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Do orthotics shorten feet?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Tom Quinton, Sep 11, 2009.

  1. Tom Quinton

    Tom Quinton Member

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    Recently a Lab Rep/Podiatrist gave a lecture on biomechanics and their lab to our year.

    During this lecture he stated that orthotics will often shorten the foot and it is important on review to check the orthotic against the foot to see whether the foot has shortened, because if it has you will need to grind the front of the orthotic back so it fits the new shape of the foot.

    The Rep stated that he was unaware of any literature on this but it obviously happened and that if I could not understand how orthotics shortened the length of the foot I should probably not prescribe rigid devices:wacko:.

    I was unaware that this occurred and was wondering whether other Podiatrists had experienced this or if there was any literature on this?
  2. Boots n all

    Boots n all Well-Known Member

    It wont shorten the foot in the true sense, the foot is still as long as it was before.

    Take a piece of string lay it out straight to 30 cm long, now put a small kink in the string,it is no longer reaching 30cm long, but the string is not really any shorter, it is still 30cm long......my head hurts now:wacko:

    A pronated foot that is corrected, may fit a 1/2 shoe size smaller as a result of a corrective orthosis,
    it is no longer straight along the ground it now has a slight kink in it
  3. Hi Tom

    1st it depends what your orthtoic is attempting to acheive. I´m guessing the guy from the lab was talking about control of pronation by using an orthotic ( which is definently not always the case )

    If we say that pronation increases the ROM of joints and there is a lowering of the Medial longitudinal arch height ( seen thru navicular drop etc ) the foot will get slightly longer. Or the foot will elongate.
    So therefore if you supinate the foot will your device you will get reduced ROM reduced distance between the the 1st met.calc ( seen in increased navicular height) there will be a slightly reduced lenghth of the foot.

    I´m sure there have been studies about foot lenght during different phases of the gait cycle. How much it is and I´m not sure that it very much to stress about.

    As for it importance in understanding before you prescibe rigid devices its not. There is much more important thing to get your head around. The patient will tell you that the device is pushing to much on their toe just grind it off.

    To get some pictures in what I´m talking about look at windlass threads it might help so whats happening to Navicular height in relationship to calc-1st met position.
  4. Donna

    Donna Active Member

    Hi Tom,

    This is something that I see a lot with patients who are hypermobile... they have gradually "sagged" into a more pronated position over many years and many foot-steps. When the orthotics are fitted, the forces causing this "sag" are reduced, and the MLA can "spring up" as a result of elastic rebound. I'll often have to shorten the MLA (on an EVA CAD-CAM device) after this rebound happens. The patient will often complain that their 1st MP joint feels "pinched" or "blocked", and after removing a few millimetres of material under the offending area, it magically feels better :D



    PS: Sorry for the not-so-technical language, but it is Friday afternoon after all ;)
  5. Tom Quinton

    Tom Quinton Member

    Thanks for the replies.:D

    Assuming on dispense the device was fitted to the patient's foot non weight bearing and you were prescribing the device for pronation control. After wearing the device for a period of time, soft tissue changes occur? Causing the foot to be in a more supinated position? So much so that the device no longer fits when the patient is weight bearing?
  6. Tom You are thinking way too much about this question.

    Ive never had to shorten my devices after the 1st review appointment. The only reason to shorten a device if it´s been made too long. As Donna and I said the patient will tell you. To be honest it normally the lab that has made a mistake by making the device too long.

    The patients foot will not get shorter overtime it will not get more supinated.
  7. You Know what I see here? A Student (I presume you are a student from where you say "our year") who hears something which sounds wrong then has the intelligence and enthusiasm to go check it himself from a (the?) independant source. We've had some depressing stuff recently, this is a bright speck in the gloom. Perhaps there is hope after all Thanks Tom:drinks, you made my morning.

    Based on what you say it sounds to me like the rep was a bit confused.

    Follow me on this. You put the foot in what for brevity we will call the "corrected position" to cast it. The orthotic is, alledgedly, made to that position. Now IF, and its a big fat hairy IF holding a sign to say "we're really not sure", the orthotic shortens the foot then the device is cast to that shorter position ALREADY.

    Put it another way. Assume the orthotic will plantarflex the first ray. this will shorten the distance between the back of the heel and the centre of the 1st met head. However if the 1st ray was Plantarflexed when the foot was cast then the orthotic will be based on that shorter distance init!

    Unless he was suggesting that the orthotics effected a perminant change to the length of the foot (ie even when not being worn). In which case, if you have a minute, thats an EVEN BIGGER "if" with its own tour bus, advertising campaign, groupies, roadies, neon signs and laser skywriting to the effect that this was a vastly massive IF with no inductive and only shaky deductive evidence.

    Also also, If we are talking about a sulcus length poly shell then just grinding the shell back won't make it fit the "new foot shape". It'll relatively lower the arch. If you want to make the orthotic fit a different shape you have to, let me see, oh yeah change the shape of the orthotic. not just saw a half inch off the end!

    So come on then Tom. Whats the rep for and what university did he get let into? This is exactly why I have reservations about letting orthotic labs supply undergraduate training!:mad:

  8. Donnchadhjh

    Donnchadhjh Active Member

    Well put Robert. I like the sense of humour there.

    David, Michael, Donna and Robert seem to have done a good job there.

  9. Tom Quinton

    Tom Quinton Member

    Robert thank you for stating that so clearly:D

    What the Rep was saying just did not make sense. I was especially suspicious as he had used the "fact" that the foot shortens to persuade us not to prescribe full length EVA orthotics because you are unable to shorten them. After questioning him he suggested I did not have the biomechanical knowledge to prescribe rigid orthotics as I did not understand something so obvious and simple. He seemed to believe that because he had been in practice for 25 years that was evidence enough for whatever he said.

    The thing that really upset me though was that some of the class agreed with what he said and thought that if he had been working as a podiatrist for 25 five years what he said would be true and should not be questioned. Two of them even came up to me and suggested I apologies to him, for simply asking him how the foot actually shortened? What literature backed this up and if he sees it every day in his practice why doesn't he publish something on it to back up what he is saying?

    I will send the rep an email to this link and hopefully with his 25 years of experience as a Podiatrist he will be able to enlighten us;) or at least he he might change his current lecture.
  10. That upsets me too (although it does not surprise me in the least!)

    How often do we here that here? "I've treated 450, 000 patients and been qualified 4 billion years". It does'nt make you right! If you don't want to be questioned, don't say anything questionable!

    Funny story! I had a similar experiance at a course once. Somebody telling me it was disgraceful for me to question the person delivering the course (who, BTW, was also a rep for a lab). Ironically enough I think the rep himself was OK with it!

    Anyone who knows their stuff will not be afraid to field questions. When I'm lecturing I love it when people ask, It shows they're awake and better yet, that they're paying attention and questioning what I'm saying.

    Of course if they are on shaky ground then they will be very anti audience participation and come down heavy on anyone who dares question them...

    That, frankly, is a crock. There are lots of pros and cons with full length shank dependant orthotics but that ain't one! Let me guess. He wasn't selling EVA orthotics.

    I get the idea you had your nose slightly put out of joint Tom. Sounds to me like you did well to question this theory and whether or not you were right (I think you were) you should feel good about yourself for not just pretending you could see the emporers new clothes. There is NO SHAME in not understanding something (especially for an undergrad) but anyone who pretends to understand when they don't is a fool. And any good lecturer would not want you to. So stop stewing. :empathy::drinks

    You are in good company BTW. I can think of a fairly prominant DPM by the name of Kevin who used to regularly dispute with his professors, who were some of the great minds of biomechanics (who actually published their work rather than just pushing it as unarguable fact). He turned out OK.

    I doubt very much your friend will come and shout his corner. He'll go up a few notches in my estimation if he does though.

  11. Tom Quinton

    Tom Quinton Member

    Thanks again Robert:D I feel a lot better after your replies.
  12. I wouldn't rule out the possibility that, over time, foot orthoses may cause shortening of the foot in some individuals. If the orthosis is able to supinate the subtalar joint and decrease the tensile force within the plantar fascia and plantar ligaments within the medial longitudinal arch over time, then the foot could measure out to have a shorter length due to the viscoelastic mechanical nature of all the structural components of the foot. However, in my clinical experience, I have only had a few patients over the last 24 years of practice definitely notice a shortening in the length of the foot over time with foot orthoses. In fact, I much more commonly see individuals who may need to buy a 1/2 size bigger shoe with foot orthoses due to their bulk decreasing the available volume inside the shoe.
  13. Donna

    Donna Active Member

    Hi Tom,

    I disagree with this statement - a full length EVA device is VERY adjustable. If you have a grinder in your clinic, it's super fast (and easy) to peel up the orthotic cover and buff from the top of the anterior MLA to decrease the thickness in this area as needed. It then takes another 10 seconds or so to reglue the cover... A small effort for a big change in your patient's comfort (and function). :D


  14. And of course you can adjust it with a heat gun, right Craig;)?

    Ok. A heat gun and a grinder. And maybe a bit of self adhesive poron. You don't even need to strip the cover!

  15. Tom Quinton

    Tom Quinton Member

    Donna thanks for letting me know how adjustable an EVA device is. I guess this displays the downside of having reps who are more interested in selling their product than education give an "educational" talk at a University, the students believe what they say.

    Thanks for your reply Kevin.

    In the patients who's feet you did notice a shortening effect secondary to the use of orthoses, I imagine the maximum amount these feet would have shortened, as Robert explained to me earlier, was to the "corrected position" they were originally casted in? It is difficult to understand how the foot could shorten any further than this secondary to an orthosis? However, if this is possible, I am sure you can explain it to me:D
  16. Tom:

    My hypothesis is that in the few patients that saw a shortening of their foot with long-term use of foot orthosis is that the orthosis was increasing the subtalar supination moment sufficiently to make the foot function less pronated/more supinated over time. The resultant increase in supinated position/decrease in pronated position of the foot resulted in decreased loading force on the medial metatarsal rays which, in turn, caused a gradual shortening of the medial plantar ligaments and medial slips of the plantar fascia and which caused their feet to measure to have a shorter shoe size over time.
  17. pgcarter

    pgcarter Well-Known Member

    Dickason's Law? is it....contracture of lax tissue over time...same as is suggested to build a supinatus over time? only this is the reverse.
    regards Phill
  18. joejared

    joejared Active Member

    More accurately, and depending on posting valgus or varus, the midtarsals twist proximally or distally, from medial to lateral and actually move longidudinally as a result. As already stated, varus posting will increase the apparent length of the foot, and visa-versa, for valgus posting.
    Last edited: Sep 15, 2009
  19. Tom Quinton

    Tom Quinton Member

    Thanks Kevin.

    I think I should have phrased my last question differently. This is now purely theoretical. I'm sorry to keep going on about this.

    If the foot shortens into a more "corrected" position, secondary to an orthosis imparting a supinatory moment at the subtalar joint and reducing the stretching forces on the soft tissue structures responsible for maintaining the medial longitudinal arch. As these structures contract the amount of supinatory force the orthotic applies to the foot reduces, because as these structures shorten they bear a greater amount of the pronatory force. Until finally (this is just theoretical) the structures responsible for maintaining the MLA have shortened so much that the orthotis is no longer able to impart a supinatory force when the patient is simply standing on the orthotis with both feet on the ground. It would not be possible for the foot to contract any further secondary to the orthosis. There would never be an occasion in which you would have decrease the length of a device to accommodate for a shortened foot secondary to an orthosis.

    Would you agree with this?

    I have a feeling a medial heel skive may always increase the supination moment at the STJ and maybe it is theoretically possible that the foot could shorten so much so that you might consider shortening the device?

    I have not heard of Dickason's Law, I believe it is Davis law. This is also why it is not recommended to use FF posting for a supinatus.
  20. Tom Quinton

    Tom Quinton Member

    Should varus and valgus be switched around?
  21. joejared

    joejared Active Member

    Oh yes, you're right. Varus posting effectively pulls the medial side of the midtarsals proximal, and lateral side distal.
  22. pgcarter

    pgcarter Well-Known Member

    I'll take your word for it being Davis....was sure it started with D not certain it was Dickason.
    regards Phill
  23. More accurately still, it depends on where the posting is, rearfoot or forefoot.

    It was Davis law. And wolfs law for bony change.

    I'm not sure I buy it as an MO for the foot shrinking though.

    If you stapled the orthotic to the foot so that it was perminantly attatched, then I could see how davis law could apply. However lets not forget we are talking about an IN SHOE DEVICE.

    When we want people to stretch muscles, or maintain their length, we give them exercises to do for a few minutes a day and that generally does the trick. One of my favourites is for patients to put the yellow pages in front of their bathroom sink so when they brush their teeth (one minute upper, one lower,) they stand with their forefoot on the book and their heels on the floor. A few minutes is enough to maintain length and / or stretch.

    Now consider the structures which would have to shorten to "shrink" the foot. How much stretching will they get all the time the patient weight bears without their shoes on? And do they wear their insoles in every pair of shoes?

    Doubt it.

    Kind regards
  24. Do calf muscles get short and strong from habitually wearing high-heeled shoes?
  25. Tom, I'm not sure you would get to the point where the orthosis could exert no supinatory force, but I think your analysis is generally well observed.

    Now, lets say we have patient who has been wearing the same pair of orthoses for 13 years without a change in their prescription, what does this tell us about foot orthosis prescription writing?
  26. I'd say yes (although I've no evidence).

    However its a little different. With heels you're looking at repositioning of the foot measured in inches, with orthotics the change in position is slight if any. With orthotics the planter apeurneurosis will still be streched at toe off (granted it will be less but they'll still be tensile force going through it), with heels the Triceps Surae will never be at full stretch while the patient is wearing them. If you assume that the apeurneurosis is one of the primary structures which limits 1st ray dorsiflexion then it is under considerable tension when the patient is standing still (which they will do within their 4 walls).

    I'm not saying its never happens, but I suspect its pretty rare for it to be measurable. I've never measured feet before and after orthotics but apart from in children, I rarely see gross morphological changes, with orthotic use. Shoe size reduction when they are wearing their insoles, yes. Structural change to the foot, no.

    But thats just an opinion

  27. It would obviously depend on how elongated the soft-tissues had become prior to treatment and how lax they were / how much change in their functional length was induced by the foot orthoses.
  28. Tom Quinton

    Tom Quinton Member

    Is there any research examining morphological changes in the foot in children with orthoses vs children without?

    For some reason this rings a bell.
  29. I remember reading something written in England where that issue a huge amount of orthotics something like 3000 and had 3000 without. They measured the arch height before and then remeasured I think 6 months later. They found that those who had orthtoics had a slight increased arch height. They measured again 6 months later and found no difference between the 2 groups . They they came to the conclusion that orthotics do not change childrens feet.

    I read this in 93-94 so the memory could be wrong, I remember the testing was done after WWII. Ive no idea of the reference but British
  30. Tom Quinton

    Tom Quinton Member

    This is something that I am trying to get my head around as well.:wacko: Should the prescription be changed?

    I don't believe it should. If we assume that over time the soft tissue structures bear more of the pronatory force and the orthosis imparts less of a supinatory force there comes a point when the soft tissues will cease to contract any further. Because the supinatory force of the orthosis has diminished we don't have to worry about it "over controlling" the foot and causing lateral issues. However it still applies enough force to stop our now contracted soft tissue structures from elongating.

    I believe there are a few holes in my reasoning. I look forward to seeing what they are:D

    This is just theoretical, although my clinical experience is pretty much zip, I believe it would be very rare for an orthosis to cause a change in foot structure.
  31. Why would you want to change the prescription if it is still working? What I was suggesting is that although the soft-tissues may have adapted the orthosis prescription still works- right? So how precise are our orthosis prescriptions in the first place, moreover how precise do they need to be?
  32. Interesting,

    "The International Strandards Organisation has defined an orthosis (plural: orthoses) as:

    An externally applied device used to modify the structural or functional characteristics of the neuro0musculo-skeletal system." Bowker et al. 1993
  33. Tom Quinton

    Tom Quinton Member

    Hmmm? I'm not to sure what I was thinking? It comes back to my original question of can an orthosis change the foot structure so much that you would need to shorten the anterior portion of the device because it was impinging on the MPJ's? Surely if this was to happen and think we have ruled out the possibility that it could, the amount of supinatory force should be reduced?

    This is a very simple answer and i'm probably missing the intention behind the question, but an orthotic only has to be precise enough to reduce a pathological force without causing any others?
  34. I think its worth clarifying what we mean by "prescription". Do we mean the morphology of the foot (the cast) or what we do to it in terms of skives, wedges, cutouts, drop throughs, sticky out bits etc.

    The former, as we have discussed many a time, is not precise at all! Leave alone that it is not the most repeatable process anyway and that there is no defined correct position, it gets cast corrected to death at the lab anyway.

    The latter is none too precise either by the time it has sunk into the shoe lining or shifted about in the shoe:eek:. And of course we have Simons famous multiple interface theory, and I've been mulling lately about adding the interface between the skin and the skeleton to the 4 interfaces already established. Thats 5 interfaces and your turn to add one Simon;)

    There is a fundamental truth to how the foot works and what forces exist within it. If one could derive the instantaneous data one could identify exactly what moments existed where, how much tensile force there was everywhere and exactly what angles and ranges were in joints.

    However the idea that an orthotic can be made to a precise prescription / morphology to match these variables is, IMO, fanciful at best. At the risk of becoming obsessive about my conspiracy theory, who has a vested interest in suggesting otherwise? The truth is out there!

    Oddly enough, this is the topic of the next Podiatry now Biomechanics column. I called it Post Modernist biomechanics although I'm sure a more descriptive name could exist... Should be out in a week or so.

  35. I beleive that Simon will mention preferred motion pathways very soon
  36. Tom:

    Nice reply and I basically agree with your analysis. I might consider shortening the orthosis if they are getting anterior edge irritation, but not otherwise. I have done so in the past, but quite infrequently.

    In regards to this possible shortening of the foot, we must remember that all the structural components of the body (bone, cartilage, ligament, fascia, muscle and tendon)are viscoelastic in nature and, as such, will shorten over time if tensile loads are reduced on them and will elongate over time if tensile loads are increased on them. Therefore, shortening and lengthening of the foot will occur during the lifetime of an adult depending on the magnitude and duration of internal stresses acting on those structures over the lifetime of an individual.

    Hope this helps.
  37. pgcarter

    pgcarter Well-Known Member

    Defintely only annecdotal but 20 yrs of fitting downhill ski boots with extremely rigid shells leads me to beleive that some feet definitely shorten when put on an orthosis. It is a response of the specific anatomy to a change in plantar forces and a change in shape as dictated by the presence of the orthosis. It's also going to have something to do with available ROM's at various joints in the foot and planes of joint axes, which of course will both influence how much and in what planes changes do occur. I believe I see feet that shift much more in the saggital plane than others, they pronate and collapse but less in the frontal plane and more in the saggital. These ones alter more in length when you pick them up to neutral.
    regards Phill
  38. Griff

    Griff Moderator

    Sorry to jump back a few posts, but I've only just picked up this thread on returning from holiday.

    Whilst lazing on the beach I finally got round to reading Dr Ben Goldacre's book 'Bad Science' which has been sitting on my shelf for months. No doubt in my mind Robert has it. In my opinion a must read for all students. And a beautifully put comment by him which is relevant to the above quotes (not to mention previous posters comments on the Arena who shall remain nameless)

    "The plural of anecdote is not data"

    Love it.

  39. Yep:D.

    Try also the website:-


    Its fantastic. And hilarious.


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