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First ray mobility and plantar pressures

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Jul 18, 2006.

  1. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1

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    The influence of first ray mobility on forefoot plantar pressure and hindfoot kinematics during walking.
    Foot Ankle Int. 2006 Jul;27(7):539-47
     
  2. Admin2

    Admin2 Administrator Staff Member

  3. Dieter Fellner

    Dieter Fellner Well-Known Member

    confused...

    So in modern parlance, reduced 1st metatarsal stiffness (Dr. Kirby has exerted peer pressure) is associated with less plantar pressure over the 1st metatarsal and more hindfoot eversion. ah hem... I am certain I have seen other research pointing to a contrary finding?
     
  4. Dieter,
    Clearly Prof. Kirby has not exerted enough pressure to allow accurate understanding and interpretation of the results of the modern "parlance" or the study quoted. You may want to re-read and interpret the results again. I'll try to help:

    "The results of this study indicate that those feet with a hypomobile first ray" = Increased dorsiflexion stiffness of the 1st ray, not decreased as you said above.

    "had significantly decreased plantar force and pressure values under the first metatarsal compared to the second metatarsal. In addition, feet with a hypomobile first ray showed significantly more hindfoot eversion compared to those with either normal or hypermobile first rays."

    Does this still fit with your view of the world?

    How was hypo, normal and hyper differentiated? Obviously artificial delineations but what RoMS?
     
    Last edited: Jul 19, 2006
  5. Dieter Fellner

    Dieter Fellner Well-Known Member

    Typo

    Simon - quite right to put me in my place, and if my name was another I might be given the benefit of doubt about the possibility of a typo. I am in between ops and have only briefly scanned the abstract and left my brain in the OR room. The meaning I intended was as you then stated and remains the same and my original question stands and I remain confused about the implications of the findings. Your subsequent interpretation shows that your own understanding was not unduly influenced by said typo.

    Since the full article is not available we are of course assuming the authors are using terminology that might mirror our podiatric understanding of "the world" in relation to 1st metatarsal excursion behaviour, and this might just be an unjustified leap of faith.
     
    Last edited by a moderator: Jul 21, 2006
  6. Atlas

    Atlas Well-Known Member



    You would think that a hypomobile/stiffer 1st ray would exert more pressure? That is what common sense tells me...

    Unless those with a hypomobile 1st ray 'prefer' consciously/subconsciously to 'avoid' pushing off through the 1st met head.
     
  7. Atlas

    Atlas Well-Known Member


    What we were taught, and what makes sense is that hindfoot eversion essentially provides a weightbearing supinatory 'stretch' to the forefoot. This is one theory behind forefoot supinatus. Stretching the forefoot into supination, stretches the first ray into more dorsiflexion. Can't see how the hindfoot eversion egg becomes the hypomobile first ray chicken?

    I am with you Mr. Fellner, this research doesn't quite fit.
     
  8. We used to call this a supinatory rock when I went to school.
     
  9. Given who the authors are, I would expect that they do. The results seem to suggest that with increased dorsiflexion stiffness we adopt a propulsive strategy which limits sub 1st MTPJ pressure. In other words, a so called "low-gear strategy". Is this really so difficult to understand? I think this probably fits with BM's view of propulsion. That is, with low gear propulsion = reduced windlass activity, lack of calcaneocuboid locking, blah blah = increased foot pronation. As I've always said BM is a genius and his concepts are rock solid. Wouldn't hear a bad word said against him etc etc etc..;) :D

    Interesting that from the abstract the authors grouped the rays by dorsal excursion. Wonder what the plantar excursions were?
     
    Last edited by a moderator: Jul 21, 2006
  10. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    One needs to be carefull in use of some of the terminology here .... hyper- and hypo- mobility used by the authors above were refering to the available range of motion.

    Whereas, 'stiffness' (the more appropriate terminology in this context) is more a measure of the force needed to produce the movement (which the authors did not measure).

    Another research question worth pursuing is the relationship of first ray stiffness to plantar pressures - I would assume there is more likely to be a relationship there than just to the range of motion of the first ray.
     
  11. I have scanned over a full text version of Cornwall et al's paper. They acknowledge that their results are contrary to previously published literature on the subject, but don't offer any possible explanations for their results other than to say that their results may have been due to using a young, asymptomatic population or to using a population with relatively small ranges of first ray mobility values. They used a plantar loading force of both 10 N and 55 N using Glasoe's first ray mobility device to determine "mobility" on a total of 164 feet.
     
  12. efuller

    efuller MVP

    Cause and effect

    This is something I've been thinking about a long time. Perhaps the increased range of motion is the result of high plantar pressures. High plantar pressures would cause more strain on the ligaments and lead to possible stretch or tear that would result in increased range of motion. This would also be consistant with the observation that you tend to see a more pronated gait with more hypermobille (increased range of motion) first rays. More pronation leads to more medail weight bearing, more force on first met head etc.

    Anybody have access to a large population of children to look at the incidence of hypermobility? How does this compare to the adult population?

    Just some thoughts,

    Eric
     
    Last edited by a moderator: Jul 20, 2006
  13. This is a good point, Eric. However, I think that Craig also makes a good point that the actual dorsiflexion stiffness of the first ray should be measured relative to the other lesser metatarsal ray stiffnesses in order to provide more answers.

    One other very important point we must all realize: just because you may be attempting to assess the passive ligamentous restraints of the first metatarsal (i.e. first ray) during a clinical exam, you are not then assessing the only means that plantarflexion moments can be generated at the first ray during weightbearing activities.

    First ray plantarflexion moments may also be generated actively by contractile activity of the peroneus longus, flexor hallucis longus, flexor hallucis brevis, abductor hallucis and adductor hallucis which can not be measured by our currently available non-weightbearing or simulated partial weightbearing clinical examination methods. In addition, as the center of mass (CoM) progresses more anteriorly, the center of pressure (CoP) will also progress more anteriorly on the plantar foot during gait. This will cause increased magnitudes of passively generated tensile force within the central component of the plantar aponeurosis which will, in turn, generate additional first ray plantarflexion moments, especially with feet that have increased medial longitudinal arch height. The partial weightbearing-knee flexed method used by Cornwall et al and described by Glasoe in this study will not load the Achilles tendon and/or plantar fascia adequately to give a good representation of how much the plantar fascia can contribute to first ray dorsiflexion stiffness (what Cornwall et al call "hypomobile" and "hypermobile"). I am sorry that Cornwall et al did not discuss all of these above problems with the Glasoe method in their paper as potential sources of their unexpected experimental results.

    I believe that we have provided a better explanation of these problems in our paper on first ray dorsiflexion stiffness: http://www.biomech.com/showArticle.jhtml?articleID=165700382

     
  14. A great point Kevin and indeed one of the problems with the "walking cadaver" work that Erin Ward and "The Nester" have done was that they can't get the plantar intrinsics "working". I think these muscles have received too little attention.
     
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