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Does plantar contact necessarily = control?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Dhonuill, Oct 18, 2006.

  1. Dhonuill

    Dhonuill Member

    Members do not see these Ads. Sign Up.
    I'm a pedorthist offering general footcare and footwear advice in a UK retail setting. I often recommend OTC pre-fab orthotic inlays designed to provide support and assistance to complaining feet, but can also provide custom-made inlays where more precision is considered beneficial. The inlays I provide sometimes offer temporary relief for those with a long time to wait before seeing an NHS podiatrist, but sometimes they seem to do the trick on their own.

    I do not diagnose and complaints outwith my scope of practice are referred.

    For planus feet and/or feet with complaints associated with that foot type, I assume calcaneal pitch to be lower than 'normal', therefore I recommend inlays that cradle the plantar heel, provide 'uplift' to the plantar calcaneus, target support of the sustentaculum tali and so encourage sub-talar neutral alignment.

    For cavus feet with pronounced arches I assume calcaneal pitch to be greater than normal. Here my aim is to provide the best plantar contact possible in an effort to spread the contact load over a wider area and so offload areas of focal pressure, as well as support the midfoot structures. Any inversion sprain tendencies I address by offering footwear advice.

    Here's my question:

    Would you agree that in the case of planus feet, although total plantar contact may not be achieved, contact in key functional areas is enough to improve mechanics and, indeed, may prove a better therapeutic solution than total plantar contact?

    But can the same be said for cavus feet? My take is that for cavus feet plantar contact is essential for offloading and improving support, particularly through the rear- and mid-foot.

    Your opinions, please, gratefully received.
    Cheers, Fergus :rolleyes:
  2. pgcarter

    pgcarter Well-Known Member

    There are no blanket right answers...but I think if you want to change load spread or ground reaction forces under a high cavus foot you do need to have the guts to reach up to the foot in order to do it. I use semi-flex plate devices....they will change the plantar load distribution but still behave dynamically.
    regards Phill
  3. Fergus:

    When I am teaching foot orthosis therapy, I try to always emphasize the following: establish the biomechanical goal for the foot orthosis before considering its design..

    Take the cavus foot for example. If the cavus foot has a laterally deviated STJ axis, and suffers from symptoms related to excessive magnitudes of STJ supination moment (e.g. lateral ankle instability, peroneal tendinitis), then I will not support the medial longitudinal arch (MLA), but will add extra medial expansion plaster to the positive cast so that the orthosis will have a lower MLA and therefore be better able to add STJ pronation moment to the foot.

    However, if I have a cavus foot that has medial tibial stress syndome from running then I will use a minimal medial expansion plaster to increase MLA height, use a plantar fascial accommodation (to avoid plantar fascial irritation) and invert the device and possibly even use a medial heel skive.

    For the cavus foot with metatarsalga I will use normal medial expansion thickness, shape the anterior edge to conform to the metatarsal neck parabola and leave the anterior edge 5 mm thick and possibly add a full length Spenco topcover (3 mm thick).

    It is not solely the shape of the foot that determines orthosis design in my practice, it is rather the patient's specific anatomical structures that are injured, the abnormal stresses that are causing their injury and their biomechanical function that I strongly consider to best direct my mechanical treatment of their injury with custom foot orthoses.
  4. Craig Payne

    Craig Payne Moderator

    Many orthotic labs do a large amount of plaster fill in the arch with the result being there is a huge gap between the orthotic and the arch, but the patients do OK as the control of the foot is via rearfoot wedging & posting and forefoot posting to facilitate the windlass. Patients tolerate these very well.

    More recently there has been a trend in some places towards more conformity in the arch with the orthotic shell, but with more flex in the orthotic shell. There can be tolerance issues with these if the casting is bad (eg supinatus not corrected) and the flex in the shell is not right.
  5. Craig:

    At Precision Intricast, and many other orthosis labs here in the US, we offer different levels of medial expansion plaster thickness to achieve varying levels of medial longitudinal arch contour. For Precision Intricast, we offer minimal, normal and extra medial expansion thickness as options on our order form and have been doing so for the past 15-20 years. So to say that "conformity in the arch" as a prescription option by foot orthosis labs is a "recent trend" is not an accurate representation of what custom orthosis labs have been doing here in the States for the past two decades. I also know that ProLab and Root Labs also offer this option as many other labs do.

    For the past 20+ years, I have been increasing the medial longitudinal arch height on the orthoses of selected patients by using the following measures:

    1. Plantarflexing the first ray during negative casting.
    2. Using minimal medial expansion plaster thickness on the positive cast.
    3. Inverting the positive cast.

    The resultant orthosis that incorporates these three design modification conforms to the medial longitudinal arch of the foot very well with just as good of a conformity as any of the orthoses made by "more recent" labs that offer higher longitudinal arched orthoses as a standard feature for their orthoses. However, I tend to not be a big fan of having too flexible of a shell on the orthosis since this will lead to decreased pronation control by the orthosis, especially in those patients with more significantly medially deviated STJ axes and more flat medial longitudinal arch contours.

    In fact, every day in my practice, I order orthoses with these design features, often times in combination with deep heel cups and medial heel skives for treatment of patients with symptoms caused by excessive magnitudes of STJ pronation moments, such as posterior tibial dysfunction and pediatric flexible pes planus deformity. I am attaching a photo of a child I treated with such an orthosis from 10 years ago to demonstrate how this type of othosis design may be used to more effectively treat these types of conditions.

    Attached Files:

  6. Craig Payne

    Craig Payne Moderator

    Kevin - when I say a trend toward more arch conformity, I mean that more people seem to be using the 'minimal arch fill' option as of late.
  7. Craig:

    I haven't noticed this same trend in the States. I see very many prescription foot orthoses that do not conform well to the medial longitudinal arch of the patient's foot. However, this seems to be highly variable dependent on the practitioner and the lab they use.
  8. Perhaps I'm out of touch now I'm in private practice, but I haven't noticed this trend in the UK or from my experiences in a Spanish School of Pod either.
    Last edited: Oct 20, 2006
  9. Craig Payne

    Craig Payne Moderator

    More and more people are telling me that they are ticking the "minimal arch fill" box --- but that may be a function of an individual labs interpretation of just what arch fill is appropriate and there is considerable variability between labs.

    I also see it coming through in a number of lectures. Tom McPoil talks more about his use of increased flexibility in the arch combined with increased conformity between the orthotic and arch. Ed Glasor is a huge fan of this as well and has some creative methods for arch "calibration".
  10. I see no problems with this type of orthosis, as long as someone doesn't insinuate, like Ed Glaser does, that the orthoses I make for my patients are worthless just because they aren't made by his orthosis lab company. Does Tom McPoil also feel, like Ed does, that rearfoot posts are unneccessary on all foot orthoses??
  11. Craig Payne

    Craig Payne Moderator

    Tom still uses heel posts.

    I am thinking about a research project to compare orthoses made of a more flexible material but more congruity to arch profile vs more rigid orthoses made with more arch fill (less congruity to arch profile) - it may well be there is no difference

    I do recall hearing about an orthotic tolerance test a few years ago (and I apologise to who it was for forgeting), but it involved having the patient standing and having them rotate the pelvis maximaly to the left and then right several times and noting arch height changes as they do this. Apparently (as I have not tried this), if there is not much raising of the arch, then they are possibly less tolerant to rigid orthoses changing the foot position......obviously this test is related to STJ axis position.
  12. Scorpio622

    Scorpio622 Active Member

    Since my student days, I have struggled to fully separate the concept of "arch support" and the intrinsic forefoot post. Since the "arch" extends from the heel to the metheads, and the "intrinsic post" is contained within this area, isn't it just a heightened distal arch support. This is different than the extrinsic forefoot post that extends beyond the arch.

    As I see it, the intrinsic post blocks motion by applying distal arch pressure, and the conventional arch support blocks motion at the apex of the arch. Am I looking at this wrong??

  13. I think that there are a number of problems with discussing foot orthoses and how well they "control pronation" and give the patient therapeutic results. One of the biggest obstacles I see in the "flexible" vs "rigid" orthosis material debate is that these two terms "flexible" and "rigid" are ambiguous, not precisely defined, and are very much dependent on the foot biomechanics and weight of the patient. Therefore, the terms "flexible" and "rigid" will mean different things to different clinicians.

    For example, I often make plastazote #3 orthoses for patients which many clinicians consider a "flexible" material but, once inside the shoe, these plastazote #3 orthoses are often times more resistant to deformation (i.e. more rigid) than the 3/16" polypropylene orthoses that I also commonly use.

    In addition, an orthosis that is "rigid" for a 100 lb lady with a normal STJ axis location will be probably be quite "flexible" for a 250 lb man with a severely medially deviated STJ axis.

    I would suggest that before we try to go further with flexible vs rigid orthosis research, we first try to determine a standardized method to discuss orthosis deformation standards (i.e. orthosis flexural stiffness) so that we can have a meaningful and scientific discussion of this important subject.
  14. Agreed. One of the major obsticles here is that even with two patients of identical weight, the geometry of the device will influence its deformation under load. So taking our afore mentioned two patients, if one has a highly cavus foot and the other a highly planus, we see very different material properties for the resultant devices. Given that custom devices are just that, it would appear a somewhat fruitless endeavour to try to study this.

    Furthermore, there are massive differences in the magnitudes of GRF during activities of daily living. The literature reveals estimates of 75% body weight to 250-300% for walking and running respectively. Thus the deformation seen in an orthotic during walking, is incomparable to the deformation seen in the same orthotic during running, or stair climbing, or standing to sitting, or sitting to standing, or ascending stairs, or descending stairs, or ascending an incline, or descending an incline, or traversing an incline, or twisting and pivoting etc, etc,. The distribution of forces upon the surface of orthotic would also appear important, and this is clearly phase of gait (time) dependent. The literature also reveals much step-to-step variation in position and velocity of the centre of pressure. That foot "flexibility" appears, in females at least, to be phasic compounds this further. In other words, so called "calibration" of shell thickness is utter non-science. At best it provides a very broad useable range.
    Last edited: Oct 22, 2006
  15. Craig Payne

    Craig Payne Moderator

    Working on that - just ordered the force gauge and a mounting platform, so should be able to measure shell 'stiffness'/deformation. Ed's the one with the really cool way of doing this - maybe he can post about it.
  16. There is so much to do in this regard, Craig, that this project alone should keep you busy for the next 10-20 years. Here a few of the variables that will affect orthosis deformation:

    Maybe Craig, Simon(s), Eric and others may want to add to this list to make it more comprehensive.
  17. Craig Payne

    Craig Payne Moderator

    I have got an orthotic lab on board and they will collect the stiffness/deformation using the contraption of each orthotic they make - should get a good number quickly and then will also get data from the prescrition form and other measure to look for the key determinants. The next step will be to collect patient tolerance data
  18. This research will be critically important toward the next step: making sure that research projects that use foot orthoses on subjects list the standardized orthosis stiffness parameters both in-shoe and out of shoe to allow better comparison from one foot orthosis study to another. I would suggest having the tests being performed at both the medial and lateral arches of the orthosis, both in-shoe and out of shoe. You may need to have the lateral arch stabilized with a given downward force when testing medial arch stiffness of the orthosis (and vice versa with the lateral arch testing) since if there is no rearfoot post added the orthosis will tend to tilt rapidly into eversion when the medial arch is loaded.

    I noticed this with the Sole Support orthoses I have seen. Slight pressure on the medial edge of the longitidunal arch of the Sole Support orthoses, since they are not rearfoot posted, caused the orthosis to tilt into eversion with very little downward manual pressure applied to it. Talk about pronation instability!
  19. Hope Craig is good at finite element analysis since I believe that this will be the only meaningful way of addressing this problem to provide data which resembles real life conditions. Anyone can put a load on top of an orthoses and see how much it bends in the medial longitudinal arch (2D) or for that matter the lateral arch, but surely this isn't satisfactory?
  20. How??
  21. Craig Payne

    Craig Payne Moderator

    Force gauge and testing stand will measure force/displacement at selected points on the shell ie how much Newtons to move shell 1mm, 2mm, 3mm etc
  22. Simon:

    I beg to differ.

    I think Craig's attempts at trying to determine the load vs deformation characteristics of orthoses, with all the permutations listed above as modifiers (i.e. Factors that Affect Orthosis Deformation), is a huge step forward for us in podiatric biomechanics. We must start somewhere with mathematical quantification of load vs deformation characteristics of foot orthoses since it has never been done to my knowledge, in a non-proprietary manner, within the long history of podiatry. Finite element analysis is a modelling technique that has its particular applications, but I think, in this case, FEA would not be as good as direct experimental measurement of the load-deformation characteristics of foot orthoses. I say that it is about time that someone did this research and I'll have to say that I am very excited just thinking about it! To put it in the language of my colleagues from Oz: Good on you, Craig!
  23. I didn't mean to detract from Craig's attempts. From small acorns... However, given the number of modifiers, do you think this is really practicable? Sure we can talk about setting up a small number of nodes on the surface of the orthotic shell and put a weight on it. A close friend who is a material scientist did something similar as part of his PhD on fracture mechanics. He set up nodes on test samples placed in an instrom and measured displacements and attempted to apply finite element techniques in experimental set-ups as oppose to just models. I'll try to speak to him regarding this problem. Craig I can let you have his e-mail address if you think his knowledge would be advantageous. But in reallity, how do you measure the nodal displacement in 3D, inside a shoe, with a foot on top of them, during gait etc etc, to account for all the modifiers?

    Moreover, I say again, since each custom orthotic is unique in terms of its surface geometry, and the surface geometry is key to the deformation characteristics, how does this help predict orthotic outcome?
  24. efuller

    efuller MVP

    Hi all,

    The study I would like to see is patient hapiness versus rigid low arched device that ends up being the same height as the high arched flexible device. Measure arch height standing relaxed, make the rigid one this high and the flexible one is made so that it is the same height as the rigid one with patient in relaxed stance position.

    Cheers, Eric
  25. Not following you Eric, are you saying high arched flexible orthotic versus low arched rigid orthotic? Because in the next sentence you seem to be saying two devices (one rigid, one flexible) of the same arch height:

    ???? or are you saying take a flexible device that deforms under load to be the same height that the rigid device is unloaded? Think I get it now my but my brain aches. BTW my money on the flexible device/
  26. Craig Payne

    Craig Payne Moderator

    Thats essentially what I am doing - its a learning curve and an exploratory exercise and I a not sure what will happen. I will post a pic of the jig when its set up.
  27. Sounds like Craig is getting ready to jump in the Payne family sedan to go to the hospital...good luck Craig and give my regards to Mimi. I remember those days, little sleep and lots of work, but lots of fun also.

    Anyway, Simon, the preliminary work on load-deformation is important to do and will give at least an idea of how the load-deformation characteristics of the orthosis may be altered by the many variables I spoke of earlier. The reason finite element analysis (FEA) may not be critical here is that we do not need to really be worried so much about internal stresses and strains in the materials we are using (we are not worried about failure of these materials generally), which FEA is very good at. Rather we only initially need to be worried about how orthoses with different design permutations respond (i.e. deform) to varying magnitudes and locations of external loading forces so that we can make more intelligent predictions regarding these design variables on orthosis function for our patients. This may more easily be done using a material testing machine (e.g. Instrom) and it seems to me to be the most logical place to start.

    Next step would then be to measure energy turnover with orthosis loading-unloading cycles to see what orthosis designs offer the best "energy return" system for the longitudinal arches for activities, such as running or jumping, where this effect may be advantageous.

    This may be the next big research avenue for podiatric biomechanics (and could potentially result in orthosis labs forking up some big bucks to have it studied) ...learning about the load-deformation characteristics of various orthosis materials-designs.
  28. deco

    deco Active Member

    Hi Kevin

    Re point 3, to what degree do you invert the cast, do you then intrinsically post to neutral on positive?


    Last edited by a moderator: Oct 25, 2006
  29. Declan:

    The technique of inverting the positive cast simply refers to balancing the positive cast, with nails plantar to the 1st and/or 5th metatarsal heads of the cast, so that the heel bisection of the positive cast is inverted to the supporting surface. I have balanced positive casts inverted up to 10 degrees previously, but typically I order more in the range of 3-6 degrees inverted.

    Balancing the positive cast inverted will modify the resultant foot orthosis as follows:

    1) Increase height of medial longitudinal arch.
    2) Increase amount of intrinsic forefoot varus correction or decrease amount of intrinsic forefoot valgus correction.
    3) Invert the heel cup of the device.

    This technique is always used when a medial heel skive is ordered to increase the overall arch height of the orthosis along with the inverted heel cup of the medial heel skive so that a more even increase in medial heel/longitudinal arch pressure is applied to the foot to exert more forceful and comfortable STJ supination moments on the foot.

    Hope this helps.
  30. EdGlaser

    EdGlaser Active Member

    Hi All,
    Thank you all for finally seeing exactly what I have been saying all along (which you all have repeatedly said was wrong).....that calibration, that we have been researching and have patented a device to accomplish, is critical. Soon you will also realize that in order to accomplish this it is necessary to be full contact and in the MASS position. BTW, I have tried all of the above suggestions and have gone far, far beyond all of it and continue to move forward at a rapid rate. It is nice to see that you are all simultaneously admitting that I was correct all along (although you do not seem to be able to actually say it) and that my team of biomechanical researchers pioneered this NEW and far more effective approach to foot orthoses. I also appreciate all of the wonderful references to my phenomenal success in business, biomechanical theory, research and product development. It is all aimed at one thing: at Sole Supports....WE MAKE PEOPLE BETTER!!!!

    It is very gratifying.

  31. Ed, you are as arrogant as you are ignorant of my views on this. I suggest you re-read what I have written here.
  32. EdGlaser

    EdGlaser Active Member

    I have read and understand your points....they are in fact points that we dealt with five years ago and overcame with further research. I am doing a new lecture now which goes over the history of callibration at Sole Supports...where it all began and still the only lab that offers it and where we are continuing to break new ground on the subject.
    Individual sensels were tried early on and failed for a number of reasons, not the least of which is the variability of geometry of the orthotic-sensel interface. We are way beyond that now.
    We invented callibration, are the only ones currently using it and are taking it to the next level. Nothing in this thread so far is NEW to us.....its all what we have already done some of which worked and much of which we threw out after testing.
    Your Nay-saying comments that it cannot be done are overshadowed by the fact that for clinical purposes we have indeed done it.....and continue to improve on how accurately we do it. Our success speaks volumes.
    At least you have some intellectual integrity.....you are consistent with your attacks on anything that varies from what you were taught or currently do. Simon, seek refuge inside the Box....its scary out here....you might have to think creatively.

    As always, Craig, I support research and would be happy to provide callibrated orthoses for the study as long as the methodogy is fair and non-biased. Please let us all know when congrats are in order.....you are entering the best time of your life.

    Good luck,
  33. I just turned base metal into gold. Have been doing it for years thanks to my team of alchemist researchers. We invented this process because "we make people richer". I can't prove this anymore than you have offered any evidence for your statements above. Look forward to reading about how you've done all of this in an index medicus linked journal and at that time I will no doubt provide objective review. I expect it will appear around about the same time I publish my guide to alchemy.

    Why not pay for an ad with google, surely this would save time?
  34. efuller

    efuller MVP

    I have to agree with simon. I did not say a high arched flexible device was better. What I said was that there should be a study on patient outcomes to see which device is better. The statement that we all agree with you also irritates me and you should not interpret our comments to say that. The outcome measure should not be STJ position or motion, but which device makes the patient feel better. More supination does not necesserily equal better. Having tried both types of devices, I prefer the lower arched somewhat flexible device to the MASS device. Given the choice, I would prefer weaing nothing to waring the MASS device because the Mass device hurt. The question is how often does my experience happen. That is the study that needs to be done.


  35. If you really support research, publish here (or anywhere) a step by step guide to your methodologies so that independent researchers (not just the ones you support financially (directly or indirectly)) may repeat your experiments and varify your results.

    Anyone remember the cold fusion claims? Strange how no-one else could do it, but the guy who said he'd done it.
  36. EdGlaser

    EdGlaser Active Member

    sounds great simon

    Hey Simon,

    Good luck with the alchemy thing. It sounds like you will help more people with that than acting as a speed bump in the road to progress in foot biomechanics.


    We are working on the article....look forward to yours.
  37. EdGlaser

    EdGlaser Active Member

    Comfort over function.... I suggest you start "Gellin" with Dr. Scholl.
  38. EdGlaser

    EdGlaser Active Member

    But you are agreeing to the importance of callibration. What are you going to do; calibrate an orthotic that is flat? What good is calibration that is incorporated into an orthotic that does not touch the foot? So what position should the foot be in.....Neutral? We should drop down to hit a neutral orthotic that is callibrated ..... Illogical captian!

  39. No Ed, what Eric is saying here is that your "callibration" doesn't work. Why would it fail like this?

    Thanks for doing the usual Glaser side shuffle and ignoring the comments re publishing your methodology. No change there then.

    The alchemy paper has a section on the FOS position, one wich I'm sure you're familiar with. You know Ed, everytime I get into a discussion with you I'm left feeling complicit in helping you promote your product- no publicity is bad publicity hey?. So to be honest, I'm not going to engage with you any more until you actually start bringing some evidence to the table. Personally, I think this will be a bigger "speed bump" (**** metaphor BTW) to your advancement. And lets face it, the only advancement you are interested in is your own financial one.
  40. efuller

    efuller MVP

    I'm not agreeing with the importance of calibration. What I am saying is that a calibrated device should be compared to a non mass device. Heck, we should compare devices that don't touch the arch, devices that do touch the arch and devices calibrated in MASS. We can't just assume that one is better than the others.

    We should also define "better". Is better a functional thing or a comfort thing. Would you rather wear a device that hurt but put you in a positoin that someone thinks is functionally better or would rather wear a device that relieves the pain that you have when you are not wearing a device? I have a problem with your assumption that MASS position is better. We should be having a debate on whether or not the MASS position is better as well as testing with outcome studies that patients are happier if they achieve the MASS position.

    Ed wrote:

    Comfort over function.... I suggest you start "Gellin" with Dr. Scholl.
    Position over comfort... I suggest you start Chinese Foot Binding. ;)

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