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"Original Root Postulate" on the Midtarsal Joint

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Kevin Kirby, Jun 6, 2013.


  1. Members do not see these Ads. Sign Up.
    I am starting a new thread based on Dr. Daryl Phillips' comments he made in the Acrylic Materials Used for Orthotics thread. Here is where we started:

     
  2. Re: Daryl Phillips' "Original Root Postulate" on the Midtarsal Joint

    The bottom line here is that, once the forefoot is loaded by ground reaction force (GRF), any increase or decrease in GRF in the metatarsal region of the plantar foot will be instantly transmitted to the STJ and ankle joint, due to the compression and tension forces with the joints making the foot more like a beam (ala John Hicks) than like a more compliant "bag of bones" seen when the foot is non-weightbearing.

    Mert Root was wrong in many things, and this is yet another one of them. There is no fixed axis for the "longitudinal midtarsal joint", there is no fixed axis for the "oblique midtarsal joint", there are not two simultaneously occurring midtarsal joint axes when considering the movements of the naviculo-cuboid unit relative to the rearfoot unit and there is not just pronation and supination possible at the midtarsal joint (since the joint axes of the MTJ are infinite and highly variable, not at all liked fixed hinges) and there is definitely no "locking" of the midtarsal joint.

    To call these ideas a "Root Postulate" is giving way too much credit to the man for something, I believe, he described erroneously and inadequately. Mert Root was very good at describing many things in podiatric biomechanics, midtarsal joint biomechanics was not one of them, in my opinion.
     
  3. Re: Daryl Phillips' "Original Root Postulate" on the Midtarsal Joint

    I tend to agree. One of the most interesting studies on the midfoot which tests the "Rootian postulate" is this one: http://www.amputation.research.va.gov/limb_loss_prevention/Midtarsal_Joint_Locking.asp

    Amongst their statements they say:
    “Unexpectedly, we found a nonsignificant trend of increased range of motion of the navicular in the frontal plane from forefoot dorsiflexion to plantar flexion when the hindfoot was inverted compared to everted (p = 0.06). The cuboid data for the same loading conditions also increased when the hindfoot was inverted, but the difference was not significant (p = 0.3)."

    "No significant difference in the frontal plane range of motion from forefoot eversion to inversion of either the navicular or cuboid while the hindfoot was everted or inverted was detected (p = 0.2 and 0.8, respectively)."

    Although the sample employed was relatively small, this study does appear to provide objective data which disproves the hypothesis presented by Merton Root. You may see a decrease in forefoot to rearfoot stiffness when the rearfoot is everted, but it isn't likely to be happening at the talonavicular joint, nor the calcaneocuboid joint as described by Root.
     
  4. timharmey

    timharmey Active Member

    This is intresting !I have often questioned the idea that the mid-tarsal locks, it is often thrown in to papers as if it is a stone-walled fact, to hear it questioned is refreshing
     
  5. Regarding "end range of motion" (EROM) at the midtarsal joint (MTJ), I believe this term EROM is poor terminology to describe MTJ biomechanics.

    Would we describe a leaf spring, when it is loaded to 1/30th of its maximum capacity as being at the "end of its range of motion"? No.

    Would we describe a leaf spring, when it is loaded to 1/30th of its maximum capacity as being "locked"? Of course not.

    Mert Root could probably load a MTJ with 10 pounds of force and this was called "the locked position of the MTJ". However, the same forefoot, during running, was likely bearing 300 pounds of force in a 150 pound individual. Is this terminology, "EROM" or "locked" the proper terminology to describe the equilibrium position of a spring-like structure under load such as is present within the viscoelastic longitudinal arches of the feet? Not in my opinion.

    What then to call this position of the MTJ where when we manually dorsiflex the metatarsal heads and the forefoot seems to stop dorsiflexing on the rearfoot?

    Locked? No.

    End range of motion? No.

    Loaded equilibrium position? Yes.

    I like this terminology that the MTJ is loaded and in equilibrium to describe the condition where the forefoot is dorsiflexed and stops moving under a given load much better since:

    1. It does not imply that the end range of motion of the MTJ has been reached.

    2. It does not imply that the MTJ has "locked" in one loaded position and doesn't move past that locked position.

    3. It allows for an infinite number of equilibrium positions which are dependent on the load being placed on the forefoot, which is the way the foot actually works.

    Loaded equilibrium position? Yes.
     
  6. Splitting hairs: the MTJ could be loaded and moving at a constant velocity and still be in "loaded equilibrium". The position in this case being time dependent.
     
  7. efuller

    efuller MVP

    Kevin, reading your post made me realize that my own definition of end of range of motion was very very similar to your loaded equilibrium position. There definitely needs to be a term for the position of a joint where ligaments are providing resistance (I had typed limiting here, but that is also a loose definition) to further motion. It could be defined as the point in range of motion in a certain direction where the stiffness changes. For example, as the cuboid dorsiflexes relative to the calcaneus, when starting from a plantarflexed position, there will be very low stiffness. At the point at which tension in the plantar ligaments develop tension there will be an increase in stiffness of the joint. Of course, this position of the joint may be slightly different from the loaded equilibrium position at a standing load. A good research question is whether that difference is significant in terms of doing research on the joint. How much stretch is there in the ligament?

    There should also be a direction associated with the term loaded equilbrium position. Taking the CC joint again, with a dorsiflexion moment on the forefoot, the plantar ligaments will be tight, but the medial and lateral ones might not be. There are still some difficulties with the precision of the terminology.

    It's not easy.

    Eric

    Eric
     
  8. Re: Daryl Phillips' "Original Root Postulate" on the Midtarsal Joint

    So is it a rigid beam with "instant transmission" of force from the metatarsal region across the subtalar joint axis, or is it a variable stiffness "leaf-spring"? The two concepts/ models seem at odds with one another unless the spring stiffness is very high. Although the force at one end of the spring will be the same at the other end.
     
  9. Good point, loaded static equilibrium would work. As Eric stated, the terminology is difficult.
     
  10. As I mentioned in my reply to Simon, "loaded static equilibrium" takes care of the rotational velocity question, but I'm not sure it needs be added since it would be understood. Adding the direction, such as "dorsiflexion loading static equilibrium position" would further add to the precision of the term and is something I considered when I first wrote my post on this subject this morning.

    Probably "dorsiflexion loaded equilibrium position of forefoot" would be sufficient since the term "static" would be understood.
     
  11. Re: Daryl Phillips' "Original Root Postulate" on the Midtarsal Joint

    It could be modeled effectively as a leaf spring with instantaneous transmission of force through the foot. It could also be effectively modeled as a compliant beam with instantaneous transmission of force through the foot. A more complex, but more accurate, model would integrate the known elastic moduli of the bones and ligaments, their geometry and their viscoelastic properties to calculate their time-dependent mechanical behavior such as could be done with dynamic finite element analysis.

    In any instance, the point I am trying to make is that we need to stop using the terms "locked" and "end range of motion" to describe a mechanical system (i.e. the longitudinal arch of the foot) that is spring-like in nature. In other words, the longitudinal arch of the foot will deform more with increasing load, it is not "locked" and is not at the "end range of motion" at lower magnitudes of loading forces.

    Good discussion.:drinks
     
  12. Lab Guy

    Lab Guy Well-Known Member

    Kevin, I really like "Loaded equilibrium position", as it applies to closed kinetic chain.

    Would it be accurate to say the following:

    Loaded equilibrium position would be between the proportional limit and the yield point of the elastic range of the stress-strain curve.

    Overloaded equilibrium position would be within the plastic range of the curve.

    Steven
     
  13. efuller

    efuller MVP

    This makes me think of a test that John Weed described. When standing, you try and run your fingers under the medial and lateral sides of the foot in attempt to assess range of motion and/or load on that side of the foot. There are feet that will have much more load medially than laterally. There is some load laterally, but very little. Is this the dorsiflexion equilibrium position? When I see these feet I assess the maximum eversion height and will make an orthotic that attempts to achieve that "position". What I believe that I'm trying to do with this equalize the load of both sides of the foot. I cast non weight bearing in an attempt to get the position of the foot where the lateral plantar ligaments are taut. Where the ligaments become taut may be the position where the most people understand as the position at the end of range of motion. They also have the term subluxed where the joint is forced beyond the "end of range of motion." If a majority of people understand, like me :D, that the definition of end of range of motion is where the ligaments become taut, then could we still use the term end of range of motion?

    Eric
     
  14. Lab Guy

    Lab Guy Well-Known Member

    If a majority of people understand, like me , that the definition of end of range of motion is where the ligaments become taut, then could we still use the term end of range of motion?

    Eric, perhaps using the term, functional end range of motion (FEROM). For example, I have hallux limitus and have my FEROM on dorsiflexion is about 15 degrees. Functionally, my joint will dorsiflex from 0 degrees to 15 degrees without problems. Beyond 15 degrees, there will be pain with each additional degree.

    I am still partial to "loaded equilibrium position". The tautness of the ligaments are bringing the angular velocity of the joint to a stand still. When ligaments stretch further, subluxation followed by dislocation will occur.

    Steven
     
  15. Jeff Root

    Jeff Root Well-Known Member

    I believe that Merton Root theorized that the midtarsal joint would be maximally pronated during resting stance in the “normal” foot. If you read his descriptions of joint compensation for osseous conditions, I think you will find that he described several situations in which the MTJ would not be fully pronated in relaxed stance. For example, when he described how the foot compensates for a plantarflexed 1st ray, he said that grf acting on the 1st met would first cause dorsiflexion of the 1st ray. If the range of dorsiflexion of the 1st ray was not sufficient to compensate the plantarflexed 1st ray (and everted ff), then the midtarsal joint would need to supinate to compensate the remaining amount of the plantarflexed 1st ray condition. In this case, the mtj would be supinated during relaxed stance.

    Root also was referring to the normal anatomical rom of the mtj and other joints when he described end range of motion. He described subluxation as that motion which occurs when joints are moved beyond their normal anatomical rom. If the mtj has no end rom, then I suppose the ankle joint also has no end rom until you apply enough dorsiflexion force to drive the dorsum of the foot into the anterior aspect of the tibia.
     
  16. Jeff Root

    Jeff Root Well-Known Member

    I will also add that Merton Root described things better than those before him did and it is up to you all (Kevin, Simon, et al) to describe things better than those before you did! Root was extremely successful in getting standard terminology adopted into a profession that was sorely lacking it. While many of the terms that have evolved on the podiatry area might be better or more scientifically correct, they have not become commonly accepted as modern American Podiatric nomenclature. You have much work to do to equal Roots success. I wish you luck!
     

  17. The observed "range of motion" for a joint will be dependent upon the load applied. If we consider the range of motion as the phenotype then this will be due to an interaction between genotype and environment and will be highly variable between individuals:
    http://www.jcdr.net/article_fulltex...h=May&volume=7&issue=5&page=790 - 793&id=2959
     
  18. There was an article in Podiatry Now this month discussing PhD's at the University of Salford: "Salford PhD student success helps build podiatry science base" (Podiatry Now June 2013 p.7). One of the successful PhD candidates, Hannah Jarvis for her PhD examined the Root biomechanical model of foot function. I quote from the article:

    "Taking data from 100 healthy individuals she has been able to test the relationship between static measures of the foot (such as rearfoot varus, and subtalar neutral), and the dynamic behaviour of the foot. She has also investigated the extent to which Mert Root's description of foot motion matches data from multisegment kinematic foot models. On both counts the Root model does not stand up to the data and her work looks set to forge a change in how we approach foot assessment and define the normal foot"

    "Chris [Prof. Chris Nester] said 'for me, Hannah's work will put to bed the debate about the Root model: its time to move to a data-led model of foot function using the plethora of data within the literature and Hannah's experiments'".

    If the decline in interest in podiatric biomechanics is to be halted in America, I should sincerely hope that educators within the USA are taking note of what has been happening in the rest of the world for the last 20+ years. I look forward to reading Hannah's PhD thesis.
     
  19. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    I have not read the article, but was it really the "Root Model" or was it the interpretation of what a lot of people use in clinical practice (in the UK) and call the "Root Model", but bears no resemblance to what Mert Root actually said and what really is the "Root Model". Making a foot orthotic with a rearfoot post made on a cast of the foot with the STJ in neutral is hardly 'Root Theory'. ..... I have no problems if it was a critique of a foot orthotic with a rearfoot post made on a cast of the foot with the STJ in neutral.

    Almost all of the critiques I have seen of "Root Theory" in recent times were all Straw Man critiques ... in that they critiqued what the perceived as 'Root Theory', but when you look at what it was they were critiquing was not really 'Root Theory' at all, but there flawed perception of what they thought it was (and I have been guilty of that in the past)

    For eg since when has the reliability of measurements used in clinical practice have to do with proving 'Root theory' wrong - its just showed that the measurements that were used in clinical practice are not reliable! I recently recall seeing someone used Bellchambers work on moments driving tibial motion pointed to a flaw in Root Theory .... I still have not figured out what it had to do with Root Theory!

    (I really enjoyed listening to Daryl Philips in Meet the Masters last week - it was a good historical reminder of what Root Theory really was)
     
  20. Admin2

    Admin2 Administrator Staff Member

  21. Rob Kidd

    Rob Kidd Well-Known Member

    Well of course, exactly this happens in the formation of squatting facets in those ethnic groups that do that - squat. Mainly Asia, but also South Africa. Yes, they do extend their EROM to such a point that the tibia and talus make contact, and leave facets in the contact area. This runs into the areas of genetic assimilation - AKA epigenetics, but that is a different story, Rob
     
  22. I agree with your points, Craig. I'll reserve judgement until I have read the thesis.
     
  23. Jeff Root

    Jeff Root Well-Known Member

    With the exception of the ankle joint, Merton Root said you only need ounces of force to move a relaxed joint to its end rom during clinical examination. As a simple example, dorsiflex your fingers one at a time to their end rom with your opposite hand. Once you reach the effective “the end rom” using ounces of force, continue to apply a dorsiflexion force. You will immediately begin to feel a pain sensation as you attempt to move your fingers beyond their normal dorsiflexion end rom. Your pain receptors are trying to tell you something. If you continually did this you would probably increase the dorsiflexion end rom and increase the total rom of your fingers. So the normal rom of a joint is dependent on how that joint is used by the individual at a given point in time. Isn’t that why we recommend stretching exercises to increase the ankle joint rom in individuals with a tight heel cord?

    As I mentioned the one joint Root recommend evaluating differently was the ankle joint. He believed that due to the size and strength of the achilles tendon, he not only used significantly more force to examine the range of dorsiflexion of the ankle joint, he also had the patient actively dorsiflex their ankle joint during the examination.

    We know from fluoroscopic studies that elite high jumpers get mtj subluxation/deformation in the talonavicular joint of their plant foot just before takeoff. But Root was not looking at such activities. He was using average individuals (not elite athletes, etc.) who mostly did average tasks such as walking. His work was prior to the running craze of the early 1970’s, so things were much different at that time. If you disagree with his methods of evaluating joint rom, fine. Come up with a better technique and publish a book with those techniques like Root did so the methods can be adopted or at least scrutinized by a larger community of experts.

    I see biomechanical examination of the foot as dying art here in the U.S. So in my view, efforts to “improve” on Root theory are failing miserably at this time in this county. Some individuals have used criticism of Root theory as justification to abandon biomechanical examination. This seems very unfortunate to me.
     
  24. There doesn't need to be a book, as this should only provide a secondary source of information. One needs to look at original work published in peer reviewed journals. When it comes to ankle joint dorsiflexion, I quite liked this one: http://steinhardt.nyu.edu/scmsAdmin/uploads/006/435/41-04 Wilken 2.pdf

    That biomechanical examination of the foot is a dying art in the USA could be due to many factors: lack of improved clinical efficacy associated with existing techniques might be one; greater earning potential from performing surgery might be another. My dollars are on the another. As an outsider, who pops over to the states to look in every now and again, the health-care system in the States is so financially driven that it's unbelievable. I guess that's capitalism at it's extremes. Is it good to live in a full on capitalist society... I'll let my colleagues who are living the "American dream" answer that one... Here's multi-millionaire Jessie J telling us her thoughts...
    http://www.youtube.com/watch?v=qMxX-QOV9tI

    "I don't think so, I think that's a lot of bull"- P.M. Dawn

    All I know is that the last time I was in the States, the workshops on "billing and coding" were better attended than the workshops which might have enabled practitioners to improve their patients care. To me, that said everything.
     
  25. Jeff Root

    Jeff Root Well-Known Member

    How clinically practical is this? Not a all! Root would check the range of dorsiflexion of the ankle with the stj in the neutral position. If the patient had ten or more degrees of dorsiflexion he believed that would be adequate for normal locomotion. If the patient had less than ten degrees, he would quickly pronate the stj and check the range with the stj maximally pronated to see if the effective rom could be increased by pronatory compensation at the stj. It only takes a few seconds. Biomechanics must be practical.

    One reason that biomechanical examination is dying in not necessarily because of surgery, but because many practitioners make orthoses for patients without conducting a biomechanical examination. They can get paid just as much and they cut out most of the labor. This is probably why there so many orthotic treatment failures.
     
  26. Jeff Root

    Jeff Root Well-Known Member

    Be careful who you listen to. Starting at the 54 second mark this poor girl demonstrates that she doesn’t even know her right from her left. LMAO! I stopped watching right after that! ;)
     
  27. You lasted longer than me, Jeff.;) Not my cuppa. To quote an old favourite: "I wouldn't trust her to sit the right way around on a toilet seat". Ironic that we have a multi-millionaire media tart telling us that "it's not about the money" - capitalism sucks and it will ultimately be the nail in the coffin of podiatric biomechanics in the States. For all it's faults, the NHS draws us back from this here in the UK. Perhaps this is why we appear to be more inclined to read the research and go with the evidence?
     
  28. The problem is, and with the greatest respect, your dad just made up the ten degrees thing... his technique of assessment had many degrees of error in terms of it's reliability/ repeatability not least because the loading force could not be standardised (as it could in the study I cited), he couldn't possibly have known the "ten degrees" was "normal" in the population of patients he was seeing, let alone any other population. Too many variables to link to an unproven ideal / "normal" call it what you will. Moreover, he clearly assumed that no-one wore shoes with a heel height differential.

    The reality is that actually here in the UK we were pretty advanced with putting the "mechanics" in the biomechanics before your dad came along, Jeff. In my humble opinion, your fathers work as well as doing some good in terms of standardising terminology, actually had a negative impact on podiatric biomechanics here in the UK. The likes of Gordon K. Rose and William Sayle-Creer were pretty much heading in the right direction before your father's work was even published. The subsequent adoption,bastardisation, and promotion of your fathers work in the UK by Langer probably did more harm than good for twenty odd years. Not your father's fault- he didn't ask Langer to bastardise it, nor promote it, but there you go. Just my opinion. I'm sorry if that sounds harsh. I truly mean you no offence in respect to your late father (I have a late father too, and understand your desire to defend), I'm merely someone who has been involved with podiatry for twenty five years, have a research degree, have specialised in podiatric biomechanics and have reviewed and lectured upon the history of podiatric biomechanics both here in the UK and abroad.

    Sayle-Creer is interesting here, since he was advocating differentially loading the lateral forefoot and medial rearfoot using contra-lateral forefoot and rearfoot wedging in foot orthoses to relieve the stress on specific tissues in 1938. I believe you father was 16 years of age at this point. And G.K. Rose was talking about changing the axial position of the subtalar joint by means of foot orthoses in 1958.

    And lastly, forgive me if I am wrong, but aren't you a fireman by training, Jeff? How many of your fathers consultations did you actually sit in on as a fireman/ son, and how did he justify your presence therein?
     
  29. Jeff Root

    Jeff Root Well-Known Member

    I have examined some of the top male athletes at our local high school because they are friends of ours who asked me to look at their feet for one reason or another. It’s interesting that you will often find limited ankle joint and 1st mpj dorsiflexion in some of these kids. This is probably due to their tendons and ligaments being stronger/tighter, thereby requiring more force to get the same rom. I remember one kid who was a quarterback, basketball player and pitcher who demonstrated severe hallux limitus. I doubt he could pitch or throw a football as well as he did without more dorsiflexion at these joints. These tighter tissue structures may be capable of storing more energy which might actually be an advantage.

    The ten degrees of ankle dorsiflexion was a guide, not really an absolute. Certainly in individuals with a decreased range of dorsiflexion there in an increased tendency for compensation (earlier heel lift or stj pronation) than in those individuals with a greater rom.
     
  30. The concept that the midtarsal joint has one position that is locked, that this "midtarsal joint locking" is able to occur with only a few pounds of force, and any plantar forefoot force past this "locked position of the midtarsal joint" will cause subluxation which is pathological is another of the things that I was taught that is erroneous.

    Just because a plantar ligament has a nominal tension within it due to a nominal plantar forefoot loading force that causes the joints of the midtarsal joint midfoot to compress, this does not mean that increased plantar loading forces acting on the forefoot does not produce further motion and that this motion is not physiological.

    How can one assume that the forces associated with running (i.e. 2.5-3.0 times body weight), which, by the way, is very much a physiological weightbearing activity of the human species, will produce the same dorsiflexion at the midfoot and midtarsal joints as does manual examination of the foot where the forces applied to the forefoot are at least 20 - 30 times less than those forces applied to the forefoot during manual examination of the foot?

    The plantar ligaments and plantar tendons of the longitudinal arch of the foot are viscoelastic structures that will elongate more with increasing tension loading forces. Therefore, these structures must stretch more with increasing plantar forefoot loads which will, in turn, cause increased dorsiflexion motion of the forefoot at the midfoot and midtarsal joints. In other words, if only 10 pounds of manual force are applied to the plantar forefoot then the plantar ligaments will have approximately 20 times less force within them than if that patient were running. Anyone that has looked at a load deformation curve of any ligament from any animal from any scientific paper will know that a 20 time increase in ligament tension will cause an increase in length of that ligament.

    In my opinion, one of the biggest problems that I will have in my remaining years as a podiatric biomechanics educator (I have been teaching biomechanics now for 29 years) is that I will need to try and "unteach" nearly every podiatrist in the United States, and many podiatrists abroad, that:

    1) The midtarsal joint "locks
    2) The midtarsal joint is "fully loaded" with only a few pounds of force
    3) The midtarsal joint only pronates and supinates about two axes of motion
    4) These two midtarsal joint axes are somehow simultaneously occurring axes.

    Who is most responsible for promoting these erroneous ideas?

    I will let you all decide.
     
  31. Craig:

    If the things that Mert Root taught numerous times in the seminars I attended is not "Root Theory", then what, do you believe, is "Root theory"?

    Remember, I heard Mert Root lecture, in person, probably at least 10-15 times between 1980-1995. He taught that the heel of the foot is easily bisectable, that the subtalar joint neutral position is the ideal functioning position of the subtalar joint and that orthoses should be made to "prevent compensation for foot deformities", including balancing the heel of the cast vertical for nearly all pathologies that he described.

    Are you now saying this is not "Root theory"?

    Don't get me wrong, I loved Mert Root. He was the greatest thing that happened to podiatry in the 1960s-1980s. However, for the sake of historical accuracy, let's not change what the man said and didn't say.....for whatever reason...??
     
  32. Jeff Root

    Jeff Root Well-Known Member

    Kevin,

    You have likened the mtj to a spring. However, during the swing phase of gait the mtj is not anything like a spring. Don’t you believe that you too are teaching erroneous concepts?
     
  33. Perhaps we should add the navicular and cuboid act as a single unit .

    I still do not get why we are even looking at them as unit, when there has been show in bone pin studies that in the subjects tested there is motion during gait between the navicular and cuboid.

    Why replace a false ie metatarsal joint locking with another false - the 2 bones act as a unit.

    Being more precise and discussing the calcaneal-cuboid and talo-navicular and for that matter the navicular-cuboid joints.

    For me would be a better step.
     
  34. Exactly increased energy storage, the interesting thing would be to know how much was developed or was genetic and thus gave them an advantage
     
  35. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    I define "Root Theory" as the two postulates of subtalar joint neutral and the max pronated MTJ and what derives from that.

    It is just that most of the critiques I see are not critiques of "Root Theory"; they are critiques of a piece of plastic that was molded over a cast of the foot taken in sublatar joint neutral in a way that was not described by Root!
     
  36. CraigT

    CraigT Well-Known Member

    Off track here but...
    Do you know which study this is???
    I have seen high speed video footage which which appears to show serious deformation, but I am not convinced that it is the foot- I though it was the shoe.
    There is a flouroscopic study of high jumpers????
     
  37. Jeff:

    Since when do the external and internal forces acting across the viscoelastic ligaments, tendons, muscles and bones of the foot stop acting like springs in the swing phase of gait? The foot is spring-like during swing phase and stance phase. The only difference between swing and stance phases is the magnitude of external forces acting across the joint axes of the foot. The foot does not stop behaving in a spring-like manner just because is has less external load acting on it during the swing phase of gait.
     
  38. Mike:

    When you aren't in seeing patients in Sweden with bone pins in their feet, how would you be able to discriminate between the cuboid moving on the navicular with only skin markers on the midfoot?

    It's all a question of modeling and how complex you want to make the model with the available data.
     
  39. Craig:

    So making a vertically balanced thermoplastic foot orthosis with a 4 degree/4 degree rearfoot post that is intrinsically forefoot balanced and ends at the metatarsal necks should not be considered to be part of Root theory? This is what Mert Root taught in his classes should be the standard foot orthosis for all but a few special cases.

    If this is not "Root theory", then who should we give credit to for making this the "standard" orthosis technique that was taught to me and thousands of other podiatry students both here in the US and abroad?
     
  40. rdp1210

    rdp1210 Active Member


    Kevin,

    Before making any replies off the cuff, I wanted a few days to just think about things.

    One of the biggest questions that comes to mind is this:
    How does your usual casting for orthotics procedure differ today from that which John Weed taught you?

    I think your response to this will be most indicative of what you really believe.

    Some important things to recognize in relation to your comments:

    1) the osseous locking mechanism of Elftman was rejected by Root in 1975. I was an employee of Milt Wille at that point in time, when Wille challenged Root on this concept, and with experimentation, they showed it to be incorrect and Mert held up production of his volume 2 for 2 years. I will agree that use of the word "locking" is poorly chosen teminology, because the podiatric use of the term does not translate into the same meaning as the engineering use of the term. Please propose a new term to say that the ligaments begin to be stressed as they resist further abduction, eversion and dorsiflexion movements.

    2) The exact synergy of all the ligaments in producing an EROM for the MTJ is still not fully understood. I know that Kiteoka has produced some work on this. I noted that Simon quoted part of the 2005 paper by Blackwood, however I would recommend that people read the full paper and not just the quotes he provided.

    3) Yes, all the ligaments plantarly are viscoelastic. This means that they exhibit the properties of relaxation and creep. Each person probably exhibits different creep rates. Question is, how much creep do you allow for? And is the creep rate time dependent? I realize that these are questions that no one can answer for any one individual yet and is probably another reason why "X" amount of pronation produces symptoms in person and not another. When running, you may have 20x tension you mentioned, but these are brief time periods, so creep does not occur, vs. just standing. Root made a foot mold with the shape of the arch (medial and lateral) that it assumed when tension first began to occur in the ligaments. Because the orthotic flexes, no one has been able to tell us how much tension are in the MTJ ligaments in weightbearing on his device.

    4) The MTJ 2 axis model was proposed by Hicks, not Root, so you may want to beat up Hicks more. In fairness to Root when he was doing the research that he published in his 1966 paper with Weed, et al., that they tried to replicate the Hicks experiment for both the STJ axis and the MTJ axes. They added a modification of the Manter experiment and felt that they had good replication of Hicks' STJ axis results, however they could not replicate the MTJ axis results. As a result they included nothing about MTJ axis in their 1966 paper. I am sure that John Weed related all this to you. I got the story from Mert himself. If you contact Tom Sgarlato, who was also an author, he'll also tell the same story. Root always knew that the 2 axis model was oversimplification, but he continued to teach it because he had nothing else to replace it with and it explained his tx modalities. He was very excited when I told him in the mid 80s that I believed the joint to be a nonorthogonal triaxial joint. I have not published anything on such because I haven't been able to put together equipment that would do the measuring I would like to do. I am writing the results of a research we did on sagittal plane angles with various forefoot-rearfoot alignments.

    5) We probably need to be more correct by talking about degrees of freedom of motion of the MTJ than about axes. It is important that we not be confused by Nester's work in thinking that just because a joint has only one instantaneous axis of motion, that the motion of the joint can't be broken into it's component degrees of freedom. What I don't know is whether there is a greater amount of motion around the classical "OAMTJ" than can be created by adding together the motion around the vertical axis of motion and the transverse axis of motion. [In discussing the work of Nester, you need to think, what Nester would have found if he had been measuing the axis of the hip joint in gait? Would he have said that there is only one axis of motion instead of 3? It's a vector algebra problem.)

    6) If there are indeed three axes of motion around the MTJ, (i.e. some type of ball-in-socket joint), is there any linkage of the motions? Why or why not? This is yet to be determined.

    I appreciate your ambition to unteach everyone. I hope that by this posting you recognize my own cognition of the weaknesses of the Root Postulate. However when you start unteaching people, you have to have something to put in its place. (Here in Florida, we have this problem with such entities that they call sinkholes. You can step into one and never be found.) That's why I asked you the question above. Root certainly continued his MTJ teaching because he had nothing to put in its place. Guess that's why the CCPM started its biomx fellowship program, to train a new generation enough to get more research. There has been a limited amount of research into the MTJ, but a LOT more needs to be done, to fully understand the ligamentous interactions and the degrees of freedom of motion and the linkages of motion. It's easy to say someone is wrong. It's harder to find something better to replace those erroneous ideas with.

    Best wishes,
    Daryl
     
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