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Overpronation: Accurate or Parachronistic terminology?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Griff, Apr 3, 2012.

  1. Griff

    Griff Moderator


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    Hi all,

    I know we've had lots of threads on here about "overpronation" over the years, but just wanted to share an early release of an article in this months SportEX Dynamic journal which puts forward the case that the term should be abandoned from medical vocabulary.

    Full article here: http://content.yudu.com/A1w1fo/32DY10-13/

    IG
     
  2. What does "parachronistic" mean? :rolleyes:
     
  3. Griff

    Griff Moderator

  4. They'll all be using it tomorrow...;)
     
  5. RobinP

    RobinP Well-Known Member

    Good article Griff.

    One thing confuses me however.

    I just thought you would have used a practical example that you would have some personal experience of?
     
  6. Admin2

    Admin2 Administrator Staff Member

  7. In the interests of his ongoing domestic bliss, can we get Ian banned from the arena? At least until his honeymoon is over ?! ;)
     
  8. Griff

    Griff Moderator

    Dont worry mate, I've not upset Mrs G yet - flight doesn't leave until 7pm tonight. Promise brain will be fully disengaged at that point.
     
  9. :rolleyes:

    Free tip for wedded bliss my friend. Always assume you HAVE upset the Mrs. Somehow. You'll be right more than you're wrong.
     
  10. Ian Linane

    Ian Linane Well-Known Member

    Will he be on here at 6:59:59 tonight?
     
  11. Ian:

    I just got time to read your whole article and I have to say you have done a very fine job here. This is a thought-provoking article that is long overdue. I have attached a pdf of the article to make it more easy to distribute and read for others.

    I would love to see this type of article in either Podiatry Today or Podiatry Management magazines here in the US since I think it would stir things up a bit and make people think more about their terminology, if you are interested. Ian, you need to be writing more for our profession!

    One thing that I think should be pointed out, to be fair to Merton Root and his legacy, was that he used the term "normal" to describe a set of morphological characteristics that he thought was "ideal" rather than the more commonly accepted meaning of "average". Unfortunately, now in retrospect, this was a big mistake on Root's part since many assume that Root meant "average" when he was saying "normal" rather than meaning "ideal" when he was saying "normal". I believe this is an important distinction to make, especially when considering the history of the term "normal" in the podiatric literature.

    Last October when Simon Spooner and I were lecturing in Orlando together, we had a good, long discussion out at the pool on what the term "overpronation" meant. I brought up the point to Simon that when clinicians say a foot is "overpronated" they are looking at a number of clinical features of the foot that makes it have a certain appearance. They see a flatter medial arch, a more convex medial border, a talar head that points too far medially and a more everted calcaneus and call the foot "overpronated".

    My point was that if a foot was maximally pronated at the subtalar joint (STJ), but had a cavus deformity, an inverted heel, a talar head that pointed toward the first metatarsal head and a slightly inverted calcaneus, that most clinicians would not call this foot "overpronated", even though the STJ was maximally pronated. Therefore, it is not the rotational position of the STJ that clinicians are necessarily referring to when they use the term "overpronated", but rather are referring to the three-dimensional relationships of the osseous components of the foot skeleton. In other words, clinicians use the term "overpronated" not necessarily to describe STJ rotational position but rather are using the term "overpronated" to describe overall foot geometry.

    I believe, in essence, when clinicians use the term "overpronated" to describe a foot, they are actually describing a foot that has a medially deviated STJ axis that has a convex medial border and a talar head that points medially rather than a foot that is necessarily in a certain STJ rotational position. This may seem rather obvious to many but, when I first realized this, it hit me like a hammer and made me think that we need rethink this term "overpronation", rethink how we describe foot geometry and what it means so that clinicians understand that often the terminology they use is misleading, inaccurate and ambiguous.

    You have made an excellent first step in this direction, Ian. Congratulations.:drinks
     
  12. Ray Anthony

    Ray Anthony Active Member

    Dr. Graham of GramMedica (Hyprocure) is likely to define a hyperpronated foot as one with a "closed" sinus tarsi; a Talar-2nd Metatarsal (T2M) Angle (http://www.ncbi.nlm.nih.gov/pubmed/22106195) of over 16-degrees, and a Talar Declination Angle of over 21-degrees on a weight-bearing lateral radiograph. He may also mention a broken cyma line.
     
    Last edited: Apr 11, 2012
  13. Griff

    Griff Moderator

    For the record I think of hyperpronation and overpronation being interchangeable --> in that I don't think either should be used. I know of others who feel the same based on my discussions with them.

    Making definitions (based on measurements of a population of 35?) is fine to do should one wish to, but they still lack context. The article linked is a reliability study --> nothing more, nothing less. The same concerns/issues outlined in the article still apply in my opinion.
     
  14. footplant

    footplant Active Member

    This question is maybe for Ian, or anyone who'd like to answer:

    Can I ask for a bit of clarification? I currently record observations of resting foot posture using the foot posture index (6 item). If a patient has a raw score of +10 to +12 (which I tend to see associated with autism or genetic syndromes) I will record this along with a statement like "+2SD from mean, excessively pronated". This is based on the assumption that not everyone who'll read the notes in future will be familiar with the FPI-6. Do you think it is at least descriptively accurate to use a term like overpronation or excessive pronation in feet of this posture?

    Thanks,

    Josh
     
  15. Greater than two standard deviations from which mean? The mean of the patients you've seen today?

    I love this statement from Feiss (1909) regarding the use of averages and "normal" feet: "As earlier stated, one hundred cases are too few on which to base a fair average. But even if thousands of cases had been used it would be fallacious to reason that all feet in which the scaphoid tubercle is higher than the average, are normal, and all feet in which the tubercle is lower, are abnormal, because the average is obtained just as much from the figures below as from the figures above. Moreover, the chief point shown in the hundred cases is that there is marked variation in the height of the scaphoid in apparently healthy feet. Consequently, as the average is based on that variation, it has no significance further than what the term indicates, representing simply an average of normal variation. Such an average, therefore, cannot serve as a basis from which to estimate deformity. "

    Which leads us to such questions as "excessivelly pronated" for whom and for what function?
     
  16. Rob Kidd

    Rob Kidd Well-Known Member

    The minute I hear the word "index", in any biological context, my alarms bells go off. The underlying assumptions of most parametric tests such as Students', and all the multivariate stuff built upon it such as Principal Components, have several underlying assumptions. One of which is a normal distribution. Even a casual search of the literature demonstrates that indexing data buggers up the normal distribution (eg Atchley et al (1976). There is another, whole different ball park of objections, largely related to size/shape issues, best found in numerical taxonomy (Sokal and Sneath), or its many antecendants. Notwithstanding, that does not mean that ratios should not be used; it merely means that they should be fully explored, with their biology at the forefront. Rob
     
  17. Griff

    Griff Moderator

    I enjoy the Feiss paper more and more with every read. Now two of my favourite papers ever essentially conclude a similar thing and were published 100 years apart [Feiss (1909), Nester (2009)]. Very cool.

    I personally don't, no. It is 'descriptively accurate' to say they are a +10 or a +12 if the foot posture index [FPI] is your weapon of choice. What context this is then put in [given the inter-rater reliability of the FPI in your department, how/if this correlates with dynamic function and ultimately how this information will be used to manage the patients] is a further debate.

    Can't add much more other that to repeat Simons socratic gem: "Which leads us to such questions as "excessively pronated" for whom and for what function?"
     
  18. As others have noted, one of the problems with the term "overpronated" is that the term is poorly defined. Clarity of language is required to make any progress on this subject.

    Here are my thoughts. The subtalar joint (STJ), when is rotates past the neutral position to where it can pronate no further, is defined as being in the maximally pronated position. When the STJ maximally pronates, does this necessarily mean the foot is "overpronated"? Not necessarily. Why? Because some feet may function quite well in the maximally pronated rotational position of the STJ during gait and much of this has to do with the spatial location of the STJ axis, which is very different from the rotational position of the STJ (Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. JAPMA, 91:465-488, 2001).

    Feet that have a highly medially deviated STJ axis (i.e. abnormal spatial location) will tend to be the feet that most clinicians call "overpronated" since these feet will function with abnormal gait kinetics caused by abnormal spatial location of the STJ axis. However, if a foot had a maximally pronated STJ, but the STJ axis was in a fairly normal spatial location, most clinicians would not likely say that this foot is "overpronated", since this foot would be more normally shaped, would function more normally and would also likely have fewer pronation-related symptoms.

    Therefore, the term "overpronation" is a useless term in much the same way that "hypermobility" is a useless term to describe first ray dorsiflexion stiffness. What clinicians are trying to describe when they use each of those terms (i.e. "overpronation" and "hypermobility") are certain mechanical characteristics of the human foot which, unfortunately, are not what the terms actually mean. What clinicians do mean when they say that one foot appears "overpronated" and another foot appears "not overpronated" refers to the structural appearance of the foot during weightbearing function (i.e. standing, walking, running, etc), not necessarily to STJ rotational position (i.e. pronated, neutral, supinated).

    The structural characteristics of the foot that tend to cause the appearance of the "overpronated foot" to most clinicians during relaxed bipedal stance include:

    1) the internal rotation and medial translation of the talus relative to the calcaneus (i.e. seen always in medially deviated STJ axes)

    2) the medial convexity of the midfoot at the talar head (i.e. seen always in medially deviated STJ axes)

    3) the flattened medial longitudinal arch (i.e. seen mostly with medially deviated STJ axes)

    4) the everted calcaneus (i.e. seen mostly with medially deviated STJ axes).

    In other words, the structural characteristics that clinicians have traditionally used to describe a foot as being "overpronated" are not related to STJ rotational position (e.g. STJ maximally pronated, STJ neutral, STJ 3 degrees pronated from neutral), but rather the structural characteristics that clinicians have traditionally used to describe a foot as being "overpronated" are related to:

    A. Significant medial deviation of the STJ axis.

    B. Significant flattening of the medial longitudinal arch of the foot.

    Mechanical modelling and mechanical simulations tell us that both of these structural abnormalities (i.e. medial STJ axis deviation and medial longitudinal arch flattening) of the foot may cause abnormal kinetics which may also be correlated to the injuries seen in feet with this unique structure. Structure, does, indeed help determine function.

    Therefore, does the term "overpronation" adequately describe these two structural parameters of the foot? No.

    However, do these two structural parameters of the foot have significant affect on the kinetics of the foot during weightbearing activities? Yes.

    Therefore, I do agree that the term "overpronation" should be thrown out, just like the term "hypermobility" should also be thrown out. But we must continue to try to find and describe structural/functional characteristics of the foot that cause significant alterations in foot kinetics so that we can better predict abnormal external and internal stress patterns that may occur from such structural deviations of the foot in order to better prevent and treat injuries of the foot and lower extremity in our patients. :drinks
     
  19. footplant

    footplant Active Member

    Thank you for your answers Simon, Rob, Ian and Kevin.

    Dropping the qualifier 'over' from overpronation, would you be happy simply with the use of the term 'pronated' (or neutral or supinated)? I am thinking purely in terms of an overall description of resting foot posture, which could be accompanied by further specific details.

    Thanks,

    Josh
     
  20. Here's a little thought experiment for you Josh and for anyone else thinking along. Lets say we take 100 feet that have all been labelled as having a foot posture index of +10. Would we expect all of these feet to behave identically in terms of their kinematics and kinetics during level walking at an identical velocity? Should we expect them to behave even similarly? Will they behave completely differently from 100 feet labelled as having a foot posture index of +9?

    In other words, let us think about the labels that we apply and, as Kevin intimated, let us think about what those labels actually tell us. We can apply whatever labels we choose, we could classify feet as Tom, Dick and Harry if we choose to, but what do those labels really tell us? Do those labels predict kinematic and kinetic behaviour? Moreover, do they predict pathology? Given that the FPI 6 is based on six different tests, there are multiple ways to achieve a score of +10- right?
     
  21. footplant

    footplant Active Member

    Yes you could achieve +10 in different ways, but as each of the 6 items is scored between -2 and +2, you need to score the maximum +2 on either 4 or 5 out of the 6 items.

    And no, I wouldn't expect foot posture to be a perfect predictor of dynamic function, but I still like to record what I see and find the FPI to be a useful tool.

    The normative values are here by the way:

    http://www.ncbi.nlm.nih.gov/pubmed/18822155

    I may have strayed from the original thread a little, thanks again for all your replies.

    Josh
     
  22. Good for you.
     
  23. Griff

    Griff Moderator

    I feel that if categorisation of feet is the goal then there is still no better tool. Personally not found it to be a useful tool clinically however. Having run the stats I know that the intra-rater reliability of it (in my hands) is moderate at best and that the inter-rater reliability (between myself and a physio colleague) was poor. This, combined with the lack of consistent correlation with dynamic function are the reasons I leave it out of my daily assessments.

    I think Simon's point re 'labels' is a good one. I've never wanted to just label a foot (whether that be a +10, an 'overpronated' foot or Tom, Dick or Harry) as I'm not sure what this adds to my assessment or how it dictates my management of the pathology in front of me.

    In the context of the normative data (normal in the statistical/distribution sense) I think a few things need to be considered. Dr Redmond found that a +4 was "normal". Does this mean someone with a +4 cannot get injured or present with pathology in our clinics... of course not. Does it also mean that a +3 should be classified as "underpronated" and a +5 should be termed "overpronated"?

    To expand on this I think most could look at images of a -12 and a +12 and acknowledge they were different. Could the same be said if they looked at a +3 and a +5? I suspect not/far less so. In the Feiss paper that Simon uploaded to another thread he uses a beautiful analogy about a spectrum of the colour yellow to make a similar point. Well worth a read.

    IG
     
  24. Attached. While you're in, you should probably read Greg Quinn: http://www.japmaonline.org/content/102/1/64.abstract and http://www.japmaonline.org/content/102/2/149.abstract
     

    Attached Files:

  25. What Redmond reported here was that mean FPI score obtained from a meta-analysis of the literature, in subjects who we're not exhibiting pathology at the time of these studies, was +4. Let us remember that this is a mean or average if you prefer.

    To reiterate, here is what Feiss said regarding means and averages:

    "As earlier stated, one hundred cases are too few on which to base a fair average. But even if thousands of cases had been used it would be fallacious to reason that all feet in which the scaphoid tubercle is higher than the average, are normal, and all feet in which the tubercle is lower, are abnormal, because the average is obtained just as much from the figures below as from the figures above. Moreover, the chief point shown in the hundred cases is that there is marked variation in the height of the scaphoid in apparently healthy feet. Consequently, as the average is based on that variation, it has no significance further than what the term indicates, representing simply an average of normal variation. Such an average, therefore, cannot serve as a basis from which to estimate deformity. "

    If you replace "scaphoid height" with FPI in the above paragraph then you'd be pretty much on the money.
     
  26. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    I did not want to start yet another new thread on this, so will hijack this one. I see the latest bog post from Mizuno is still based on prescribing from the "overpronation" model:
     
  27. How then, Craig, should runners with no medical training be advised to best buy running shoes by non-medical ly-trained shoe salespeople? In other words, if not "excessive pronation" or "underpronation", then what would you suggest would be a better criteria for a shoe salesperson to use to advise runners on how runners should best select their running shoes to prevent running injuries?
     
  28. toomoon

    toomoon Well-Known Member

    Kevin.. maybe it is as simple as the Benno model.. if it feels comfortable it is likely to protect and perform. You have hit the nail on the head.. non medically trained people advised by non medically trained people on a model that does not work and has not for years..
     
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