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'Dynamic' casting leads to better foot orthoses

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Oct 23, 2011.

  1. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1

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    Influence of casting method on effectiveness of foot orthoses using plantar pressure distribution: a preliminary study.
    Stajer T, Burger H, Vidmar G.
    Prosthet Orthot Int. 2011 Oct 19. [Epub ahead of print]
     
  2. Griff

    Griff Moderator

    If our only clinical aim when issuing foot orthoses was to redistribute plantar pressure more effectively (however that is defined) in asymptomatic patients whilst they are at work then I suppose it may be time to get excited about dynamic casting...but as it isn't... I'm not.
     
  3. DaVinci

    DaVinci Well-Known Member

    I often wonder the same thing. Why do so many studies try to measure the function of foot orthotics with plantar pressures when none of us are trying to change plantar pressures with functional foot orthotics clinically?

    I can't get the paper, what do they mean by dynamic casting? Its not what I think it might be is it?
     
  4. Griff

    Griff Moderator

    Not sure exactly what they mean, as I can't get the full text either. I guess whether this sort of negative model production gets ones pecker up will come back to the value one places on kinematics/visual alignment.

    The concept of kinetically quantifiable casting is more exciting in my opinion.
     
  5. efuller

    efuller MVP

    Outcome of coefficient of variation??? We don't even know if that is a good thing to reduce. A plantar pressure could be very high in a particular location. Patient symptoms could get worse if that high pressure didn't change.

    Eric
     
  6. davidh

    davidh Podiatry Arena Veteran

    Twelve healthy volunteers:rolleyes:?
     
  7. I know! Where on earth did they find 12 healthy volunteers?! ;)

    I'd love to know more about the dynamic casting. I'm getting a sniff of a formthotics type system here. Could be wrong.
     
  8. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    12 is not an unusual sample size in the biomechanics literature. If you are doing a between groups comparison you need a bigger sample size. If you are doing a within groups/subject comparison (ie each subject acts as their own control)(which is what this study did), you can get away with a smaller sample size, but 12 would be close to the lower end of what is acceptable. Need to look closer at the subject subject responses - if the response was systematic, then I have no problem with 12.

    The "healthy" bit could be problematic, as there is no indication that the subjects even needed foot orthoses..... ie I hope they report something like the FPI, so we can make a judgement on the foot types.

    I have not had a chance to look at the full paper yet.
     
  9. Beat me to it re: sample size. Regarding fpi and foot types- how does that predict whether or not a subject needs an orthosis?
     
  10. There is a system capable of obtaining dynamic digital scans of the foot. I can't remember the name and I'm about to board a plane. Phil wells will tell you what it's called.
     
  11. Alternatively they might just have walked people over foam boxes.
     
  12. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    Speaking generally, if you are going to use 'healthy' or 'asymptomatic' subjects then you need to know that if they had symptoms then in a typical clinical situation they would have been given foot orthoses if they had symptoms. One way to do that would be to a certain FPI as part of the inclusion criteria. For eg if the FPI was above, say, 7, then you could assume that if they had symptoms then they probably would get foot orthoses in a typical clinical situation.
     
  13. As a device is somewhat static and gait dynamic at what point does the device stop changing shape dramatically and be moulded.

    It does sound somewhat Formthotic in nature -
     
  14. CraigT

    CraigT Well-Known Member

    There is a 3D volumetric scanner from Lion Systems in Luxembourg- uses scattered light at (I believe) 30fps.
    So the question would be- what would you actually use it for?
    Do you choose a particular frame to base your orthosis on? Would you combine information from multiple images? What information would you use?

    Just thinking out aloud...
     
  15. RobinP

    RobinP Well-Known Member

    Depends on what you do at work, but if these healthy volunteers had desk based jobs then it would occur to me that a static, semi weight bearing plantar capture of the foot may well be preferable if they are looking at plantar pressure redistribution
     
  16. man0os

    man0os Welcome New Poster

    In Denmark we learn to take the functional feetprint by using a thin evazote-sole for 14 days and then examine the pressure-marks in that sole, and use it as a guide for the final product.
    I don't know if this is even considered a "dynamic" way of doing it?
     
  17. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    Finally got the paper. Here is what they did for the dynamic casting:
     

    Attached Files:

  18. I really don´t know what to say. But why was this paper published and why did it even need to be written.

    1 step forward 10 steps back

    EDIT :

    Read the full text thank you Sir - still really don´t get why but anyway.

    Anyone care to explain this to me

    we have healthy patients and the plantar pressure changes when we introduce a device - ok not problems with this

    But we conclude that the redistribution is better - how can they be if the patient is healthy or symptom free

    Ie the whole normal debate thing again
     
  19. Looks pretty static to me...
     
  20. The "cast" method captures the lowest heights from the supporting surface that each contact point of the foot achieves. Probably very comfortable.
     
  21. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    Its bizarre; the casting method is really going to capture the foot in its worse compensated position!
     
  22. Like I said, probably very comfortable because it's only going to attempt to arrest motion at the end of range of the motion envelope; its not attempting to change anything in terms of kinematics.
     
  23. CraigT

    CraigT Well-Known Member

    My experience from seeing quite a few approaches from around the world is that the aim of practitioners 'prescribing' orthoses is incredibly variable. Having said that, there must be some apparent benefit or they wouldn't keep making them (or so I would hope).
    Pressure redistribution is certainly one aim that is recurrent...
     
  24. efuller

    efuller MVP

    The only reason that you would choose coefficient of variation over peak plantar pressure or even mean plantar pressure was that those other measures were not significant. I don't see how this variable proves that pressure "redistribution" is better.

    I would hope the casting method would reduce peak plantar pressure. Was that even reported? If it didn't reduce peak pressure better than a foam box then it is worse than a foam box because of the degree of dificulty
    Eric
     
  25. Agreed on what they aim. I'm not convinced that's what they will get though.

    I wonder. If you had someone whose COP is medial of the midline, would that mean the medial area on the heel and forefoot would be more squashed and give you a lateral wedge?
     
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