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Isometric function of the flexor hallucis longus muscle in normal gait

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Jun 10, 2008.

  1. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1

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    Evidence of isometric function of the flexor hallucis longus muscle in normal gait.
    Kirane YM, Michelson JD, Sharkey NA.
    J Biomech. 2008 Jun 4;41(9):1919-1928. [Epub ahead of print]
     
  2. Stanley

    Stanley Well-Known Member

    This corresponds to the research done on birds that walk great distances.
    The longer tendons have a greater ability to stretch, so they can respond better to variations in terrain and still allow for an effecient gait.

    Stanley
     
  3. What does this tell us about functional hallux limitus/ windlass function etc.?
     
  4. Stanley

    Stanley Well-Known Member

    It goes along with the plantar fascia storing energy to allow for efficient propulsion in the normal foot.
     
  5. efuller

    efuller MVP

    Just a thought. If the flexor hallucis is providing isometric force, it is essentially reinforcing the plantar fascia. It may be an explanation of the why the spur is not really at the attachment of the fascia. Muscle tension could be the cause of the spur instead of the fascia.

    Treatments designed to decrease tension in the fascia would also reduce tension needed in the muscle.

    Is this flexor hallucis as well as abductor hallucis?


    Regards,

    Eric
     
  6. Adrian Misseri

    Adrian Misseri Active Member

    Hey Eric,

    Simon Smith's research is demonstrating that the spur is occuring in the insertion of flexor digitorum brevis, and not in the plantar fascia. But certainly, any intervention designed to reduce tensile forces across the plantar fascia (i.e. low dye taping), should reduce these forces to all the short structures under the foot, i.e abductor hallucius, flexor hallucis brevis. However, can this mean that then the FHL tendon has to activate harder under loading if the pressure across the plantar fascia is mechanically reduced such as in low dye taping, as it is working over a slightly shorter distance?
     
  7. efuller

    efuller MVP


    One interesting thing from the Hicks experiments was that Flexor Hallucis Longus (FHL) activation (pull on the tendon) raised the arch when the foot was standing. So, something that would reduce tensile forces needed for the plantar fascia would also decrease the need for high tension in the FHL muscle.

    One distinction to make is the difference between stress on anatomical structures and position of anatomical structures. I really doubt that a low dye strap, stuck to the skin over the bone can actually keep the arch higher than when the foot does not have the tape on. However, it can create a plantarflexion moment when the foot is loaded in a relatively flat position and take some of the stress off of the fascia and muscles. There is a difference between plantar flexion motion and plantar flexion moment.

    On muscle length and force produced. If you look at the maximum force produced versus muscle length curves, there is usually a range over which the maximum force can be deveoped. Within a given range of motion the force developed by the muscle is independent of the length of the muscle. However, the FHL is quite interesting in that within physiologic range of motion of the joints that the muscle crosses it can lose power. You can test FHL strength with the ankle dorsiflexed and see a strong muscle and you can test it with the ankle plantar flexed and the muscle will develop very little moment at the 1st IP joint. The muscle is shortened enough with plantar flexion of the ankle it cannot produce any additional shortening to plantar flex the IPJ. Thinking about it makes sense in the time in gait in which you would want to produce moment at the IPJ is at the time the ankle is maximally dorsifexed.

    Cheers,

    Eric
     
  8. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
    1
    Contribution of the flexor hallucis longus to loading of the first metatarsal and first metatarsophalangeal joint.
    Kirane YM, Michelson JD, Sharkey NA.
    Foot Ankle Int. 2008 Apr;29(4):367-77.
     
  9. Stanley

    Stanley Well-Known Member

    Nice hyposthesis, but it doesn't work this way in real life.
    The Functional Hallux limitus results in a stretching of the plantar structures (capsule and sesmoidal ligaments). This results in a tightening of these structures and a decrease in joint range of motion.
    A little ultrasound and deep friction massage to the plantar structures will increase the motion in the first MPJ by 10 degrees.
    First palpate for the tender sesmoidal ligaments. Usually the best direction to rub is distally, then follow up with orthoses, and the joint range will continue to increase if there is no osseous restriction.
     
  10. Adrian Misseri

    Adrian Misseri Active Member

    Stanley, is this for isolated functional limitus, or can it be aplied to all hallux limitus situations without actual osseous joint blocks, ie. metatarsus primus elevatus with mo exostosis growth aroudn the first MTPJ?
     
  11. Stanley

    Stanley Well-Known Member

    Adrian,

    The technique I described is to increase the range of the first MPJ without bony blocks. If there is a bony block, I can get only a few degrees more range of motion.
    I also use this in conjunction with orthoses, as the change will be short lived without them (you have to treat the cause in addition to the results).
    Regarding the metatarsus primus elevatus, my understanding is this occurs in long standing FnHL. Orthoses are the best way to treat it. If there is a decrease in the range of motion of the first MPJ, then this would be an adjunctive treatment.
    The sesmoidal ligaments are not the only ones that should be evaluated. The medial collateral ligament should be checked (especially after HAV or Hallux limitus surgery) and also rubbed distally. If there is pain when inverting or everting the proximal phalanx, then check the capsule at the dorsal aspect of the first MPJ.
    Try these techniques and let me know what you find.
    Just for a little history, there was a device known as the Budin Traction Apparatus that was used to increase the first MPJ range of motion using traction.
    http://www.google.com/patents?id=aX...a=X&oi=book_result&resnum=9&ct=result#PPA1,M1

    Regards,

    Stanley
     
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