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Midtarsal joint locking

Discussion in 'Biomechanics, Sports and Foot orthoses' started by mike weber, Nov 19, 2009.

  1. Just read the paper. When, in the second paragraph of the paper, the authors stated "The idea of a locking and unlocking mechanism in the foot has been previously explained using the convex curvature axes of the talonavicular and calcaneocuboid articular surfaces (Elftman,1960). Inversion or eversion of the subtalar joint changes the direction of the convex curvature axes of the talonavicular and calcaneocuboid articular surfaces, which might lock or unlock the midtarsal joint and contribute to either a rigid or flexible foot structure (Tweed et al., 2008;Elftman, 1960)", I immediately lost much interest in the paper. Elftman? Really! The paper by Elftman was a joke and would never be published today. Yet, Elftman's paper forms the basis for the authors' contention that the midtarsal joint "locks". In the Journal of Biomechanics, no less!

    For those of you not familiar with Elftman's often-quoted 1960 paper, Elftman used his eye of a connoisseur method to inspect the joint morphology of the midtarsal joint visually and claimed there was a major and minor “axis of curvature” in both the talonavicular joint and calcaneocuboid joint (Elftman H. The transverse tarsal joint and its control. Clin Orthop. 1960; 16:41-44). He proposed that when the major axes of the talonavicular joint and calcaneocuboid joint were parallel to each other with the subtalar joint pronated, there would be more midtarsal joint motion available. Unfortunately, podiatric schools around the world are still teaching this idea that alignment of visually determined midtarsal joint “axes” are what make the midtarsal joint more compliant in pronated feet, even though there is not a shred of research evidence that supports Elftman’s theory.

    In addition, there was no mention of the windlass effect of Hicks to explain the MTJ plantarflexion during propulsion and there was not a single mention of the mechanical effect of the plantar fascia in stiffening (i.e. "locking") the midtarsal joint. Disappointed!
     
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    NewsBot The Admin that posts the news.

    Articles:
    1
    Design of a Robotic Foot with Midtarsal Joint Locking Mechanism
    Kazuma Enomoto; Tsung-Yuan Chen; Takumi Kawasetsu; Koh Hosoda
    2022 IEEE 5th International C...
     
  3. efuller

    efuller MVP

    The funny thing about the flawed idea of the locking mechanism of the midtarsal joint is the confusion between range of motion and stiffness. There is a phenomenon in the foot with STJ range of motion there is an increase in range of motion of the midtarsal joint. Specifically the location of the end of range of motion changes. By end of range of motion I mean as you move the joint through a range of motion in a particular direction there there is a zone where the resistance is the mass of the forefoot (almost zero). As you keep going there is a point where resistance increases and you can then measure the stiffness at that point. What I think happens with motion of the subtalar joint is that the location of the end of range of motion changes. The stiffness at the end of range of motion does not necessarily change.

    Theory of the locking mechanism was mistakenly applied in that it was expected that the foot became a loose bag of bones when the STJ was maximally pronated. However, you could see people running, with their STJ maximally pronated and exhibiting a very stiff midtarsal joint (minimal deformation with high load). The point at which the joint becomes stiff may have changed, but when it gets there it can be stiff.

    The abstract in the paper above does not say whether they changed stiffness or range of motion. Decreasing the stiffness would probably lead to less efficient gait even though they are trying to improve the efficiency.
     
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