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"Wring Theory" of foot function - The Missing Link?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Dieter Fellner, Oct 10, 2012.

  1. Dieter Fellner

    Dieter Fellner Well-Known Member

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    “WRING THEORY” old biomechanics with a new twist

    A novel interpretation of form and function that incorporates anatomical study with bioengineering principles. Is this the "missing link" that might unify biomechanical paradigms?

    Grab a pot of coffee... and enjoy!

  2. Craig Payne

    Craig Payne Moderator

    Interesting ideas ... its going to take a while to digest this one!
  3. efuller

    efuller MVP

    After a very quick look.

    The Wring idea i've seen before. I believe Sarafian copied it from someone earlier. Oh no not tensegrity. You can analyze tensegrity structures with classical mechanical principles. The foot is not a tensegrity structure.

    The author did put a lot of work into it.
  4. Rob Kidd

    Rob Kidd Well-Known Member

    A quick look suggests to me that there is nothing new here - I will retract if required after a proper read. Rob
  5. RobinP

    RobinP Well-Known Member

    Is a theory of foot function required?
  6. efuller

    efuller MVP

    Well, I would say there should be if you are applying mechanical therapy. There are different levels to live at. You could measure the location of the STJ axis and give the person a medial heel skive because they have a medially positioned axis. That's one level. See something and respond because it worked in the past. Another level is measure a medially positioned STJ axis and give the person a medial heel skive because you know that the ground will cause a larger pronation moment in this foot than other feet and you want to decrease that pronation moment.

    If you don't like the STJ axis example, think about reasons for giving someone a forefoot valgus intrinsic post.

  7. I concur.
  8. We talked about here: http://www.podiatry-arena.com/podiatry-forum/showthread.php?p=277433
  9. I had been told about this "theory" of foot function a while ago. To me, it seems like a rehash of Sarrafian's twisted plate idea which Simon mentioned. What specifically new does this "wring theory" tell us that was not already present in Sarrafian's twisted plate idea?

    In addition, I agree with Eric that "tensegrity" has no place in discussing foot function since tensegrity specifically addresses systems with no compression forces at the intersections of two elements of the system. Since when do the foot joints not have compresion forces acting within them?

    I don't think this "paper" could ever be accepted for publication in a peer-reviewed journal as it is. However, a vastly shortened form of this "paper" may be acceptable for publication, if it could be shown to present truly original ideas.

  10. Kevin, do you have a full text of Sarrafian's paper please?
  11. No, but I wish I did. Anyone have it?

    By the way, Sarrafian's twisted plate idea came from MacConail and Basmajian's idea of the "lamina pedis" (MacConail MS, Basmajian JV: Muscles and Movements: A Basis for Human Kinesiology, p. 246, Baltimore, Williams and Wilkins, 1969).

    http://books.google.com/books?id=I8... Basis for Human Kinesiology, p. 246,&f=false
  12. I was thinking about this model today and I perceive a problem with it: while it predicts the increase in dorsi/ plantarflexory stiffness at the midfoot observed with increasing rearfoot supination , this same model should also lead to a decrease in abd/ adduction stiffness at the midfoot with rearfoot supination and an increase in abd/adduction stiffness of midfoot with rearfoot pronation due to the 2nd moment of area- does this model reflect what we see in-vivo?

    Anyway, to answer the original question: "Wring Theory" of foot function - The Missing Link? No. Next...
  13. The opeing third is basically lamina pedis with some nice pictures, the middle portion is mainly Hicks, with some observation of pulley systems at the cuboid and medial malleolus, the final third is really just an anatomy book description of various structures in the foot (I don't know why this final section was included to be honest). As Eric observed the author (whomever they may be) have put a lot of effort in, but why wouldn't you attempt to publish it in a peer-reviewed journal? Unless you already have, and it's been rejected.:morning:
  14. efuller

    efuller MVP

    More bad mechanics. Has a picture of a truss and notes how truss has tension in one member under load. Figures 10 and 11a-c draws triangles but there is no analysis of load. The transverse and coronal trusses don't have tension members.
  15. The author is Paul Clint Jones, DPM (see end of article), also known as Clint Jones who practices in Spokane, Washington. Daryl Phillips seems to know him and thinks he is a promising young podiatrist in the field of podiatric biomechanics. I don't think I have ever met Clint. Certainly, we need more of these types like Clint here in the States because all the rest of us who are interested in advancing knowledge in podiatric biomechanics are not getting any younger.

    I will send Clint an e-mail to see if he wants to discuss his "Wring Theory" on Podiatry Arena.
  16. Aren't they arguing that the tendons (peroneus longus and tibialis posterior) are the tension members?
  17. Thanks Kevin, I didn't read beyond the glossary of terms :eek:. When I first read this, I initially thought "what's this guy selling" and thought Ed Glaser might be involved somewhere, I note now that a Noah Glaser of Sole Supports is acknowledged at the end too. Never mind.
  18. efuller

    efuller MVP

    I guess you are right. The problem is actually load analysis in the transverse and coronal planes. There is no load across the coronal "truss" as he calls it, because the ends of the turss don't bear weight. It's similar with the transverse truss. Compared to vertical loads, the transverse loads are miniscule.
  19. I think the problem is that he has chosen to call them "trusses" and suggest that this is the "new bit" in that we have multiple windlasses in each cardinal plane, when in reality, he's describing the "simple pulleys" which modify the direction of the tendon pull as the tendons wrap around the bones, i.e. peroneus longus about the cuboid and tibialis posterior about the medial malleolus that have obviously been described previously. As you intimated, in terms of the peroneus longus (for example), where are the columns which are in compression? If it is the proximal transverse tarsal arch, then surely there is bending moment across the elements of this- which would invalidate the tensegrity model too. Not that there isn't bending moment across the metatarsals in the windlass mechanism described by Hicks.
  20. Just spoke with Clint on the phone and he promised to come onto Podiatry Arena and defend his theory for us.

    OK, Clint...the floor is yours...
  21. Thank you for the invite. You will have to be patient with me. This is the first time I have posted and am still figuring this forum out. Dr. Kirby mentioned hearing of this before. There was a watered down version published in Podiatry Management, September 2011. This may have been where you saw it. As for discussion of the theory, I will request that those who want to post regarding this theory first take the time to read completely through my article a couple of times before joining into the discussion. Please be sure to review each of the videos and figures. Figure one is a gross representation of the resulting biomechanical model of the whole paper. The paper then proceeds to break down each component contributing to this resultant model and how nature has achieved this complex function. I want to clarify that this article has been 4 years in the making and I have had to step back repeatedly to make sure this theory represented the current/past schools of thought and then fill in where I believe the holes are. In addition, the article is to simplify foot biomechanics by breaking it apart and remeshing it in a stepwise fashion. This serves to allow the student to understand the foot from its rudimentary components to its final symphony of function. In this way, I hope to overcome many of the hurdles I encountered in learning it myself. I present it now as I need to make sure I have not overlooked any details, which in this case, are very complex. Does some of it sound familiar? Of course it should. It incorporates many of the past thoughts and articles upon which current theories are based. Thus the title, "old biomechanics with a new twist." I will need a little time to answer some of your current posts, so please be patient. I am excited to talk with the likes of you.
  22. OK, Clint, two questions:

    1. How do you think your "wring theory" is different that Sarrafian's twisted plate model, since, to me, it looks nearly identical to it?

    2. How can tensegrity be used to understand foot function when tensegrity specifically doesn't produce compression or moments at the joints of the tensegrity elements and any bending moments of the tensegrity elements? The human foot does have compression forces existing at its joints, does have moments existing at its joints and does have bending moments acting across some of its osseous components. Therefore, the foot cannot be a tensegrity structure.
  23. Actually, on re-reading Sarrafian today, he suggests that loose packing and viz. decreased stiffness is achieved with rearfoot supination and forefoot pronation... In which case the model doesn't work on any level regarding the 2nd moment of area. As he said: "In the plantigrade position when vertical loading and external rotation are simultaneously applied by the tibiotalar column on the foot, the hindfoot and the midfoot are supinated, and the forefoot is pronated. The medial longitudinal arch is higher, the foot is shorter, and the plantar aponeurosis is relaxed. The foot is then more flexible. With vertical loading and simultaneous internal rotation, the hindfoot and the midfoot are pronated, and the forefoot is supinated. The medial longitudinal arch is lower, the foot is longer, and the plantar aponeurosis is tense. The foot is then more rigid and a better lever arm."

    See this section from the book too: http://books.google.co.uk/books?id=...=0CCEQ6AEwAA#v=onepage&q=lamina pedis&f=false

    So, Sarrafian's contention (which I recall Craig commented upon in Past, present, future...) is that the foot is stiffer when pronated than supinated (in which plane? Is the obvious question)
    I'll await Clint's answers to Kevin's questions above, before posing any of my own. Tick tock...
  24. Not exactly "the missing link".......more a renaming of an old idea....as far as I can see....but it does make me appreciate, even more, how there is nothing new under the sun.:cool:
  25. Ecclesiastes 1:9
  26. Ecclesiastes 1:9 (NIV)

    "What has been will be again,
    what has been done will be done again;
    there is nothing new under the sun."
  27. David Wedemeyer

    David Wedemeyer Well-Known Member

    Not to derail Simon but isn't Ray McClanahan the main contributor to that group email about the subject of barefoot running a couple months back. He created the silicone spacers for the toes that fix anything and everything?
  28. Yeah, Ray didn't like my Barefoot Running Club posting. He sent me a private e-mail that wasn't very pleasant after that tongue-in-cheek posting. Of course, Ray also thinks that his toe spacers Correct Toes will cure the following problems also: Correction of: bunions, hallux limitus and rigidus, tailor’s bunions, corns, ingrown toenails, heel pain, plantar fasciosis, neuromas, capsulitis, lower leg pain, and runner’s knee with no surgery or medications required!

    This is not someone that I would recommend consulting before writing a paper on foot biomechanics.:bang::bash:
  29. Tick, tock, tick...

    Anyway, if the soft-tissues which Sarrafian described decrease in tensile strain when the hind foot is supinated, but the dorsiflexion/ plantarflexion stiffness of the midfoot is increased due to the increase in 2nd moment of area with the foot in this position, then the increase in 2nd moment of area appears to be a compensatory mechanism to maintain dorsi/ plantarflexion stiffness of the foot when certain soft tissue tension is reduced. Or, vice versa. The reverse of this would also seem true, i.e. the reduction in the 2nd moment of area which should result in decrease in midfoot dorsi/ plantarflexion stiffness which occurs with hind foot pronation should be negated by the increase in the soft tissue tension which Sarrafian described. Which begs the question- is the foot really stiffer in one rearfoot position or another, or does it pretty much stay constant? Viz. is the mobile adapter to rigid lever hypothesis even valid?

    Something tells me the spirals within the double helix model Clint built should have opposite directions (one clockwise, the other anti-clockwise) such that within mid-range of the foot the double helix is unwound, but as we approach the end of range in either direction: supination or pronation, they should tighten- isn't this what we see- a close packing of certain structures with maximal pronation and close-packing of other structures with maximally supination? Just a thought since Clint appears to have vanished up his own wring theory.
  30. Simon:

    I think you are scaring him....he's seen your photo with Yoda....;)
  31. OOOOOh, get my pistols. Yep, carrying a Wookie and a Jedi master during my training in Orlando... But remember I've still got video of Uncle Kevin in the rubber tyre, now that is scary.
  32. You will have to admit that my pool demonstration was a great example of the conservation of angular momentum....:drinks
  33. Looks like Clint has gone missing here. I wouldn't think it would take much time to answer a few questions regarding someone's "theory".

    In that regard, didn't Ed Glaser also go missing for long stretches when we were trying to ask him questions here on Podiatry Arena about his MASS "Theory"? Is there a connection betwen Ed and Clint??? Looks like Ed's son, Noah, helped Clint with his Wring "Theory" (see end of paper).

    Regarding Ed Glaser, he now has another propaganda video on YouTube that is rather comical....lots of great quotes out of this one.....:butcher::bang::eek:

    Last edited by a moderator: Sep 22, 2016
  34. I have written and lectured quite a bit about the load-deformation characteristics of the medial and lateral longitudinal arches of the foot and have long tried to emphasize the spring-like characteristics of the medial and lateral longitudinal arches, including the midtarsal and midfoot joints. At the California College of Podiatric Medicine (CCPM) we were taught about the "locking mechanism" of the midtarsal joint, while the concept of load vs deformation was never mentioned.

    "Midtarsal joint locking" was taught in the sense that that both the "oblique" and "longitudinal" midtarsal joint axes had a "locked position" when the examiner dorsiflexed the lateral forefoot against the resistance of the Achilles tendon. It was not emphasized at CCPM that the foot (and midtarsal joint) will certainly flatten more at the medial and lateral longitudinal arches with increasing loading forces. In fact, during my time there as a student and Biomechanics Fellow from 1979-1985, to my recollection, no one questioned the belief that the midtarsal joint "locked" and no one suggested that the foot acted as a spring type mechanism.

    I had read about Sarrafian's "twisted plate" idea many years ago and had seen MacConail's idea about the "lamina pedis" during my Biomechanics Fellowship in 1984-1985. I thought this was an interesting idea but rather a much too simplified model of the human foot to be of much value. However, the "twisted plate" and "lamina pedis" did have the advantage of recognizing the spring-like characteristics of the human foot, thereby discarding the idea of "midtarsal joint locking". Root and coworkers never mentioned the "lamina pedis" or "twisted plate" ideas at any time that I remember, and certainly didn't recognize these ideas in their books.

    For me, in skimming over the Wring "Theory", it seems to be basically a reintrooduction of the 43 year old idea from MacConail of the "lamina pedis" which was later modified by Sarrafian 25 years ago into a "twisted plate" idea. Maybe Clint will come onto Podiatry Arena and enlighten me as to how I am wrong. However, for now, it seems we have yet another author taking some older ideas, reintroducing us to them, and giving these old ideas a new name.

    The renaming of these rather old ideas into a new "theory" of foot function, reminds me somewhat of Ed Glaser claiming he was the first to make a high-arched orthosis, somehow forgetting to mention the fact that high-arched foot orthoses were invented over a century ago by Whitman and Shaffer. This is why it is so important to know the history of biomechanics and foot orthosis therapy.... so that the clinician can be savvy enough to know when something truly new and original is introduced into our profession.
    My Theory is my own and I have meary run it passed others, as I have with you, to see where there may be potential issues.

    As for the foot having a tensegrity component or not is to be seen. I introduce it, because it best describes the interplay of the suspension/tension seen in the structure of the foot. Yes, Dr. MacClanahan did introduce it to me, (awesome guy by the way) but “after” I had written the paper. I love how he has stepped beyond the traditional views. Good thing Columbus, Edison, and Einstein did. They were deemed fools of their time. The point of my paper was to look at all the thoughts out there and attempt to understand what gave birth to them. I have then tried to see how they interplayed with my concept, and if they did not, I have introduced something to replace them. Tensegrity is a much more involved science than we like to give it credit. It is still yet evolving, as to it application. The science has several authors and each tend to focus and give credit to their own particular segment of it. Tensegrity at its roots is Tensional Integrity. It is defined by the interaction of tensile and compressional components.
    Synergetics 700.011:* “The word tensegrity is an invention: it is a contraction of tensional integrity. Tensegrity describes a structural relationship principle in which structural shape is guaranteed by the finitely closed, comprehensively continuous, tensional behaviors of the system and not by the discontinuous and exclusively local compressional member behaviors.”3
    Fuller, R. Buckminster, 1975, Synergetics, Macmillan, pp 372
    (Dr. Ingber has shown that this science plays an integral part in the function of the biological cell. He has shown that mere pressure on a cell membrane can alter cellular physiology as well as cellular membrane permeability, etc. If the body uses it at its most basic cellular structure, why would it reinvent the wheel for the macro scale of the body. Interestingly, at least in the cellular world, it has a preference in for Dr. Ingber has become well known in the application of tensegrity to biological structures, begetting the term, “biotensegrity.” He has shown how this compression/tension interaction can alter biochemistry and allow cellular membranes to change their permeability. This cellular, architectural property can be induced just by adding pressure or tension to a cell membrane. A very simple approach by nature to achieve a very complex, functional cell. His work has shown the biological shapes of nature have a preference for “spirals, pentagons, and triangulated forms.”)
    When everything is balanced, there is no motion. When out of balance one sees a rotation. (Rotational Equilibrium Across the Subtalar Joint) This does not eliminate potential torque, the play between the lengthen of an object and gravity. It is just a matter of whether or not everything is in equilibrium.
    Tensegrity, as used in my paper, is about how the foot uses rigid (compressive), and soft structures (tensile) to hold itself together. Grabbing a toe can create and effect into the rearfoot, and visa versa. (A dominant characteristic, of the coronal windlass mechanism, is the combined interaction of the posterior tibial and peroneal longus tendon and the dorsal ligaments. The coronal windlass mechanism is able to induce a rigid or flaccid construct, by the simultaneous contracture or relaxation of the posterior tibial and peroneal longus tendons. This wraps / unwraps the midfoot region, like the lashing of a bundle of sticks. With the relaxation of the peroneal longus and slip of the posterior tibial tendon, the individual bones of the coronal windlass mechanism are able to shift freely within the confines of their own contiguous joint capsules / ligaments. As the dynamic side of the windlass mechanism is shortened, the external ligaments or 'extrados,' are brought under tension and the resultant tensegrity effect induces an internal compression between the osseous components of the coronal windlass mechanism. Compression induced by tension. This action creates a suspended, rigid coronal arch of the midfoot articulations.
    This coronal arch is a plantar based truss and beam with the windlass mechanism represented by the peroneal longus, inserting into the plantar portion of the medial cuneiform and first metatarsal and then coursing obliquely lateral.(Fig. 20-a,b) It pulleys through the cuboidal, peroneal groove and finally, courses proximal. This windlass pulley, (the cuboid), is stabilized by the medial draw of the posterior tibial tendon and the navicular tether. The engagement of this mechanism results in a helical moment of the forefoot. This induces distal, medial, coronal plane, eversion against a proximal, lateral, coronal plane, inversion, along with progressive, rigidity of this midfoot complex. The loss, or attenuation of the stabilizing effects of the posterior tibial tendon and navicular, on the cuboid, (ie; Subtalar joint pronation, Posterior tibial tendon rupture, Surgical advancement of the posterior tibial tendon without reefing the spring ligament and cuboidal slip, etc.), results in the instability of the cuboid at the midtarsal joint, and disabling the coronal windlass effect of the peroneal longus against an unstable Cuboid. This is due to a loss of tensioning of the dorsal and inter-cuneiform ligaments to 'screw home' this midfoot arch. Essentially, it would be like drawing a bucket up from a well, on a pulley, not fasten to the top of the well. The pulley would, whimsically, roll away with the rope each time one tried to reel in the bucket. As a result, the coronal truss fails to lock, and loss of medial arch height occurs, because the first metatarsal base cannot 'screw home' and stabilize itself into a stable, coronal truss. )
    This is why I explain that the foot is more than a keystone arch, inspite of its many features there of. It remain intact and functional regardless of position, open/closed pack, open/closed kinetic chain.
  36. David Smith

    David Smith Well-Known Member

    Clint aka DrWring

    I like your analogy, description and analysis of foot function even tho I think it needs some refining it is a useful model. I don't think it is new, it is one, or similar to one, which I have used for many years and recently described in another thread. It uses parts of older models and previously described mechanisms but you have gone some way to formalising this model and introduced it as a distinct and independent concept that can be used apart from but also in conjunction with other models and concepts. I particularly like the analogy of the well bucket pulley, which gives a much better intuitive understanding of the midfoot coronal plane mechanism than locking or screwing up analogies commonly used in the past.

    One thing you wrote -
    . I always use the law that 'all the forces and moments in any mechanical system whether static or in motion are always in equilibrium'.

    Regards Dave Smith
  37. Thank you Dave,
    Clint is what my friends call me.
    I appreciate your objective kindness. It is obvious you have taken the time to objectively read the whole paper as many of the questions already asked, are answered in the paper. Please share the link to drwring.wordpress.com around.
  38. Equilibrium is, of course, important.

    However, equally important is the concept that the exact same external forces applied to a foot (i.e. ground reaction force), acting in the exact same anatomical location, with the exact same magnitude, direction and three-dimensional location may cause vastly different internal forces within different feet, depending on their three-dimensional morphologies.

    This is one reason why I believe that the lamina pedis, twisted plate and wring models all seem to be lacking. Neither of these models accounts for how different foot geometries drastically affects the internal loading forces within the joints of the foot in response to the same external forces.

    An effective foot model must allow us to not only understand how the foot deforms under load, but also must allow us to understand the mechanical effects of three-dimensional morphology on the internal forces within the foot under load. The wring model does reintroduce some old concepts for us to consider, and, certainly, that isn't so bad.
  39. Thank you. In those regards, I share the same frustrations. Roots original religion was that if one could properly analyze a given foot, one could consistently predict and reproduce a given result by the external forces applied. This obviously proved to be more difficult than originally planned. Even something as restrictive as a UCBL could not consistently yield a consistent result. Combine this with the result of application of a given device, or even surgery on an adult and then the same thing on the child of said adult, the results can be totally different. This why I have always been dissatisfied with the original foot model I was taught.
    There was a comment as to why I included an anatomy book at the end of my article along with a glossary. If you read it and compare it to anatomy books you will find that several cases it does not follow the typical descriptions of the joints, and muscles. I am a sculpturer at heart, and that is how Dr. Phillips and I first met. I am very visual. He was my professor and in an attempt to understand the things he was teaching I needed a 3-D representation of the foot, especially of the STJ, as that seemed to be at the heart of all the discussions. The end result was a 24" long calcaneus and proportional talus that I drilled a hole, parallel to each cardinal plane, so I could place a dowel in and see an exaggerated motion in each plane. It turned out to be an effective teaching tool. All the pictures, dissection, and video you see in the paper are my personal work. I wrote a description of each joint and how it was contoured. Very interestingly, with few exceptions, they have a helical twist like a propeller. This is a helix. Look at the description of the 1st, 2nd cuneiform joint. No this does not answer how to predict and control its interface with external forces, but it is a solid basis from which to start.
    Kids need me, will try to continue tomorrow. Thanks
  40. javier

    javier Senior Member

    I like it too and I also think it needs further development.

    What thread David? Thanks.

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