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Discussion in 'Biomechanics, Sports and Foot orthoses' started by fabio.alberzoni, Dec 11, 2014.

  1. fabio.alberzoni

    fabio.alberzoni Active Member

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    Yesterday I was thinking about how to treat a patient with 7° of tibial stance in varum, supinated forefoot of 6° bilateral, tibial angle of 0°, RCSP 0°, NCSP of 5-6° inverted.
    the ankle was a muscular equinus with 0° of ankle dorsiflexion.

    In last time I start to introduce in my examination two new ideas:

    1. BOOK TEST: I call it in this way cause I often use to put under the heels a book to lift them.
    I usaully use the first book of kevin kirby...I think is 2 cm thick. Some times I use thiner or thicker if is an important or not equinus.

    When the heels are over the book I measure the RCSP again.
    In the end I compare the measurement with and without the book to understand how many degrees of pronation are caused by the equinus.

    I usually avoid important rearfoot posting or skive or inverted cast when I see that eversion decrease a lot...may be 2/3 degrees.
    If the patient wears an enough heeled shoe I make an orthosis with less antipronation function.

    2014-11-25 22.14.28.jpg

    Kirby initially described his medial skive like a development of Blake's Inverted Orthosis for children with rounded heel.

    I use this picture to compare.

    I think that both modifications have maximum moment nearby the edge of the medial part of the shell.

    Considering this modifications I think that if the the most medial part of the rearfoot post were of the same thickness the anti-pronation force would be really similar.

    I'm beginning to think that Medial skive is usefull not in rounded heel and orthosis in which I want a low arch.
    BIO, for me, is usefull to change the geometry of the orthosis resulting in a more rigid and higher arch.

    I try through this thinking to make my therapy more reasonable.

    I need your opinions.

  2. fabio.alberzoni

    fabio.alberzoni Active Member

    I want to clarify that I use that book cause I always have it with me. That book is one of the most important I read and I love the other three books too...
  3. Only if the surface angulation, frictional characteristics and stiffness were the same in both devices.
  4. Fabio:

    The Blake Inverted Orthosis (BIO) technique involves a number of different positive cast and orthosis modifications, whereas the medial heel skive technique involves just one positive cast modification. As such the medial heel skive is normally combined along with other positive cast and orthosis modifications to produce the desired orthosis geometry and stiffness (i.e. load-deformation characteristics) that is necessary to reduce the pathological stresses on the injured musculoskeletal components of the patient, improve their gait function and prevent other pathologies from occurring.

    In actuality, the medial heel skive will work better at "controlling pronation" in a patient with a more rounded plantar heel than will the BIO since the BIO produces the inverted heel cup shape by purely inverting the cast, which will have little effect at producing an inverted heel cup shape on a spherical-shaped plantar heel. I described this fact in detail in my paper on the medial heel skive. Here is the illustration I drew for my paper where I show how a BIO modification produces little alteration in plantar heel cup shape when performed on foot with a spherical shaped plantar heel (Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992).

    Hope this helps.:drinks
  5. Agreed. We can also get around this by casting the foot semi-/weightbearing or just loading the patients heel with the heel of your hand during casting all which will flatten the heel section in the negative model increasing the influence of the inverted balance on the finished device.

    Further, the inversion in the Blake will tend to increase the height of the medial longitudinal arch section of the orthosis, whereas the heel skive effectively lowers the arch of the shell. When we have medially deviated subtalar joint axes, I find many patients cannot tolerate the pressure exerted by high arched devices in the location of the axis, since this creates tissue compression without rotation. Generally speaking, while I do invert some casts, the heel skive is more often my weapon of choice.

    Hope that helps.
  6. fabio.alberzoni

    fabio.alberzoni Active Member

    thanks kevin.
    I explained really bad what I mean .
    I have a few time to produce orthosis and ,if is possible, I prefer control pronation always with medial skive...is really faster to do. In Italy we produce the orthotic directly and time is so precious.
    Is correct to invert the cast in blake's way mainly when I want that the arch is higher? Some times I use both techniques when I should need more control than 4mm of medial skive. In less important cases I use only medial skive on the rear foot.
    when do you advise me to prescribe inverted orthosis?
  7. fabio.alberzoni

    fabio.alberzoni Active Member

    great trick! I have to try it!

    And what about my first idea? the one to try to understand the influence of limited ankle ROM measuring RCSP with a heel lift under the heel?

    thanks a lot
  8. Fabio:

    When I want a higher arched orthosis with a medial heel skive, I will invert the positive cast 3-5 degrees and use a minimal arch fill on the positive cast. In addition, one can plantarflex the first ray/medial column during negative casting if you want the medial arch even higher. I haven't used the Blake Inverted technique for the last 20 years since I feel I have better control of the shape of the resultant orthosis by using the medial heel skive technique along with the other modifications I mention above.
  9. fabio.alberzoni

    fabio.alberzoni Active Member

    ok thank you. I feel more sure about what I did.
    I wrongly intend an inverted cast as a BIO.
    To intend a BIO should we talk about inverted orthosis with an inversion with a ratio of 5/1°of pronation?
    thanks for attention and your answers.I appriciate so much that you all share your knowledge.
  10. Dr Rich Blake

    Dr Rich Blake Active Member

    Fabio, I am just getting active in this wonderful forum. Yes, the Blake Inverted Technique is based on a 5 to 1 ratio (cast correction to actual foot change). The Inverted Technique can comfortably to be used to correct 14 degrees of heel valgus, vital in PTTD patients and juvenile flat feet. When you combine this with stable shoes, varus wedges under the orthoses or in the midsole, Kirby skives when needed, power lacing, now 20 degrees of valgus can be corrected for, and you can predict the amount of correction achieved with pretty good certainty. This is what I have tried to accomplish and I have studied the results over these last 40 years. I hope this helps understand the Technique. Rich Blake

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