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Orthotics and Biomechanics guide

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Brightsoles, May 25, 2023.

  1. Brightsoles

    Brightsoles Welcome New Poster

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    Hi amazing Podteam!
    I’m a new grad pod who is not feeling very confident in the biomechanics side of Podiatry. However, it’s a side that I would love to explore in further and grow my skill set.

    I understand there’s no one fits all “recipe” when prescribing orthotics so I would like to actually understand the fundamentals of how and which orthotics would be supportive/ accomodating for a certain foot condition.

    Could you please advise me of some books/ guides that I can read to broaden my understanding about why and when a certain orthotic style/ modification would be used. I’ve searched a lot of books online but wanted to ask here from the experienced pods about what helped them best. This would definitely come with experience but I am looking for a starting point so I have the basics down before I start constructing a building :)

    Thankyou for your time and guidance. Looking forward to some exciting reads as I believe biomechanical/ MSK conditions are a big part of Podiatry and I want to get to it right away otherwise it’ll always be this big scary thing that’s too complex to understand.
  2. Craig Payne

    Craig Payne Moderator

  3. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    Rothbart BA, 2002. Medial Column Foot Systems: An Innovative Tool for Improving Posture. Journal of Bodywork and Movement Therapies (6)1:37-46
  4. Dan T

    Dan T Active Member

    Where did you graduate? Biomechanics was taught horribly (imo) @ Uni. Lots of inapplicable academia, needless graphs, stats and measurements when neither me or my peers new an arse from an elbow when it came to diagnosing pathology.
    This book is by far the best all round bog basics I have found - https://www.amazon.co.uk/gp/aw/d/B0915N25FH?psc=1&ref=ppx_pop_mob_b_asin_title
    I would start there for the basics and keep watching YouTube videos on below knee anatomy for first 12 months.
    I can vouch for Craig's bootcamp program - got a lot out of it. Gives you a solid grounding then Kevin Kirby has some good articles you can access on Research Gate. Namely "Subtalar Joint Axis Location and Rotational Equilibrium Theory of Foot Function", and then, "Subtalar joint equilibrium and tissue stress approach to biomechanical therapy of the foot and lower extremity". The latter being a pretty comprehensive guide to most foot pathology you'll run into and personally one of the things I have found most helpful. Again, I can attest that it works as described in the paper.
    Get a couple of years regular practice and do Craig's bootcamp. Once the penny starts to drop read absolutely everything and sort the wheat from the Chaff, (fyi, there's a whole lot of chaff)
  5. Dan T

    Dan T Active Member

    I also wrote a concise presentation on paradigms I can send you if you have an email
  6. DaVinci

    DaVinci Well-Known Member

    Do that. Sounds as though that is exactly what you need.
  7. efuller

    efuller MVP

    In the above paper the author claims that over 95% of feet have a single pathologic foot type. The author has since said the data there is no longer valid.
  8. efuller

    efuller MVP

  9. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    In 2002, I estimated that upwards of 80% of abnormal (gravity drive) pronators (not 95%) had either RFS or PCFD. 20 years of further research suggest that estimate was too high. Currently, based on clinical research, I believe it is closer to 60%.

    Tissue stress and/or surgical interventions are not effective when treating RFS or PCFD.

    A recently published study concluded that generic proprioceptive interventions are very effective when treating RFS,
  10. Dan T

    Dan T Active Member

    Here is an article describing the practical application.
    Entry level question of the day.
    RE arch fill I tend to ask for quite a bit in lateral deviation if I cast them?? Generally only cast tricky ones. I see in the article it's recommended light pressure of the fingers to indicate.
    However, is arch profile really necessary on orthotic for most pathologies in a 'supinated' foot in your opinion? I have a colleague who will laterally post devices with quite significant arch profiles so as not to throw out knee kinematics. I understand in principle (I think), but if one has a truly laterally deviated STJ and we pronate it by laterally posting > half of their maximum eversion height, assuming they have a functional medial column won't the arch maintain itself with its numerous contributory structures. Shouldn't a moderate medial arch collapse be desirable into midstance.
    Surely the knee would only be at risk if we laterally posted a "normal" to medial deviation without medial support or am I coming at that the wrong way?
    I've had good results with a simple laterally posted Xline & small heel raise with nil arch support for peroneal tendinopathy, medial knee OA, and 5th/1st PMA Callus/ulcers in supinated peeps. No knee complaints have come back with these guys.... yet?
    Guess I'm concerned I'm inadvertently knackering people's knees in the meantime
    Struggled to get a definitive answer to this...
  11. efuller

    efuller MVP

    Brian, you should reread your 2002 paper. You stated a number that was over 90% that had that foot type. In that paper you described a way of measuring for this foot type and you have since said that you no longer use that measurement. It is intentionally misleading to refer people to a paper you have stated has incorrect information.

    Brian, You have said that physics makes your head hurt. Do you even know, or understand, what a tissue stress intervention is? How can you know it is not effective?
  12. efuller

    efuller MVP

    With a laterally deviated axis (supinated foot) the problem is too much supination moment from the ground. This will tend to cause inversion ankle injuries and peroneal tendonitis. I will tend to add more arch fill with laterally deviated STJ axis feet making their arch lower. I agree that you don't need the medial arch of the orthosis so much in feet with a laterally positioned STJ axis.

    A lateral post (or a lateral skive in the heel cup of the orthosis) will tend to shift the center of pressure more laterally. This will change the moments at the STJ and the knee. At the knee you have to think about how the shift of center of pressure under the foot will affect the knee and whether this is a good or bad thing. For this you need to do free body diagram analysis. To do this you need to understand the concept of a force couple. The farther the forces of a force couple are apart, the greater the moment created by the force couple.

    In static stance you can look at the frontal plane angulation of the tibia (genu varum or genu valgum). It will probably be helpful to draw the picture that I'm describing. Viewing a tibia, in the frontal plane, which is inverted compared to vertical, the center of pressure under the foot will be medial to the location of the center of pressure of knee joint. Draw the forces acting on the tibia. Body weight from above is pushing downward at the knee and ground reaction force is pushing upward on the bottom of the foot. This will create a moment that will tend to put an external adduction moment on the tibia. To remain in equilibrium, the tibia needs to have increased compressive forces at the medial compartment and increased tension forces in the lateral collateral ligament. Now think about what shifting the center of pressure under the foot will do to the existing static moment at the knee in an individual with tibial varum. If you gave this person a valgus wedge (lateral post) to move the center of pressure more lateral, you would be moving the forces closer together and this would decrease the adduction moment at the knee.

    The result of that is a lateral post is good for genu varum and bad for genu valgum. Vice versa for a medial post.
  13. Dan T

    Dan T Active Member

    Understood. Cheers Eric
  14. Brightsoles

    Brightsoles Welcome New Poster

    Hi Dan. Thanks for your reply. Looking forward to the bootcamp program, it looks very interesting!

    That would be extremely helpful! My id is j e n n a j a n e p o d @ g m a i l . c o m

    PS: it didn't let me post my email since I'm a new member, hence the space in between.

    Thank you!
  15. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    You are referring to research published nearly 30 years ago! I reread my 2002 paper, and you are right: at the 1995 Annual AAPM conference, my colleagues and I presented a workshop where we suggested nearly 95% of all abnormal (gravity drive) pronators had the Mortons/Rothbarts Foot structure. (Not clear in the paper, one could take the estimate to mean the population as a whole). This estimate changed as my research into foot embryology evolved.

    Also, in 1995 we thought Rothbarts foot might be a subset of Mortons foot. We now recognize them as two entirely different foot structures.

    I would encourage you to read my more current research to understand how my work has evolved over the years.
  16. Ted Dean

    Ted Dean Member

    Boot camp is great. Highly recommend.

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