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Question about measuring hyperpronation

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Kelsey, Nov 7, 2005.

  1. Kelsey

    Kelsey Member


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    I have a question about experiments involving measurements of hyperpronation. I know taking the calcaneal bisection and measuring it in neutral and relaxed position, but that can be highly variable and subject to the experimenter. How does anyone quantify hyperpronation (has there been an established degree of eversion?)? Thanks in advance for your replies.
     
  2. davidh

    davidh Podiatry Arena Veteran

    Hi,
    To my knowledge there is no definitive (ie accepted by all) definition of hyperpronation.

    Accurately quantifying any movement of biological tissue in-vivo is, as you suggest, fraught with difficulties.

    I seem to recall a paper published some years ago (I don't have the ref, but perhaps someone else can help here) where tiny ball-bearings were inserted into bony landmarks, and resultant movement was quantified radiographically.

    This may be a good place to start your search.

    Cheers,
    davidh
     
  3. Ann PT

    Ann PT Active Member

    I wonder about the significance of measuring subtalar neutral in prone-which I always do-and relaxed calcaneal stance, which I also do. I have a patient who had subtalar joint fusions when he was young but now stands with over 10 degrees of calcaneal eversion. In prone, he appears to have no subtalar joint motion. I believe the classic school of thought is that normal eversion is 0-4 degrees.

    Ann, PT
     
  4. Craig Payne

    Craig Payne Moderator

    Articles:
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    Why do you want to do it. If its for research, what is the research question?

    Measuring the difference between NCSP & RCSP is one way of doing it, but it is problematic becasue:
    1. We used to beleive that the NCSP is the ideal position for the foot to function around - we now know that this is not the case.
    2. It only measures frontal plane motion of the posterior aspect of the calcaneus when the STJ pronates about a triplane axis (see the Brainteaser)
    3. More rearfoot pronation occurs at the MTJ's
    4. Huge reliability issues with all aspects of the measurement (ie bisecting calc; locating STJN/NCSP; etc)

    Option then is to measure navicular drop and drift and the ratio between the two (and control for foot length, depending on why you are doing it for) when the foot is in NCSP & RCSP --- this does address the midfoot part of pronation but not the other issues above.

    We have also used malleolar drift as another measure of rearfoot pronation.

    We use the Foot Posture Index as a teaching tool to teach students to look at all components of "pronation" and as a screening tool for inclusion nto a study (eg our most reacent kinematic study had an inclusion criteria of FPI>6).

    We also at the stage where we now know that the magnitude of "rearfoot pronation" is not predictive of of dynamic function and injury and changing it is not related to clinical outcomes with foot orthoses, so why bother measuring it??? Sould be measureing what actually predicts dynamic function, injury and orthoses outcomes.

    Hylton Menz's JAPMA paper is worth a read:
    Alternative techniques for the clinical assessment of foot pronation
     
  5. There are a number of problems with hyperpronation. For this reason, I avoid the word like the plague.

    First of all, "hyperpronation" was never a word used at the California College of Podiatric Medicine when I was being trained. It is a word that someone made up somewhere else since I never heard it come from the lips of Mert Root, John Weed, Chris Smith, Ron Valmassy or Rich Blake, who were a few of my instructors in biomechanics. The reason I don't like the word is because it is ambiguous and non-scientific. In other words, does "hyperpronation" mean 1) a maximally pronated subtalar joint (STJ) rotational position; 2) an excessive pronated appearance to the whole foot (e.g. like using Tony Redmond's foot posture index); 3) excessive magnitudes of STJ pronation velocity; 4) excessive magnitudes of STJ pronation moments???? I have heard it used to describe all of the above by different podiatrists. Therefore, I highly recommend discarding the terminology. By the way, any paper that I review for JAPMA or JFAS will not be accepted for publication by me if that word is used within the paper, unless the author can precisely define the word for the reader (which, so far, the author has never been able to).

    The biggest problem with "hyperpronation", especially if it is used to refer to STJ rotational position, is that the maximally pronated position of the STJ does not always cause a foot to have pronation-related pathology. For example, if the STJ is maximally pronated in a foot with a large degree of tibial varum and limited STJ range of motion, that foot will quite likely have supination-related pathology due to the relative medial position of the Achilles insertion and plantar calcaneus relative to the STJ axis (i.e. these feet will be more prone to have lateral ankle instability even though they have "hyperpronation").

    Maybe again, "hyperpronation" refers to an appearance of the foot such as the basis of the "Foot Posture Index". Again, without measuring the STJ axis spatial location and the position of the center of pressure on the plantar foot, then one will not have any idea of the direction and magnitudes of STJ moments that are acting on the foot from ground reaction force (GRF). In my opinion, determining STJ spatial location in a foot is much more indicative of whether a foot will have pronation related pathology or supination related pathology than measuring the external geometry of the foot.

    The calcaneal bisection can not be used as a predictor of foot function!!! Please, please, please, spread the word that this measurement variable has nothing to do with foot function. The calcaneal bisection should only be used as a way to determine where the STJ is within its range of motion during standing or during gait, not as an absolute measure of foot function.

    Now, in retrospect, the use and reliance of the calcaneal bisection as the main reference of biomechanical measurements by Root et al was, in my opinion, the greatest failure of their treatment theories. They never did account for the extreme variability in STJ axis spatial location caused by changes in spatial location of the talar head and neck within the foot, probably because the talar head is much more difficult to measure. Unfortunately, because of the failure of Root et al to note the correlation of talar head and neck spatial location to foot function (and therefore not understanding the significant correlation of STJ axis location to foot function) their use of the calcaneal bisection have so far prevented their measurement techniques in being able to determine the function of the foot during gait.

    I think that if I were to want to do an experiment on "hyperpronation", I would first take 50 asymptomatic subjects (100 feet), and determine where each foot was in its STJ rotational position. [Forget about the STJ neutral position since it is too variable from one examiner to another to be useful as a tool of reliable experimental measurement of the STJ rotational position (especially if you want other researchers to be able to duplicate your results).] Then put these feet in the maximally supinated position of the STJ and measure that position (while in relaxed bipedal stance). This would then give you either a number of degrees from maximally pronated or a percentage of STJ range of motion that these subjects stood in, which would serve as a good baseline for future researchers to allow us to better understand the average STJ rotational position during relaxed bipedal stance and the frequency of asymmetrical STJ rotational position during relaxed bipedal stance of asymptomatic subjects relative to their maximally pronated STJ position.
     
  6. Ann PT

    Ann PT Active Member

    Kevin,
    Referencing your third paragraph, if the STJ is "maximally pronated" does this imply calcaneal eversion in stance? If so, can you have a maximally pronated STJ and limited STJ ROM if the calcaneus is everted in stance? If an everted calcaneus is not implied, is it safe to assume "maximally pronated" refers to adduction and plantarflexion of the talus on a stable, neutral calcaneus in stance?

    Thanks,
    Ann
     
  7. Craig Payne

    Craig Payne Moderator

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    I see many maximally pronated feet in which the calc does not go past vertical
     
  8. Ann PT

    Ann PT Active Member

    I also see many feet that appear maximally pronated and have a vertical calcaneus. If defining "maximally pronated" by the talus hitting the calcaneus in the region of the sinus tarsi, and the calcaneus is not everted, then I assume the maximally pronated position is achieved by movement of the talus. I'm wondering about the patient who appears to have no subtalar movement in NWB (manually trying to invert/evert the calcaneus on a stabilized talus) but stands and achieves maximal pronation with a significant amount of calcaneal eversion...Ann
     
  9. Craig Payne

    Craig Payne Moderator

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    It all depends on were the calcaneus starts from --- eg in a tibial varum, it has to maximally pronate just to get the foot flat on the ground.
     
  10. If the STJ is maximally pronated, then the STJ is at its end range of pronation whether the lateral process of the talus abuts into the floor of the sinus tarsi of the calcaneus. This maximally pronated STJ position may either occur when the calcaneus is everted, vertical or inverted in relaxed bipedal stance, depending on the tibial frontal plane position and the amount of range of motion in the STJ.
     
  11. Ann PT

    Ann PT Active Member

    My patient has fused subtalar joints (done as a child to correct "flat feet"), no tibial varum and a large forefoot supinatus and stands with significant calcaneal eversion. Would he have been fused in eversion?? To correct overpronation?? How else would he get all this eversion if he is fused?

    Are we all saying the same thing about the relationship between maximal pronation and calcaneal eversion? If it can move to compensate for tibial varum or other forces driving pronation, it will. If it can't or the motion comes easier from somewhere else (poosibly a hypermobile midtarsal joint) then it's the talus that moves to pronate the subtalar joint. Am I correct? Ann
     
  12. " Hyperpronation " was used in the late 70's by the US east coast podiatric contingent, commercially and S.Subotnik per my recollections.
     
  13. Ann PT

    Ann PT Active Member

    Does anyone have any thoughts about my patient who has fused subtalar joints since childhood but also stands with significant calcaneal eversion? Usually I don't post a fused subtalar joint but in this case...Thanks, Ann
     
  14. Craig Payne

    Craig Payne Moderator

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    ~20 degrees inversion/eversion is usually available at ankle joint - is there any?
     
  15. Ann PT

    Ann PT Active Member

    Thank you for the reply Craig. I am not familiar with how to measure inv/ev at the ankle. Do you have a reference? If the eversion was coming from the ankle, would the calcaneus be everted 10-12 degrees as his is? That's what confuses me...assuming his subtalar joints were not fused in eversion since they were trying to correct overpronation, and when prone on the table his calcaneus is vertical bilaterally, how does he stand with so much calcaneal eversion? Thank you for your thoughts. Ann
     
  16. Craig Payne

    Craig Payne Moderator

    Articles:
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    You can't specifically measure ankle inversion/eversion --- it occurs when you think you are moving the STJ in inversion/eversion.

    I have heard a number of surgeons comment that intra-operatively when they are fusing the STJ, that they can still get reasonable amount of frontal plane inversion/eversion of the rearfoot --- it must be occuring at the ankle.

    There was a publication a few years ago in Foot & Ankle Int (I think) that showed how much the ankle inverted and everted.
     
  17. Berms

    Berms Active Member

    Ncsp

    Craig,
    I am a newcomer to this so please bear with me. You mentioned in a previous reply that:- "We used to believe that the NCSP is the ideal position for the foot to function around - we now know that this is not the case" - in relation to midstance and "hyperpronation". In practice we often attempt to fabricate orthoses to place the foot in a position as close to NCSP as possible. Could you elaborate on what the ideal position for the foot to function around is if it is not the NCSP?
    Many thanks,
    Adam
     
  18. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    I always used to do that as well - now the evidence is that it does not matter - there is no correlation to between changes in the pattern of rearfoot motion and symptom reduction. We discussed here:
    http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=214
     
  19. Kent

    Kent Active Member

    Ann,

    I'm no surgeon but I believe when they fuse the subtalar joint, the position is slightly pronated/everted.
     
  20. Cameron

    Cameron Well-Known Member

    Netizens

    The subtalar joint neutral, in relation to the stance phase of gait, is both an anathema and tautology. Each gait cycle is unique and the timing of the so called neutral subtalar position likely to occur on a time space continuum which would replicate infinity and defy simple description. The frontal plane arc of pronation to supination during stance phase prior to heel lift would prefer a supinating heel to co-ordinate with closed chain mechanics and lock the rearfoot against forefoot during late propulsion, but this is not always possible. By tilting the heel-ground interface on an inverted incline (varus wedge) the time spent in subtalar pronation may be reduced. This in turn may lessen the effects of compensatory patho-mechanics which would have an outward sign of subsiding symptoms. These effects might be amplified by exercise to tolerance and change of footwear. This is usually the podiatric experience.

    Hyper pronation is a silly meaningless term. The etymology of “hyper” means overexcited and is attested from 1942, when it was used as an abbreviation for hyperactive. The corollary of hyperactive pronation would be hypo-supination. But neither term is complete and omits both time and place which would be important as a defination.

    What seems more likely to be described is a pronated heel during late stages of propulsion.

    Cameron
    Hey, what would I know?
     
  21. efuller

    efuller MVP

    Where does it hurt?

    You may have already done this, but carefully check the position of the bone under the skin. The fat pad often moves significantly making the heel appear more everted than it actually is.

    I have heard surgeons say "thou shalt not fuse in varus." The reason for this, I feel, is to prevent lateral column overload. The lateral column appears less adaptable to imperfect position of the forefoot when the rearfoot is fused. If the foot is fused in a position where the medial forefoot would bear more weight the medial arch will tend to "adapt" and then flatten to the point where there is even weight bearig across the forefoot on level ground. It is possible to fuse it too far everted.

    I'm not sure about your question. In the first paragraph you are referring to a fused STJ. Are you discussing a fused STJ in the second paragraph?

    STJ motion is motion of the calcaneus relative to the talus. If they are fused there is no pronation of the STJ. I'm not sure what you mean by the talus moves to pronate the STJ.

    Say a STJ was fused so that the medial forefoot does not contact the ground. Ground reaction force is on the lateral forefoot and would cause a pronation moment at the STJ, if there was an STJ. The force under the lateral forefoot would probably be lateral to the center of ankle force and this would create an eversion moment at the ankle. I've seen radiographs where the ankle joint, in the frontal plane, has developed a rounded appearance after an STJ fusion. I believe it is one of the outcomes that you are supposed to warn your patients about when performing an STJ fusion. They call it a "ball and socket" ankle joint. This does not happen all of the time. It might be because of the ankle of the forefoot to the ground when the STJ is fused.

    Cheers,

    Eric
     
  22. Ann PT

    Ann PT Active Member

    Thanks Eric. I did make a mistake in how I worded the talus moving to pronate the STJ. I should have said the ankle is everting rather than the subtalar joint pronating. In my patient I assume the motion was coming from the ankle since he had no motion at the STJ in NWB. I believe what appeared to be an everted calcaneus was really the talus and calcaneus moving together on the tibia. Would you post the hindfoot in this patient? I usually do not post if the STJ is fused. I also appreciate your thought about the position of the forefoot at the time of fusion and its possible contribution to the everted position of the ankle. Thanks, Ann
     
  23. efuller

    efuller MVP

    Yes, I would post. If there is an eversion moment from the ground, acting at the ankle, instead of the STJ, then you can reduce that eversion moment. In my opinion, that eversion moment at the ankle is even more likely to cause arthritis at the ankle than if there was a normal STJ. A medial post (Medial heel skive with rearfoot post on the device) will reduce the eversion moment at the ankle.

    Eric
     
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