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Pros and Cons of DC wedge orthoses

Discussion in 'Biomechanics, Sports and Foot orthoses' started by geelm, Sep 15, 2006.

  1. Being that the STJ is probably the joint of the foot that is the most highly constrained (i.e. forces applied at any direction and to any point on the calcaneus will still tend to make it rotate very close to its axis), then, yes, a decrease of motion in one plane will influence the motion in the other planes that it normally rotates in.

    Compare the STJ to the midtarsal joint (MTJ), where the MTJ is one of the least constrained joints of the midfoot. This means that the MTJ rotational axis will be dependent on the magnitude, direction and point of application of the external force applied to the forefoot and, as a result, the MTJ axis spatial location will be highly variable, depending on the mechanical situation.

    I will be including this concept of joint constraint in my lecture on MTJ mechanics at the PFOLA meeting in Chicago in December.
     
  2. markjohconley

    markjohconley Well-Known Member

    simon, for example, a stj axis that does align instantaneously 16 degrees from the sagittal plane, 42 deg from the transverse plane, and 44 deg (2sig.fig.) from the frontal plane .. wouldn't it take a greater "wedge" reaction force from the sagittal plane "wedge" than the transverse and frontal plane "wedges" .. triplane force / 16 >> triplane force / 42 (or 44)
     
  3. markjohconley

    markjohconley Well-Known Member

    gents, why wouldn't a combination of rearfoot, forefoot, and lateral column support wedges? adhered to the sock lining perform as efficaciously as a custom orthoses in altering the CoP, reducing tensile and compressive forces, and reducing symptoms (assuming no plantarwards force amidfoot from the shoe upper that a custom orthoses of sufficient rigidity would counter?), cheers, mark
     
  4. That's kinda what I was trying to say. I don't think we have the answer to this though as it is dependent on so many factors.
     

  5. Who says it isn't?
     
  6. David Smith

    David Smith Well-Known Member

    Can you describe what you mean by the term 'lateral heel release' please

    Cheers Dave Smith
     
  7. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    Thats a term I not used in a while!

    It refers to the addition of plaster in the lateral plantar aspect of the heel, so the the lateral heel area of the orthotic is flat - ie no lateral heel cup
     
  8. David Smith

    David Smith Well-Known Member

    I was a bit confused as to what was the difference in real terms between a DC wedge and a Medial skive and why it might be that, if as DC claim, the DC wedge only requires 20% of the rearfoot inclination than does that of the Blake inverted device to achieve similar kinematic changes. So I did a few diagrams and it seems to me that the DC wedge causes a triplanar change in rearfoot angular position whereas the other two, in their basic form, are single plane changes.

    So to explain, the DC wedge technique is to add plaster at the lateral heel so that it carries what is effectively a medial skive or a medial post (if you define a post as not crossing the heel centre line and a wedge is across the whole width of the heel) and projects it into the lateral foot, i.e. the lateral side of the heel centreline, and below the normal horizontal plane that would correspond to the ground plane. (see diagrams below.) This therefore causes a lowering of the orthosis heel on the lateral side relative to the ground plane and the cuboid, thus creating a a triplanar wedge that tends to dorsiflex the calcaneus in the sagital plane and rotate it thru inversion and adduction.

    Added to this the DC modification ends up being a wedge (as the name denotes) whereas the Blake modification is effectively a post even if you only rely on the forefooot modification and shell stifffness to achieve this. And so the vertical displacement of the medial heel in terms of height rather than degrees is more per degree on the DC than than blake because of the wider wedge across the heel cup base. (See 2nd diagram) G1 = original ground level G2 = new relative ground level after modification.

    That's if i've understood the DC nmodification correctly of course!!

    [​IMG]

    [​IMG]


    Cheers Dave
     
    Last edited: Jun 5, 2014
  9. Dave:

    The Blake Inverted Orthosis modification involves an inversion of the positive cast by 15, 25 or 35 degrees, an addition of extra medial expansion plaster, a standard plantar fascial accommodation and a standard flat rearfoot post. To say it is only a "single plane change" is not even close to the truth.

    Blake RL, Denton J: Functional foot orthoses for athletic injuries. JAPMA, 75:359-362,1985.

    Blake RL, Ferguson H: Foot orthosis for the severe flatfoot in sports. JAPMA, 81:549, 1991.

    Blake RL: Inverted functional orthoses. JAPMA, 76:275-276, 1986.

    Blake RL, Ferguson H: "The inverted orthotic technique: its role in clinical biomechanics.", pp. 465-497, in Valmassy, R.L.(editor), Clinical Biomechanics of the Lower Extremities, Mosby-Year Book, St. Louis, 1996.

    The medial heel skive is also not a "single plane change" since the medial heel skive affects the three dimensional shape of the heel cup of the orthosis and the relative depth of the heel cup of the orthosis relative to the rest of the orthosis.

    And, for your, and everyone else's information, nearly the exact same modification as the DC wedge was being done by one of the orthotists, Notty Bumbo, that worked at the California College of Podiatric Medicine at least ten years before the DC wedge was created. Notty claims he was making "inverted heel" orthoses for Ronald Valmassy, DPM, by adding lateral heel cup plaster to the positive casts of orthoses back in the early 1990s. Notty told me about this modification he used after he read about my medial heel skive modification in JAPMA in 1992 (Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992). However, Notty never published his orthosis technique but it definitely predated the DC Wedge orthosis by at least a decade.

    Just trying to get things real here.
     
  10. David Smith

    David Smith Well-Known Member

    Kevin

    I understand (read and studied) the whole process of the Blake inversion modification but only just now looked at the 'DC' or lateral heel fill (LHF) modification and of course I'm very familiar with the 'Kirby' or medial skive and very useful it is too.

    I am well aware that the effect of the medial skive and the Blake inversion and for that matter any wedging or posting has a 3D effect but the basic design itself is single plane unless you modify the concept.

    The main concept of the Blake inversion is a matter of rolling the cast over by a large angle in the frontal plane and adapting the cast mainly so the orthosis will fit in a shoe and be comfortable to the foot whilst attaining maximum kinematic effect.

    The Medial skive is just cutting a slice off the heel of the positive cast, the basic skive is a varus or frontal plane rotation modification but of course you can (as I often do) change the orientation of the skive wherever you choose for maximum kinetic effect. I think your abstract of your 1992 paper agrees with this i.e. it improves pronation control (3D) with a varus (single plane) modification

    J Am Podiatr Med Assoc. 1992 Apr;82(4):177-88.
    The medial heel skive technique. Improving pronation control in foot orthoses.
    Kirby KA. Author information Abstract
    A new method of foot orthosis modification that enhances the pronation controlling ability of foot orthoses is presented. The medial heel skive technique involves selectively removing small amounts of the medial portion of the plantar heel of the positive cast of the foot to create a unique varus wedging effect within the heel cup of the foot orthosis. The resulting increase in supination moment across the subtalar joint axis of the foot clinically produces significantly improved pronation control on pediatric flexible flat feet, posterior tibial dysfunction, and other types of excessively pronated feet.


    In the LHF modification the fact that the heel depth is lowered on the lateral side neccesitates that the heel cup must be relatively lower than its was and so the wedge must be re-orientated in three planes and cannot be single plane even if you want it to be.

    Thanks for the history, just shows - nothing new under the sun eh, but I'm more interested in understanding how the different designs are advantageous to the clinical effect required. Following reading this post and thinking about those parameters and effects of each design, I've just sent off a cast with a prescription for a 15dg Blake inversion modification plus a 5dg LHF and posted 5 dgs under the LHF only and no lateral heel cup plus a high medial flange. Will be interesting to see how this performs and how comfortable it is for this patient with post tib pain and a foot that is a very compliant cavus foot in open chain that is pes pancakus and severely f/foot abducted in closed chain..

    regards Dave
     
  11. Dave:

    The medial heel skive exists in all three body planes regardless of how I needed to briefly word the description of the medial heel skive "varus wedging effect" into the abstract of my 22 year old paper. Remember, the medial heel skive is rounded to the shape of the plantar heel and therefore is three-dimensional or tri-planar. The medial heel skive is not a flat varus plane which would be uni-planar. All curved surfaces are three dimensional, not uni-planar, so I don't understand why you are trying to pigeon-hole the Blake Inverted and medial heel skive techniques as being "uniplanar".

    I don't think many engineers who saw the surface of a curved object change from one curved shape to another curved shape would call the change in shapes of the object as being "uniplanar". Tell me, Dave, how does a change in a curved surface of a pre-medial heel skive positive cast to another curved surface of a medial heel skive positive cast become a "uniplanar" change when there are no flat planes involved?

    Rather, Dave, I believe that important point that you should focus on with all three of these varus heel wedge modifications for foot orthoses (i.e. the Blake Inverted Orthosis Technique, the medial heel skive technique and the DC Wedge Technique), is that they all introduce an increased "varus wedging effect" into the heel cup of the orthosis which, in turn, will shift the center of pressure medially under the heel and will increase the external subtalar joint supination moment. It really doesn't matter how you arrive at the varus heel cup shape in the orthosis, if the three-dimensional shape of the heel cups are the same and the stiffness of the heel cups are the same, then each technique will produce the same biomechanical effect.

    The Blake Inverted Orthosis Technique, the medial heel skive technique and the DC Wedge Techniques are all three-dimensional orthosis modification techniques, none are uni-planar and one is not necessarily better than the other.

    The key to successful orthosis therapy is to not know how to change the heel cup shape of an orthosis , but rather the key to successful orthosis therapy is:

    1) being able to know when to use a change in the heel cup shape of an orthosis to increase the therapeutic success of the prescription foot orthosis,
    2) being able to know what to do when the change in the heel cup shape does not work to relieve the symptoms or alter the kinetics and kinematics of gait, and
    3) being able to know what to do when the change in the heel cup shape causes increased symptoms or new symptoms.
     
  12. Dr Rich Blake

    Dr Rich Blake Active Member

    In my conversation with David Smith, I am trying to understand exactly how the DC Wedge works. This is a wonderful post so thank you Craig. We need a pronating patient of more than 5 degrees heel Valgus or medially deviated STJ axis to be fit for these technologies to begin our next 10 year process. Modified Root, Kirby, Inverted and DC wedge and PC wedge. Thanks Rich
    I believe each of these technologies each have subset of patients that they will be best for
     
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