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Dorsal orthotic to plantarflex first ray

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Jun 11, 2013.

  1. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
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    This patent was filed in 2009 and has just been granted:
    Orthotic device and method of use
    link
     

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  2. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    Link to patent
     
  3. [​IMG]

    This is what happens when people think in kinematics instead of kinetics.

    So much fail!
     
  4. bit harsh there Robert

    well maybe not really and certainly there will be a lot of FHL tendon issues and probably be uncomfortable , but would it work - in theory maybe

    there is of course a whole lot wrong with the wording the patient , but if we throw that out with the bath water

    and look at the mechanics pushing the distal aspect of the 1st down by using a pad and shoewear cause a change in halux dorsiflexion stiffness

    probably would imo

    not as effective as other methods described and be uncomfortable probably

    might go put some felt on my 1st and try
     
  5. Could be, but I don't think so.

    Heres my logic.

    FnHL, best defined, is the situation which exists when internal plantarflexion moments (b) exceed external dorsiflexion moments (a) in the hallux.

    Most of the internal plantarflexion moments in the hallux are caused by tension in the plantar fascia.

    Most of the tension in the plantar fascia is caused by external dorsiflexion moments in the 1st metatarsal (B) (vis, the ground pushing up under the 1st MH.)

    So in this terribly drawn diagram, the way to reduce dorsiflexion stiffness (or eliminate FnHL as they quaintly put it) is to reduce internal plantarflexion moments (b) which we usually try to acheive by reducing external dorsiflexion moments in the 1st met by reducing GRF under the 1st MH (B). The EFFECT of this is sometimes plantarflexion in the 1st met.

    Now enter the new force into the equation, the pad pushing down on the 1st met head from above. Which of course is all a pad can do, push. We introduce C.

    However, owing to the well known principles of newtons 3rd and ground reaction force, if you push down on a weight bearing joint like the first met head, the ground will push up just as hard. You increase GRF by the same amount you increase the downward force. Stick your hand on the desk and press down on one of your knuckles and you'll feel it.

    In which case while we HAVE introduced an external plantarflexion moment to the 1st met, we have also increased the external Dorsiflexion moment to the 1st met by the same amount. Net result, no change to the system.

    Or, in more common and everyday if slightly less accurate parlance, if a joint is already on the ground, you can't plantarflex it through the ground by pushing down on it from the top.

    Make sense?


    [​IMG]
     
  6. Paul Bowles

    Paul Bowles Well-Known Member

    Correct....unless the supporting surface under the 1st MTPJ is soft :)
     
  7. nice work fella
     
  8. For what it is worth I just had a patient who I pushed down ( ie increased plantarflexion moment acting on the distal aspect of the 1st ray ) seemed easier to dorsiflex the hullux but I might have been looking for it and it maybe could be explained with increased tension in the FHL .

    anyways I see what your saying Robert will have a ponder
     
  9. True enough. I did say it was slightly less accurate parlance ;), but I wanted to put a bumper sticker version for folk who didn't fancy wading through my ramble.
     
  10. David Smith

    David Smith Well-Known Member

    [​IMG]


    Thinking??
     
  11. David Smith

    David Smith Well-Known Member

    Just stand up, then bend down and push very hard on top of your 1st ray and see if it moves much, hold it for a while and see if it hurts much:wacko:
     
  12. Bruce Williams

    Bruce Williams Well-Known Member

    Robert and all;

    This is why the Cluffy Wedge actually works quite well. Force under the hallux will decrease or eliminate the internal PFion moment in the 1st mpj. There is usually much more to controlling FnHL than that, but it is a start.

    I do disagree with Robert's statement, "(vis, the ground pushing up under the 1st MH.)". Actually pressure under any of the soft tissue under the first ray can initiate this issue. It will of course worsen as you move distal towards the 1st mpj, but the issue in many feet starts far more proximal than most suspect.

    Bruce
     
  13. Yep, I'll give you that.
     
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