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The Root Postulate - Part I

Discussion in 'Biomechanics, Sports and Foot orthoses' started by rdp1210, Jan 3, 2015.

  1. rdp1210

    rdp1210 Active Member

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    As I said to Kevin, I will start this thread.

    I Propose the following designation: "The Root Postulate"

    Definition: "The foot is most stable when the midtarsal joint is fully pronated."

    I would like to confine this thread to the following 2 items
    1. Have I correctly stated the Postulate, or should the Postulate be reworded.
    2. Is there literature before 1977 that made this proposal either directly or indirectly.

    Again this is an open invitation to all who read the literature to contribute. I'm not sure that we've ever had a community effort to collect all the literature on any one topic. Most discussions focus around one person's defense of an opinion using selected sources. This Part I thread is NOT a discussion of whether the Postulate is correct or valid. Hopefully this combined effort will also result in a resource for better representation of the literature by those who are and are going to do research.

    After it is felt that adequate literature has been collected, we can then discuss whether we will all use the term, "The Root Postulate" when referring to this concept. After that we can start the process of analyzing the Postulate for validity and mechanical soundness.

    Again we are looking for factual evidences and arguments that the term and definition are well stated, and pre-Root literature that could be used to say that the Postulate is not unique or should not be ascribed to Root.

    Thanks to all who will join in this effort.
  2. Thanks for starting the thread, Daryl. Right off the bat, I think we are going to have a problem.

    First of all, since the midtarsal joint has a very large number of possible axes of motion then the terms "midtarsal joint pronation" or "midtarsal joint supination" are meaningless since "pronation" and "supination" indicate tri-plane motions of eversion-dorsiflexion-abduction and inversion-plantarflexion-adduction. Nester and colleagues have clearly shown these motion don't always occur at the midtarsal joint with the normal "pronation-supination" midtarsal joint axis only occurring in midstance (Nester CJ, Findlow A, Bowker P: Scientific approach to the axis of rotation of the midtarsal joint. JAPMA, 91(2):68-73, 2001).

    Secondly, please define "foot stability". What exactly does that mean?

    Thirdly, considering that midtarsal-midfoot joints are spring-like structures, how do we choose which point within their range of motion is "maximally pronated" if there is such a position? Don Green's fluoroscopic video clearly shows the midtarsal joint continually deforming during the midstance phase of gait. Therefore, to say "The foot is most stable when the midtarsal joint is fully pronated" is equivalent to saying "the shock absorber is most stable when it is compressed to some degree".

    This discussion revolves on whether the midtarsal joint ever "locks" as Root, and many other podiatrists, frequently said. I contend that the midtarsal joint of the human foot never "locks". Rather the midtarsal joint temporarily stops deforming under the load it is currently being subjected to, or, in other words, the midtarsal joint is analogous to a spring that will stop deforming under the load that it is currently being subjected to, but will still deform more if it is subjected to an even greater load.

    Should be an interesting discussion.
  3. To be honest I have issue with the concept of thinking of the midtarsal joint as a ridged body.

    Bone pin studys have clearly shown motion at the navicular-cuboid joint. While some may argue that motion is not significant. My question is what the magic number when motion at a joint becomes significant?

    I am much more supportive of a discussion which looks at motion or position of the talo - navicular and calcaneal-cuboid joints rather than the concept of a 2 bone rigid midtarsal joint
  4. Mike:

    None of us are saying the midtarsal joint is a rigid body. Rather, I believe what you are trying to say is whether we should be modelling the midtarsal joint as one joint, or as two joints. The answer is that both modelling choices (i.e. modelling the midtarsal joint as one joint vs two joints) are valid as long as each of their limitations are appreciated. This really needs to be a separate discussion on modelling of midtarsal joint motion which, if you want, could be started as another thread.
  5. I agree that we can model the midfoot joints in different ways and either model may be valid, within the limitations of the model. But I do believe it deserves discussion here also and do not think such discussion should be removed from this thread.

    I've attached some of Nester's graphs showing the movement at the CCJ and TNJ obtained from bone pin studies. Can anyone tell me if and when either of these joints are "stable" in Nester's subjects? Moreover, can anyone tell me why stability might be desirable in a dynamic moving structure?

    Here's Nester's view: "As with ankle and subtalar motion, there is no consistent pattern between people in the range of motion the talonavicular and calcaneocuboid joints display. For one participant of Lundgren et al [26] study, a total of 21° of motion was observed in the frontal and transverse planes during stance, yet only 5.2° and 6.0° in another participant. Remarkably, despite these stark differences, in the sagittal plane the same participants displayed 8.0° and 8.1° range of sagittal plane motion, respectively. Quite how such inter-subject variation is integrated into a clinical conceptual model of foot kinematics has yet to be determined. However, given these data are from asymptomatic feet, the data makes a mockery of any notion that a clinician should seek to alter the foot biomechanics of all patients such that their feet achieve some hypothetical mechanical ideal (i.e. one foot model fits all feet). It is far from fitting that in the year we celebrate the 150th anniversary of Darwin's 'discovery' of essential variations in nature, that foot health professionals continue to use a clinical model of foot function which seeks to eliminate all variation between our patients. Furthermore, remaining as a 'variation' of nature rather than a clone of the hypothetical 'Root' foot type is likely to be central to a person remaining symptom-free for most of their lives, since their own body will have adapted to adequately cope with its own variations."

    Attached Files:

  6. That's a good quote from Chris Nester and company. Those participating in this debate would do well to read this quote at least a few times.
  7. The following was stated by Dennis Brown within a patent which was filed in 1974 and published in 1976:

    "Now consider the range of motion of the midtarsal joint when the subtalar joint is in its neutral position (neither pronated nor supinated). As one might expect, the range of motion of the midtarsal joint in this instance is greater than when the subtalar joint is supinated but less than when the subtalar joint is fully pronated. In all of these instances the midtarsal joint locks in its maximally pronated position or in other words, the midtarsal joint is locked (stable), it is fully pronated.

    At this juncture it is important to expand and clarify the importance to these relationships. Again note that when the subtalar joint is neutral the midtarsal joint locks in its position of maximum pronation. Also note that when the subtalar joint is maximally pronated the midtarsal joint locks in its position of maximum pronation. However, in the last instance the midtarsal joint is more pronated than in the first instance (albeit that both are maximally pronated). Thus the actual position at which the midtarsal joint locks depends upon the position of the subtalar joint. This system is further complicated in the pathological (abnormal) foot. If the subtalar joint were maximumly pronated and if the midtarsal joint were fully pronated but in an unresolved pronatory force (equinus, forefoot varus, rearfoot varus) was applied to this mechanical system then the midtarsal joint would not lock (or it would remain unlocked) and result in hypermobility of the foot. It must be emphasized, however, that both locked and unlocked states of the midtarsal joint are physiological. At heel contact the foot functions as a mobile adapter and in this state the midtarsal joint is unlocked during the major remaining portion of the stance phase of gait the foot must become a rigid lever requiring the midtarsal joint to become locked. In the case of the maximum pronated subtalar joint and the increase in range of motion of the midtarsal joint a potential clincal problem is noted. If the subtalar joint is maximally pronated and midtarsal joint at its end of range of motion and if there is a significant pronatory force present on the foot then the midtarsal joint will unlock rendering the foot hypermobile. It is the unlocking and subluxing which renders the foot hypermobile and an inadequate mechanical system for stable weight bearing.

    It is the midtarsal joint which makes the foot a rigid lever and thus imparts stability to the foot." http://www.google.com/patents/US3995002

    Perhaps it's the "Brown postulate"? Clearly Root may have influenced all of this, but Brown seems to have published it prior to 1977 which is what you asked for.

    For those that don't know, Dennis Brown: http://www.nwpodiatric.com/story

    Hope that helps, Daryl.
  8. Dr. Chris Smith and Dennis Brown were partners in their Northwest Orthotic Lab business and also created Superfeet Insoles together. Chris Smith was one of my professors in biomechanics at CCPM, was a classmate of John Weed and was a student of Mert Root. The words you read here, probably come directly from Chris Smith, since this is exactly what he taught us in podiatry school when I started in 1979. In addition, this is pretty much what John Weed and Mert Root said also when they lectured on this subject in the 1980s.
  9. I agree, however, we were requested to provide a publication pre-1977, this is what I have provided.

    To be honest, I can't really see the point in Daryl dictating that we can only discuss whether anyone said what he calls "the Root postulate" prior to 1977, without discussing whether it stands up to scrutiny. It doesn't matter who said what about the midtarsal joint in 1977 or before then; Elftman, Inman and many others noted how a change in the position of the rearfoot relative to the forefoot influences midfoot motion. Is it such a stretch of the imagination to say the same thing in terms of change of forefoot on the rearfoot. I'm really more interested in what the best part of forty years of research since then has told us about biomechanics of the midtarsal articulations. Anyway, we already discussed his "Root postulate" with him in a thread here last year: http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=90588

    I did find this paper today though from 1964 in which the authors provide a criteria for the normal foot and define foot deformities such as forefoot varus, forefoot valgus, rearfoot valgus, rearfoot varus etc. All interesting to the historian, but not necessarilly going to move the profession forward. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1927557/pdf/canmedaj01070-0007.pdf

    Oh, and I came across the the original 1953 patent for the forefoot to rearfoot measuring device again; attached. This device was used to measure forefoot to rearfoot alignment and "balance" the insole so that the correct amount of forefoot wedging was applied.

    Attached Files:

  10. Agreed. The "Root Postulate" does not stand up to scrutiny in 2015. Therefore, the way I see it, the "Root Postulate" should be discarded as an ambiguous and inaccurate description of midtarsal joint function. Whether Root thought this idea up first that "the foot is most stable when the midtarsal joint is maximally pronated" is of no concern to me since I think the whole statement itself is ambiguous (i.e. what does "stable" actually mean biomechanically) and inaccurate (i.e. the midtarsal joint does not have a fixed pronation-supination axis that would allow only pronation motion to occur and, if pronation motion was a motion that did occur, under what magnitude of loading force did this "maximally pronated position" occur?).

    In other words, when the leaf spring of a truck is compressed to half it's capacity do we say the leaf spring is "maximally compressed"? No. We say the leaf spring is loaded and has the potential to both compress further and to spring back to a less compressed position. In much the same way, the midtarsal joint, and the midfoot joints, are never "maximally pronated" but, rather, these joints are loaded and have the potential to both dorsiflex further and plantarflex further under varying loads.

    Maybe a better question to ask is which of the ideas that Root and colleagues proposed back in the 1960s and 1970s still stand up to scientific scrutiny in 2015?
  11. Agreed.
  12. Agreed as well
  13. One of the most complete assessments of the Root idealogy was performed by Hannah Jarvis in completion of her PhD. It is freely available to download here: http://usir.salford.ac.uk/29381/1/HannahJarvis_PhDThesis.pdf

    In the abstract to her thesis she concludes: "This suggests that the key principles of the current model [Root] used to describe the biomechanical function of the normal foot in podiatry are incorrect and the methods used by podiatrists [employing the Root model] in clinical practice are not valid."

    It's a :deadhorse: :cool:
  14. rdp1210

    rdp1210 Active Member

    So far I see some good responses. Most of the responses are responses to Part II of the discussion. What I would like to have first is a discussion of properly formatting what the Root Postulate was (or is). I am not saying here that it is correct.

    Fully pronated means that it is at its EROM of eversion + EROM of abduction + EROM of dorsiflexion. It doesn't matter how many axes we're talking about, nor do we have to have coupling of motions. EROM itself is a nebulous concept for any joint. In the pre-1977 model, Root took strictly the Eltman model of EROM of the MTJ. He softened that after 1977, but never really defined, then, what constituted EROM. How much tension is in the ligamentous restraining mechanisms before one has reached EROM?

    This part of the discussion is to set nomenclature so that we're all talking about the same principle. It's no different than establishing nomenclature such as "The Heisenberg Uncertainty Principle" or "Euler's Identity". The other part of this, Part I, is to find out if there is literature pre-1977 that would say that the Root Postulate was really not Root's idea.

    I'm sorry, have not had time this morning to wade through all the comments yet, but should get some time later, after I've finished my patients and charting. Thanks to Simon for the PhD reference, I'll download and read it. The important thing to remember is that we must be as critical of new research as we are of old ideas.

    Happy 2015,
  15. May I ask: why? To what ends? I spent several hours yesterday searching antique papers on your behest, I really am struggling to see the point though- who really cares what was and was not "the Root postulate", surely it is far more important to understand the biomechanics of the midtarsal complex based on our entire body of scientific knowledge, not just one person's point of view?

    I linked a publication prior to 1977 earlier in this thread, however, it is clear from reading Elftman, Inman and others that they were all aware of this concept.

    And it's also important that we are as critical of Root as we are of any other author, regardless of our personal feelings towards them.
  16. rdp1210

    rdp1210 Active Member

    And I thank you kindly for looking up any papers. I believe that in order for us to understand where we want to go, it is important that we know where we've been. A thorough knowledge of all contributors to the general concepts of biomechanics is important. I have tried to mention many such in my posts. For example, if we look at pre-Root research on the STJAxis, I find that Manter did the best methodology, that there are definite problems with Hicks approach and Inman made a major geometrical error in the idenification of the STJ axis. Root tried to mix the methodology of Manter and Hicks and as a result is guilty of the Hicks error. I want us to be critical of Root, but let's be precise in our criticisms. Many of the "invalidity" statements offered in these various posts are generalized and ambiguous statements, intended not to define truth, but to defend the world-view of the writer. Such ambigous statement are then turned into paradigms and then dogmas to become themselves factoids. If you want to criticize a thought, you've got to know what that thought was.

    Will look forward to more of your thoughts,
  17. Then why not loose the "Root postulate" and look at the published evidence as a whole on biomechanics of the midfoot? And, to date, as opposed to up until 1977? It was a good year, I enjoyed it, but I don't think that it's anymore significant than any other year up to 2015. Why are you attempting to single out one author and one time period as being important?

    Did you see the publication prior to 1977 that I linked for you?
  18. rdp1210

    rdp1210 Active Member

    Sorry, Simon, I haven't had time today between patients to get to everything. I saw the 1964 paper by Ritchie & Kiem, which was not groundbreaking. Perkins 1948 paper was definitely a landmark publication, and I have referred to it anytime I have written or talked about FF deformities. I looked quickly at the 1953 patent for measuring the forefoot, and will spend more time looking at it (looks kind of interesting). I will get to the 2013 PhD thesis later. Is there another one you want me to pay attention to?

    I picked 1977 as the year because that is when Root formally had to back away from the Elftman MTJ EROM Hypothesis, though he didn't make any strong alternative explanations.

    I know the name Root brings about a knee-jerk emotion in you, like no other name. However the simple fact is that he is a pivotal person in history of the profession, no matter what you see as any real contribution. To ignore Root is like any Englishman ignoring John I, Richard Neville, Henry VIII or Thomas Crapper. (I'd be happy to discuss with you how much difference each of these people made in the entire world) You don't have to like the guy to recognize their influence on history. Do you think that I would be in podiatry today w/o Mert Root? Or do you think that Kevin Kirby would have been in podiatry today w/o Mert Root? And what would be your story if there had been no Mert Root? What would you have done your PhD thesis on and why?

    Take care,
  19. No you don't. What you recognise is my frustration with those that continue to defend his name in the face of a mountain of good science which shows he was wrong. P= G+E + (GXE): variation rules. End of story.

    Yet strangely, I do perceive this knee-jerk emotion in you, whenever anyone criticises Root.

    Perhaps we should do better to cut to the chase and attempt to answer Kevin's question: which of the ideas that Root and colleagues proposed back in the 1960s and 1970s still stand up to scientific scrutiny in 2015?
  20. rdp1210

    rdp1210 Active Member

    What I'm trying to do is prevent the rubbishing the name of Root, that he was either all-right or all-wrong. This thread about the Root Postulate is to start the process of exactly what Kevin was talking about. Identifying one particular point of what Root said, (which I believe is really the crux of Root) identifying whether or not it was a Root concept or whether it had been formulated at some time before, and then identifying literature that supports and literature that contradicts the idea and then discussing the validity of the literature on both sides of the coin.

    I have no problem in admitting my biases. My father went to many Root lectures, and I have 400 hours of tape recording from those conferences. My father also was not satisfied that Root knew it all, and he also worked on improving Root's ideas. My father got me interested in podiatry through the biomechanics lens that Root had implanted. My father made several changes in the Root orthotic cast correction process that he felt were improvements. I have previously recorded my experiences with Milt Wille who greatly influenced my thinking. I reported recently that Milt passed away in 2010. But the simple fact is, whether he was 99% right or 99% wrong, Mert Root is a pivitol person and I would not be in the profession today without him. From what you've written so far, many of your biases seem to be tied into your sense of nationalism, which I can understand very much. (Same way I don't expect you to fully understand the importance of Benjamin Franklin in world history, though he was an English citizen for >80% of his life) Much of the Root dogma has been spread in an evangelistic manner more than in a manner of scientific inquiry, which needs to be corrected.

    You brought forward the Perkins Paper. What do you think Mert reiterated, and what ideas did the Root Postulate make that could be considered an addition to Perkins? The way I see it, Mert tried to refine Perkins idea of diagnosing forefoot varus.

    Thanks for your participation,
  21. Daryl, quite frankly I've read Root's work, I've read many thousands of papers that were published before and after his books, I'd rather go with what the best science tells me in 2015, than what I thought good old Mert thought because good old Mert's thinking has been found wanting by modern science. History is interesting, but I'm too busy to go over the same old ground, over and over and over and over and over and over again. As a Doctor of Philosophy, I feel that I have a reasonable handle on critical evaluation of scientific publication and the scientific method in general, so bias is something I understand too. Do you have a different tune you can play? :boohoo: The man is dead, his best work was published forty years ago, the rest of the world and the profession has moved on. Yet, by your own admission, you haven't even read Kevin's books. I should have thought that any podiatrist with a passing interest in biomechanics would have made the effort to read them, let alone someone who positions themselves as a bastion for the old guard; do you not think you should read the literature before you critique it? Moreover, do you not just want to read them in order to be well read in your subject field? I find it astounding that you have not bothered to find the time to read these works, yet you find time to read Rupert Sheldrake- never mind. For the record, I read his "seven experiments" in around 1993.

    I just don't have time to have the same conversations we were having on podiatry mailbase 15 years ago over and over and over and... well you get it. You haven't managed to change my opinion of Root during all this time, I really doubt you are going to as more and more scientific literature is published which detracts from his ideas and little, if any, is published to support them. For the record here's my opinion of Merton Root: "he was an important historical figure in the development of our understanding of podiatric biomechanics, as were countless others"- you can quote me on that. But good luck with your crusade nonetheless.

    As for nationalistic, I just don't like those narrow-minded, ill-read podiatrists from the USA who think the podiatric world revolves around the USA and the only podiatrists who count are from the USA, when in reality these people themselves have never travelled, taught or read outside of the USA podiatric literature base. You know the type, when asked to identify an area of Central America, they answer: "Kansas". That said, I love the USA and many of its inhabitants, but I love my own country more. If that means I am nationalistic, then yes I am.

    Would you like to talk about how the midtarsal complex works based on our knowledge in 2015 now or shall we keep trying to hold our profession back in the 1970's?
  22. Trevor Prior

    Trevor Prior Active Member

    I can see why Daryl wanted to try and tie down the references and concept as a basis for discussion but can also see Simon's point. For all of us with more than a passing interest in Podiatric biomechanics, one of the frustrations has been determining an accurate model that can be applied across the spectrum of patients with a clearly validated assessment process and subsequent prescription pathway.

    I think Chris and his team have been doing a terrific job with their reserach although Hannah hits on the crux - a functional based assessment which can be validated and then direct management - the holy grail?

    Until then, we have to use what we have which for me, is a a conglomeration of the many concepts that have been discussed over the years, assessment of the effect dynamically and modification - oh and of course my clinical experience which really means what did and did not work previously for a similar set of circumstance and structural alignment / dynamic function.

    I see Mike has started a separate thread although it would be great to have a discussion as to how we might be able to determine a dynamic model. Range and direction of motion and joint coupling would seem logical. How does the direction of motion induced by the pelvis / leg influence the foot and vice versa?

    Happy New Year belatedly.


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