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Kinetic wedge function and levels of success

Discussion in 'Biomechanics, Sports and Foot orthoses' started by codybloke, Jun 15, 2007.

  1. codybloke

    codybloke Welcome New Poster

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    Hi....just wondering if anyone can give me an explanation on how a kinetic wedge functions and share their experiences in regards to how successful they have been in treating functional hallux limitus.
  2. Admin2

    Admin2 Administrator Staff Member

  3. efuller

    efuller MVP

    There is less argument on whether it works as compared to the amount of argument of why it works.

    Functional hallux limitus occurs when there is near normal range of motion non weight bearing, but weight bearing the hallux is very difficult to dorsiflex. One explanation is that medial column (first met and toe) ground reaction force causes a dorsiflexoin moment on the ray. There is a plantar flexion moment from tension in the fascia that counteracts the dorsiflexion moment from the ground. You can palpate a tight fascia in functional hallux limitus in static stance. Tension in the fascia causes a plantar flexion moment at the MPJ that prevents dorsiflexion of the toe. This is why the toe is difficult to dorsiflex weight bearing. The other explantion does not directly explain which anatomical structures prevent the toe from dorsiflexing. The kinetic wedge or a reverse Morton's extension or a 2-5 extension decreases the total force on the ray, decreasing the tension in the fascia, which then allows the toe to dorsiflex in gait.


    Eric Fuller
  4. Jonatan García

    Jonatan García Active Member

    Before the presence of a functional hallux limitus we find tension in the fascia that cause when MPJ that prevents dorsiflexion of the toe plants flexion moment at the, for what we find an increase in the pressure on the hallux, if the kinetic wedge works, we will find during it use a decrease in the pressure on the hallux, Rambarran et to. (Http://www.health.uottawa.ca/biomech/lab/docs/asb25_kr.pdf) though they found a decrease in the pressure on the hallux it was not statistically significant when they were using the kinetic wedge, for what we might not conclude that the kinetic wedge is effective for the treatment of the functional hallux limitus. If we assume that you cause the tension of the fascia when MPJ plants flexion moment at the our aims they should go directed to eliminating this tension to promote the movement in the MPJ, if this tension in the fascia comes from an excessive pronación we would use a medial heel skive, besides it seems to be that to wedge under the wings aspect of the forefoot reducing strain in the to plant aponeurosis (J. Bone Joint Surg. Am. 81:1403-13, 1999), for what this wedge would be a part of the treatment. I personally would treat it with an ortesis that had a medial heel skive and other elements of control of the pronación (as the Dr. Kirby comments in his books, longitudinal internal arch with his forces reactivate of the orthesis, etc.) and to wedge under the wings aspect of the forefoot.

    Cheers and sorry for my english.

  5. efuller

    efuller MVP


    Thanks for providing a link to the study. The study did say that the 1st met head pressure was lower with statistical significance. The hallux pressure had a trend to lower pressure. Two comments: The total force on the ray is less in this session and therefore the structures that hold the ray down (i.e. the plantar fascia should have less tension in them. So, the data from the study support the notion that the kinetic wedge decreased tension in the fascia.
    The second point is motion of the MPJ was not examined. If there was more dorsiflexion of the hallux that would create a step that was not directly comparable to the Non Kinetic situation. Was there the same amount of power output at the ankle. Without the kinetic wedge was the foot lifted off of the ground with less ankle push?

    On using other anti pronation features in the orthosis. You have to look carefully at the cause of STJ pronation. In some feet (more medially positioned STJ axis) the ground is causing the pronation. In other feet (more laterally deviated STJ axis) the muscles are causing the pronation. A rearfoot varus wedge effect device (i.e. medial heel skive) will paradoxically increase pronation in feet with laterally deviated STJ axes. The muscular pronators (those feet whose pronation is caused by the muscles) contract there muscles to prevent oversupination and you will often see these feet exhibit a gait where there is some early pronation, then a stopping or slowing of pronation and then near heel off a later phase of pronation. This may appear worse with varus heel wedge effect devices. The pronation from the muscles causes a high load under the first metatarsal and this high load will cause tension in the plantar fascia.

    The load in the fascia is related to STJ position and load on the ray.


    Eric Fuller
  6. Jonatan García

    Jonatan García Active Member

    Dear Eric Fuller,

    Thank you for your response, I have to learn more english.

  7. Stanley

    Stanley Well-Known Member

    Eric, I enjoyed reading your theory, but I am confused. :confused: According to Gray’s anatomy (http://education.yahoo.com/reference/gray/subjects/subject/131), the plantar fascia does not insert into the first metatarsal head. How does the plantar fascia hold the first ray down?

    Thank you for trying to help me understand foot function. I can't wait to apply your concept. Just one question, which foot type requires a rearfoot valgus wedge effect device that will paradoxically increase supination in feet, the type in which the muscular supinators (those feet whose supination is caused by the muscles) contract their muscles to prevent overpronation, so that the supination from the muscles will decrease the load under the first metatarsal and decrease the high tension in the plantar fascia.


  8. kevin miller

    kevin miller Active Member

    Bruce Stanley,

    As always you are right. The midfoot mechanism is way to complicated to go into here, and I really didn't post to expound on their position or malpositin. What I wanted to add to the mix was the neuromuscular adaptarion that occurs when a set of joint receptors are activated. There are a series of them ranging from the ones in the joint, in the capsule, and the tendon. (yes the GTO has effets away from the site of insult). we are waiting on a michine to quantify this, but you can check yourself on a patient with equinus talus. Thier hip Abdutors will be weak on the involved side. Other muscle are transiently weak as well, but this one is the easiest to find. As soon and you fix the foot, all is well. Now, consider what a set of week rotary muscles in the hip do to the back. The point is we don't need a serious biomechanical problem to get proximal symptoms, just muscle imbalance. have fun....
    kev ps how do you spell check on this thing?

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