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Foot Orthoses - Placebo

Discussion in 'Biomechanics, Sports and Foot orthoses' started by podomania, Jan 27, 2011.

  1. podomania

    podomania Active Member

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    I would like to ask if there is any information in the literature regarding the placebo effect of foot orthoses. To be more specific, are there any double blind studies comparing the clinical significance of foot orthoses versus placebo insoles?
    Thank you in advance
  2. Define placebo orthotic.

    Ie even a piece of flat soft rubber will change to foot shoe interface, which may change the mechanics of the body during gait.

    So I don't think there ever could be a true placebo device.
  3. podomania

    podomania Active Member

    Ok then...I could distinguish the 2 terms in a more appropriate way. Lets say that a placebo orthotic is a non functional orthotic device like a flat soft rubber or a plain eva flat insole which is provided to the patient as if it is functional..I am repeating that i am interested in the clinical significance and not the mechanical effect!
  4. That's the whole point, in order for it to be classed as a placebo, you first need to demonstrate that it has zero mechanical influence.
  5. This is the Landorf study in which a "sham" orthosis was applied:

    But what we don't know is how the "sham" orthoses influenced the foot-surface interface characteristics, specifically in terms of friction, topography and load /deformation. If the "sham" orthoses altered any of these, then they would have influenced the mechanics of the surface and viz. had a mechanical effect. In which case, they should not be considered as "inert", "sham" or "placebo" etc.

    Personally, I think it's impossible to put any physical object into a shoe without altering at least one of these characteristics. Thus, there is no such thing as a placebo orthotic. Viz there can never truly be a placebo controlled trial of foot orthoses. But the study I cited above, is probably the best attempt to date.
  6. podomania

    podomania Active Member

    I tended to think that non funcional devices would not be given as treament for pathologies caused by biomechanical abnormalitites hence one would not take into consideration whichever mechanical influence they may demonstrate. I should then rephrase my question and class as placebo effect no orthoses at all.
  7. podomania

    podomania Active Member

    Thank you for the study simon..To be more specific about the 'no orthoses at all', the patient should not be aware that there is not orthotc in the shoe.
  8. I think I see the problem here, and it stems from the idea of "functional" vs. "accommodative" orthotics. Foot orthotics work by changing either the friction characteristics, the surface topography or the load/ deformation characteristics at the foots interface, or a combination of these factors. The terms "functional" and "accommodative" when applied to foot orthoses are outmoded/ outdated and at best serve only to confuse.
  9. There is always this one.*

    What they call a pre fab orthotic is a flat piece of 3mm open cell foam. Which is still going to have a functional effect but is probably as close to a placebo as one can get.

    That it is treated in the study as a valid insole which makes a fit comparison to a high arched poly device enhances its validity as a placebo as it appears that the tester was "blinded" to its nature as well as the subject.


    *Yes Ian, again.
  10. Josh Burns

    Josh Burns Active Member

  11. Sorry Josh, didn't mean to exclude your highly relevant study. Did you attempt to measure the mechanics of your "sham" orthoses?
  12. Josh Burns

    Josh Burns Active Member

    Yes at length, we were intrigued to find that the 3mm flat latex foam sham insole reduced in-shoe pressure by 9% (compared to a 26% reduction with the custom device):


    Interestingly, recent re-analysis using the Regression Factor (RF) index show that
    while customised foot orthoses continue to significantly improve the plantar pressure distribution, there is no difference observed in the sham group.

    The RF index is a normalisation method producing a more global measure of pressure, independent of gait speed.


  13. podomania

    podomania Active Member

    Thanks very much
  14. Not a placebo then, unless the pressure change was produced psychologically. What of materials testing?

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