, edited by Canata et al, then clearly is a relevant source of information.1 (This book is published as part of the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) (free for members) book publishing programme. You can find more information on this programme in this issue of the journal 1–7.) Medical books, like by Canata et al, are used as references and typically bundle information that has been published in peer-reviewed journals in the years preceding publication of the book. As such, medical books do not contain new information. Publishing tends to occur many years after research has been conducted. The content is written by an expert or a team of experts. Textbooks are commonly not peer reviewed with the same diligence as journal articles. Often they are not peer reviewed at all. This means that their content is not held to the same standards as the content of peer-reviewed scientific journal articles.

Let’s take another example―outside of our field, but not too far. Antibiotics such as penicillin are compounds produced by bacteria and fungi, which are capable of killing, or inhibiting, competing microbacterial species. We all remember how penicillin was discovered. We can picture the spore, as it floated through the window, and into Fleming’s lab, and settled on the famous Petri dish, and we can picture Fleming’s surprise when he came back from holiday and saw an open space on the dish, and then saw it expand. The story has become a fairy tale. A scientific fairy tale. However, we can also see it as a metaphor of the way science works.

Imagine that open space on the Petri dish. Imagine its outer edges, where the penicillin producing spore meets the bacteria. Here there is activity. When the bacteria is weak, the penicillin can expand steadily. However, when the penicillin meets a resilient bacteria, it slows down and becomes cautious, and if it meets another penicillin producing colony, it may stop altogether, simply because there is nowhere for it to go.

Modern science is rather like this. On the periphery—the outer edge, where science meets reality—there is plenty of activity. However, the growth is gradual and comes through a thousand tiny steps, with missteps and confusion, reversals and the occasional triumph, and all this is reported through articles that require careful checking, because where there is excitement and enthusiasm, there will also be bias. We are scientists, yes, but we are also people, and people tend to fall in love with their own ideas and will defend them even against evidence to the contrary, which is why articles need peer review.

Journals are like bulletins from the outer edge and the unknown, and this makes them exciting. However, many articles are transient. Some will be challenged, and some will be overturned. Some will be combined with others, like pieces in a jigsaw, which slowly grows until we can recognise ‘the bigger picture’, and some are merely fashion trends, soon to be replaced by the next fashion. In short, articles are a good way to learn the news—to find out what is going on—but they are a slow way to acquire knowledge.

Behind the penicillin colony’s growing edge, however, there is a large area that does not change, where everything seems settled and somehow safe. It is the same for any science. This is the core of the science, where everything has become ‘established’―and what we call knowledge. Young scientists need to learn this core, and learn it efficiently, before they can begin their careers, and this is where they need books, specifically textbooks, which summarise this established core. Books are a concentrated way to learn. They do not reveal the latest new thing—what we revere as ‘knowledge’ but may be little more than fashion—but they do bring us to the point where we can start looking and judging for ourselves.

ISAKOS started a book publishing programme in 2013 and has published 24 books since that time. The complete content of the electronic version of these books is freely available for ISAKOS members at all time, accessible through their ISAKOS account. This year alone, during the biannual ISAKOS congress in Cancun, at least seven new books will be launched and made available for members electronically. In this issue of the journal, you can find information on these books.1–7

One of the books in the ISAKOS publishing programme is the book Normal and Pathological Anatomy of the Shoulder by Bain et al, which is published in 2015.8 This book was special, because it suggested a different way of viewing the shoulder. It created a new paradigm. It argued that we should analyse the shoulder as if it was an industrial crane, whose primary function is to position loads in space.

The book begins by describing the normal anatomy, and then addresses the changes and pathology that follow from lifestyle and from injury and disease. It combines anatomy with symptomology and stresses the importance of imaging studies. In short, it provides a good overview of the field. This overview is important, because the shoulder is notably complex. It employs both static and dynamic stabilisers, which together enable greater movement than any other joint. Shoulder anatomy is therefore complicated; its weakest link being the rotator cuff.

The authors argue that we can prevent abnormal forces from damaging these vulnerable structures and prevent a symptomatic shoulder, but only if we understand the shoulder’s biomechanics.

At this point, the authors introduce their new paradigm—a new mental image for the shoulder. They use the structure and workings of an industrial crane to provide that picture, and this changes our approach to the biomechanics. In particular, it suggests a suspensory cascade, which extends from the skull and the cervical spine through the trapezius onto the clavicle, the coracoacromial ligaments, the coracoid process, through the coracohumeral ligament onto the humeral head.

Any disruption of this system will increase the load on the rotator cuff, the long head of the biceps and the superior labrum. The coracohumeral ligament plays a key role in protecting these delicate structures. The authors position the coracohumeral ligament as a sensory organ that works as a servomechanism and redirects the forces and direction-of-pull of the rotator cuff, and thereby provides stability, control and motion.

The crane model adds to our understanding of shoulder biomechanics by changing our mental image of this anatomical area. As such this pearl deserves a harder look. Therefore, for this issue of JISAKOS, we asked the authors to provide us with a scientific article describing the model, one that we could put through a rigorous peer-review process to test the concept.9

And yes, the traditional way would have been to publish the concept of the shoulder crane model as a scientific article first and only secondly—after it had proven itself―as a book chapter.

But we at JISAKOS have no reservations about the unorthodox. I am convinced you will discover more of these pearls in these ISAKOS books—books full of valuable knowledge, available free to ISAKOS members! Sometimes reality is better than a fairy tale.


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  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Commissioned; internally peer reviewed.

  • Patient consent for publication Not required.

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