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Challenging the foundations of the clinical model of foot function

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Jan 31, 2017.

  1. I´ve done both, last 11 years I make my own
     
  2. Jeff Root

    Jeff Root Well-Known Member

    When using an outside lab you need a way to communicate the frontal plane orientation of the cast/orthotic to the lab in addition to all the other information that is required to produce the product you want for your patient. When you used an outside lab, how did you communicate the frontal plane orientation of your cast/orthotic to your lab?
     
  3. But you are posing more questions without answering any of mine, Jeff... So... no. Answer the questions posed of you.
     
  4. Jeff Root

    Jeff Root Well-Known Member

    There are scientific papers that test elements of foot orthotic therapy and foot function. Some of those apply to Root theory and some don't. I know Kevin has previously posted as list of research papers that demonstrate efficacy of foot orthoses. For example, McPoil found that orthoses influenced tibial rotation/STJ motion which is one of the things Root said they can do. Perhaps Kevin can share those papers he believes are applicable here.

    The heel bisections can be used to help identify foot types and subtalar joint motion and position. Heel bisections can be used to increase consistency in the position the cast for orthotic fabrication and can be used to confirm that the practitioner's cast reflects the amount of ff to rf relationship that the practitioner was expecting the lab to find in the practitioner's cast, which is an important element of the quality assurance process when the device incorporates intrinsic or extrinsic forefoot support/posting. If there is some other method for orienting the cast in the frontal plane that has been tested and has been proven to be more consistent and reliable than Root's heel bisection technique, and that is scientifically sound and which has been proven to be clinically as or more effective than heel bisection, I would be very interested in knowing what it is.

    As to how prefabs work without a heel bisection, prefabs mimic the shape of custom orthoses and were developed as an alternative to custom orthoses. They are based largely on the structure of custom orthoses and on the structure of the foot. The contour and material composition of some prefabs can make them very effective in treating foot symptoms and/or improving comfort for the same reasons that custom orthoses can. Prefabricated orthoses are an economical and important modality and are often used as an initial form of treatment. Prefabs don't require a heel bisection because they are fabricated and made to a predetermined shape as determined by the manufacturer. Since they are not patient specific and are not custom made, they don't require nor can they employ a heel bisection.
     
  5. Jeff Root

    Jeff Root Well-Known Member

    Merton L. Root in the fall 1981 Podiatry Arts Lab Newsletter:

    "Without being the least bit facetious, the Root Functional Orthotic was developed from 1958 to 1959 by trial and error. Prior to 1959 I had developed a modified Levy Mold technique for making an orthosis over a non-weight bearing neutral position cast. The orthosis was made of oak wood flower and latex pressed onto leather that had been molded and shaped to the cast for the previous 24 hours".

    "After being dried and properly ground at the edges, the orthosis was dispensed and worn for two weeks. Subsequent visits were used to add triplane wedges under the medial side of the heel seat and along the lateral border of the heel. This orthosis very effectively prevented abnormal pronation of the foot and was very comfortable to wear. The orthosis also had disadvantages. It broke down from perspiration in a year or two, it became hygenically distasteful, it needed frequent reinforcement of the korex triplane pad which compressed, its strength was dependent to some degree on the rigidity of the shoe, and numerous adults noted low back pain developing after prolonged use. Today, we know that back pain resulted because the orthosis prevented normal pronation of the foot at heel strike. Normal pronation of the foot in the contact period is necessary to promote normal absorption of the shock of heel strike

    I devised the triplane pad on the basis of physical principals. If one wishes to prevent rotation of an elongated round body, a resistant force must be applied as close to perpendicular to the long axis of that body as possible. The long axis of the calcaneus sits in the shoe at an angle to all three body planes; hence the problem of heel control required a triplane shaped device directed against the sustenaculum tali. Thus, the triplane pad was conceived. It is still in use today in many offices in pad form, and was the precursor to the rear foot post used on functional orthoses".

    "Extrinsic forces from the leg that concentrate on the medial side of the calcaneus to cause excessive pronation or on the lateral side of the calcaneus to cause lateral postural instability initially caused control problems. Those control problems were eventually solved by altering the height of the sides of the heel cup and by flaring the rear foot post.

    Medial distribution of extrinsic forces necessitates shifting the rearfoot post medialward to better resist those forces. The medial side of the heel cup of the orthosis was increased in height while the lateral side of the heel cup was proportionately reduced in height. This heel cup height variation in conjunction with a medial flare of the post was quite effective in improving control of pronation in such cases".

    "The Root Functional Orthotic has not yet been fully developed. It is still developing as more specific variations of the human foot are identified".

    I tried to upload the full newsletter but it is too large to upload. As you can see, in 1981 Root acknowledged that the Root type functional orthotic was not fully developed. This contradicts those who suggest that Root thought of his device as the be all, end all. Root was open to change but like me, not just for the sake of change. The change has to be because it is an improvement over the existing options. Root's triplane pad, which he patented, is essentially an extrinsic medial heel skive that was placed in the shoe or attached to the device to improve pronation control. I guess he was practicing TST.
     
  6. Jeff Root

    Jeff Root Well-Known Member

    Merton L. Root in CCPM's Pacesetter Newsletter March-April 1982:

    "It is only in the hands of a podiatrist who really understands biomechanics that functional orthoses prove their value. Such a podiatrist can examine the lower extremities and identify those forces acting on a foot that cause malfunction. He can also determine whether or not there is a direct or indirect cause and effect relationship between the abnormal mechanics and the symptoms to be treated. He is also in the best position to determine which treatment method or combination of methods (medical, mechanical or surgical) will prove most beneficial to the patient.

    When an orthosis is selected as a method of treatment, knowledge of biomechanics enables the practitioner to select the best casting position to resist the abnormal forces acting on the foot. The knowledge he has gained during examination also determines what he prescribes to have an orthosis made that will most effectively resist abnormal forces. Biomechanical knowledge also enables the practitioner to immediately evaluate the effectiveness of an orthosis just dispensed".
     
  7. Trevor Prior

    Trevor Prior Active Member

    Kevin

    Thanks for taking the time to come back on this. I will taken aim 1 as read.

    Regarding aim 2, there are some gross factors that can be analysed but I treat many patients that do not have an antalgic gait or obvious asymmetry. There are many factors that can be altered with orthoses that are very difficult to evaluate clinically without objective assessment.

    After all, we regularly discuss with tissue stress how one can alter joint moments without altering joint position. Thus, if there is no change in position that we can observe there is a potential that we have placed an excessive force at another site that cannot be appreciated.

    I except that many will use the approach you describe for aim 3 and in many instances, this may be the only option we have.
    However, I constantly asked myself the question of how I teach someone with less experience not only how to change the load on the structure, that part is relatively straight forward, but how to try and predict where altered load may be applied and whether or not that may have the potential to cause other pathologies or problems.

    Thus, whilst your responses provide an answer, there is more that we can do and should do if we want to be able to have a much more common approach and importantly, a basis for teaching and further research.

    I think you some this up quite nicely in part of a response to another member:
    In the final analysis, we should all appreciate what your father did for us. However, we must also realize that some of his ideas about foot function and foot orthoses are erroneous. With that in mine, if we want to improve ourselves as a profession, we need to come up with better ways to evaluate foot structures so that we can continue to move forward intellectually in understanding the biomechanics of the foot and lower extremity and the biomechanics of foot orthoses.

    I would agree with you that I do not know how my intervention is going to affect gait/pathology 100% of the time. However, accepting the limitations of any assessment approach, I do use inshoe analysis and 3-D gait analysis to evaluate the effects of my interventions on a percentage of my patients.
    I am unable to measure joint moments but I am able to attain some idea as to how the force (and importantly the loading pattern over the step) and kinematic positions are influenced by my interventions and this regularly helps direct my management.

    I do not use this on every patient but if I have a patient who is not responded well to orthoses (final others), has had recurrent injuries or multiple injuries or has a condition that we know can be helped by either orthoses or a rehab program then I will use these to help my decision making process.
    The challenge, and this is a question I am asking myself, is to determine a process by which to quantify how we take this approach and then investigate this rigorously to see if there is any validity.

    To add my 2 cents to the argument, I feel an assessment of structural alignment is important but what is clear is that that alignment alone is not predictive of the final gait outcome. However, the nearer the gait can be described by or attributed to the alignment, the more it can be used for orthoses design. In addition, it can be used to determine whether or not the pathology in question could be related to alignment or whether or not there are other factors.

    Tissue stress allows us to treat conditions without the need for alignment and is therefore extremely useful when alignment is not a factor but the risks of other pathologies or dysfunction in those instances might be greater and therefore require closer monitoring.

    So going back to my original comments, there are many aspects of gait altered by orthoses that we cannot visualise and I feel we should strive for a process whereby wait-and-see to determine whether or not we have potentially cause the problem has to be the way forward. If we are able to achieve this, we are much more likely to have a valid paradigm on which we can all agree and can only be of benefit to patients.
     
  8. cpoc103

    cpoc103 Active Member

    Trevor can I ask, when you mention alignment - However, the nearer the gait can be described by or attributed to the alignment, the more it can be used for orthoses design.
    What alignment are you looking at, is it foot to leg, foot to ground or something else?
    Cheers

    Col.
     
  9. Trevor:

    Thanks for the long reply.

    Regardless of whether you use in-shoe pressure analysis or 3D video analysis of an individual, you will still not be able to accurately assess internal tension, compression and torsional forces on the structural components of the foot and lower extremity using these methods. Of course, these tension, compression and torsional forces are what produce the injuries which can occur after we place our foot orthoses inside the shoes of our patients. Even if you were to do inverse dynamics analysis, which would require you to use a force plate, instead of a in-shoe pressure analysis system, and then also use fine-needle electromyography, basically spending a whole day analyzing one patient's gait, you would still not be able to know all the tension, compression and torsional forces that can produce injuries within the foot and lower extremity.

    Thus, regardless of the world's best available biomechanical assessment technology, there is no way for us to know whether our orthoses will be causing injuries to patients in the future since we can't know all the internal loading patterns that have changed with our orthoses and especially don't know all the congenital or acquired structural abnormalities within the foot or leg that may eventually lead to injury in the individual after our foot orthosis therapy. The prediction of potential future pathologies becomes even more complicated since we currently know so little about how the central nervous system responds to various plantar stimuli that may arise from the foot's mechanical interactions with orthoses.

    Therefore, as I stated earlier, the only way we will truly know if our orthoses will be causing injury, given our current state of knowledge and technology, is to follow our patients for some time after orthosis dispensing to ask them how they are doing and see if we can find any objective evidence of gait abnormalities or other pathologies developing. In that regard, making orthoses using Tissue Stress Theory principles is no different than any other available method of evaluation and prescribing of foot orthoses for our patients.
     
    Last edited: Jun 8, 2017
  10. efuller

    efuller MVP


    Jeff, I've answered this question more than once and you have never responded. Most recently, in post #137 in this thread, I wrote:

    How to communicate what I want as a clinician to the orthotic lab: Say I send a cast that the lab technician would have determined that there was a perpendicular forefoot to rearfoot relationship. If I saw a maximum eversion height of 3mm, I would ask for a 3mm intrinsic forefoot valgus post. When you put that forefoot valgus post on the cast the heel bisection will evert. Say I saw a medially deviated STJ axis in this individual. I would then ask for a 4mm medial heel skive to overcome the three degree everted position of the heel and the net effect could come out to what would look like a 2mm medial heel skive, on a vertical heel bisection cast, as you set the cast on the table.

    It is possible to communicate with a lab, and get an orthotic, without using a heel bisection. If you still don't believe me, I'll bring a cast to your lab and show you, the next time I go up to Lake Tahoe.
     
  11. Trevor Prior

    Trevor Prior Active Member

    I look at the motion of the hips, rearfoot range, forefoot position NWB for general range, direction and symmetry. I look at RCSP, tibial / knee position, arch height / mobility, FPI, talo-navicular deviation (there are some adjuncts I use at times, but these would be standard) and LLD static WB and then frontal and sagittal walking or running. I try to get a grasp of rotation but this is hard to assess clinically other than gross rotation at the knee and angle of gait. I do not worry too much regarding the heel to leg position other than the compensated position and range / direction of motion.

    If I identify asymmetry NWB and look to see if it is replicated WB and dynamically. If I see symmetry NWB but asymmetry we / dynamically, I look for potential causes. If the overall alignment etc does not fit with stress to the injured tissue I may look for other potential causes (i.e. muscles / strength / flexibility / control / training & loading / footwear etc.). I can still manage the latter using tissue stress approach but they may not need the degree or longevity of control once the condition has resolved and they have done the necessary rehab for their activity levels. Of course, I look at the additional factors for all patients but, if their alignment marries their dynamic function and relates to their injury, then modifying the forces around that alignment is logical and they may need the control for longer / long term.

    This is where I have arrived to over the years and I do not have all the answers but you asked so I have answered.
     
  12. efuller

    efuller MVP

    You left out that the Root system is not internally consistent or coherent. How do orthotics work?
     
  13. Jeff Root

    Jeff Root Well-Known Member

    Eric, I understand that a practitioner can prescribe an orthosis in which the forefoot is placed in a prescribed angle to the floor. But what is the significance of that angle? Are you attempting to fully pronate the MTJ with your orthosis? Are you using a prescribed degree of forefoot position in an effort to influence the position of the rearfoot? I thought TST was more about kinetics than kinematics. One of the chief complaints that I here from TST advocates is that we don't see kinematic changes with foot orthoses. Your approach seems to contradict this. I realize that some TST advocates practice radically different than others, which may be one of the reasons that I have such a hard time finding structure to the whole TST approach. I have one client who bisects the heel and then raises the medial arch until the heel bisection reaches his desired frontal plane position. He then measures the height of the arch and has the device made to a prescribed medial arch height in order to get the heel into the position that he is trying to achieve. There are many was to skin a cat.

    Rarely do we have practitioners ask us to position the corrected (modified) cast according to some angle of the forefoot relative to the floor. Why is this? How many other practitioners are using your approach?
     
  14. Trevor Prior

    Trevor Prior Active Member

    I was quite careful in my response as I know there is lots we do not know and that there are limitations to the technology I choose to use. I do not disagree with anything you have written and do not claim to know all of the answers.

    My experience with inshoe has shown me that, when I do assess orthoses, I can see if they have made the heel unload more quickly, if there is a high pressure point in the arch, if they have directed force medially or laterally, made the loading pattern closer to an expected normal or further away, caused the Hallux to plantarflex etc. If I see a foot that clearly moves towards eversion with lowering of the arch etc. (i.e. relatively more pronated) but all the load is along the lateral border of the foot, either there is a range issue or something outside the foot influencing function. If I see step to step variation (i.e. the foot loads laterally one step and medially the next or the hallux plantarflexes very early in stance, there are generally some control issues. If there may be 2-3 prescription options I could choose, I can look to see if there is any significant difference in the loading pattern and I may opt for the one which appears to give the best loading pattern.

    Now clearly, this type of analysis helps to show the effect of function of foot loading but does evaluate any proximal contributions / effects. I have now used the 3d on a regular basis (I acknowledged we cannot measure moments as we do not use a force plate and model) and I regular see changes occur from ankle to pelvis. In my experience, some become less excessive and some more and it identifying the overall effect that helps make a judgment. The effect of arch height / flexibility and shoe stiffness on tibial rotation has been extremely enlightening. I have seen a small number of patients with medial knee OA who have high tibial rotation and increased arch movement - providing orthoses that reduce the arch movement and thus tibial rotation has helped reduce symptoms. As we also assess the step length (actually it is how far ahead of CoM the foot strike occurs), step width etc., we can also see if these factors may be contributing to the dysfunction - so at times it helps me to determine if I want to focus on orthoses / rehab or gait re-training or a combination.

    What I alluded to in my post was essentially this is how I use the technology and the challenge is how to put this into a logical process so that it can then be evaluated and compared to analysis with moments etc. and then related back to clinical tests that allow the concepts to be applied more generally. Indeed, because I realise that I do not have all the answers and that there are great thinkers out there, I have discussed with some triyng to pool thoughts and devise appropriate investigations - not as easy as one might suspect.

    I accept fully that the methods you described are what is used but that should not stop us trying to be more objective and hopefully predictive to improve that process. This is why I believe the second too aims are unanswered - we may get a general improvement in gross gait movements and we have to suck it and see (my inshoe and 3d simply provide a more objective and broader assessment of the effects on gait and whether or not it makes someone more or less extreme).
     
  15. By modifying the GRF.
     
  16. drhunt1

    drhunt1 Well-Known Member

    cpoc103-did you watch the animated videos I produced...and if so, do you agree or disagree with the content?
     
  17. drhunt1

    drhunt1 Well-Known Member

    Partly correct.
     
  18. efuller

    efuller MVP

    I'm not asking for an angle, I'm asking for a size of wedge. With simple trigonometry you can convert angle to height of wedge. My rationale comes from something John Weed used to teach. He would attempt to place his fingers under the lateral forefoot to assess how much load there is there. Often there is little load (in contrast to what you would think if you thought the foot had a longitudinal axis of the midtarsal joint) on the lateral forefoot. I'm not trying to pronate the midtarsal joint, I'm trying to increase load on the lateral forefoot. Tissue stress and Root theory, may produce the same orthosis for different reasons.

    Other times, when you do that test described by John Weed you will see a high load on the lateral forefoot, yet when you ask the patient to evert there is plenty of additional eversion range of motion. Most of the time those feet have lateral STJ axis position. In those feet I'm adding a forefoot valgus wedge to pronate the STJ. This will tend to move the axis more medial when standing on the orthosis. So, yes I am trying to influence STJ position some of the time. So, again we might be making the same orthosis, but for entirely different reasons. It makes more sense to attempt to pronate the laterally unstable ankle as opposed to trying to make it more stable by casting it in neutral position. (or whatever reason that you believe is how orthotics work under Root theory).


    The point is that an orthotic can work without kinematic changes. You may have kinematic changes, or you may not. Either way you should have Kinetic changes.

    A lot of Root disciples practice radically different from each other. The Blake inverted was a radical changes. What rationale and what measurements do Root disciples use to decide to use the inverted cast technique? I would recommend that they palpate the location of the STJ axis and only give the more inverted devices to those with a more medial STJ axis location.


    There was a time when the vast majority of sailors thought the Earth was flat. They still made it to back to port, most of the time. The percentage that thought the Earth was flat changed over generations. They just had to change the textbooks so that the new sailors would think the Earth is round. The problem is resistance to change in the face of mounting evidence.

    On a more practical matter, you may not see practitioners ask because they don't want to take the time to have to have the phone conversation with lab to educate the orthotic technician.
     
  19. efuller

    efuller MVP

    Matt, you complain that tissue stress proponents make things too complicated. You also rarely defend your position or explain your reasoning. What else do orthotics do other than alter ground reaction force?
     
  20. drhunt1

    drhunt1 Well-Known Member

    Let me answer your question by asking you, hopefully, some thought provoking questions.

    1) Does GRF change when a person walks vs. runs?

    2) Does the orthotic modify GRF at heel contact?

    3) How does an orthotic modify GRF in the propulsive phase of gait?

    Oversimplification doesn't serve anyone...in particular, our patients.
     
  21. efuller

    efuller MVP

    Yes, yes. The orthotic does not modify GRF in the propulsive phase of gait unless there are some orthotic modifications under the met heads. Matt, you are proving my point that don't defend your assertions. How does the above have anything to do with the question that I asked?

    What else do orthotics do other than alter ground reaction force?
     
  22. Act as a placebo.
     
  23. Jeff Root

    Jeff Root Well-Known Member

    Just to set the record straight, I'm not sure why Simon's post immediately above attributes the following quote to me (computer glitch perhaps). For clarification purposes, it was Eric who said: "What else do orthotics do other than alter ground reaction force"?
     
  24. Modulate stiffiness at Foot interface it has always been a thought of mine and maybe this is the place to put it out there
    ( but maybe this just an extension of the By modifying the GRF.)
     
  25. This would be via alteration of GRF. Actually, to be clear it's not really placebo in the strictest sense either because you can't have a placebo foot orthoses, but via a psychological impact is what I mean.
     
  26. Funny that as I replied to Eric, not you Jeff.
     
  27. drhunt1

    drhunt1 Well-Known Member

    I disagree with your answers, (what's new). Yes, maybe and you really didn't read my article, (or even lateral wedge techniques as purported by Orthos, Scherer and Kevin), are how I would answer my questions. For instance...at heel strike...does the orthotic have a rear post? If not, is GRF modified substantially as opposed to heel strike barefoot? While it's easier to determine a modified GRF at midstance, (static stance), with an orthoses, it becomes a leap of faith to state that GRF is modified before or after that. Eric, you have no point...so I not inclined to defend my assertions other that what I already have. Show me the data that proves GRF is modified at heel strike...or at the propulsive phase of gait, then we'll "talk".
     
  28. Jeff Root

    Jeff Root Well-Known Member

    After putting a patient in orthoses you will sometimes notice a change in one or more of these areas on the plantar surface of the shoe; the heel wear pattern, the wear pattern in the midfoot region and the wear pattern in the toe area. There is a force between the foot and the orthotic in the swing phase because the device is in contact with the plantar surface of the foot and it is held in place by compression of the foot/orthotic by the shoe. Unless you have a very tight or tightly laced shoe; or unless you have a device that is radically different than the shape of the plantar surface of the foot, the orthotic reaction force during the swing phase isn't high and it will always be much less than when shoe is in contact with the ground. So if we notice a difference the heel wear pattern then we can probably assume that in some cases, the foot is striking the ground differently. If the foot is striking the ground differently, because of a change in STJ position, leg rotation, angle or base of gait, lower leg angle or for some other reason, then there must be a change in swing phase mechanics. For example, if we reduce STJ pronation and in the process the foot resupinates more with orthsoes than it previously did without orthoses, then the foot is entering the swing phase in a different position, and that change in position might alter then entire swing phase of gait.

    In addition, changes in muscle strength and function over time due to orthotic intervention may also play a role changing the swing phase of gait. If you want to see a graphic example of how an orthoses can influence swing phase mechanics, take a look at this before and after AFO video from the Richie Brace website.
     
  29. Jeff Root

    Jeff Root Well-Known Member

    From another thread: "Considering that some Australian universities no longer carry a copy of the out of print Root or any other recent (in the last 10 years) books on how to manufacture functional foot orthoses, I would be most interested if the majority of new foot orthoses are led by guidelines from the orthotic laboratories.
    I think it is very concerning that new pods don't have access to good recent books on the topic. Please let me know if there are any books currently in print relating to foot scanning or orthotic prescription writing". The above quote can be found on this thread: http://podiatryarena.com/index.php?...custom-made-foot-orthoses.108922/#post-384705

    I think the terms Root Theory and Tissue Stress Theory are doing more harm than good. Root's body of work is not a single theory and many of Root's theories and their subcomponents, his examination techniques and his orthotic fabrication techniques are independent or somewhat independent of each other. For example, you can take a neutral position NWB cast of the patient's foot but prescribe an orthotic differently than Root's original method recommended. I think we all do this at times or in some cases, always. Therefore the term Root Theory, a term I have never liked, is doing the profession a disservice. On the same token, tissue stress theory employs components of Root's body of work and there, is not really an independent theory as the name might imply or as some have argued.

    I assume the quote above is from a student or a relatively young practitioner. I echo their concern about a lack of good educational resources, especially a comprehensive book or a series of books that might teach basic biomechanical theory, practical examination and orthotic Rx writing/fabrication techniques. Without good educational resources how can we expect the schools to turn out good practitioners who are comfortable with how they were taught to practice?
     
  30. drhunt1

    drhunt1 Well-Known Member


    Good job on the AFO which addresses the foot drop and PTTD...all in one device...as it should. It looks like the prosthetist also addressed the LLD. Anyway, I don't agree on the force developed during swing phase of gait. Whatever force there is, is supplied by the tightness of the shoe strings...a pittance compared to GRF. Further, people whom are severely pronated throughout swing phase of gait, it appears the orthotic does little to correct that deformity, IMO. Here's a decent synopsis of LE biomechanics:

    http://www.drpribut.com/sports/spgait.html
     
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