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Defining Abnormal Pronation

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Brian A. Rothbart, Oct 14, 2019.

  1. Brian A. Rothbart

    Brian A. Rothbart Active Member


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    I suggest abnormal pronation is not a measurement of the degree of pronation, but the timing of pronation in stance phase:

    Gravity Drive (abnormal) Pronation vs Hip Drive (normal) Pronation

    Gravity Drive Pronation - Timing of the foot's Pronation/Supination is determined by gravity acting on the foot's structure
    Gravity Drive: Gravity pulls the foot inward and downward (pronates the foot) until the entire foot rests on the ground.
    Rothbarts (Primus Metatarsus Supinatus) Foot:
    • The 1st metatarsal and hallux are structurally elevated
    • At mid-stance, the body's weight in concert with gravity pulls the foot to the ground until the big toe rests on the ground
    Hip Drive Pronation - Timing of the foot's Pronation/Supination is determined by the transverse plane (internal/external) rotations of the pelvis
    Hip Drive Pronation and Normal Foot Pronation are synonymous terms
    • Internal hip rotation pronates the ipsilateral (same side) foot
    • External hip rotation supinates the ipsilateral foot

    Animations available at: http://www.iarpt.com/hip-vs-gravity-drive-pronation.html
     
  2. efuller

    efuller MVP

    If that were true, we'd never see sprained ankles. Pronation moments, or torques cause pronation. Supination moments cause supination. Depending on the location and direction of the force, ground reaction force and body weight can, at different times, cause pronation or supination.




    Dudley Morton described first ray insufficiency before you did. Root et al, described forefoot varus in the 1960's. Beware of the practitioner who names stuff after themselves.
     
  3. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Interesting comments regarding torques (rotations) and moments. But I donot follow your logic regarding sprained ankles. Possible, you could elaborate more.

    The point remains, how does one define normal vs abnormal pronation, normal vs abnormal supination. Close and Inman were among earlier researchers that demonstrated the link between transverse plane oscillations of the pelvis and motion in the foot. This is where the concept of hip drive pronation originated.

    My work with the Primus Metatarsus Supinatus and PreClinical Clubfoot Deformities led to the concept of gravity drive pronation (gDP) . On my research site you can see an example of gDP: http://www.iarpt.com/gait-analysis-hip-drive-vs-gravity-drive.html

    Regarding forefoot varus, from an embryological point of view, this foot structure cannot exist. That discussion would be best served on another post, but if one is interested, I have provided a great deal of information on this subject at http://www.iarpt.com/foot-embryology.html

    Dudley Morton's foot is a short second metatarsal, the Primus Metatarsus Supinatus is not a short second metatarsal. It is a structurally elevated and inverted medial column (talus, navicular, medial cuneiform, first metatarsal and adjoining phalanges). Again this discussion would be best served on another blog, but the basics can be accessed here http://www.iarpt.com/rothbarts-foot.html

    cheers,
    Professor Rothbart
     
  4. Brian A. Rothbart

    Brian A. Rothbart Active Member

  5. efuller

    efuller MVP

    It appears that you are claiming that gravity causes pronation. Gravity also causes supination and supination is required for sprained ankles. One can use the location of the center of pressure of ground reaction force and the location of the STJ axis to determine the direction (supination or pronation) of moment from ground reaction force.


    It appears you are saying that the Rothbart foot cannot exist. How does the Rothbart foot differ from what Root Orien and Weed described as the forefoot varus foot?

    No, the Morton's foot is a short first metatarsal. You can google it. Where are you a professor?
     
  6. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Morton's foot is a short 1st metatarsal, sorry for the typo.

    In both the Primus Metatarsus Supinatus and PreClinical Clubfoot Deformity, gravity pulls the elevated medial column to the ground, e.g., Gravity Drive Pronation.

    You wrote: One can use the location of the center of pressure of ground reaction force and the location of the STJ axis to determine the direction (supination or pronation) of moment from ground reaction force.

    Very pedantic, kindly describe this in more detail.

    You wrote: It appears you are saying that the Rothbart foot cannot exist.

    No, what I said is that Foot Varum does not exist. I thought this was almost universally accepted by DPMs. Apparently, not. Instead of rehashing this subject, I refer you to Kidd's excellent paper - Kidd R 1997. Forefoot Varus - Real or False, Fact or Fantasy. Australian Jour Pod Med; 31(3).
     
  7. efuller

    efuller MVP

    Briefly, the center of pressure is the average point of ground reaction force on the foot. This point can be considered the point of application of ground reaction force in terms of moments created around the axes of the foot. When this force is lateral to the axis ground reaction force will cause pronation. For more info see Center of pressure and its theoretical relationship to foot pathology.
    Fuller EA.J Am Podiatr Med Assoc. 1999 Jun;89(6):278-91.

    The upward force from the ground lateral to the STJ axis with any lever arm at all will create a much greater moment than the force of gravity acting on the first ray.




    The description of how the forefoot varus foot behaves and the how the rothbart foot behaves is almost identical. What is the difference between rothbart foot and forefoot varus?

    So how is the rothbart foot different from the Morton foot?
     
  8. Brian A. Rothbart

    Brian A. Rothbart Active Member

    You wrote: The description of how the forefoot varus foot behaves and the how the rothbart foot behaves is almost identical. What is the difference between rothbart foot and forefoot varus?

    From an embryological point of view, forefoot varus can not exist. If you want to go into the details of foot embryogeneis which would explain the impossibility of this hypothetical foot construct, I would be happy to do so, but on another thread. Start that discussion and we can proceed.

    You wrote: So how is the rothbart foot different from the Morton foot?

    Mortons Foot: The 1st metatarsal is shorter than the second metatarsal, but not elevated or inverted (e.g., in supinatus)

    Metatarsus Primus Supinatus: The entire embryological medial column of the foot, starting from the head of the talus, and extending the entire length of the column to the hallux, is in supinatus. This places the first metatarsal in an elevated (elevatus) and inverted (invertus) position when the subtalar joint is placed into joint congruity. The first metatarsal is not short.

    So succinctly, the 1st metatarsal is in supinatus (elevated and inverted), but not shortened.

    I have written in more detail about this foot structure on my research website: http://www.iarpt.com/rothbarts-foot.html

    Cheers,
    Professor Rothbart
     
  9. scotfoot

    scotfoot Well-Known Member

    Abnormal pronation - occurs during gait when a foot pronates to a position from which it cannot adequately supinate during the later stages of gait to allow optimal push off ?

    A bit like going so deep in squat that you can't get out of the position . The solution ? Perhaps a medial arch support or strengthening of the arch muscles or both . A medial arch support , supplied by an appropriately qualified individual , is likely the most effective solution especially for those who have become overweight ( or , going back to the squat analogy , those who have ended up squating with to much weight on the bar ).
     
  10. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Hi Gerrard,

    I appreciate you joining the discussion. Your comments are well taken and I agree. If pronation proceeds past a certain point in the gait cycle, the foot will be unable to recover (your analogy of a deep squat is very appropriate).

    My intent in this discussion was to arrive at a definition of normal and abnormal pronation that we are can agree upon. I have suggested the following definitions:
    • Normal pronation is where the timing of the foot's pronation pattern is determined by the transverse plane (internal/external) rotations of the pelvis. This is referred to as Hip Drive Pronation
    • Abnormal pronation is where the timing of the foot's pronation pattern is determined by gravity acting on the foot's structure. This is referred to as Gravity Drive Pronation.
    Your comments above dovetail with Gravity Drive Pronation

    On my research website I have provided more detailed information – see http://www.iarpt.com/hip-vs-gravity-drive-pronation.html

    Comments?
    Brian
     
  11. scotfoot

    scotfoot Well-Known Member

    Hi Brian ,
    Let me start by saying I am not a podiatrist but that I do have a keen interest in biomechanics in general , and in foot and ankle biomechanics in particular .

    Re the terms "Hip Drive Pronation" and "Gravity Driven Pronation " I think I may agree , at least in part , with what you are saying .

    My understanding of pronation is that it is initiated with hip drive (motion in the transverse plane where the shank of the leg moves relative to the foot ) .This causes an unlocking of the midtarsal bones and then , in the normal course of events , the plantar ligaments ,plantar fascia and tibialis posterior help to prevent further excessive pronation caused by gravity acting on body mass .

    Excessive body mass may result in ground reaction forces which exceed the competence of the structures of the medial arch of the foot causing overpronation . This would place the foot in a position from which it might not be able to adequately supinate , into a rigid structure ,in time for push off .

    I would say that , in cases were overpronation is caused as a result excessive body mass , the degree of pronation and its timing are linked .

    But what you are saying is that the initial hip driven pronation occurs earlier in stance than gravity driven pronation and so the foot has longer to recover into supination ?

    Perhaps one could say that hip driven pronation is the key which unlocks the midfoot and allows gravity driven pronation to disparate forces and store energy. Thus hip driven pronation is always followed by gravity driven pronation .
     
  12. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Hi Gerrard,

    Yes, hip drive pronation is driven by the transverse oscillations of the pelvis. It also drives the supination of the foot during midstance to heel lift (effectively making the foot a rigid lever in preparation for heel lift).

    Go to http://www.iarpt.com/normal--hip-drive--pronation.html On this webpage I have provided a detailed explanation of normal pronation (e.g., hip drive pronation) as seen (in what I term) the plantargrade foot.

    These fortunate people typically have good posture and donot develop non traumatic musculoskeletal pain.

    Gravity drive pronation, is abnormal pronation. However, it is a symptom not a primary etiology. These unfortunate people have distorted postures and develop chronic muscle and joint pain (in many cases debilitating).

    The question is - what causes gravity drive pronation.

    In 2002 I published a paper on two abnormal inherited foot structure previously unrecognized (still hotly contested by many of my compeers). I termed these inherited abnormal foot structures Primus Metatarsus Supinatus (PMS) and the PreClinical Clubfoot Deformtiy (PCFD). Both of these abnormal foot structures result in Gravity Drive Pronation.

    On this webpage I describe how this occurs in the PMS - http://www.iarpt.com/abnormal-pronation-observed-in-rothbarts-foot.html

    On this webpage, I describe how this occurs in the PCFD - http://www.iarpt.com/preclinical-clubfoot-deformity.html

    The specific pattern of pronation/supination in these two foot structures are not identical, but they both are classified as Gravity Drive Pronation.

    Understand, all that I have written above is still hotly debated/contested. I have started this discussion simply stating, here is my research, your input is welcomed.

    cheers,
    Brian
     
  13. scotfoot

    scotfoot Well-Known Member

    If you can get glut/hip driven unlocking of the midfoot with subsequent gravity driven pronation , can it work the other way ? That is , can you use the gluteal muscles to keep the midfoot locked and so prevent gravity driven pronation . Actually , you probably can .

    When performing squats or dead lifts I was always taught to squeeze the glutes together . This prevents the knees from adopting a valgus position under heavy load .I now see that will also cause the feet to have a tendency towards external rotation , keeping the midfoot locked and resistant to gravity driven pronation . So we have hip driven supination resisting gravity driven pronation .

    In the world of track and field hammer throwers adopt a basic position , during entry into turns , where the the toes are turned out , the spine is vertical and the athletes look somewhat bowlegged . This is a very stable position from which to apply and resist forces . Some hammer coaches teach the position using the following cue ;" Imagine that you are sitting down and trying to pick up a pencil with your butt cheeks " .

    Quite earthy but it seems work !

    Gerry
     
  14. Brian A. Rothbart

    Brian A. Rothbart Active Member

    You can definitely used your pelvic floor muscles (including your gluts) to temporarily diminish the impact gravity drive pronation has on performance. However, it is fatiguing when done for protracted periods of time.

    It is must easier (and with no effort) to use the appropriate proprioceptive insole to normalize gravity drive pronation. (Note, if the wrong proprioceptive insole is used, it can exacerbate gravity drive pronation).

    Using the appropriate proprioceptive insoles in competitive sports dramatically improves performance. Take a look at this page showing the change in power lifting - http://www.iarpt.com/power-lifting.html

    Brian
     
  15. scotfoot

    scotfoot Well-Known Member

    Brian ,
    Wouldn't the accuracy of propriocepive information coming from the foot be at its optimum in a barefooted situation , or as close to it as you can get ? As far as I am aware Eddie Hall holds the world record for the deadlift and this was set wearing nothing more on his feet than a pair of socks .

    Having said that , textured insoles (proprioceptive insoles ) , seem to improve postural sway in shod individuals .
     
  16. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Yes, the accuracy of the proprioceptive information (signal) would be optimal in a barefooted situation. But not very practical if you need to use the insoles all day long.
    That is why we are so concerned with shoes. An analogy would be constructing a well built home (proprioceptive insole) on quicksand (inside unstable shoes). In both cases the results would be less then optimal.

    The following webpage demonstrates the impact improper (biomechanically dysfunctional) shoes have on the proprioceptive signal being sent to the cerebellum. Unstable shoes can negate the effectiveness of the proprioceptive insoles and in many cases actually increase the patient's postural distortion. Axiomatically, as their posture destabilizes, their chronic muscle and joint pain increases.
    http://www.iarpt.com/shoes---importance-in-therapy.html


    Re Eddie Hall, I watched him deadlifting 463kg. His foot mechanics was excellent, no indication of gravity drive pronation - no need for using proprioceptive insoles. (or, he may be overusing his pelvic muscles to prevent gravity drive pronation from engaging)



    In his case (assuming he is blessed with hip drive pronation), when deadlifting 1000 lbs, he would do better wearing only socks. This eliminates the possibility of shoe dysfunction while lifting.
     
    Last edited: Oct 20, 2019
  17. Dananberg

    Dananberg Active Member

     
  18. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Hi Howard,

    Once the heel leaves the transverse plane (e.g., at heel lift), you are no longer in gravity drive pronation. The windlass mechanism is engaged.

    To recapitulate -

    Gravity drive pronation (which distorts the proprioceptive signal to the cerebellum) is only engaged while the entire plantar surface of the foot is on the transverse plane.

    Once the heel leaves the transverse plane (e.g., heel lift), the proprioceptive signal to the cerebellum is disengaged.

    Brian
     
  19. efuller

    efuller MVP

    The "unlocking theory" comes from very weak research and should not be used. (Eye of the connoisseur, rather than actual measurements were used for the basis of the research. The 1983 Van Langaalan paper gave a good explanation of why the "research" behind the unlocking paper should not be used.)

    If the hip were to drive pronation, the hip would have to attempt to move the lower leg internally relative to the foot. How does this happen?

    A better explanation of why the foot pronates after heel contact is that ground reaction force on the lateral forefoot creates a pronation moment at the STJ. Try pushing upward on the lateral side of the foot and see what happens at the STJ. Look at some pressure distribution roll over processes. You will see force on the lateral forefoot before you see force on the medial forefoot.
     
  20. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Hi Howard,

    Let me expand on my last response. The term pathologic pronation/supination, to a practitioner working in the field of Posturology, translates into what motion (pronation/supination) distorts the proprioceptive signal to the cerebellum.

    Current research suggests that the proprioceptive signal being sent from the foot to the cerebellum is only engaged while the entire plantar surface of the foot is on the ground. The foot signal to the cerebellum is not engaged at heel contact, becomes engaged at flat foot stance phase and then disengages at heel lift. (This insight comes from current research into neural activity using qEEG analysis).

    This being said and conditionally accepted, the Posturologist evaluates the patterns of stimulation (proprioceptive signals) generated during this interval of stance phase. And it is during this exact interval of stance phase that gravity drive pronation engages and distorts these patterns of stimulation.

    A maxim in looking at this link between the foot and cerebellum is that Hip Drive Pronation results in a non-distorted proprioceptive signal to the cerebellum (the body is just hardwired that way). And that gravity drive pronation always distorts the proprioceptive signal to the cerebellum.

    Keep in mind, gravity drive pronation is a symptom, not a primary etiology. One must determine the abnormal foot structure that results in gravity drive pronation. On my research website (http://www.IARPT.com) I discuss two abnormal inherited foot structures that result in gravity drive pronation - the Primus Metatarsus Supinatus foot and the PreClinical Clubfoot Deformity. The distorted proprioceptive signals differs between these two foot structures; however, both result in a postural distortions.

    Brian
     
    Last edited: Oct 21, 2019
  21. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Regarding the unlocking theory, in Posturology this is not relevant.

    One can easily demonstrate hip drive pronation: (If they have either a PreClinical Clubfoot Deformity or Primus Metatarsus Supinatus foot structure, this maneuver will be obfuscated)
    • Standing, rotate your pelvis counterclockwise. The right foot automatically pronates.
    • Then rotate your pelvis clockwise, the right foot automatically supinates.

    Inman and Close were one of the first to write about this pelvis to foot link. In 1988 I wrote more about it (Rothbart BA, Esterbrook L, 1988. Excessive Pronation: A Major Biomechanical Determinant in the Development of Chondromalacia and Pelvic Lists. Journal Manipulative Physiologic Therapeutics 11(5): 373-379.) and later termed it Hip Drive Pronation

    Your suggestion regarding a ground force on the lateral forefoot creating a pronatory moment at the STJ is duly noted. I know this commonly stated on the Podiatry forum; however, I just do not agree with it.
    • When either the PreClinical Clubfoot Deformity or the Primus Metatarsus Supinatus foot structure is present gravity drive pronation is engaged.
    • In a plantargrade foot, hip drive pronation is engaged.
    Regarding hip drive pronation moving the lower leg internally relative to the foot, I do not follow you. Can you expand upon this?

    Brian
     
  22. efuller

    efuller MVP

    Brian, It appears you are saying that gravity stops when the heel lifts off of the ground. If you meant something different, please explain.

    Also the windlass mechanism can be supporting the foot before heel lift. In some feet you can palpate a tight plantar fascia with the heel on the ground. What do you mean by the windlass engaging?
     
  23. Dananberg

    Dananberg Active Member

    Brian,

    You’ve accomplished the impossible....making Eric and I agree! Gravity continues to act throughout the step, and the effect multiplies as body weight is raised and advanced during the 2nd half of single support. The Windlass begins to engage when the calcaneus starts to unweight following peak heel load. Your explanation does not match the timing of the events taking place during the step

    Howard
     
  24. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Howard,

    You said that my explanation does not match the timing of the events taking place during the step. Kindly be more specific. What exactly does not match?

    Is it you disagree with the construct of Hip Drive Pronation?

    Or do you disagree with the construct of Gravity Drive Pronation?

    And if so, exactly why do you disagree with either of these two constructs?

    Brian
     
  25. efuller

    efuller MVP

    Standing, rotation of the pelvis counter clockwise, (looking from above) does not automatically cause pronation of the right foot. The usual, but flawed, theory is that the hip has a solid connection to the femur, which has a solid connection to the tibia, which has a solid connection to the talus and when the hip rotates all the other bones rotate when the foot is held in place by its contact with the ground so the leg will cause internal rotation of the talus which is a component of STJ pronation. The flaw with this theory is that there is not a solid connection. The hip can rotate on top of the femur without causing the femur to rotate. When you palpate the extrinsic foot muscle tendons of people rotating their hips you will see the peroneal muscles get tight and that is what is causing the pronation and not the hip rotation.

    Brian, when do see the pelvis rotate counter clockwise in gait when the right foot is on the floor? When are you saying that hip drive pronation occurs?
     
  26. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Totally disagree.

    The link between the pelvis and foot, as described by Inman and Close is observable and demonstrable. And it is this straight forward link that is the basis for understanding Hip Drive Pronation.
     
  27. Dananberg

    Dananberg Active Member

    Brian,

    What I disagree with is the timing. Pronation at heel strike is normal, and coincides with internal hip rotation. However, pronation in the 2nd half of stance phase is a separate event and well known to be pathologic. How is either hip or gravity pronation linked to this late stance phase?

    While gravity plays a significant role, it is far more related to lifting body weight than contacting the ground. The stress of trying to lift body weight and simultaneously advance beyond the planted foot in the 2nd half of stance coordinates with the late phase pathologic pronation event.

    In the late 70's, I had the pleasure of hearing James Ganley, DPM give a lecture in which he described a series of dissections he performed on deceased patients with severely pronated feet. The comment that shook my biomechanical foundation was that he found that the calcaneus could NOT evert beyond zero degrees! After pondering this for several years, I eventually came to understand that pathologic pronation was not impact related but instead a failure to effectively lift body weight. The fulcrum the body requires to lift and advance in single limb support is the MTP joints (think of the wheel on a wheel barrow). And not only does this action occur, but when properly active, engages the Windlass. The issue is that this joint does not necessarily rotate in a timely fashion....and timing is everything.

    When I initially described Functional hallux limitus as a contibutor to pathologic pronation in the early 80's, the error I made was making the hallux the focus. What I have come to better understand is that once the hallux touches the ground, it does not move again until toeoff. The restriction to movement is in the metatarsals and proximal structures, not the hallux. When the metatarsals cannot rotate through the sagittal plane, counter rotation occurs across the midtarsal joints, with visible arch lowering resulting. (There are postural accommodations as well but for another discussion.) Since the entire limb above the foot is dependent on midfoot support to maintain its positioning, lowering of the MLA results in a falling of body weight. This is what we see in late phase pronation.

    Trust that this explains my comments.

    Howard
     
  28. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Howard,

    Yes, your explanation explains your comments.

    Below I have addressed your query regarding how I view hip drive and gravity drive during late stance phase. I only ask you to temporarily suspend your belief system in order to follow my logic (I am not asking you to agree with me):

    Hip Drive Pronation follows Inman and Close’s paradigm, namely in the absence of pathology (a structurally or functionally unstable foot), the pelvis directs the motion in the foot (pronation/supination) from heel contact to heel lift. And we use this pattern of motion in stance phase as the normative. Any deviation from this pattern of motion we consider aberrant.

    When you observe an aberrant movement during stance phase (which is a symptom, not a primary etiology), one must determine the etiology behind that aberrant gait pattern.
    Now for the sake of this discussion, I ask that you to (1) entertain (not accept) the paradigm of Gravity Drive Pronation and (2) entertain the existence of the Primus Metatarsus Supinatus foot structure.

    What I am suggesting is that the PMS foot structure engages/forces the foot into Gravity Drive Pronation. The reason is apparent when one visualizes the ontogenetic retention of supinatus in the PMS foot structure. The entire embryological medial column of the foot is in supinatus (structurally elevated and inverted relative to the embryological lateral column of the foot).

    Treadmill analysis of the PMS foot structure: At flat foot, Gravity pulls medial column of the PMS foot downwards (pronation at the STJ) until the entire plantar surface of the foot rests on the ground. That is where the pathologic foot motion commences, at flatfoot, e.g., heel contact is not pathologic.

    You can view a treadmill example of the PMS at:
    http://www.iarpt.com/gait-analysis--rfs-.html

    I realize this is very different from how many view foot mechanics, but it is how I view it. Whether I am right or wrong, time will time.

    Brian
     
  29. Dananberg

    Dananberg Active Member

    Brian,

    The part I have considerable trouble with is your assumption that forefoot supinatus as a fixed osseous deformity ultimately being responsible for contact pronation. This is inherently incorrect. I have been able to reduce this with a simple midfoot manipulation and have done this countless times. Elevation of the 1st ray is most commonly due to inhibition of the peroneus longus and/or in combination with Functional hallux limitus. Using 1st ray orthotic cutouts and TN joint manipulation are highly effective in resolving these issues rather quickly and permenently. Your posting concepts make no sense to my way of thinking, and seem actually quite detrimental to normal foot function. I can still recall your telling me many years ago how multiple times/year, patients ended up in the hospital in acute muscle spasm following extreme 1st ray posting. In the thousands and thousands of orthotics I dispensed over my career, this NEVER happened even once. The tennent of the Hippocratic oath of "above all, do no harm", is something I have always taken very seriously. In keeping with this view of medical practice, I cannot condone or accept your principles of foot mechanics, no matter how determined you are to dress them up with new terms. I do wish you well in the future, but cannot accept the erroneous principles which you have described.

    This will be my last posting on this topic.

    Howard
     
  30. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Howard,

    Let's agree to disagree.

    What you have successfully manipulated so many times in your practice, is as you describe, a functional hallux limitus due to a contracture deformity. That is an entirely different 'animal' then the PMS foot structure, which is an osseous deformity

    From an embryological perspective, PMS is simply a very mild Clubfoot deformity without the calcaneal supinatus. If you deny the existence of PMS, you are denying the existence of the Clubfoot Deformity.

    I do not ask you to accept my paradigms, nor can you expect me to accept yours. The only thing that we should expect from each other is civility and professionalism.

    And finally, We all took the Hippocratic oath when we graduated. And we all take that oath very seriously, the first tenant being, do no harm. And fortunately, I can stand on my many years of clinical practice knowing I have kept to that oath.

    with regards,
    Brian
     
  31. AtomAnt

    AtomAnt Active Member

  32. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Interesting paper. What is your slant on it?
     
  33. Brian A. Rothbart

    Brian A. Rothbart Active Member

    The reason I find Nigg's review so relevant, is he breached the same subject - namely, how can we talk about 'pathologic pronation' (as Howard called it) when we do not have a working definition of 'normal' pronation.

    Is it reasonable to adopt Hip Drive Pronation as the accepted definition of normal pronation?

    If so, we can then agree upon what is abnormal pronation (which I suggest is Gravity Drive Pronation).
     
  34. scotfoot

    scotfoot Well-Known Member

    Brian ,
    Would you agree that push off from the contralateral foot helps prevent over pronation in the reference foot during walking . That is , the push off phase helps move the center of mass from between the two feet to immediately above the talonavicular joint in the reference foot ?

    A recent experiment (Farris et al , see below ) has shown that with a tibial nerve block to prevent the contraction of the foot intrinsics , push off could not be fully completed during gait and that participants adopted a shorter stride pattern and increased hip muscle activity .

    My interpretation of these changes in motor strategy is that through executive function , the body quickly adapts to loss of push off force and hence incomplete shifting of the COM in the transverse plane during gait , by adopting a shorter stride and using abnormal hip activity .

    During gait , if the COM cannot be moved from between the feet to over the foot with each stride , then gravity driven pronation will be a problem .

    In short , intrinsic foot muscle deficits lead to abnormal gait and ,in my opinion , possibly to pathological pronation .



    The functional importance of human foot muscles for bipedal ...


    https://www.pnas.org › content

    by DJ Farris - ‎2019 - ‎Cited by 12 - ‎Related articles17 Jan 2019 - Contrary to expectations, the intrinsic foot muscles contribute minimally to supporting the arch of the foot during walking and running. However, these muscles do ...
     
    Last edited: Oct 24, 2019
  35. scotfoot

    scotfoot Well-Known Member

    Question ; If deficits in the intrinsics can impair push off and so alter gait , can such deficits also cause problems during weight shifting , the most common time for the elderly to suffer falls ?
    If an older person wishes to shift weight but lacks push off power then might a more difficult to control " lean/sway strategy " be employed ?

    Interesting .
     
  36. efuller

    efuller MVP

    No, it is not reasonable. The hip is a joint and cannot cause motion. What are you saying causes a pronation moment at the STJ? Sorry to be pedantic, but if you want define something you should be clear.
     
  37. Brian A. Rothbart

    Brian A. Rothbart Active Member

    Hi Gerald,
    Your questions regarding compensations resulting from muscle dysfunction are well taken, and would be best discussed on another thread.

    It was my intent to reach a consensus on the definitions of normal pronation and abnormal pronation.

    Hopefully more input will be forthcoming.
     
  38. scotfoot

    scotfoot Well-Known Member

    Intrinsic muscle function . Difficult to assess over the phone /internet .
     
  39. efuller

    efuller MVP

    Why do you want to reach a consensus? This is not something to vote on. If you want to believe the pelvis, the hip joint, or the femur somehow cause pronation of the STJ, then you should produce evidence for this. Are you familiar with Winter's work on joint powers? Those kinds of measurements would produce this evidence.
     
  40. Dananberg

    Dananberg Active Member

    Aside for affecting the intrinsics, a tibial nerve block causes anesthesia of the plantar foot as well. It is well known in neuroscience that during periods of instability, humans increase double support phase and decrease single support. A numb foot is clearly a cause of instability. So the decrease in push off has varied causes and may not be at all related to intrinsic muscle failure.

    Howard
     
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