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Challenging the foundations of the clinical model of foot function

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Jan 31, 2017.

  1. efuller

    efuller MVP

    So what is the advantage of comparing foot types. What literature evidence do we have that comparison of foot types is useful. In thinking in terms of theory on why might this might be useful I can think of one foot type distinction that could predict what type of pathology might occur and what treatments should and should not be used. A partially compensated varus foot will tend to have high lateral loads. However, you do not need neutral position to figure out if someone has a partially compensated varus. (Making a distinction between forefoot varus and rearfoot varus is not helpful in decision making with a partially compensated varus.) The maximum eversion height test can show a partailly compensated varus without looking at netural position. What additional advantages are there in using foot types based on neutral position? If there is lack of evidence, I'm willing to listen to theory. What are the benefits of using neutral positon?

    Kinetics happen in static stance too. Free body diagram analysis can be done when you know the acceleration. (net Force = mass x acceleration) In static stance we know the acceleration is very close to zero.
    What structures are stressed when the STJ is not in neutral position? If there is no evidence, I'm willing to listen to theory. What structures are stressed to keep the STJ in neutral position?

    I think a beginner can do just fine by just learning the anatomy. Neutral position is taught as a theoretical position where there is the least stress on the entire foot. Where is the analysis that shows this is true? This concept has just been accepted as fact without any science. At the same time people who believe there is less stress when the STJ is in neutral position, also believe that there will be less stress when the heel is vertical. This will confuse the new student. How does having neutral position help the new student? It's just one more factoid they have to learn.



    Why would finding a position of equal passive tensions in a joint in a non weight bearing position have any relation to stress on the foot in the presence of weight bearing forces? Before you go to all the work of putting strain gauges on tendons to figure out what is the best definition of neutral, you should answer this question. Especially, if you think a vertical heel is a position of least stress.
     
  2. rdp1210

    rdp1210 Active Member

    Because biomechanics of any tendon requires that total tension = active muscle force + passive tension. You forget that passive tension is part of the total equation. You are also not considering that muscles can exert maximal contractile force at or near the point where the passive tension starts to increase from zero.

    I didn't say that a vertical heel is a position of least stress on the tendons and ligaments. The most desirable condition is when the vertical heel and the neutral STJ position coincide. If they don't, then tradeoffs have to be made because there is no ideal to be accomplished. I maintain that

    A vertical heel is a position where the inversion and eversion moments created by gravity alone are equal. I did an unpublished study while at Iowa on 5 cadavers, and found that the heel bisection drawn on the posterior surface of the heel, using a caliper method similar to that advocated by LaPoint, was vertical to the ground when the heel alone was placed on a flat surface with no weight from above and the inversion and eversion moments equalized so that it did not roll into further inversion or eversion. I realize that is like balancing an egg on one end, but it can be done. Now this was just an informal study, and didn't have all the controls on it that one should have to make it a good research paper, it was intended only as a pilot project. However for those of you that need a student research project, this is an idea that could be paramount to better melding clinical practice and mathematical-based biomechanics.

    In fact I will propose this definition of the posterior heel bisection be adopted by the profession: "It is that line that is drawn on the posterior heel, that is vertical to the ground, when the forces of gravity produce equal inversion and eversion moments on the heel alone." Please note that the inversion/eversion plane is that plane perpendicular to the plantar bisection of the heel (assuming that the plantar surface of the heel is perpendicular to the ground. Please see my 1992 paper on definitions of the rearfoot coordinate system)

    Will reply more later,
    Daryl
     
  3. rdp1210

    rdp1210 Active Member

    Thank you for those kind words, Kevin. As you know, the majority of my practice is in the world of chronic diabetic foot ulcers. A look at the surgeries I did last year shows that 75% were for osteomyelitis. Doing surgery for osteomyelitis carries with it tremendous biomechanical consequences, just amputating the distal phalanx of one toe has its effects, especially when that toe is the hallux. Therefore I am getting ever more conservative in my treatment of osteomyelitis - not every case has to be treated with surgery.

    One of those life changing lectures that I attended was in 1991, at ISB in Perth, where Peter Cavanaugh gave his keynote address on Ulceration, Unsteadiness and Uncertainty (which was published in 1993 in J. Biomech and is required reading of all my medical students rotating for wound care). We give a lot of lip service to prevention, however I wonder how practice would change if we had a condition in the US similar to that in Germany (from what I have been told) in which diabetic shoes would not be compensated for unless there is pedobarographic data to show that they actually were doing something. I great learning experience for me was when I finally put my diabetics wearing their custom orthotics under the pedobarograph exam and found out how little those orthotics were alleviating the abnormal pressure. At our clinic we have adopted the terminology advocated by Dave Armstrong: we no longer say that an ulcer is healed or has reoccurred, we say that an ulcer is in remission or has relapsed. New termology yields a different approach. For example, I check diabetic orthotics a minimum of every 6 months, more often in many, as there are changes in the orthotics as well as feet that have to be kept up on. Fortunately I utilize an orthotics lab to make my diabetic orthotics that listens very closely to my instructions and doesn't try to tell me what to do, and I have capabilities at my workplace to make modifications. Many I still find myself making changes in the orthotics from my original prescription to fully meet the needs of the patient. Maybe we need a payment system for diabetics that will pay us every month that the patient doesn't develop a new ulcer, and then withholds payment in the months that the patient has an ulcer. Wonder how practice paradigms would change.

    Best wishes, hope to see you at IFAB,
    Daryl

    BTW - don't know if you've heard Howard Dananberg lecture on modeling the foot with a 4-bar linkage system. Very interesting concepts that we need to look at. Howard is definitely one of the great thinkers.
     
  4. Petcu Daniel

    Petcu Daniel Well-Known Member

    I looked back at the Root ["Neutral Position-Casting Techniques", 1971] and Langer [A practical Manual for a Basic Approach to Foot Biomechanics", 1973] books and, indeed, the original technique proposed by Root [talo-calcaneal congruency] was changed by Langer in talo-navicular congruency , as far as I understand without an explanation but with the same purpose of finding the STJN as a "maximally functioning position". It is strange for me that the talo-navicular congruency was assumed further as one indicator of STJN, inclusively by other professions, in defining techniques as those for measuring navicular height/drop. Probably the talo-calcaneal congruency or incongruency has other mechanical effect than talo-navicular one but, again probably, the last one is easier to use in practice. But, logic, how can we discuss about STJ neutral when in practice one of the original techniques was changed without any explanation/justification? From this point of view, Chen's article [Assessment of subtalar joint neutral position: a cadaveric study, https://www.ncbi.nlm.nih.gov/pubmed/18701029 ] I think is not of value reported to the original STJN theory as it is studying the maximal contact area in the wrong joint [talo-navicular instead of talo-calcaneal] !
    Daniel
     
  5. efuller

    efuller MVP

    I don't see how the above addresses my original question which was: "Why would finding a position of equal passive tensions in a joint in a non weight bearing position have any relation to stress on the foot in the presence of weight bearing forces?

    The bigger picture for this question was why neutral position? The answer was because this is a position of least stress. This particular position of least stress has nothing to do with weight bearing.

    Is there a difference in importance between heel vertical and neutral position? What trade offs do you make and why?

    A vertical heel drawn on the back of the calcaneus is a single plane observation. The calcaneus is a three dimeinsional object and to assess moments on it you need to look at the three dimensional object. When examining the forces on the heel the constraints on motion caused by the joint surfaces and ligaments must be considered. When the upward force on the heel is medial to the STJ axis the STJ will supinate and when the force is lateral it will pronated (evert).



    There are times when you can learn something by removing part of an object and see what happens without the removed part. This is not one of those times. If we want to know the position of least stress of the entire foot, when weight bearing, then we need to examine the entire foot weight bearing. To find the position of least stress we can go back and look at the Hicks paper on the function of the muscles. The experimental set up was a cadaver foot on a board with weight from above pushing downward. Under the board there was a pin that could be moved. Hicks moved the pin until the foot balanced. With tension in no muscles the pin balanced underneath the intersection of the ankle joint and the subtalar joint. This makes perfect sense because this would be the position of the pin at which no moment would be created at both of those joints. That pin is the center of pressure.

    The position of the heel bisection should not be used to predict stress because it is a single plane measurement, the movement of the heel will occur about the STJ axis, and the heel bisection ignores the influence of the forefoot.

    Eric
     
  6. rdp1210

    rdp1210 Active Member

    I'm totally confused why you believe that length of the muscles crossing the joint has no effect on the joint moments. Also why length of the muscles crossing the joint as no effect on the force those muscles can exert. These effects are critical to "normal function" in a dynamic situation. You want to talk about tissue stress -- these muscle lengths are a big piece of the tissue stress paradigm. Without them, your tissue stress model is like a bicycle that has half-circle wheels.

    Second - Lovett and Cotton in 1898 introduced a term called "the reserve of pronation." If you have a person walking or running, would you rather have that person hitting the ground with a significant reserve of pronation or almost no reserve of pronation? Does reserve of pronation have any consequences, especially when doing things like turning in one direction or the other?

    You can put up your arguments why there shouldn't be a neutral position - however, I look at them more as excuses, not reasons. The advantages far outweigh the disadvantages.



    If the two coincide, that is ideal. Wright, Desai and Henderson made heel vertical their STJ neutral position. However Root said that they aren't necessarily the same, that many people stand up with the heel vertical, yet some will develop pronation symptoms and others will develop supination symptoms.

    I'm not saying that it isn't a 3-D object. You're arguing first that we only need to consider vertical forces around the STJA, and then you're accusing me of being one-dimensional. In your argument, your vertical forces have an effect only on the frontal plane moments around the STJA. However what about the transverse plane forces ML and AP? Not once have I ever heard you discuss the inclination of the STJA. Yet my calculations shows that the ML forces produce 1.45 times higher moments around the STJ axis in the forefoot in a patient with a 40 deg inclination angle vs. a patient with a 30 degree inclination angle of the STJA. You may say that the ML forces are only 10% of the vertical forces, yet the lever arm of the ML forces in the forefoot are 10 times the lever arm of the vertical forces. Therefore ML forces are as important as vertical forces in the moments they create around the STJ, especially as the COP moves into the forefoot. I can throw the 3D argument right back at you as I consider that you want to boil the foot function down only to frontal plane moments around the STJA and plantar fascia.



    And I'm not arguing with Hicks. What Hicks didn't do is see what the angle of the posterior heel bisector was to the ground. I bet it was vertical.

    It is part of the total package of stress, and it doesn't ignore the forefoot because without a heel bisector you have no forefoot to rearfoot alignment measurement nor any prediction of how the forefoot influences the rearfoot as to heel position. Could write a lot more about this, but it's now time to go see patients this morning.
    Take care,
    Daryl
     
  7. efuller

    efuller MVP

    I never said that the length of the muscles don't have an effect on joint moment.

    [​IMG]

    There is a range over which muscles can develop force. The above graph is force developed with maximal muscle stimulation. With lower amounts of stimulation less force is developed. The question is whether you need peak force in the muscle to carry out the activities of daily living. I doubt it. We also need to look at muscle length relative to joint position. Very few joints have the range of motion to put the the muscle outside of its useful force producing lengths. When you test the posterior tibial muscle it can produce quite a bit of force over its entire joint range of motion. The joint doesn't have to be at its peak force producing length to function normally. In fact we don't know that the posterior tibial muscle doesn't produce the most force at the maximally pronated position of the STJ.

    What I did ask is why looking at passive muscle tension would have any relation to stress on the standing foot. Passive muscle tension is not the force needed to generate movement.


    Now we are talking ideal versus reality. We have to treat the foot that is in front of us. There is a lot of redundancy in the systems of the body. Some feet will not have a reserve of pronation. Sometimes that lack of reserve will cause pathology. We can't make a foot that lacks reserve of motion have more motion.

    You haven't mentioned any good advantages yet. You did claim that it was easier for students. Neutral position makes it harder for students. How does neutral position make life easier for students? The emphasis on LMTJ and OMTJ moves the students away from thinking about the anatomy. These are not excuses, they are questioning of acceptted dogma that should not have been accepted in the first place.

    You also mentioned neutral position can be used to tell if a foot is pronated or supinated. Now we are back to the circular definition. Why do we need to know if a foot is pronated or supinated. Does that explain why a foot hurts?



    It's the ap forces that are 10% of vertical forces. Medial lateral forces are 1% of vertical forces in gait. In static stance, ap and med-lat are much smaller. So, the vertical component is the most important even with a more vertical axis of the STJ. Yes, the moments will be smaller with a vertical axis, but the direction of the moments will be the same.

    Your point about the horizontal components is a better argument against the use of heel bisection than it is about the use of positon of STJ axis.




    My point about the Hicks experiment was that the heel bisection didn't matter. What causes the heel to invert or evert are the moments about the STJ and not whether the heel is vertical.
     
  8. rdp1210

    rdp1210 Active Member

    So Eric, you were fresh on my mind this morning when a patient presented themselves with unilateral Achilles tendon enthesopathy at the insertion.
    Standing up it is noted that symptomatic side (denoted as S) shows the heel 4 deg inverted and the asymptomatic side (denoted as A) shows the heel 3 deg inverted from perpendicular. (virtually the same).
    Side S shows an arch height in stance slightly higher than side A.
    Tibial stance position is 3 deg inverted on the left and the right side (identical).

    Which foot shows the STJ more pronated, if the RCSP is the same and the leg-heel angle is the same?

    So I plotted the STJA onto the bottom of the foot. Both S and A had normal identical location at the posterior heel. Side S showed the axis under the center of the fibular sesamoid and side A was under the medial plantar condyle of the 2nd metatarsal head.

    Wouldn't you expect the foot with the more medially located STJA to pronate more than the more laterally STJA?

    So I measured the available ROM in the STJ. Side A had maximum inversion 10 deg, maximum eversion 0 deg. Side S had maximum inversion 12 deg and maximum eversion 8 deg. NP measured at 3 deg inv on side A and 0 deg on side S.

    So this means that patient stands up and side A is no reserve of pronation available, however side S has 100% of reserve available.

    Then I looked at the LAMTJ ROM (qualitatively). Side A is estimated to have 10 deg ROM. Side S is estimated to have 2 deg. ROM.

    So please use TST to explain:
    Why the more medial STJA pronated more.
    Why the Achilles tendon is asymptomatic on the side in which the STJ is more pronated.

    Thanks
    Daryl
     
  9. rdp1210

    rdp1210 Active Member


    First of all, there are inversion and eversion moments on the os calcis itself, around its COM, not just around the STJA.

    My statement is that the heel bisection is that line connecting the top and bottom of the heel, where vertical force from the top and vertical force from the bottom produces equal tension-compression forces on both sides of the os calcis and produces a net of zero inversion or eversion moments. That's called TST. The true heel bisection then would overlie the COM of the heel. Maybe Simon could do us a finite element analysis on the os calcis to show us the deformation in the side walls of the body of the calcaneus with various directions and locations of force from the top and bottom

    I don't understand your statements about students being confused. If they're confused, it has to be due to the teaching and therefore we need to reassess not the theory but our methods of teaching. Even a poor theory can be taught without confusing the students.

    Thanks
    Daryl
     
  10. efuller

    efuller MVP

    It took me a while to get that A side was asymptomatic. For a second I thought you were making things a lot harder than they needed to be.

    How does explaining why one side pronates more help this patient's Achilles tendonitis
    What does STJ pronation have to do with Achilles tendoinits?
    Does neutral position theory have an explanation for Achilles tendonitis.?

    Daryl, you might want to recheck your numbers. What is 100% of reserve available. There's a tarsal coalition on the asymptomatic side. Of course that could be protective for Achilles tendonitis. Especially if the patient is a high jumper who jumps off of their symptomatic side.
     
  11. I'll fess up from the start, I didn't read the overly-long post about, let me guess a paper that was published 120 years ago, Cotton and someone?... Yet, I offer an answer to this question pasted above: because in this individual, as in many others, in fact in all of the published literature that we have to date... the degree of "STJ pronation" is not predictive of Achilles tendon pathology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4282737/ etc. And your point is?

    A measurement which high quality evidence tells us is not predictive of any, nor the given specific pathology in this case, and yet you offer the same measurement as not predicting the pathology and we are supposed to go: like wow man, how can that be? A measurement which the best evidence tells us does not predict pathology, didn't predict the pathology in a specific case? Seriously, WTF? Tell me what the prescribed response should have been, Daryl? From me it gets a: yeah? and? so? what?
     
    Last edited: Mar 26, 2018
  12. efuller

    efuller MVP

    You can calculate moments about any point in space. The answer you get for net moment on an object should be the same. (I didn't believe this the first time I read it in an engineering textboot and after doing it a few times, sure enough the engineering textbook was right.) The forces are the same no matter which point you choose to calculate the moment about.

    The subtalar joint surfaces and the ligaments constrain the possible motion of the calcaneus so it makes life easier to calculate moments about that axis. When you palpate the location of the STJ you are doing this exact experiment.




    Daryl, what you are talking about here is the center of pressure of force above and below the calcaneus. The center fo pressure from above is going to be far anteriorh (the average of forces at the talo calcaneal joint surfaces) to the center of pressure from below, so there will be a large plantarflexion strress on the calcaneus.


    If the students don't understand a theory it can be one of three things. It could be the students. It could be the teacher, or it could be the theory. How does STJ neutral theory help students?
     
  13. Jeff Root

    Jeff Root Well-Known Member

    Well, you could start out by teaching them that there is no such thing as "neutral position theory" and that the theory of a neutral position is just one of a much broader system of related and unrelated theories about foot function.
    P.S. FYI, I have been very busy and haven't had an opportunity to keep up with all the discussion for a week or so.
     
  14. Better, don't mention "neutral position theory" at all, as there really is no need. Erase it from history... nah, just tell everyone why it was wrong.
     
  15. Jeff Root

    Jeff Root Well-Known Member

    Get your podiatry degree in one day of instruction. Class dismissed. ;)
     
  16. efuller

    efuller MVP

    So you don't have a reason to teach it? It has been said that the benefits outweigh the disadvantages. What are the benefits of neutral position theory?
    I'm not advocating teaching nothing. I'm advocating the teaching of theory that has a coherent explanation of its use.
     
  17. And many of those who prescribe foot orthoses around the globe do just that. Are their outcomes any worse?
     
  18. rdp1210

    rdp1210 Active Member

    Eric, I will post more later in response to your questions about advantages of neutral position. However in going through my patient notes this morning, I came across this MRI. If we assume that `this is the position of the bone structure when the patient is standing, please do a TST analysis for us. I would be very interested in your assessment of the tension and compression forces on the medial and lateral walls of the os calcis as well as your analysis of the articular cartilage assessment.

    I realize that WB CT technology is just beginning to be done and that MRI WB technology is still far down the road.

    Thanks,
    Daryl Everted calcaneus MRI.jpg Everted calcaneus MRI.jpg
     
  19. efuller

    efuller MVP

    In tissue stress approach we start with the chief complaint. What is this patient's problem?

    You can't analyze the articular cartilage with just one slice.

    This slice is distal to the weight bearing surface and we don't have the center of pressure of the weight bearing surface. We also don't have the center of pressure in the talo calcaneal joint facets. The analysis you request cannot be done with a single one plane picture of the calcaneus. Which is the point about heel bisections. You should not base mechanical analysis on a line that is drawn on the back of the heel.
     
  20. Petcu Daniel

    Petcu Daniel Well-Known Member

    So, which could be the explanations for the adoption in practice of the Langer's technique [talo-navicular congruency] instead of the Root's original one [talo-calcaneal congruency] ?
    Daniel
     
  21. Trevor Prior

    Trevor Prior Active Member

    Now that's an interesting question. When I was focussed around determining STJ neutral as the key to my assessment, the concept of using the TNJ to obtain neutral seemed a little daft to me as, to my knowledge, it was basically designed to allow us to take a cast.

    However, as I have become more focussed on how the forces acting on the foot maybe affected by the structural alignment and, in turn, effect load on the tissues, part of that process has been to consider the position of the STJ axis. As this is dynamic and alters through stance, the case study presented by Simon and Kevin using the STJ axis locator demonstrated that the bisection of the head and neck of the talus closely reflected the transverse plane position of the axis and thus the TNJ congruency gives us a guide to the axis in our patients.

    Thus, if we have a foot whereby this line is deviated medially, or laterally, trying to realign the position, has the potential for us to provide a better 'balance' (for want of a better word) of the forces acting around the subtalar joint. The ability to achieve that will be afected by many factors but it certainly has more relevance to me now, than it did previously but not due to STJ neutral.
     
  22. Petcu Daniel

    Petcu Daniel Well-Known Member

    Now, the "luck" (somehow a forced term in the context) was that they have had a foot surface where to mark the projection! I think it would be interesting to see where the other 2 projections are positioned. Maybe the frontal one would be an indicator of the importance of a rearfoot mark as the bisector could be while the sagital one would be related with navicular drift and transversal movement (high navicular drift = high STJ axis ??).
    On the other hand, the original casting method described by Root is using talo-calcaneal congruence and not the talo-navicular one! So till Simon and Kevin's article, which has used Morris and Jones technique, without any link with the talo-navicular congruency, this congruency was already assumed by podiatry and other professions!
    Daniel
     
  23. Trevor Prior

    Trevor Prior Active Member

    I am not sure I have understood all you are saying but:

    1. we have no idea if the navicular drift is related to the height of the stj axis and I supect it is as much if not more to do with the amount and direction of motion of the joints int he midfoot / forefoot.
    2. Whilst root may have described talo-calcaneal congruance, many used TNJ for STJ approximation for taking casts - someone has described the history earlier in this discussion.
     
  24. Petcu Daniel

    Petcu Daniel Well-Known Member

    Yes, you've understood!
    1. I think it would be interesting an experiment using Simon and Kevin' device and projecting the line between the anterior and posterior pointer [STJ axis] on the sagital and see if it is corelated with navicular drift
    2. I understand the description of history and its link to a position of maximal functionality, but, in the context of the precision required for taking the biomechanical measurements, I don't understand how a key concept was so easy changed and accepted! Because, for example in the case of navicular drop test, the reference of the talo-navicular congruency as an indicator of STJN is wrong. As you've mentioned, this congruency is reflecting the position of the axis in the transverse plan and not a neutral position of the axis. At least this is what I understand!
    Daniel
     
  25. Jeff Root

    Jeff Root Well-Known Member

    Navicular drift (navicular adduction) is a transverse plane motion and navicular drop (navicular plantarflexion) is a sagittal plane motion. STJ pronation is a triplane motion. Therefore it seems logical that the STJ axis, which closely follows the long axis of the talus would adduct with navicular drift and also plantarflex with navicular drop. This brings us back to the all important issue of reference points and planes. As the leg internally rotates with STJ pronation during midstance, the talus is adducting relative to the sagittal plane of the body but it adducts more relative to the forefoot because as the STJ pronates the forefoot is pronating (abducting and dorsiflexing: i.e. oblique axis pronation) relative to the rearfoot. As a result, the STJ axis adducts more relative to the forefoot than it does to the sagittal plane of the body. In addition, as the talus plantarflexes , so too must the STJ axis because the STJ axis follows the motion of the talus. So, as the talus plantarflexes relative to the floor, it plantarflexes more relative to the forefoot than it does to the floor due to closed chain dorsiflexion of the forefoot on the rearfoot.
     
  26. Not sure I agree with you're add on to Navicular drop Jeff

    Navicular plantatflexion?

    Let' not confuse things for no reason. Navicular drop and drift are international terms let's stick to them
     
  27. Jeff Root

    Jeff Root Well-Known Member

    Mike, what don't you agree with? I'm not attempting to confuse things for no reason, I'm commenting on and expressing my understanding of STJ and MTJ closed chain motion in response to Trevor's comments. Therefore my comments serve a purpose for me and perhaps for others. Navicular drop/drift is influenced by both STJ and MTJ closed chain motion. During closed chain STJ pronation the navicular plantarflexes relative to the floor but there is a degree of navicular dorsiflexion relative to the talus. In other words, the talus and the navicular both adduct and plantarflex during closed chain STJ pronation, but the navicular doesn't plantarflex and adduct as much as the talus, so there is relative dorsiflexion and abduction of the navicular to the talus. Does that make sense to you? If the navicular doesn't plantarflex relative to the floor then how does it drop?
     
  28. Navicular Plantatflexion indicates rotation around an axis. And I am not sure the Navicular plantarflexes within the confines of the joint. And not what we are recording. I see you added relative to the ground after I made my point. Just seems a mouthful when 2 words describe what we are discussing

    It just confuses things Navicular drop is what is discussed in every thing I have ever read on the subject.
     
  29. Nope, not unless the forefoot moves vertically upwards away from the floor; otherwise it's downward displacement is the same relative to the forefoot as it is to the floor.
     
  30. Jeff Root

    Jeff Root Well-Known Member

    The bases of the central mets become lower during closed chain STJ pronation and simultaneous forefoot abduction and dorsiflexion as the arch lowers. As a result, if the bases of the central mets move plantarly while the met heads are stabilized against the ground, then this motion is dorsiflexion of the metatarsals relative to the transverse plane of the body. The inclination angle of the 1st, 2nd and 3rd mets decreases during closed chain STJ pronation and simultaneous forefoot abduction and dorsiflexion and increases during resupination. During resupination, which converts the foot to a more rigid leaver, the arch height begins to increases prior to heel lift and the 1st met plantarfelxes.
     
  31. Trevor Prior

    Trevor Prior Active Member

    When we assess the lateral view of an xray for someone with a flat foot deformity for instance, we look at where the p-tosis occurs, i.e. where is the movement that contributes to the deformity.

    In patients with a naturally low arch profile and low calcaneal inclination, the joint may all be congruent. In some, the ptosis happens at the TNJ, others the NCJ and others the MCJ.
     
  32. Rather than the bases of the metatarsals which really are more midfoot than forefoot (as they move in the same direction as the talus in your example, they should reduce the vertical displacement of the talus relative to their bases rather than increase it, BTW), let's take a point at the forefoot, let's take the skin under the first metatarsophalangeal joint that interfaces with the floor: we'll call this point X, now plantarflex the talus by 10mm, has the talus displaced 10mm in the sagittal plane toward the floor? Has the talus plantarflexed 10mm towards point X? Yes, that's right it has, which makes your statement incorrect, Jeff. To re-iterate, as I see you have since edited in your original post, you stated that:

    "So, as the talus plantarflexes relative to the floor, it plantarflexes more relative to the forefoot than it does to the floor due to closed chain dorsiflexion of the forefoot on the rearfoot. "


    The question becomes: will your ego allow you to admit that your assertion above was wrong? Doubtful.... So, lets see if logic can sway you: Unless any point of the forefoot, let's say the centre of the 1st metatarsal head, is moving vertically upward away from the floor, then your assertion is always incorrect. Next.... which part of the forefoot is moving vertically upwards away from the floor with increased plantarflexion of the talus? Yep, I got mine, let's see if you can spot it? Ego won't let you back down though- this my fellow "passengers", is why I get annoyed with Jeff et al. Even in the face of something unarguable, he'll still choose to argue rather than admit his assertion was wrong...

    And Jesus wept... Happy Easter.
     
    Last edited: Mar 28, 2018
  33. Jeff Root

    Jeff Root Well-Known Member

    Simon, I did not edit my post. I will be away from my computer for the rest of the afternoon so I will have to respond later. However, before I go, I'm trying to explain a closed chain situation. For example, if the foot is firmly planted on the floor and the proximal aspect of the tibia is moving anteriorly then this motion is closed chain dorsiflexion of the foot at the ankle joint even though the foot hasn't moved relative to the floor or to the transverse plane of the body. In other words, the angle between the tibia and the foot is decreasing not because the foot is moving but because the proximal segment (leg) is moving. This is the same concept that I was trying to explain about relative dorsiflexion of the forefoot and the mets. When I get time I will reread what I wrote. If there is an error or if I was incorrect I will be happy to acknowledge it.
     
  34. rdp1210

    rdp1210 Active Member


    Simon
    Do you think that you could write one post on this circus arena without being snide, or sarcastic or insulting? You're definitely destroying the image we all have on this side of the pond of the English being polite and respectful. You talk about ego? Your arrogance is overwhelming. I suggest you read the book, "The Science Delusion,' by one of your own countrymen there at Cambridge.

    Please resubmit your argument without all the nasty stuff.
    Daryl
     
  35. Jeff, lets stay on track: we were talking about your statement: "So, as the talus plantarflexes relative to the floor, it plantarflexes more relative to the forefoot than it does to the floor due to closed chain dorsiflexion of the forefoot on the rearfoot."
     
  36. Do you think you could write without being condescending and patronising? Do you remember when your daughter went missing at that summer school on our side of the pond? I do, wind your neck in Daryl. Your boy Jeff is wrong here, let's see if he can admit it....
     
  37. Jeff Root

    Jeff Root Well-Known Member

    Mike, both you and Simon have accused me of editing my posts. If a post is edited it is indicated at the bottom of the post. If you look at my posts you will see that they were not edited. As an example of an edited post, take a look at Simon's post #633 above you will see that it was edited and the edit is indicated at the bottom right corner of the post which says "Last edited: Today at 11:56 AM". Now go back an look at my posts that you and Simon referred to and you will see that they were not edited. I do often edit my posts because I'm not a great typist and I'm not good at proofreading my own writings so if I see a grammatical error I will go back and edit it so that it reads correctly. I would appreciate it if you would both stop making false accusations.
    Thank you.
     
  38. Were did I say edit.

    You added towards the ground in your 2nd post. After the 1st post where you introduced Navicular Plantatflexion

    You can edit your posts as much as you want Jeff I do.


    People need to chill out. No wonder Podiatric Biomechanics doesn't get anywhere.

    Number 1 rule of the internet never read the comments section under an article.

    Number 1 rule should be write in the same way you would talk to that person face to face
     
  39. rdp1210

    rdp1210 Active Member

    Eric, I said that I would critique your article in February issue of Podiatry Today on orthotic writing. It is important to remember that Podiatry Today is not a peer reviewed journal, so I cannot hold your article to the same rigorous scientific writing I would if you submitted it to JAPMA -- most of the writings in Podiatry Today magazine are opinion. Even though I tried to write my latest article with as many references as the editors would allow (there is a lot more than those I listed), still there is opinion mixed in.

    #1. "...This is different than what we learned in the past, namely that just the position of joints can explain pathology of the foot.
    The first step in tissue stress biomechanics is to identify the injured anatomical structure."

    Sometimes, Eric, I wonder if we really did graduate from the same school within a few years of each other. First and foremost I learned in school that when a person complains of pain, that the first thing the practitioner has to do is identify the anatomical structure that is injured. I can't pin this teaching on any one teacher. Interestingly, Mert Root in the entire curriculum, gave less than 5 lectures, but I do know that he made a statement about joints not hurting unless they tried to move beyond their EROM. So I'm wondering if you learned the same things I did. Or did the curriculum somehow change after I graduated, to teaching you look first at function and then at anatomy. I'm not disagreeing with the statement you made about where you start, but I'm saying that this concept of identifying the injured structure is not new -- it should be the start of every theory and every practice of medicine. Biomechanics is clinically useless if you don't know your anatomy. Should it be basis of every theory and model? Absolutely! If anyone believes that Root taught that anatomy isn't where you start, then something got lost, but let's not blame it on Root, let's blame it on those who thought they were Root's disciples (and I definitely disagree with some of them about many things).

    Your statement that the position of joints can explain pathology of the foot is a straw man argument if you mean that it can explain all pathology. I'm not sure if you mean that you learned at our common alma mater that position of joints can explain all pathology, then something went really wrong in the interval between our graduation dates. I learned a lot about motion of the foot, what constituted normal and abnormal motion of the foot. I also learned that ligaments are not injured unless they are stretched too much. I learned that orientation of joint axes determines direction of motion. I learned that some compensations can be seen with a person just standing, but some cannot. I learned that evaluating a person just standing isn't enough, that you had to also observe dynamic function. Now I will admit I did a lot of reading after graduating, and found that not enough emphasis had been placed in the curriculum on understanding tissue biomechanics. And maybe that lack of emphasis got worse after I graduated. So maybe you did get cheated in your education and you came away with the opinion that you expressed. If that happened, then course corrections need to be taken to restore and improve the education in tissue biomechanics. When I was teaching full time, I certainly tried to make course corrections in teaching those segments of biomechanics that I felt needed more emphasis. Hopefully the students I taught learned more about tissue biomechanics than I did. And if I was teaching full time today, I would be teaching more than I did way back then about tissue biomechanics.

    In summary, I find your opening statements to be divisive, and I think it's time to end the divisions among us. For you to say that you have a whole new theory of biomechanics and orthotic making is truly disingenuous. Just as I don't feel that Root invented biomechanics, but only added some thing things and helped organize some previous concepts to be more coherent, so I see you adding a few ideas, and Kevin adding a few ideas, and everyone else adding a few ideas to try and bring all observations into a complete coherent theory. I would like to see the phrase "Root theory" totally eliminated as there is no such thing. Likewise I would encourage you to quite using the phrase "Tissue Stress Theory." Tissue Stress does not explain everything, it is only a part of the total picture. Therefore I cannot recognize it as some type of new or separate theory. And the posts coming from Simon just say that the name "Root" only says to him that the Americans are trying to dominate the podiatric scene on the world wide stage. Having lived (not just visited) abroad myself, I understand those feelings more than he could imagine. (BTW, Simon, one of my 9th great grandfathers sat on the jury that convicted Charles I. Of course Charles II got his revenge on him. And my DNA is 77% English). So Simon, I do try to give credit to those in history who do come up with the original ideas, no matter which side of the pond they're on. And of course we also have to recognize that sometimes people come up with the same "original idea" without any knowledge of each other. Rupert Sheldrake has coined the term "morphic resonance field theory" to explain this concept, which at best is very controversial, but the facts he uses to support it cannot be ignored. Kevin writes that Root didn't invent neutral position -- I believe I said the same thing many years ago when I found the same concepts written about in 1898, yet had gone totally ignored by over two generations of practitioners and had not been further developed. And so it is apparent that Root was totally ignorant of those writings -- and we are left to ask, was there indeed a morphic resonance field that influenced him to revive and refine the idea of neutral position? That is for the reader to discern and decide.

    Now the problem with the lectures and articles given so far by you, Eric, is that you give me no forward view as to the prevention of symptoms. Since I have been most involved with the diabetic biomechanics world over the last 20 years, the prevention of the diabetic ulcer should be one of the big issues being addressed as the health consequences of such are devastating. Sorry that in my old age I look at the people who are limited to running 50 miles/week instead of 100 miles/week as a group of self-absorbed narcissists. Every day in the clinic and the hospital I make many decisions that truly are limb threatening and life changing decisions. Eric -- if you can explain to me how you propose to decrease the risk of diabetic ulcerations with your theory, then count me in. If you tell me that it's all about the location of the STJA, then I'm on a train to a different depot. A good friend of mine will be giving a talk at Superbones East next weekend on the problem of not intervening soon enough in the prevention of diabetic ulcers. You can really count me as being on that train.

    (Only 25 more critiques to make, Eric. So stay tuned for critique #2)
    Take care,
    Daryl
     
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