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Transverse arch stiffness and ankle and hip joint moments

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Mar 27, 2017.

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  1. scotfoot

    scotfoot Active Member

    "The problem with that explanation is the difference between a foot and your bamboo construct"
    In terms of the principals under discussion , what is this difference ?
     
  2. efuller

    efuller MVP

    The half circle of wood is rigid. The bones are not rigid in the frontal plane like the half circle of wood is.
     
  3. scotfoot

    scotfoot Active Member

    One half circle corresponds to the tarsal bones .Are you saying that during terminal stance ,the midfoot provides no rigidity
    to the foot in the frontal plane ?

    Also would you accept that as terminal stance progresses and the heel lifts off the ground , met heads #2 and possibly #3 move distally relative to the other met heads causing the transverse ligament to become tensioned ?
     
  4. efuller

    efuller MVP

    I don't think it is know how much the bases of the metatarsals move relative to each other. The orientation of the ligaments is much more anterior to posterior, so there can't be much restraint of movement of the bases of the metatarsals relative to each other. However, where the model really breaks down is distally where the metatarsal heads can, and do, move independently of each other. This can be seen on clinical exam.



    No. The ligaments at the bases of the metatarsals would prevent this from happening.
     
  5. scotfoot

    scotfoot Active Member

    "where the model really breaks down is distally where the metatarsal heads can, and do, move independently of each other. This can be seen on clinical exam "

    The model explains only a general principal . When applied to the foot the system is DEPENDENT on the metatarsal moving independently of each other ,creating tension in the transverse arch .


    "No. The ligaments at the bases of the metatarsals would prevent this from happening " No, they would not . I don't think you are getting this bit .

    Back to the hand . Try it for yourself and see how, to remain straight , the finger tips of the middle two fingers of the four , MUST move distally . And with no strain at the knuckles . (the fingers are analogous to the metatarsals ) . The metatarsal parabola means this happens in the foot .
     
  6. scotfoot

    scotfoot Active Member

    If it helps , think of the distal half circle of wood as being representative of the deep transverse ligament and the ground under the metatarsals . As the forefoot becomes weight bearing the metatarsal heads are locked in position by ground reaction forces and strain in the transverse ligament acting in different directions . Hence , the unshod foot first adapts to the underfoot terrain and then in later stance , provides a bespoke rigid lever , for propulsion and traction . ( in the sense of grip )

    So to summarize , the foot first adapts to the underfoot terrain then becomes rigid in the most appropriate configuration . This adaptability is most apparent in the forefoot .
    An amazing structure .
     
  7. efuller

    efuller MVP

    What principle are you trying to explain?

    What anatomical structures are you claiming make up the transverse arch?



    You are right, I don't understand what you are saying.

    You wrote: "Also would you accept that as terminal stance progresses and the heel lifts off the ground , met heads #2 and possibly #3 move distally relative to the other met heads causing the transverse ligament to become tensioned ?"

    How can a metatarsal head move distally relative to another metatarsal without the base of the metatarsal moving distally as well. For a metatarsal to move distally relative to other metatarsals the base of the moving metatarsal would have to separate from the bone proximal to it. The ligaments prevent that separation.
     
  8. efuller

    efuller MVP

    I question your assumption of ground reaction force locking the metatarsals in place. They obviously move when heel lift occurs. The transverse intermetatarsal ligament actually connects to the plantar plates and the metatarsals pivot over their repspective plantar plate.
     
  9. scotfoot

    scotfoot Active Member

    "the metatarsals pivot over their repspective plantar plate. "
    I didn't know that Eric . Many thanks . So the met heads glide forwards to different extents to provide a more rigid structure as I thought . Also , its not the met heads that are locked in position but the respective plantar plates to which they are closely associated . Excellent . The theory develops !
     
  10. scotfoot

    scotfoot Active Member

    Well no . The met head can't move forwards relative their plantar plates and so the plates are largely irrelevant to the theory at hand . For a second or two there I thought we might be getting onto the same page .
     
  11. scotfoot

    scotfoot Active Member

    Eric
    You said this-

    "How can a metatarsal head move distally relative to another metatarsal without the base of the metatarsal moving distally as well. For a metatarsal to move distally relative to other metatarsals the base of the moving metatarsal would have to separate from the bone proximal to it. The ligaments prevent that separation. "

    Understanding what goes on here is pivotal to the discussion .

    Bear with me here . Back to the hand . Place you hand flat on the table with your finger tips a little spread apart . Now , keeping the fingers in line with the palm of the hand and not bending them at the knuckle , lift the heel of the hand off the desk and raise it whilst keeping the finger tips in place (tuck the thumb out of the way ) . What happens to the previously straight middle fingers of the hand ? Forget the foot for the moment .
     
  12. efuller

    efuller MVP

    The finger tips don't stay in place. If you don't bend the mcpj's the shorter fingers have their tips lift off of the surface. This is what you see in gait with the metatarsal heads.
     
  13. scotfoot

    scotfoot Active Member

    Or , to keep all the fingers straight and finger tips on the desk ,the tips of the fingers must move forwards . In the case of the foot this means the met heads move distally along with their respective toes .

    By a happy co- incidence Professor Hylton Menz has just placed radiographs of a foot in a flat shoe and
    in a high heel side by side in his latest post on twitter . Have a look and note the arrangement of the metatarsals .
    I have included a link but am not sure if it will work .
    https://twitter.com/hyltonmenz?ref_src=twsrc^google|twcamp^serp|twgr^author
     
  14. scotfoot

    scotfoot Active Member

    Ok the link works and you now have pictures . I can add no more .
     
  15. efuller

    efuller MVP

    Why would you model the finger tips staying on the surface when this is not happen in the foot relative to the ground?
     
  16. scotfoot

    scotfoot Active Member

    This is interesting especially "Other factors may be responsible for. the observed pressure increase, such as reduced range of motion of the metatarsophalangeal joints and increased stiffness of plantar soft tissues ".


    Plantar pressures and relative lesser metatarsal lengths in older people with and without forefoot pain

    Authors

    • Hylton B. Menz,
    • Mohammad R. Fotoohabadi,
    • Shannon E. Munteanu,
    • Gerard V. Zammit,
    • Mark F. Gilheany

    • Conflicts of interest: None of the authors have any financial affiliations or competing interests to declare.
    Abstract

    Forefoot pain is a common problem in older people. We determined whether plantar pressures during gait and the relative lengths of the lesser metatarsals differ between older people with and without plantar forefoot pain. Dynamic plantar pressure assessment during walking was undertaken using the Tekscan MatScan® system in 118 community-dwelling older people (44 males and 74 females), mean age 74 (standard deviation = 5.9) years, 43 (36%) of whom reported current or previous plantar forefoot pain. The relative lengths of metatarsals 1–5 were determined from weightbearing X-rays. Participants with current or previous plantar forefoot pain exhibited significantly (p = 0.032) greater peak plantar pressure under metatarsal heads 3–5 (1.93 ± 0.41 kg/cm2 vs. 1.74 ± 0.48 kg/cm2). However, no differences were found in relative metatarsal lengths between the groups. These findings indicate that older people with forefoot pain generate higher peak plantar pressures under the lateral metatarsal heads when walking, but do not exhibit relatively longer lesser metatarsals Other factors may be responsible for. the observed pressure increase, such as reduced range of motion of the metatarsophalangeal joints and increased stiffness of plantar soft tissues. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 427–433, 2013
     
  17. scotfoot

    scotfoot Active Member

    So looking at the above and the phrase "Other factors may be responsible for. the observed pressure increase, such as reduced range of motion of the metatarsophalangeal joints and increased stiffness of plantar soft tissues. " has started me wondering about increased stiffness in the feet of diabetic patients and the possible impact this might have on plantar pressures under met heads #2 and #3 in particular .
    Earlier in the thread I wrote "Metatarsal parabola + terminal stance = distal transverse arch . Can't be any other way . "

    For this to be true the met heads must be able to move relative to each other thus allowing a spread of pressure across the forefoot during gait . But what if diabetes induced stiffness prevents this from happening ? With the met heads unable to move relative the each other , then ,during late stance ,the pressure under head #2 in particular may cause repeated ulceration .

    So what can be done ? Professor Isabel Sacco has done a lot of work in the area of mobilizing foot and ankle tissues made stiffer by the effects of diabetes , and she has shown that these tissues respond well and become less stiff , using physiotherapy methods such as strengthening and stretching .

    So how can you stretch the forefoot across the met heads ,their associated capsules and the deep metatarsal ligament .

    Possibly as fallows . First an extract from earlier in this thread -

    "First I found myself a suitable surface such as linoleum . Next I took off my shoes and socks and stood next to a wall for support . Then , taking most of my weight initially on the right foot which was kept flat on the ground ,I put my left foot into toe off position so that only the ball of the foot and the toes were in contact with the ground . Then I carefully transferred some weight onto the left foot and finally,with the ball of the foot and toes under some pressure , rotated the foot outwards producing torque . I found that the toes played an important part in resisting the outward rotation and that they also began to become spaced out from each other possibly engaging the adductors .( please note that I am not suggesting that anyone copy the above exercise sequence or injury may result )
    So perhaps the toes can significantly aid grip on a flat rigid surface ? "

    This stretch might work to mobilize the tissues in question allowing met head movement and the avoidance of very large pressure under #2 , causing ulceration . However the stretching method could easily cause tissue tears between the toes if not done under expert supervision , at least during a learning process for the patient , and so should not be attempted without supervision by a podiatrist (and even then only following proper trials ) .

    Can the risks eventually be reduced if the exercise is found to be beneficial ?
    This might be possible by only carrying out the exercise in a seated position to reduce the stretching forces involved . Also ,instead of a material like linoleum being used underfoot a suitable gel like material might be used ,the consistency of which would allow the gel to distort or even tear , if a patient ,perhaps with sensory neuropthy , is applying stretching forces likely to case tissue damage .
     
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