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Investigation of the podiatric model of foot biomechanics

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Nov 2, 2013.

  1. Jeff Root

    Jeff Root Well-Known Member

    Kevin,

    I remember his lectures too. I remember he would talk about knee flexion after heel strike and how knee flexion was an important part of shock absorption and that as the stj pronated, the tibia would need to internally rotate further and faster the femur. I have to believe that was what he was referring to.

    One of the simple clinical tests he did was to have the patient stand and then rotate their shoulders as far left and right as possible while observing the frontal plane movement of the rearfoot or rearfoot bisection as the legs rotated. When he did this the patient's knees were extended and he did this to get a simple sense of the patient's range of stj rom on weightbearing. So as I said, I think his comment was probably taken out of context and was probably made with regard to dynamic function during gait. That said, yes you can move the stj with the knee fixed.

    Jeff
     
  2. The last story I have to tell of those days of having disagreements with Dr. Root and his followers during meetings was when I was at one of the Weed Memorial Meetings where Bill Orien, DPM, was lecturing (Bill Orien was one of the coauthors of Root's and Weed's textbooks). My guess that this was in the late 1980s or early 1990s.

    Dr. Orien made the statement, during one of his lectures, that "we all know that gravity causes pronation". This actually was a common belief at the time with the most common illustration used to explain it was that of an arrow pointed downward from the center of mass of the body, passing between the feet, and causing pronation since the "downward pulling" arrow representing gravity was located medial to the subtalar joint axis.

    I raised my hand from the audience and made the statement to Dr. Orien that his comment that "gravity causes pronation" was only half true since gravity also caused supination, in some feet. To the best of my recollection, here is how our exchange went after that.

    Dr. Orien said with a slightly condescending tone , "Kevin, where did you learn your physics from? The physics textbooks I have read show that gravity pulls the body downward, not upward."

    I said, "Gravity has the ability to both pronate and supinate the subtalar joint, depending on the location of the subtalar joint axis. I suppose I will need to write my own book to explain it."

    This was about six years before I published my first book, my fourth book is due to be published within a few months.

    These were exciting time for me and those of us that attended these meetings. I learned a lot from Mert Root and John Weed and the other members of the Biomechanics Faculty at CCPM during my student and Biomechanics Fellowship years. I wouldn't change anything that happened during that time and greatly enjoyed the intellectual challenges of debating with the individuals, who, at the time, were considered the best in podiatric biomechanics in the world.

    Lesson to be learned? Don't be afraid to challenge authority in your field of expertise, especially if you feel certain in your knowledge. Progress in knowledge within any field of specialization demands such behavior, even though it may be difficult and uncomfortable at the time.

    It is now time for the next generation of young podiatrists and researchers to push our knowledge forward so that we can continue to provide the best foot-health care to our patients in the future.
     
  3. Jeff Root

    Jeff Root Well-Known Member

    Eric,

    As Dr. Root wrote, casting the foot for orthoses with the stj in the neutral position and with the mtj fully pronated was developed by trial and error. I won't bother to explain his reasoning again, since I have done it so many times before on the Podiatry Arena. He did not always cast in that position and did sometimes use other positional combinations, but that was his primary casting position. If someone wants to advocate other positions, they are free to do so.

    As for osseous conditions of the foot and leg and Root's theory of how the body might compensate and function as a result of those conditions, I believe it is easier to see it in the extreme examples than it is in the more subtle ones. It is not absolute in part because there are many variables in addition to the condition being described (i.e. ff varus or valgus are influenced by rf varus, tibial position, joint stiffness, etc.). I believe the ability to examine and compare the osseous structure of one subject to another is an important clinical skill and tool in the treatment of lower extremity pathology. One of the biggest problems we currently face is not a lack of knowledge, it is the fact that no one seems to be organizing the facts and knowledge that we do have into a more useful model for treating the foot. Yes there have been improvements in techniques to treat the foot since Root et al, (medial heel skive, casting out supinatus, etc.) but what is lacking is any clear systematic approach in both education and treatment that provides todays clinician with a better roadmap for treatment. That is why we have such a fragmented system (if you can even call it a system) of examination and treatment today.

    Jeff
     
  4. Jeff Root

    Jeff Root Well-Known Member

    Kevin,

    I can assure you that my father had far more respect for those who questioned and challenged him, yourself obviously included, than he did for those who blindly followed. Anyone who attended a few of my father's lectures can probably recall him calling his profession lazy for wanting to take a "cookbook approach to biomechanics". Although exhausted and suffering with symptoms from severe RA, he would often sit down after lectures and respectfully talk for hours on end about biomechanics with those who might happen to agree or disagree with him. Like you, the perception of the person at the podium is different than the individual in a more conducive environment to interpersonal communication.

    Jeff
     
  5. Lab Guy

    Lab Guy Well-Known Member

    Simon,

    The golden era for reimbursement for Podiatric surgery was in the 70s and 80s and we were paid much more than as it was all private insurance. Orthotics were also prescribed heavily as it was a covered benefit under most insurance plans during that golden time.

    The 90s up to the present time became more difficult as managed care became more promient. Different states were hit harder than others in the USA. The year 2000 to the present time has been very challenging with most private insurance insurance plans paying the same as reimbursement as Medicare. Medicare Advantage plans for seniors over 65 pay even less, 30-40% of the Medicare allowable. It is not rewarding doing a first MPJ arthrodesis for $250.

    Reimbursement has been so low in the USA for Podiatric surgeons in the last 10 years that the majority have shoe racks in their office and dispense diabetic shoes to their patients. This would have been unheard of in years past and these patients would have been referred out to Pedorthists but the revenue is needed to offset the low reimbursement for surgery.

    Over-the-counter orthotics are also sold by most Podiatrists for a profit as custom orthotics are rarely covered by insurance as they used to be and patients are tight with their money during this economy.

    Every profession has members that are motivated more by dolllars than anything else and Podiatry is no different. In the USA, Podiatrists that have a passion for surgery become cerified in the American Board of Podiatric Surgery. They must complete a residency and submit cases for approval to sit for a difficult 2 day written and oral exam. Many of the questions are on pathomechanics to ensure an understanding of the mechanics of the deformity so the appropriate procedure will be selected. About 40% pass both sections the first time. It takes a great deal of work and dedication to become certified in this board and every ten years they must retake the exam to become recertified.

    With that said, I truly think that many members of the ABPS have a passion for surgery and will do surgery when appropriate despite lower reimbursement because it is indicated and they love doing surgery. There are also many Podiatrists that have stopped doing surgery as it did not make sense to pay high malpractice premiums while receiving low reimbursement. As a result, many residency programs have closed down as surgical numbers are down.

    There are easier ways to make money in private practice than doing surgery as no matter how competent you are, complications and failures will happen with the potential of being sued. The stress and emotional toll can be heavy as you feel directly responsible.

    I wrote this post to stand up for the American Podiatric Profession. No question about it, there are bad apples in our profession as in any other. But in my unbiased opinion ;), the driving force and intention for American trained Podiatrists is to provide excellent foot care for their patients.

    Steven
     
  6. efuller

    efuller MVP

    I think it is to their credit that they were looking at what works rather than sticking entirely to the the theory. However, it does get confusing for the student who is being taught the theory and then is told that we don't follow the theory because when we do it this other way it works better.


    I would have to disagree with you on the no one seems to be trying to organize the information that we do have into a more useful model statement. I do think the tissue stress approach is a more useful model that does incorporate the teachings of Root et al. One example is the partially compensated varus with a high lateral load. Tibial varum and subtalar eversion and forefoot to rearfoot relationship can all be boiled down to the maximum eversion height measurement. High lateral load and no eversion range of motion. You should make an orthotic with a forefoot varus extension. Kevin has said that John Weed felt that you did not need to add extensions to orthotics. I don't know how Mert Root felt about extensions. This foot scenario does not do well with an orthtoic that ends behind the metatarsal heads. Using tissue stress you would do something different, and in my opinion better, than what was taught before. This example shows how the information that was used before can be incorporated into a new paradigm.

    You mentioned the need for comparing foot types to one another. Two points related to that. I agree with you that at the extremes the of forefoot varus and forefoot valgus function dramatically different from one another. I said so earlier in this thread. Jeff, this is a concept that you helped me see in a post made here on the arena long ago. Understanding how the extremes of forefoot varus and valgus effect STJ axis equilibrium is an important concept that can explain how feet function differently.

    Second point on comparing foot types. We don't need to necessarily compare one foot type to another. We need to know how to reduce stress on the anatomical structures that hurt in the foot that is in front of us at a given point in time. We don't need to compare that foot to a "normal". We do need to understand the mechanics of feet and, sometimes, it may help us to choose a treatment if we compare the foot in front of us to an average foot. Other times it might not help to compare to the average. If there is pain in the first MPJ then we can reduce stress on the MPJ and see if the pain resolves. We don't need to know what normal is in that case.

    Eric
     
  7. Excellent post, Eric!!:drinks
     
  8. I agree with Eric in that I do think that understanding the Subtalar Joint Neutral (STJN) Model can be very helpful when teaching the Tissue Stress Model. The good part of the STJN Model is that it nicely describes the basic segmental components of foot and lower extremity structure using the STJ neutral position as a reference. Unless a better model comes along for accurately describing the segmental characteristics of the foot and lower extremity, I think Root's model is the best for describing the structure of the foot and lower extremity. However, it must be understood that Root's model can't be used to predict function.

    The beauty of the Tissue Stress Model is that you can use it to isolate the specific anatomical tissue that is over-stressed and injured, determine how best to reduce the pathological stress levels on that injured tissue (i.e. with an orthosis, stretching, strengthening, different shoe, etc) and can use the knowledge of the STJ axis spatial location along with the measurements advocated by Root et al to help understand how the structure of the foot may be affecting the production of the pathologies the patient is suffering from in order to recommend the best conservative or surgical treatment for the patient.

    I believe that using the Tissue Stress Model is a much better way to approach foot orthosis therapy and, at least in my hands, is a highly successful method of treating patients. However, when it comes to surgical treatment of the foot and lower extremity, the measurements advocated by Root et al are particularly helpful for establishing inter-individual differences in foot and lower extremity structure and how these relationships may be surgically corrected for the benefit of the patient.
     
  9. I've managed to source a rough transcript of the text from this paper. I think Feiss's paper is a significant contribution to the podiatric literature, being the first to describe the significance of the measure of navicular drop as a delineater between the "normal" and "abnormal" foot. He goes further, discussing how variation is quite normal and warns of the problems of artificial delineation and gives warning of the erroneous nature of basing diagnosis on skeletal alignment. He bases his observations on measurments obtained from a sample of 100 healthy young males.

    I've tried to tidy the transcript up a bit and copied some of the work below, I should still appreciate a copy of the paper if anyone can help with that (this is a lost gem, if you haven't read it you should, particularly in light of modern research on navicular drop- he was clearly aware of the need to standardise for foot length- even though this passed over the heads of several modern authors). Also worth noting is that these measures have been shown by modern research to be predictive of dynamic function:


    Conclusions From The Table.
    In studying the table we must remember that when there is a large variation within normal limits, conclusions based on only one hundred cases are of slight value; but the object of the observations was to determine the nature of the variation rather than its average extent. The important point is that the height of the arch as measured by its index, the tubercle of the scaphoid, does show this marked variation. This variation
    in a series of non-weight-bearing feet suggests the rule which applies to the individual foot with weight-bearing. In other words, the physiological variation (so far as the scaphoid tubercle is concerned) during weight-bearing function of the individual foot, is a prototype of the anatomical variation of a group without weight-bearing. This conclusion is one which has always been understood by the anatomists. It is simply a perhaps novel method of checking off the older observations; but the main question which is still open is, What is the normal foot ? What kind of a foot are we to use on which to base the estimation of a deformity, and in what should a diagnosis of a pathological foot consist ? These and allied questions require careful consideration, and to this I shall now proceed.

    The Average Foot.
    It was found that in one hundred cases the average depression of the tubercle of the scaphoid from the
    connecting line was about one-half an inch. As earlier stated, one hundred cases are too few on which to base a fair average. But even if thousands of cases had been used it would be fallacious to reason that all feet in which the scaphoid tubercle is higher than the average, are normal, and all feet in which the tubercle is lower, are abnormal, because the average is obtained just as much from the figures below as from the figures above. Moreover, the chief point shown in the hundred cases is that there is marked variation in the height of the scaphoid in apparently healthy feet. Conse-quently, as the average is based on that variation, it has no significance further than what the term indicates, representing simply an average of normal variation. Such an average, therefore, can-
    not serve as a basis from which to estimate deformity.

    The Normal Foot.
    The problem is not what is the average, but what is the extent of variation which we have a right to expect
    in the normal physiological foot? In attempting to answer this question we deal with a problem in classification, the same problem which necessarily presents itself in the study of any series of graded
    objects. Given a series of objects animate or inanimate, which differ from one another only to a slight extent, it is impossible to state just where we should draw the line dividing one group from
    another. If we take one hundred shades of color, say yellow, and arrange these shades in a graded series from a light yellow to a brown, the differences between the individual shades which are placed next to each other are so slight as not to be detectable. Yet if we
    compare the beginning with the end of the series, the difference is very striking. The same holds good in a given structure in the human body in which the individuals are arranged in a series according to the variations in that particular structure. If we take one
    hundred feet and arrange them in a series with reference to a given point, such as the height of the scaphoid tubercle, and attempt to base a classification on that variation, it is impossible to state where
    the normal variation ends and where a deformity begins, although the two extremes of the series are strikingly different. This, then, is our problem; the difficulty in dividing the series is apparent; there is no natural dividing line in this arrangement which can be used
    to define the limits of normality. I did, to be sure, find that the great majority varied between one-fourth and three-fourths of an inch, yet I can lay no stress on these figures, because it is evident that if more than one hundred subjects had been used, the gaps between the figures would have been filled up. Nevertheless, as will be seen, such an arrangement in a graded series is of considerable importance, even if the dividing line between the normal and the pathological does not exist, because this method will help to organize our knowledge on the subject.

    The "Type" Foot.
    It has been shown that the average foot is not a fair basis from which to estimate a deformity, and that it is not possible to make a sharp distinction in the series for purposes of classification. What, then, is a sensible method for systematizing our views ? The only course which remains is to make an artificial distinction between the normal and the abnormal, but an artificial distinction which is not only practical, but which has a reasonable theoretical basis. If we study the table of the one hundred cases, we note the two extremes of the series, namely, the one extreme, in which the tubercle is not depressed at all, and the other extreme, in which the tubercle is depressed one inch. There can be no two opinions as to which extreme approximates more closely the physiological foot. There can be no doubt that the foot in which the tubercle is near the connecting line is a better foot than the foot in which the tubercle is one inch below the line. The reasons for this are twofold.

    In the first place, as has been shown, the ordinary foot without weight-bearing has its tubercle higher than the same foot with weight-bearing. Now, we certainly know that the foot without weight-bearing has a greater strength and greater efficiency than the foot with weight-bearing, because the power of the former is not yet expended. On the other hand, the foot with weight-bearing is in a static position in which part of its power is already used; consequently, a weaker
    foot for further purposes than the foot which has not expended its power. It seems, therefore, that, other things being equal, the higher the scaphoid tubercle is, the greater the efficiency of the foot. Consequently, if we see a large number of feet all under the same static conditions, that is, all without weight-bearing, and find this variation of elevation of the scaphoid tubercle, it must mean that those feet in the group with the highest scaphoid (of which the
    prototype in the individual is the non-weight-bearing foot) must approximate the highest functional extreme.

    In the second place, it is apparent from what has come before, and also from a number of healthy feet in which I studied the functional power (besides those used in the present investigation), that all those feet in which the tubercles were high with respect to the
    connecting line presented high arches and high insteps. It is, I admit, very seldom that the tubercle falls exactly on the line, but quite a few fall very close to it, either just above or below. All feet which showed this property I have found to be extremely well formed.
    In addition to the elevated arch and high instep, the proportions were extremely attractive and corresponded to what an art critic would deem a beautiful foot, ^^^ly is it that the artist considers such a foot beautiful? Simply because, as part of the body, it seems well adapted to carry on its functions. From his point of view, it is a more graceful thing than when it is not so well adapted. It is, there- fore, plain that the commonly acknowledged beautiful foot is not acknowledged so because some men happened by chance to call the thing beautiful, but simply because it is the natural kind of foot which seems best fitted for its purpose. In short, both from the point of view of the physiologist and from the point of view of the artist, the foot with the high arch expresses strength and adaptability to function. Therefore, such a foot connoting strength and suggesting beauty, coming naturally at the extreme of a carefully selected series, must have some significance. Why not select this as an arbitrary type, remembering, of course, the method by which the type was chosen ? If we do this, and bear in mind that it is only an artificial selection, we have a fair starting point on which to base our estimation of deformity. Even if it is asserted that such a method is not completely scientific, it is at least reasonable, certainly more
    reasonable than having no method at all. A fairly good typical foot is illustrated in Fig. 6.

    The Estimation of the Deformity of the Foot.
    Let me, therefore, suggest the following rule for estimating the deformity of the foot : Other things being equal, the foot is deformed in direct ratio to the deviation of the scaphoid tubercle from the line connect- ing the lower tubercle on the head of the first metatarsal bone with the lower posterior corner on the internal malleolus. Now, I am careful to state, "other things being equal," because I believe that no estimation is of the slightest value without considering these other things. In any problem of this sort we have no right to take one physical sign by itself and make our estimation on that sign alone;
    we must always consider that point in relation to other clinical evidence. In flat foot, for example, we may have a number of considerations before us — the abduction of the foot, the pronation of the ankle, the prominence of the internal contour, etc. All these things may be correlative to the lowering of the scaphoid tubercle; if they are, we are probably dealing with a pathological foot, but if they are not, we must consider the relative value of each piece of evi-
    dence, depending in each case upon the individual circumstances of that case. I believe that the lowering of the arch is an important point in considering the deformity and that the best index for estimating the lowering of the arch is the scaphoid tubercle, but
    that is all the farther I am willing to go. A lowered arch does not necessarily mean a deformity, it simply means a variation; but a badly lowered arch ' means deformity, and what is bad we must determine in the individual case. As will be shown (Case V), a
    foot may be very abnormal even if the tubercle is above the connecting line. The other physical signs in such a case are more pathognomonic than the height of the tubercle.

    The Consideration of the Size of the Foot.
    With regard to the application of the rule to individuals of different size and age, I believe that its language is sufficiently broad to cover all ordinary cases, provided that one uses reasonably good judgment in the individual. Of course, an equal lowering of the scaphoid tubercle in two feet, one large and the other small, would necessarily be of
    greater significance in the latter. Thus a depression of the tubercle of three-fourths of an inch in a six-year-old child is of greater con- sequence than an equal depression in an adult.

    The Definition of Flat Foot.
    It has been shown that the variation within normal limits in a group of feet is similar to the normal change in the individual foot with weight-bearing. From
    this it was naturally inferred that the more depressed a non-weight-bearing foot is, the less it is able to change with weight-bearing, and consequently that such a foot has lost part of its latent strength. Reasoning from this, I showed that a sensible classification could be made if we regarded such a foot as typical ofhighest function and beauty which most closely resembled the healthy non-weight-bearing foot, namely, one in which the tubercle is close to the connecting line, providing no other pathological sign co-exists. Flat foot, therefore, may be defined as a position of the bones, resembling that of physiological weight-bearing, which does not disappear when weight is removed, the amount of flattening being in the ratio of the lowering of the scaphoid tubercle.

    From the above, it is clear that if we are to take such a foot as typical of beauty and function as has been described, then we can consider few feet well formed, and that we must regard the great majority of human feet as flat. This is true; but if we regard them
    in this manner we must speak of the great majority as physiologically flat, or, better, as anthropologically flat. They are only flat as based on the estimation from a type, the type being based on the considera-
    tion of the highest function and beauty, and consequently, of relatively rare occurrence. It therefore becomes clear that if only a few feet are best adapted to carry on their function from this point
    of view, and if the great majority of feet are more or less deficient as compared with the high standard that has been set, the diagnosis of flat foot can have little practical weight unless it connotes bad
    function and pain. If we consider an individual foot, and note that it is moderately flat, it does not mean that the foot is unable to carry on its function; it simply means that it might have been better if it were built more according to the type. If, however, there are signs of disability accompanying the signs of depression of the arch, such as pain and muscular spasm, then our diagnosis is established. We have a similar problem in the consideration of the physical
    signs of other parts of the body, for example in the consideration of hypertrophy of the heart. Hypertrophy of the heart may occur in apparently healthy individuals, and may not in itself cause symptoms ; but once urge that heart to carry on functions beyond the power of compensation, and it loses its resistence to future dilatation much more readily than the heart which has not previously been hypertrophied.

    From what has gone before, it is evident that the use of the bony landmarks of the foot as an aid to diagnosis must be made with the greatest caution. When one considers the extreme variation in the
    normal, when one considers the artificial manner of selecting one kind of foot as typical, one feels some hesitation in advocating the measure as an aid to diagnosis at all. Nevertheless, if the observer is careful, he may in many cases derive some value from such a method. But if he uses it, he can never lose sight of the value of the other points in diagnosis; he simply has one more physical sign to use as evidence. If he goes farther than this and bases his whole diagnosis on that one sign, he is likely to fall into grave error." -Feiss H.O. 1909

    Amen to that.
     
  10. Got it!
     

    Attached Files:

  11. Jeff Root

    Jeff Root Well-Known Member

    “The Estimation of the Deformity in General. In examining the malformations of the body there is no process more valuable than that of studying the relationship of bony landmarks to one another. In fractures of the wrist and of the ankle the relation- ships of the ends of the long bones are of extreme importance. A splendid example of valuable relationships is Nelaton's line. I may further call attention to such important methods as Bryant's triangle and Meyer's line. These simple geometric methods can hardly be omitted for a clear and proper elucidation of the deformity.

    The Selection of Bony Landmarks of the Foot. In the case of the foot no such method has ever been advanced, so far as I know, and with this in mind I have selected certain landmarks for study”. -Feiss H.O. 1909

    In 1909 Henry O. Feiss, M.D. recognized that “there is no process more valuable than that of studying the relationship of bony landmarks to one another”. He stated that “geometric methods” were necessary for the “proper elucidation” of deformity. Furthermore, he stated that to the best of his knowledge, in 1909 no such method had been proposed for study of the foot. He developed a system for standard positioning of the foot using a wooden box and compared landmarks in a semi-weightbearing foot to the same foot weightbearing to compared positional changes. He then compared and contrasted one foot type to another.

    During the 1950’s, a chiropody student at the California College of Chiropody recognized that the college had no real educational or clinical system for comparing feet except that of arch height and that feet were categorized as beening pes planus, pes cavus or normal in arch height. That student also recognized, as did Henry O. Feiss, M.D back in 1909, that “geometric methods” can hardly be omitted for a “clear and proper elucidation of the deformity”. It appears to me that Dr. Feiss and Dr. Root had a very similar philosophy and thought process with respect to the importance of anatomical comparison and the need for practical methods for which to compare feet. The Feiss article is a very interesting piece of history related to foot orthopedics. Amen to that and to his real appreciation for the need to compare foot structure. I wonder how his article might have influenced others after Dr. Feiss? Did others use or appreciate it or was it simply dismissed due to lack of repeatability or due to a lack of validation by independent research? There is no question that some of the earlier pioneers in foot orthopedics had some excellent thoughts and may have contributed to today’s body of knowledge. The question is how much did they contribute, especially if their work wasn’t known to their followers?

    In this day and age we can sit in the comfort and convenience of our home or office and instantly find a wealth of information with the simple click of a mouse. During the 1950’s, chiropody students had a library at the college and access to the public library. They did not have instant access to millions of digitized documents nor did they have easy access to a large body of physical documents and resources. I don’t believe that some of the “younger generation” can fully appreciate this fact. I believe this is why Eric Lee posted, with respect to our historical perspective on things, a quote from the book The Master which says “I consider the greatest mistake any commentator can make…..is to pass judgment on “then” in the context of “now”. To do so is to ignore, either through ignorance or deceit, the prevailing atmosphere of a particular era and hold it up to unjust scrutiny or ridicule by applying to it standards that nowadays prevail in a completely altered set of circumstances.”

    Jeff
     
  12. DrBob

    DrBob Active Member

    Have I missed something? The way I see it:

    1. There is clear and strong evidence that the dynamic biomechanical function of the human foot cannot adequately be explained by the simple models based on static measures that have been a mainstay for several decades.

    2. Biological variability alone is sufficient to demand that our approach needs to be tuned for the individual.

    3. Conclusion? We need to dynamically measure each individual and assess our interventions likewise. Until we do this, we will continue to go around in circles.

    4. Objective? Find a way to do this that is inexpensive, quick and effective (and stop getting side tacked by all the other approaches that do not comply with this logic - they will simply bring us back to where we are now; again, and again, and again, and ...)

    I know that the stethoscope looks like it is loosing popularity, but "we" really need a podiatric stethscope.

    Kind regards,

    DB
     
  13. rdp1210

    rdp1210 Active Member

    Eric,
    I'm going to agree with most of what you said. I agree totally that we can't judge history in light of today's paradigm. A prime example is many ofthe framers of he Declaration of Independence did not give independence to 100% of the population. Yet in terms of where society was at that point in time, they made a giant leap forward.
    I'm sure that you were at the first John Weed Seminar in 1994, when Mert Root was asked to speak a few words. He noted that when they published their 1977 text, he fully expected that it would be replaced within 5 years with something that was better. He was surprised in 1994 that it had lasted 17 years. The writing style, in the 1970s, was still not what it is today in terms of people expressing doubts within the texts. We therefore have to give the writers the same leeway in terms of their style as well as their knowledge base.

    I can discuss with you ad infinatum the neutral position concept, both in theory and practice, both the positives and negatives. However the fact that many of the people who decry neutral position biomechanics are still taking casts for orthotics with the Root technique shows me that for all their posturing, there is still something in the Root logic. People like Glaser and Shavelson are the ones who criticize Root and then back it up with action by not doing Rootian casting technique. (not that there's anything right with their theories). My position is: don't subscribe just to one theory. Try to incorporate and blend as many theories together as possible in order to create a system that is totally consistent, both internally and externally. I utilize everything that Root taught, that I've found works, however I'm not tied to only Root's theories as there are a lot of things he didn't discuss. I think we'll look back in history on Root the same way physicists look back on Isaac Newton. He contributed a lot, but you can't build a computer based on only on Newtonian mechanics.

    In response to Dr. Bob -- I heard Mert Root lecture quite a lot, and found that your statements #2 & #3 are the same things that Root was saying 30 years ago. He also looked and advocated for a better stethascope.

    Best wishes,
    Daryl
     
  14. efuller

    efuller MVP

    Point one does not naturally lead to conclusion 3. The static measures that were examined in the study did not predict dynamic function. That does not mean that other static measures cannot predict dynamic function. There was a study that looked at x-ray measurments of relative length of first and 2nd metatarsals. There was a correlation between 2nd met length and dynamic 2nd metatarsal head plantar pressure. So, a static measurement can predict dyamic function. You just have choose the correct static measurement. Two stataic measures that I believe will predict dynamic function are STJ axis position in the transverse plane and the maximum eversion height test.

    Eric
     
  15. efuller

    efuller MVP

    Daryl, I would like to point out the difference between finding a succesful protocol and the logic used to explain why that protocol is succesful. I believe that Root et al came upon their protocol more through trial and error than through theoretical principles. It certainly is a success to come up with a good protocol. However, when you start to talk about the logic of why that protocol works you start to run into some problems. One of the problems is that is really hard to pin down people who "believe" in Root's logic as to what exactly that logic is. There is the support the deformity school (e.g. forefoot valgus) school and there is the push the foot closer to neutral position school of thought. (Some have taken this farther to a cast taken in neutral position will put the foot in neutral position. Most good Root thinkers know this last one is not true.) I've written on some of these problems in this thread above.


    Here I would like to point out the differences between observations and explanations of those observations. Root et al, made the observation that orthotics casted in neutral position seemed to work better than those that were not. I've had the pleasure of making myself devices from foam box impressions taken fully weight bearing and partially weigth bearing. I liked the partial weight bearing one more because there was more pressure under the medial arch. I think this is a very similar observation to the casts taken in neutral position seem to work better. I would also like to point out that the firsts neutral position casted orthotic that was made for me hurt like hell. It was much better after a plantar fascial groove was placed in it. Later, I took the same cast and added a little more arch fill and the orthotic made from this iteration of the cast was also comfortable. So, I'm quite convinced some pressure in the arch will make the orthotic work better. There is a too much, too little, and a range of just right. So, the neutral position cast is good because it allows to make an orthotic with a higher arch than you would if you took a weight bearing cast. Neutral position cast is not good because neutral position is ideal. Again, I'm not quite sure what the Root theory is behind a neutral position cast, but I like the observation that it works.

    So, we have to separate out the observations from the explanations. We don't have to use all the theories at the same time. Nor do we have use some theories some of the time and other theories at other times. We need to find a theory that can explain all of the observations all of the time. This is where I like the mechanical engineering approach. You give a patient an orthotic with a high arch and you note that they tend to resupinate more in gait. With the engineering approach you can look to various reasons as to why the STJ might supinate more. What are the sources of supination moment? Pressure in the medial arch will shift the center of pressure more medially. However, in some feet it may not be shifted far enough. (Those with a lot of resistance to supination with the supination resistance test.) Another source of supination moment is the posterior tibial muscle. So, it is likely that some of the time you see resupination with an orthotic because of increased activity of the posterior tibial muscle. This is the reason that I like to use only the tissue stress theory and not other theories. With tissue stress you can look for mechanical explanations of observations.

    Eric
     
  16. Eric:

    I agree. The way forward for podiatry is to "think like an engineer" using the mechanical principles that form the basis of statics, dynamics and materials engineering technology. I believe it is helpful to be knowledgeable of the Root theories but they simply are not needed to make patients better with orthoses or to diagnose and effectively treat mechanically based pathologies of the foot and lower extremity. I am devoting one of my lectures in next week's seminar in Zaragoza, Spain to this very concept which, I'm sure, you will enjoy.

    Unfortunately, those that hold onto Root's theories too tightly are likely to be left behind, clinging to unsupported opinions of one man that are, simply, outdated and incorrect. It's time to move forward as a profession. After all, it is 2014, not 1964!!
     
  17. DrBob

    DrBob Active Member

    Hi Daryl, Eric and Kevin,

    First, regarding Eric's comment on static measures and their relevance to dynamic function.

    Yes, a small number of papers have found links between static measures and dynamics (and it would be absolutely amazing if there was absolutely no link what so ever), however, the numbers are very small in comparison with the those studies that have looked and reported no correlation (the odds are therefore simply against success, sorry).

    Also, when papers have reported a correlation the associations tend to explain something in the region of 30% to 35% of the variance (Peter Cavanagh's teams produced some excellent work on this). So, they give you about a 30% chance of predicting the dynamic action correctly. Now, any good engineer would never put his career on the line with those odds because they are indicating that you've got a 65% to 70% chance of getting it wrong! Sorry, not a good approach.

    In my experience, good engineers ask good and penetrating questions - I've worked with them a lot. Here is the one that most of them ask me, "If you want to know what the dynamic function is, why don't you measure it"? When I chat to colleagues and student's about our podiatric approach to this problem, I put it this way. Imagine you want to know someones height? Well, one way to try and predict it is to measure their weight then use a body-mass index formula to calculate their height. Often, you should get somewhere close (the statistics are in you favour with a normal distribution) but frequently you will be off by a mile! Just like podiatric biomechanics! Of course, you could just invent a height measuring device, and measure their height. Why do we want to stay with an approach that will never be really satisfactory? Let's concentrate our efforts else where?

    Daryl, I never met Dr Root. I think he made a great contribution. My opinion on that, for the little it's worth, is that he gave us a systematic approach to the clinical problem, and as a young pod in 1978 I was very grateful. As a profession, we should have taken his offering with gratitude and built on it, not tried to squeeze it into something it was never going to be.

    And, if he did advocate for a podiatry stethoscope all that time ago, then I take my hat off to him.

    I've been looking for a podiatry stethoscope for 30 years. I think that it must work both barefoot and in-shoe, it must be easy to use, fast and inexpensive, and above all, it must give some immediate feedback, especially regarding therapeutic interventions...

    Kind regards,

    DB
     
  18. While I tend to agree, it also must be recognized the the vast majority of such correlational studies have only attempted to fit linear models to the data in its raw form; curvilinear models and data transforms may yield far greater r square values and better explain the relationships between the variables of interest. The other problem is an over reliance on bivariate models.

    The point regarding prediction of variables such as height which can be easily measured anyway is well made. However, via modeling we can begin to ask the "what if" type questions, for example predicting future values. Further, the dependent variable may not be so easily accessible a measure as body height and may require invasive techniques which could be deemed inappropriate for day to day clinical work-up. Here a good predictive model should come into its own.
     
  19. DrBob

    DrBob Active Member

    Hello Simon,

    I hear what you are saying but...

    First, can anyone out there seriously argue with this question: If you want to know about dynamic function, why not measure it?

    Notice, I'm not saying that it will be easy or putting any other caveats on it, but isn't the basic logic sound/attractive?

    Second, you can spend your life doing transforms and fitting the data to nonlinear equations - I did my fair share for my PhD - but, if there is a strong link - and we want a strong link not something that really has to be teased out - then it will stand out like the nose on your face and transforms will refine it. No one has found it yet.

    Third, I agree, models are extremely important, but there is a point in the modelling cycle that demands that the model is "tested against reality to determine whether it is performing in a useful manner". Therefore, the catch is that you must be able to provide real data (in fact you should provide it twice, the first time to create the model then the second to test it, and maybe refine it). In this case the data will be dynamic data. So, if you have to provide dynamic data to ensure that the model is sound, why not go the whole hog and provide dynamic data straight to the end user? If you take that approach, you can build models forever-and-a-day!

    Kind regards,

    DB
     
  20. Rob Kidd

    Rob Kidd Well-Known Member

    Fitting linear models in biology is simplistic at best. Most would agree that there are no straight lines in biology - all equations are ones with an exponent in them. Sure Y=MX+C may approximate to what you are trying to quantify, but in reality, it is far more likely to be Y=MX to the K (sorry- cannot type that). There is nothing new in this; Julian Huxley knew this in the 1930's with his bivariate allometry (sp?)equation - in reality an adjustment of Y=MX+C.

    Having said that, and I stand by it, oddly, ratios - which are all mx at the end of the day, seem to describe biological form well, if not best,

    As always people, we are back to thinking carefully about what we have in front of us.
     
  21. You are correct, at some stage someone has to do the direct measurement in order to build and test the model. But as I said previously, if the direct measurement is too invasive and/or prohibited by cost, then a good model may be far more practicable in a clinical situation.


    What we want is a model which is practicable and explains as much of the variance in the dependent variable as possible. There is a pay off between loss of degress of freedom and increase in r square as we add x terms, but if you're only looking for a straight line and a straight line doesn't "stand out like the nose on your face", then you're probably going to miss the bigger picture; noses come in lots of shapes and sizes.

    Perhaps, you could let us know your real name and the title of your PhD?
     
  22. Dr. Bob (It would be nice to know your real name and what your PhD was on):

    First of, there has never been a "podiatry stethoscope" and there never will be any more than there will be an "orthopedics stethoscope", a "rheumotology stethoscope" or a "neurology stethoscope". The complaints that our patients present to us with are multifactorial, often times involving structures within the body that we don't have direct access to in order to measure.

    Healing the patients who come into our offices requires a detailed knowledge of foot and lower extremity anatomy, a good working knowledge of biomechanics and physiology, and the knowledge of and technical skills to provide the various treatments that available to treat the numerous pathologies that a podiatrist can treat....not a "podiatry stethoscope".

    I got into podiatry to be a doctor of the foot and lower extremity that used many tools to heal my patients, not a technician that had one tool that was easy to use, fast and inexpensive, since I knew that the profession I was getting into was challenging intellectually and would require much more than one simple instrument to get the job done.

    There is no "podiatry stethoscope", and personally, I'm very glad that there isn't.
     
  23. efuller

    efuller MVP

    Well, that is sort of the point. Bad static measures won't be predictive. Good static measures will be predictive. This is sort of an engineering question. What aspects of the static anatomy will be predictive of that same anatomy in dynamic function. So, what if there are a lot more bad measures. We only care about the good ones. So, the odds of finding a good one are irrelevant. If there are good ones we should use them.

    And an engineer should ask what do you mean by dynamic function and what do you want to do with it? For example, if we wanted to predict 2nd metatarsal head pressure should we look at 1st MPJ dorsiflexion in gait? Static relative metatarsal length might be better than 1st MPJ dorsiflexion in predicting 2nd met head pressure. Not everyone is going to go out and buy a Harris mat let alone a pressure distribution sensor. And both of those may not be as good as looking at the impression in the sock liner of a shoe that has been used for more than a month. The insistence on dynamic measures of foot function is almost an insistence on no measures. What are you going to do if you don't have a dynamic measurement system. Also, you still need good dynamic measures. When I wrote my chapter on computerized gait analysis in 1994 there weren't really any dynamic measures that had been shown to be predictive of pathology.

    Eric
     
  24. Rob Kidd

    Rob Kidd Well-Known Member

    Just in case there is any confusion - I am not DrBob. I am Rob Kidd. Since we are both writing on this thread, lets be clear what is from me and what is not. My Doc calls me Doctor Bob though! Rob
     
  25. Petcu Daniel

    Petcu Daniel Well-Known Member

    Yes, and (among other things) I don't understand how much it was the mean RCSP (used as "0" reference) because I would like to visualize what means : "In most feet, the calcaneus was inverted relative to the tibia in NCSP with a mean of 9.2? (SD= 5.0?) on the left, and 9.0? (SD = 5.1?) on the right (Table 6.12)" and "No. of feet INV angle =97%" - page 267.

    To me is much more easily to visualize a movement relative to supporting surface as a reference system. So it is a little difficult to visualize it when it is reported relative to tibia which doesn't have the movement depicted relative to any other reference system. At least this is my understanding.
    Any help with these issues will help me to better understand this work which I found very interesting !

    Daniel
     
  26. efuller

    efuller MVP

    The tibial varum measurement (frontal plane angulation to the ground) will give you a global reference when you look at calcaneal bisection relative to the leg. Of course trying to add the measurements together can compound measurement error.

    Eric
     
  27. Petcu Daniel

    Petcu Daniel Well-Known Member

    This is my problem: I don't see / understand how much it was the mean tibial varum because I don't see it reported in thesis.

    Daniel
     
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