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"Auto-support" of the foot

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Simon Spooner, Nov 30, 2009.


  1. Members do not see these Ads. Sign Up.
    All,

    I'm keen to explore the concept of "auto-support" of the foot. My first introduction to this term was in Howard Dananberg's paper "gait style as an aetiology to chronic postural pain part 1"- too many years ago. As memory serves the mechanisms that are supposed to contribute to this are:

    1. windlass mechanism
    2. calcaneo-cubiod joint locking
    3. locked wedge/ truss effect

    Does anyone else think it might be time to re-examine these and moreover, the concept of auto-support per se?
     
  2. Starter for ten:
    I just walked backwards and sideways, there was no real observable dorsiflexion of the toes, my feet didn't collapse. Has anyone ever seen a foot with arthrodesis of all MTPJ's or a foot with amputation of all toes- were these feet incapable of supporting themselves, or did they just adopt a different position of rotational equilibrium and function differently during flat, level walking?
    Do joint's lock? Say no more...
    Interesting one.........
     
  3. Auto-support::cool:;):eek:
     

    Attached Files:

  4. You got me. Laughed out loud! Just what I needed Prof. Kirby.:drinks
     
  5. Mart

    Mart Well-Known Member

    My understanding of autosupport is not as extreme as this.

    I think that the intent was to imply that a well functioning windlass is likely to mittigate deforming forces acting though the foot generally. In addition if those forces became injurous (by causing structural overload) improving windlass would by implication be therapeutically helpful.

    I agree that the premise may be flawed but it seems pausible and not neccessary undermined by your comment above.

    Good subject :drinks


    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  6. Ok so the "premise may be flawed", and yet "seems plausible"- OO, I think these might be yours that I'm holding in my hands, Martin. Only joking. Explore this with me..

    Lets take a look at the definition of "auto-support" first. I'll need to go back to the original paper, which will take some literature review- anyone provide it?
     
  7. Got a good return-chuckle with this one, Dr. Spooner. In fact, I just may nominate this one for our upcoming vote on best Podiatry Arena quotes for 2009.:drinks
     
  8. Mart

    Mart Well-Known Member


    I had not realized that this term was coined by Howard Dannenberg, I will try and dig out his paper unless someone has a scanned copy. Unfortunately it is doesn’t seem to be available digitally so will need scanning.

    I was just thinking about why “autosupport” seems plausible to me.

    Mostly I think because it has a mechanically pleasing aesthetic. I find the notion of evolution selecting for energy efficiency in gait as a major determinant for why things are the way they are appealing given alternatives.

    Since we are largely attempting a reverse engineering exercise in creating theories to explain foot function and dysfunction it seems reasonable to look to that as a highly ranked clue.

    I think it was you that introduced me to the notion of “mechanical intelligence” and this superficially seem to fit that moniker.

    What I lack of course is evidence that windlass does improve energy efficiency, but it does seem intuitively probable. I think this was Dannebergs implied perhaps explicit premise but haven’t read his stuff for ages.

    Would you let us know how your feet feel after walking backwards for 30 mins?

    Don’t do this without supervision though.

    Cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  9. Mart

    Mart Well-Known Member


    Now you will have to spell this out for me . . . . . I have to admit that it has gone completely over my head :eek:


    cheers (I think)

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  10. Martin:

    Just Simon being himself.....with tongue in cheek....I'm sure no harm intended.

    BTW, talk about rotational equilibrium.........hope that truck doesn't suddenly lose its "auto-support" of 4 x 4's and crush our budding auto mechanic.:D;)
     
  11. Sammo

    Sammo Active Member

  12. Mart

    Mart Well-Known Member


    fair crack of the whip . . . . I could feel some incipient paranoia which is a bit of a hazard after smoking a bit too much podarena for one day.

    :drinks
     
  13. Thanks Sam got to have them on the computer now not paper copies.

    Here some other articles for people who don´t have them.
    1 eric about windlass and the other about high and low gear which explain cuboid-calcaneal compression.
     

    Attached Files:

  14. Morning Simon.

    I´ve just done your little sideways, backwards walk.

    What I considered that COP was very different to walking forwards and equilibrium is found in very different ways.

    I beleive that Windlass is a none muscle support mechancism that helps in re supination. So auto-support may not be the best term as it indicates that the foot would collapse without windlass. But if you consider that it is an important mechancism which occurs without a direct brain influence ( ie auto) and windlass will support the Medial Longitudial arch ( MLA ) then the term works.

    Without this automatic mechanism muscle function on the medial aspect of the Subtalar Joint Axis must be increased to have resupination.
     
  15. Supination = good; pronation = bad

    Is this still believed?
     
  16. I don´t think so.

    Pronation and Supination are both motion that are important its the stopping them that causes the problems ( to modify Craigs quotes on this subject)


    But I still beleive resupination is an important mechanism. Do you think I´m wrong in thinking this ?

    EDIT maybe it would be better not to say resupinated but to be going thru the motion of supination at from heel lift to toe-off in the gait cycle.
     
  17. I think Craig's pearl regarding the shank driving the foot and not the foot driving the shank may be of considerable importance.
     
  18. I put that edit in while you were posting.

    If I get what Craig says. The Plantar fascia would be the shank of the foot(?)

    The above statement would only be correct when there is dorsiflexion of the 1st mtp joint and windlass. In negative windlass the foot and body drive the shank ?
     
  19. Michael, when I use the term "shank" I am referring to the leg. Craig's assertion was that the leg drives the foot. So depending on the activity the leg may internally rotate, externally rotate or not rotate at all.
     
  20. ok thanks for clearing that up..

    Heres the quote you refer to
    Before I go off again on the wrong path once again . Would this have alot to do with the "preferred motion pathways and EMG " stuff by Nigg et al that you gave up to read in the orthoses thread ?
     
  21. I don't know. I'm just thinking out-loud, Michael.

    If we were walking forward in a straight line on a flat level surface would it be most efficient for the support leg to be: a) internally rotating; b) externally rotating; or, C) not rotating in the transverse plane during the propulsive phase of walking? in other words would it better for the foot to be pronating, supinating or neither pronating nor supinating?
     
  22. I would say C. Not pronating or supinating.

    Here´s my reasons.

    1. Would allow the strongest plantarflexion muscles to have better propulsion effect ( gast,sol)
    2. Greatest energy efficent in relation to muscle fatigue.
    3 Body would travel in same direction as propulsion.
    4 better use of vasoelastic effect of plantar foot muscle and fascia.
    5 reduced compression stress in the medial or lateral knee joint.

    thats what I got for now

    1 more it would create a more efficent lever arm . ie motion travels straight over foot not across at an angle
     
  23. Ive just thought about this statement it may not be so correct and choosing the easier path of motion that´s the whole idea about high low gear of Bjosen-Moller ........off to think a bit.
     
  24. OK, Michael. While you are there, think about this: lets say our right leg is the support leg, again walking on a flat level surface but this time we want to veer off to the left in our direction of travel. Is it more efficient for the foot to be pronating , supinating, or neither pronating nor supinating during propulsion? Now think about veering off to the right.
     
  25. I think I need PA support group. Came to pick up a pair of orthotics to recover in the lab, but found myself at the computer.

    Question 1 right foot-support veer of to the left. more efficient to pronate

    Question 2 right foot support veer to the right more efficient to supinate.

    I beleive this to be the case because of the mass of the body. If we want to change direction we get the COM of the body moving in that direction. It make no mechancial sense to accelerate the COM in one direction then stop it an accelerate it in the other. The body as a whole will take the easier path even if the foots motion path is not the easier path.

    The foot is connected to the body is a signiture Ive seen somewhere on PA, maybe we forget that
     
  26. OK so now you have a range of propulsive strategies, one requiring pronation, one supination and one neither. Hmmm.

    Now try this: take a weightbearing foot then take each digit in turn and dorsiflex it, like a Jacks test but not just the big toe (I call this the lesser digit dorsiflexion test when testing digits 2-5). What does the dorsiflexion of each toe do to the STJ in each case?
     
  27. OK so now you have a range of propulsive strategies, one requiring pronation, one supination and one neither. Hmmm, what does this tell us?

    Now try this: take a weightbearing foot then take each digit in turn and dorsiflex it, like a Jacks test but not just the big toe (I call this the lesser digit dorsiflexion test when testing digits 2-5). What does the dorsiflexion of each toe do to the STJ in each case?
     
  28. 1st I believe it will depend on the stj axis. So will be different to every person Mine is quite lateral.

    so 1st dorsiflexion ( d) - supination
    2nd d-supination but less
    3rd d- supination but less again
    4th d- no movement
    5th d pronation.

    That the body as a whole will take the path of least resistance to move the COM
     
  29. Maybe it will, but what I hoped to lead you to was that the need for "re-supination" may well be task dependent.

    I'm sure the STJ axial position is significant in this. On my right foot I get pronation on all but the 1st MTPJ.

    So does this mean that if I use a lateral propulsive strategy , i.e push off from metatarsal heads 2-5 my windlass mechanism will generate a net pronation moment?

    Lets go back to veering off to the right. You said it would seem advantageous for me to veer off to the right with my right foot supinating-right? To this I'd add that it would also probably help to push-off obliquely through my lateral axis (low-gear axis). However in this situation my windlass mechanism through my low-gear axis may be generating a net pronation moment which is working against what my STJ wants to do. So how do we still achieve the preferred movement pathway?
     
  30. Ok I´m not so sure about this but considering whats been said

    The body would cause the tibia to externally rotate. Which will then cause a Supination moment at the STJ which will then causee a lateral deviation of the the stj axis which will mean more of the 2-5 toe ( low gear) will be medial to the STJ axis which will mean now there is a greater windlass effect. This will also mean the the low gear toes will still be able to provide acceleration in the direction of movement to aid in propulsion to the right in this case.

    hope that make sense.
     
  31. I agree with pretty much everything you have written here. The bit I don't like is: "more of the 2-5 toe ( low gear) will be medial to the STJ axis which will mean now there is a greater windlass effect". It is important to realise that there is a "windlass effect" whether it generates net supination or net pronation moment.

    Now do the same analysis for veering off to the left using a "high gear" strategy.
     
  32. Mart

    Mart Well-Known Member

    Nice citation, however the Irish Sea is not a representative environment for normal demands on the human foot or the shank. Spike could definitely think outside of the box, perhaps he was onto something. :drinks

    cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  33. ok Internal Tibial Rotation which will cause a stj pronation moment which will lead to medial deviation of the stj axis. now here where things get a bit tricky

    idea 1 - the deviation of the stj axis is so medial that the insertion of the medial band of the plantar fascia is lateral to the stj axis which will mean a greater pronation moment.

    idea 2 the medial deviation of the stj axis causes a FHnL which means there is no windlass.

    idea 3 the pronation moment from the interal tibial rotation is greater than the windlass supination moment so pronation still occurs. ( this one is sending a few alarms bells off in my head but will put it ou there anyway)
     
  34. Remember that the plantar fascia has insertions (not singular) so as the axis shifts medially the net supination moment is reduced or put another way the net pronation moment is increased. Michael, you've pretty much arrived at something I noted back in about 2002, that is, in association with low gear propulsion we see lateral deviation of the STJ axis, viz. STJ supination and with high gear propulsion we see medial deviation of the STJ axis, viz. pronation. And that the function of the windlass mechanism is likely to be partially dependent upon the STJ axial position. I hope you can see that "windlass function" may not always = re-supination or even net supination moment.

    So, we have a hypothetical situation in which the windlass mechanism may result in increased foot pronation, pronation should result in loose packing of the midfoot- right? In this situation is the windlass adding to the foot's auto-support?
     
  35. Graham

    Graham RIP

    simon,

    Or visa Versa!

    __________________
    However, the heel is raising at this point - ankle plantar flexion, which is not an element of "pure" pronation.

    thoughts?
     
  36. Mart

    Mart Well-Known Member

    If I use a normal stride length I can't avoid dorsiflexion of hallux at foot contact in which case windlass takes immediate effect. I would estimate more effective stabilisation from windlass walking backwards since acceleration onto hallux would be higher and not inhibited at onset by metatarsal head ground reaction forces.

    Also if windlass doesnt have some form of protective function ie stabilising capacity of midfoot what better explaination might here be that fasciotomy see m to create problems in this region?

    cheers

    Martin
     

  37. [QUOTE I hope you can see that "windlass function" may not always = re-supination or even net supination moment.

    Thats the thing that takes time. Normal thought windlass supination moment, but we must consider where in relation to the stj axis the pull comes from. you still have the windlass effect. nice ( only 7 years after not bad :D)

    So, we have a hypothetical situation in which the windlass mechanism may result in increased foot pronation, pronation should result in loose packing of the midfoot- right? In this situation is the windlass adding to the foot's auto-support?[/QUOTE]

    2 things in the pearls of biomechanics thread Blinda said something about negative windlass and tension of the PF. Here it is

    might be something to consider.

    As for the autosupport mechnism the correct answer is sometimes depending on the position of the STJ axis.
     
  38. Graham the visa versa is that saying that windlass function may not always = pronation or a pronation moment or are you saying that the windlass mechanism will effect the stj axis position ?

    becasue I think we have discussed that windlass can cause and change in STJ axis position. whether the axis moves laterally or medially will depend on the position that the stj axis is in when the 1st mtp begins its pull on the PF.
     
  39. Mart

    Mart Well-Known Member

    When walking sideways my leading foot supinates and the trailing foot pronates. The leading foot then seems to adopt autosupport configuation I assume because of rapid lateral decelleration force at contact and external sub-talar joint supination moment applied from this.

    Evolution seems to have imparted autosupport then irrespective of direction.

    cheers

    Martin


    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
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