Welcome to the Podiatry Arena forums

You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members, upload content, view attachments, receive a weekly email update of new discussions, access other special features. Registered users do not get displayed the advertisements in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!

  1. Everything that you are ever going to want to know about running shoes: Running Shoes Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
  2. Have you considered the Critical Thinking and Skeptical Boot Camp, for taking it to the next level? See here for more.
    Dismiss Notice
  3. Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
Dismiss Notice
Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
Dismiss Notice
Have you liked us on Facebook to get our updates? Please do. Click here for our Facebook page.
Dismiss Notice
Do you get the weekly newsletter that Podiatry Arena sends out to update everybody? If not, click here to organise this.

Lateral arch on orthosis: do or don't?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Kenva, Nov 20, 2010.

  1. Kenva

    Kenva Active Member


    Members do not see these Ads. Sign Up.
    Hi all,

    I was (again) confronted today during an local conference on the use of orthotic therapy that flattening the lateral arch is something that is NOT DONE because you completely 'botch up' the locking mechanism of the midtarsal joint, ...
    If you go back to the locking mechanism decribed by bosjen moller in 1979, a lot is written on how it (the locking mechanism) is suppose to work:



    and a few nice threads have already discussed this topic, but nothing really says how, if the theory would be considered correct, an orthotic device would add to the effect of locking the midtarsal joint.

    If I would want to make a device that has a maximal inversion moment (ie as treatment in childeren with a "serious" valgus position of the calcaneus and, and when walking ,"overpronating"...) i would want the device to push on the medial side of the calcaneus. As a result of this I often ask (my lab) for the lateral arch of the foot to be lowered or even flattened completely so that the inversion effect of the device is maximal and the patient isn't pushed on a bump on the lateral side of the device. Now according to my colleague, this is absolutely not done. I was wondering if there was any good, preferably evidence based, explanation to this statement. I'm always keen to learn and to adjust my scope on biomechanical treatment. However,this just could be another case of contextual relativism... Can anyone enlighten me here please...

    Thanks
    K.
     
  2. Kenva

    Kenva Active Member

    Hi all,



    I was (again) confronted today during an local conference on the use of orthotic therapy that flattening the lateral arch is something that is NOT DONE because you completely 'botch up' the locking mechanism of the midtarsal joint, ...

    If you go back to the locking mechanism decribed by bosjen moller in 1979, a lot is written on how it (the locking mechanism) is suppose to work:





    and a few nice threads have already discussed this topic, but nothing really says how, if the theory would be considered correct, an orthotic device would add to the effect of locking the midtarsal joint.



    If I would want to make a device that has a maximal inversion moment (ie as treatment in childeren with a "serious" valgus position of the calcaneus and, and when walking ,"overpronating"...) i would want the device to push on the medial side of the calcaneus. As a result of this I often ask (my lab) for the lateral arch of the foot to be lowered or even flattened completely so that the inversion effect of the device is maximal and the patient isn't pushed on a bump on the lateral side of the device. Now according to my colleague, this is absolutely not done. I was wondering if there was any good, preferably evidence based, explanation to this statement. I'm always keen to learn and to adjust my scope on biomechanical treatment. However,this just could be another case of contextual relativism... Can anyone enlighten me here please...



    Thanks

    K.
     
  3. Re: Lateral arch on arthosis: do or don't?

    Simon Knows all about the locking mechanism of the mid tarsal joint. I'm sure he'll explain it better than me! ;)

    Seriously, I don't know that there is much by way of evidence for this and as you've said, a good case can be made on both sides of the argument. I guess it depends on the foot because as we know, the same insole will behave differently in different feet.

    But as you know, I generally flatten my lateral arches (or dorsiflex the 5th met if you prefer), especially in paeds. So you're not alone.
     
  4. Kenva

    Kenva Active Member

    Re: Lateral arch on arthosis: do or don't?

    Thanks Robert,

    The thing is, I know I'm not alone on this, and this is what i've been teaching my students for the last 5 or so years... but I'm just trying to build my case, if not for myself (and my ignorance) for the people who have the 'illusion' of knowledge.

    I think i'm going with a new quote here;):

    "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge". Stephen Hawkins
     
  5. efuller

    efuller MVP

    Evidence: There was an article that a valgus wedge decreased tension in the plantar fascia in cadavers.

    Some thoughts that might need more explanation in relation to your question.

    Kemba, are you aware of how an intrinsic forefoot valgus post will raise the lateral arch of an orthosis. A forefoot valgus intrinsic post is theorized to work like a valgus wedge.

    Some folks leave a wet foot print that has no water under the lateral arch. Those folks, in my experience, are more likely to develop problems related to high pressure on the forefoot. Bringing the "ground" up to lateral arch will increase the area of contact and therefore reduce the pressure on the forefoot (in stance and before heel off in gait.)

    The right amount of lateral arch is dependent upon the shape of the foot when there is some load (from plantar to dorsal) on the forefoot. In that position the plantar ligaments will have some tension and will be resisting some load applied to the metatarsal heads.

    Too much arch may feel like a lump under the lateral forefoot.

    Hope this helps in your quest to figure out how much lateral arch there should be.

    Eric
     
  6. Kenva

    Kenva Active Member



    That I have read and understand well, but the question is more orientated towards locking the MTJ and a Lateral arch (shaped by lateral calcaneus, cuboid 5th met) support





    This one is not really clear for me. I know an intrinsic rearfoot post (varus/valgus)

    But please explain what you mean with intrinsic forefoot post. Is this positioning the rearfoot in valgus (letting muscle activity pull the 5th met back against the ground?)





    I absolutely would think the same way here, but again, the question is more in the direction of an intrinsic rearfoot varus post (where we want to push on the medial side of the calcaneus) to create an inversion/supination moment around the STJ, I would tend to decrease the lateral arch. But does this mean "theoretically" that I slow down the locking of the midtarsal joint (preparing the foot for propulsion)?



    Ken
     
  7. efuller

    efuller MVP

    I've moved away from the concept of locking the MTJ. There is something there, but the term is not precise. What I get from the term is that when you load the MTJ there is a point when you will get increased stiffness. That point is when the ligaments become tight.

    I prefer to think in terms of load. Some feet in stance will have very little load under the lateral forefoot. (John Weed used to describe having patients stand on hand with his hand under the lateral forefoot. Sometimes, you could leave it there all day, others it really hurts.) For those will little load on the lateral forefoot you want to bring the ground up to the forefoot with a forefoot valgus wedge so that the load becomes more evenly distributed. I think this is why "locking" the midtarsal joint works.


    Development of the functional orthosis. Root ML.
    Clin Podiatr Med Surg. 1994 Apr;11(2):183-210.

    That articles has pictures. I believe Ray Anthony also wrote a book about construction of the cast.

    When the orthotic is made with an intrinsic forefoot valgus post the distal lateral tip will curl away from the foot when the foot is placed in the position that it was casted in. This curl will raise the height of the lateral arch and in so doing will create a wedge effect in the orthosis.

    Since the metatarsal shaft is supported, the only way to get the 5th met to the ground is break the metatarsal.



    Sometimes the problem is caused by excessive medial forefoot load and not by STJ pronation moment. Yes, you can try to decrease load on the first met head/medial forefoot by trying to supinate the STJ. However, a lot of feet won't change position when you try to supinate the STJ, so you have to decrease the load on the medial column some other way (e.g. increase load on lateral forefoot). Yes a forefoot valgus wedge will tend to increase pronation moment from the ground, but you have to focus on what structure you are trying to reduce stress in. You can have a medial heel skive and forefoot valgus post in the same device.

    Eric
     
  8. Kenva

    Kenva Active Member

    This almost sounds painfull :wacko:


    You mean pronation moment arount the MTJ?
    I think the focus should indeed be on the structure that is "working overtime" because that's where your therapy is gonig to have the most success.

    Now from the replies I had, would it be fair to state that:
    The absolute necessity to maintain the lateral arch in order to prepare the foot/MTJ for propultion is not scientifically proven and possibly obsolete?

    Regards
    K.
     
  9. Ken Ive written this 3 times. Are you talking about MTJ locking or high-low gear propulsion ?
     
  10. Kenva

    Kenva Active Member

    Hi Michael,
    Where exactly did you write this 3 times?
    I suppose my colleague means locking the MTJ to go for a High Gear Propulsion...
    Since the lateral arch is in the midfoot I have to guess that he's stricktly talking about MTJ locking as HG/LG push off is a possible result of this...

    K.
     
  11. Ken Ive written and then not pressed submit not that you have not answered, sorry for the confusion:drinks - I was just a bit confused by the whole locking thing.

    Thanks for clearing it up.
     
  12. efuller

    efuller MVP

    I meant pronation moment about the STJ.

    In my earlier post I gave a couple of reasons to maintain the arch, but they were not for the reason of preparing the foot for propulsion. How would a foot be prepared for propulsion by the arch of orthotic?

    Eric
     
  13. Kenva

    Kenva Active Member

    But then I suppose that when you place a valgus wedge under the forefoot, the midtarsal joint (or 3,4 and 5th met head) should reach end range of motion (dorsifexion/stiffness) for it to influence the STJ (causing pronation).

    My question exactly :bash:...!!
     
  14. Another point to note is that by elevating the orthosis to form a lateral longitudinal arch, this section (depending upon the material properties of the device) may effectively become "non-shank-dependent" whereas in the case of a flatter lateral orthotic section which is in contact with the shoe, this portion is effectively "shank-dependent". Think also how the curvature of this area of the orthotic shell influences the stiffness characteristics both here and of the device overall. For example, if the lateral midfoot section is now relatively more compliant then the medial midfoot segment is relatively stiffer in comparison and vice versa. How will this influence centre of pressure position and pathway?
     
  15. Kenva

    Kenva Active Member

    Hi Simon,

    This is a very good point indeed. It all comes down to where you want the device to be pushing against the foot (and how much).
    The problem of the initial question is one of theoretical framework I suppose. I tend to lean towards Tissue Stress as this model makes more sense to me than difficult, still not scientifically proven (unless anyone can point me in some direction) statements...
    I'm open for new insights, the guy is quite convinced of his 'right' and my 'wrong'...
    K.
     
  16. And when.
     
  17. both ideas could be right or wrong depending on the patient and what you trying to acheive.
     
  18. Kenva

    Kenva Active Member

    But the guy is in the 'not done ever' phase it is, according to him, not biomechanically sound. Now even if his mindset is Root biomechanics ( what I've been thought 10 years ago), I've still never heard of the lateral arch statement before...
    K.
     
  19. Correct. What needs to be understood is how changing the shape of the orthotic shell influences the mechanical behaviour of the orthotic and ultimately the behaviour of the foot on top of it.
     
  20. efuller

    efuller MVP

     
Loading...

Share This Page