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Foot casting with vertical calcaneum

Discussion in 'General Issues and Discussion Forum' started by nicholas, Oct 25, 2005.

  1. nicholas

    nicholas Member

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    Can any one please give me some advice about the school of thought that says that the foot is supposed to function in a pronated position. I have recently been talking to a podiatrist of many years experience that says that he doesn't believe in the stj neutral theory when he is casting for orthotics, he tells me that he feels that the foot functions normally in a position that remains pronated throughout the gait cycle and therefore when he casts he always does so from a position of the calcaneum in a vertcal position even if the neutral position of the stj is varus.

    Now, from my understanding of foot function the purpose of the use of orthoses is to hold the foot in such a position as to ensure that the stj is in a neutral position at midstance so as to enable the foot to be in the optimum position to resupinate prior to propulsion. My confusion regarding casting in the vertical position is that if, for example, the calcaneum has a neutral position of 10 degrees varus when in neutral, then casting in the vertical position would effectively place the stj 10 everted and therefore still pronated at midstance. To my mind this would be the same as late stage pronation with the resulting unlocking of the mid tarsal joint, dorsiflexion of the 1st ray, functional hallux limitus and loss if Hicks windlass mechanism and result in the pathologies that are usually seen in the pronating type of foot. My question is therefore, how can this be an appropriate way to cast the foot if the aim of orthoses are to re establish the sequence of events occuring in the gain cycle in order to make the foot function correctly. Cheers, Nick ( the rookie, still green, and wet behind the ears podiatrist) any advice appreciated.
  2. pgcarter

    pgcarter Well-Known Member

    I think we need to get past thinking that we are trying to hold the foot in a particular position, we are trying to give it a position that it can move into and out of without developing pathology over time.....efficiency, or we are trying to modify symptoms by changing the balance of forces at work in the chain.

    What may need to be done will vary so much from case to case that while I enjoy discussions of theory and ideas...I actually believe that they are of limited clinical value, because no one paradigm will be applicable in all situations......first choose the right theory for a particular foot and if none of them seem right you still need to get on with your job.
    Many different ideas have some merit and are useful in some cases.
    Regards Phill
  3. Craig Payne

    Craig Payne Moderator

    1. We now know that when you cast a foot with the calcaneus vertical (or in whatever position) and add a rearfoot post to hold it at that angle, the calcaneus does not actually get held in that position.

    2. We now know that it does not matter where the calcaneus is held by the foot orthoses, it actually has no relationship to clincal outcomes.
  4. First of all, while it is true that most feet function in a pronated position, this does not mean that Root's ideal of the "normal feet" is the same thing as "most feet" or as "average feet" or as "asymptomatic feet". The studies that I am aware of that have concluded that the "normal foot" functions in the STJ pronated position have serious flaws associated with them. First of all, they have not been conducted on Root "normal" feet, but rather on feet that were asymptomatic, that had no previous serious injuries and had no previous foot surgery and were generally very young feet. Root "foot deformities" were not considered in determining whether these feet were "normal" or "abnormal".

    Secondly, since the determination of STJ neutral is so variable from one clinician to another, then how a clinician/researcher determines STJ neutral position has a huge effect on any conclusions drawn from the research.

    For example, let's say that Clinician/Researcher A tended to determine STJ neutral to be, on average, 4 degrees more supinated than did Clinician/Researcher B in each foot examined. Then, both clinicians experimentally measure the STJ rotational position during the middle of midstance phase of gait of the same 100 young asymptomatic subjects. How would you expect the conclusions of Clinician/Researcher A and Clinician/Reseracher B to differ?

    What you would probably see is that Clinician/Researcher A claims "the normal foot functions during the middle of midstance in a STJ position that is 3 degrees pronated from neutral position" and, for the same 100 subjects, Clinician/Researcher B would declare "the normal foot functions during the middle of midstance in a STJ position that is 1 degree supinated from neutral position". Now you may see why the bias of the researcher in how they determine STJ neutral position may greatly affect their experimental results when they attempt to determine the rotational position of the STJ joint during gait in a group of subjects.

    I have been personally told by the physical therapist researcher that published the research claiming that feet functioned in a STJ pronated position that he learned how to determine STJ neutral position from a single podiatrist in private practice. This certainly worries me since I have seen other well-trained podiatrists and I determine STJ neutral position to be sometimes 5 degrees from each other.

    I therefore wouldn't take this research too seriously since, I believe, it is inherently flawed due to the known interindividual measurement error associated with determining STJ neutral position and also not making any attempt to exclude Root abnormal structural feet from the study group.

    The goal of orthosis therapy should not be to try and get the foot to necessarily function in the STJ neutral position as is currently still taught at most podiatry schools.

    The goal of foot orthosis therapy is three-fold:

    1. Reduce the pathological stresses on the injured structural components of the foot and lower extremity so that more rapid healing of the injured structure may occur.

    2. Optimize gait function for that individual's specific structural characteristics.

    3. Cause no other gait pathologies or symptoms to occur.

    (Kirby KA: Goals of Foot Orthosis Therapy. February 1999 Precision Intricast Newsletter. In Kirby KA.: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 3-4.)
  5. GarethNZ

    GarethNZ Active Member

    Correct, not in the exact position, but the foot can get closer to the intended position!?

    What evidence are you referring to? The study/ies that you conducted with regard to Plantar fasciitis showed this result (from memory), which is similar to what we are seeing in clinical setting. Are you suggesting that the same is the case for other conditions?
  6. Craig Payne

    Craig Payne Moderator

    Thats not what we found. Subjects had RCSP and NCSP measured by 2 clinicians and mean value used. Then they were casted in STJN and polyrop orths made with a rearfoot post added to hold positive cast in NCSP. When subjects stood on the orthoses, they were closer to RSCP than NCSP (its 'in press')
    We have just submited this. We measured changes in rearfoot motion pattern in those with and without foot orthoses if they had symptoms due to "pronation" (most were plantar fasciitis) - this change was correlated to symptom changes at 4 weeks --> there was no correlation.
    Last edited: Oct 26, 2005
  7. nicholas

    nicholas Member

    Kevin, can you please explain to me how if 2 clinicians, A and B both measured stjn position and A recorded this position on average to be 4 degrees more supinated than B, why would the stj rotational position of A be 3 degrees pronated from the neutral position and B be 1 degree supinated from the neutral at midstance.
  8. GarethNZ

    GarethNZ Active Member

    I am/as will everybody else interested in biomechanics, be looking forward to reading your research paper. Which journal should we be looking in and when?

    When you take a STJ neutral cast, in most cases if the foot as good ROM, it may appear reasonably close to neutral when the positive cast is sitting on the bench in the lab. Your saying that the positve cast was balanced to it's NCSP? How often does any clincian try to post the orthotic to NCSP. I am a novice in the research area, and it may mean that there is little reliability, but would you not be better to post to the required prescription to control reduce the symptoms and then measure whether there has been a change. Use the STJ axis and supination resistance theories to effectively control the foot. I would expect if the NCSP and the RCSP were similar and the posting amount was minor then you would not expect there to be a change and in your suggestion (which I do believe) it should be closer to the RCSP.

    Wasn't there an article that suggested that the RCSP showed no relationship to the rearfoot position during gait? Most of the time we are providing treatment for people that are moving and not just standing? (Well some maybe standing while at work!)

    I am interested to see this research too...

    We to in Christchurch, New Zealand have been using softer EVA orthotics with minimal, soft EVA postings and finding that the excessively pronated foot is still responding to softness rather that firmer control. We almost see is as a crime to cast and prescribe a semi-rigid device as a first line of treatment for any proximal plantar fasciitis.
  9. To explain this more clearly, let's say that the subtalar joint (STJ) has 30 degrees of total range of motion (ROM). However, instead of using STJ neutral position (np) as our frame of reference to indicate where the STJ is positioned within its ROM (i.e. its rotational position), I will define that the maximally pronated STJ position is +0 degrees, and the maximally supinated position is +30 degrees, with thirty equally spaced one degree increments from the maximally pronated to the maximally supinated position of the STJ.

    Now, as stated in my previous posting, Clinician A will tend to measure the STJ neutral position 4 degrees more supinated than Clinician B. Therefore, for a given foot, Clinician A may measure the STJ neutral position at +13 degrees and Clinician B may measure the STJ neutral positon at +9 degrees (i.e. +13 degrees is 4 degrees more supinated than +9 degrees by the convention I established above).

    These clinicians next measure the mean STJ rotational position during the midstance phase of gait in 100 subjects to be at +10 degrees, even though, instead of using my convention above, they are using the STJ np as their frame of reference, rather than the ends of range of motion of the STJ. Clinician A determines that the feet are 3 degrees pronated from their STJ np of +13 degrees and then claims "feet during midstance do not follow the teachings of Root since they are pronated from STJ np in the middle of midstance". On the other hand, Clinician B determines that the feet are 1 degree supinated from their STJ np of +9 degrees and then claims "feet are supinated one degree from STJ np in the middle of midstance".

    Do you see now how communicating STJ np as a reference, whether in a experiment in a journal or in clinical conversations may, in fact, be a relatively futile exercise unless you are absolutely sure that the researcher or clinician you are communicating with determines STJ neutral position in all subjects exactly the way that you do????

    Therefore, Nicholas, don't get too worried about research that claims that STJ np was not achieved during gait unless you are absolutely certain how the researcher determined STJ np in his experimental subjects.
  10. Philip Clayton

    Philip Clayton Active Member

    Max pronation & supination of stj

    From my experience with students just measuring the ROM of the STJ proves problematic for some people. I am assuming that these measurements to have any value in practise will be taken generally by one operator, in which case their personal strength has a bearing. I have found that people with stronger grips can rotate the foot to greater angles and also have a better ability to hold the foot steady in this position whilst measuring. This also assumes that they are able to sub-divide the calcaneus and lower third of the leg. As always the old methods just create a whole plethera of variables, leading to the obvious critisisms of inaccuracy and meaningless measurements. I am not sure how best to progress but there are some measurements that can be repeatable, which is after all what the scientific community would expect outside of Podiatry.

    1. The height of the navicular and other such markers static or moving.

    2. The pressures measured at certain points of the gait cycle, i.e. heel strike.

    3. The degree of stiffness (once Kevin provides us with one of his inventions!)

    What we need to get away from are the UN-REPEATABLES, yes? No?

    Craig, I have also seen patients stand on quite high medial rearfoot posts and just slide to the RCSP especially one rather large 25 stone student! I suppose that they probably need high Kirby scives. Although curiously forefoot posts seem to hold the foot nearer to the NCSP in these extreme patients (standing), but I am sure that on a previous thread you said you don't post the forefoot medially anymore? :)
  11. Berms

    Berms Active Member

    Craig, could this finding be due to the orthotics not adequately controlling the foot, therefore allowing the foot to pronate (heel to evert) on the devices giving the impression that there is no correlation between rearfoot posts and calcaneal position :confused:
  12. Craig Payne

    Craig Payne Moderator

    The orthoses held the positive plaster cast to the prescribed NCSP when cast placed on orthoses --- so they worked like the textbook said they should - they just did not hold the live foot in the same position they held the cast .... could be for any number of reasons.
  13. Berms

    Berms Active Member

    NCSP and orthoses

    Thanks for your feedback Craig, all very interesting stuff... and its great to see research coming out of the Uni that challenges the way we think about the things we do everyday in our practice. :)

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