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Forefoot varus orthotic prescription question

Discussion in 'Biomechanics, Sports and Foot orthoses' started by AdamB, Mar 14, 2014.

  1. AdamB

    AdamB Active Member


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    Hi all,

    Just a quick question about cast corrections for true FF varus deformity.

    I had a patient with a 3 month history of plantar fasciitis and among other treatments I am prescribing an orthotic. Biomechanically he has a true FF varus deformity which I can "almost" reduce with a fair amount of force applied to the 4th / 5th rays with STJ in neutral.

    In resting stance he is excessively pronated - I'm guessing partly as a compensation for the FF varus. He has a low - moderate Supination resistance.

    In terms of correction, do I balance to verticle (ie correct the FF) or do I balance "as is" and use external FF and RF posting?

    Thanks for any advice. I don't see many actual FF varus cases.
     
  2. efuller

    efuller MVP

    Re: orthotic prescription question

    Treatment of "forefoot varus" was one of the things that confused me most when I was a student. How do you support the deformity with an orthotic that ends behind the metatarsal heads? Won't you loose the support after heel off in gait? Why do we treat the forefoot to rearfoot relationship in neutral position when the foot in stance is at its end of range of motion in the direction of pronation (or some other non neutral position?)

    Without ever getting a good answer to those questions I've changed how I've designed my orthotics. If the plantar fascia hurts make the orthotic so that it will attempt to reduce tension in the plantar fascia. If there is a medially deviated STJ axis increase the supination moment from the ground with a varus heel wedge effect device (ie. medial heel skive). In stance, if there is eversion of the forefoot range of motion available add a forefoot valgus intrinsic post even though you measured a forefoot varus. (This will also tend to evert the heel cup so additional medial heel skive may be needed to get the heel cup to have a varus wedge effect.) Add a reverse Morton's extension to decrease dorsiflexion load on the first ray. I could add more, but that might be enough for you to think about for now.

    Eric
     
  3. AdamB

    AdamB Active Member

    Re: orthotic prescription question

    Thanks Eric, that's very helpful. I'm not sure he has any eversion ROM of the FF in stance - that's why I hesitated on using an intrinsic valgus post or reverse Morton's extension.

    Adam
     
  4. efuller

    efuller MVP

    Re: orthotic prescription question

    When a patient has a medial slip of the plantar fascia problem and no eversion available in stance, I will often use a reverse Morton's extension. With any orthotic modification the goal is to reduce stress in a particular structure. Often reducing stress in one structure will increase stress in another structure. The Reverse Morton's may increase pressure sub second metatarsal. You have to evaluate for that when you use the extension.

    Eric
     
  5. HUGHESA1

    HUGHESA1 Member

    Re: orthotic prescription question

    Hello Adam. Firstly, what is it that you are actually treating? Is there any pain or pathology as a consequence of this forefoot varus and how is the subject compensating for the varus and the pain in stance and during locomotion, are there any degenerated joints (particularly 1MTPJ) that may have an influence on what you may be able to achieve with your orthotic. Do we actually treat "forefoot varus" or do we treat pathologies that have an association with foot alignments and compensations. Once you have worked all that out you can then start to define what you actually wish the achieve with a device, i.e. improve functional ROM at 1MTPJ.
     
  6. Bennepod

    Bennepod Active Member

    Re: orthotic prescription question

    Eric
    You offer that you could say more on the subject, I invite you to do so, please explain the rationale and mechanics of rf varus and ff valgus posting on a device.

    Thanks
    Brendan
     
  7. efuller

    efuller MVP

    Re: orthotic prescription question

    I really like the invention of a forefoot valgus post. There is not much difference between intrinsic and extrinsic posts functionally. There are some practical shoe fitting and manufacturing differences. The forefoot valgus post is great for the laterally deviated STJ axis foot. You often can get the foot to pronate far enough that the axis moves to a more medial position. Even if there is not a lot of eversion available you can shift the center of pressure far enough lateral that you can releive peroneal overuse symptoms. There is a too much forefoot valgus wedge and this too much will be quite different for different people. I use the maximum eversion height test to determine what is the maixmum forefoot valgus post that I can use.
    Discussed here
    http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=69595

    I will often use the intrinsic forefoot valgus post when I want to decrease load on the medial forefoot. There is a paper that shows that there is a decrease in tension in the plantar fascia with a forefoot valgus wedge.

    The forefoot varus intrinsic post just raises the height of the medial arch and is quite ineffective for the partially compensated varus foot that does not fully load the medial forefoot and does overload the lateral forefoot. It's fine if you want to raise the arch height of the device, but you often already get that by casting the foot in neutral position. Most orthotics are made from casts with some medial arch fill that lowers the medial arch any way. If you need to increase medial forefoot load then you should use an extension that goes out under the metatarsal heads.

    Let me know if you want more.

    Eric
     
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