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More strain in the plantar fascia in higher arched feet

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, May 27, 2011.

  1. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1

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    Biomechanical analysis of foot with different foot arch heights: a finite element analysis.
    Sun PC, Shih SL, Chen YL, Hsu YC, Yang RC, Chen CS.
    Comput Methods Biomech Biomed Engin. 2011 May 1:1-7. [Epub ahead of print]
     
  2. Admin2

    Admin2 Administrator Staff Member

  3. efuller

    efuller MVP

    Their results don't make mechanical sense. The moment from the force couple of an anterior force from the cuneiform acting on the metatarsal combined with a posterior force from the proximal phalanx acting on the metatarsal head will create a greater moment in a high arched foot as opposed to a low arched foot because of a greater distance between the forces. Moment = force times distance. One would have to look at their assumptions in creating the model that they tested.

    Eric
     
  4. David Smith

    David Smith Well-Known Member

    Eric

    That was my first thought, but in terms of assumptions made, what about if the arch length was the same for the low arch and the high arch. Then the moments due to vertical GRF about the apex would be the same but the moments due to horizontal GRF could be higher during propulsion since the moment arm available to the horizontal anteriorly directed forces would be greater, while at the same time an equinus ankle that is stiff to GRF dorsiflexion moments would have a greater tension in the Achilles tendon at this time and so plantar fascia tension may be greater than the low arch foot at this time in the stance phase.

    Does that sound feasible?

    Regards Dave
     
  5. Eric:

    The results don't make mechanical sense to me either. John Hicks clearly showed that a low arched foot would have higher plantar fascial tension than a high arched foot. In addition, a flatter "tied-arch structure" will have a greater tension force within the horizontal tie member than in a more curved "tied-arch structure". Anyone have the paper so I can look at their methods section more closely?
     
  6. These authors obviously had never solved my questions from my original Thought Experiment #1: Tie Tensile Force in Loaded Arch, from over 5 years ago. This first Thought Experiment for Podiatry Arena clearly shows that a lower tied-arch structure needs greater tensile force within it's tension-bearing horizontal member than a higher tied-arch structure under a given vertical load.
     
  7. efuller

    efuller MVP

    Dave, the moments from the vertical ground reaction force applied to the foot are the same. The internal moments have to be the same. But, the lower arch will need higher forces in the plantar fascia to generate the same moment because the distance is smaller.

    I don't quite understand your point about the horizontal forces. Why would they be different for the high arch foot if they only change was arch height?

    Eric
     
  8. dragon_v723

    dragon_v723 Active Member

    cannot contribute further on the mechanical side but from my clinical experience I really dont seeing many patients with high arch complaining of plantar fascia related problem....btw, how do they define high arch?
     
  9. Because the inclination angle of the rearfoot and forefoot segments of the "triangle" will be lower in the low arched foot? Basically it's the same discussion we had for low and high arched orthoses- right Dave?
     
  10. David Smith

    David Smith Well-Known Member

    Yes right Simon,
    I was just trying to find some time to do a comparison analysis of the two models with some real numbers to see if there actually is a time when the high arched foot could have greater tension in the plantar fascia. Of course peak forces are not the whole picture, loading rate (jerk) and force integral (time and magnitude) are significant considerations in terms of tissue stress and pathology.

    Dave
     
  11. If the FEM study done was static, which it likely was, and if the conditions were not set correctly to have the center of pressure toward the forefoot, and less toward the rearfoot, when there is maximal plantar fascial strain/stress, then this could cause the discrepancy in the experimental results.
     
  12. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    Gender differences in multi-segment foot kinematics and plantar fascia strain during running
    Sinclair J, Chockalingam N and Vincent H
    The Foot and Ankle Online Journal 7 (4): 2
     
  13. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    Multi-segment foot kinematics and plantar fascia strain during treadmill and overground running.
    Sinclair J, Taylor PJ and Vincent H
    The Foot and Ankle Online Journal 7 (4): 4
     
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