Forefoot Varus Predicts Subtalar Hyperpronation

Also internally generated muscular force. We must realise that force = mass x acceleration and that gravity is only one source of acceleration.

 

Otherwise, GRF would max out at mass x gravity, yet it doesn't. End of story.

 

Eric, Simon, Daryl, Jeff and Colleagues:

In all fairness to Matt, I also don't agree with Mike's contention that there are "no normal and abnormal feet". Certainly we can all agree that there is a normal range of structural variances within the feet and lower extremities of the human population with some being "normal" (normal in this context meaning average, not Root's "normal" which meant ideal), and some being abnormal. For example, do we say that the person with a middle facet osseous tarsal coalition has a normal foot? No. We say the tarsal coalition is abnormal and may, or may not, cause symptoms over time.

I agree with Daryl, Jeff and Matt that structure is important in determining certain pathologies since abnormal structure can cause abnormal forces and abnormal moments. Certainly these concepts that abnormal structure may cause pathologies are century-old concepts from orthopedics and the early podiatric profession which I believe we can adopt to a certain extent within our more modern analyses of why certain pathologies occur.

However, I have a problem with the way that structure was classified by Root and colleagues since I feel it left out many important biomechanical factors (i.e. 3D position of talar head relative to plantar foot) and relied too heavily on STJ neutral and heel bisections. Certainly there must be a better way to classify foot structure and "normal" and "abnormal" so we can make more progress in this direction. I believe that maybe we can find some common ground here so we can try and move forward as a profession.

 

Kevin,

It always bothers me when I hear our local meteorologists use the term normal when they should be using the term average. For example, they might say something like we are two inches below normal rainfall for the year or that we are having above normal temperatures today. The reason that if bothers me is because normal in this case is based on historical data which can be used to calculate the average. It is normal for some days or years to be warmer or cooler than average and it is normal for some days or years to be dryer or wetter than average. So they should say that today the temperature was X number of degrees above average, not it was X number of degrees above normal.

Whenever possible, it serves us well when we can quantify things in order to establish the average. Unfortunately the structure and the range of motion of joints within the human body is not always easy to measure or quantify. And even if we did have averages, we don't necessarily always see pathology when some individuals function well away from some of these averages. But as you said, structure is important and so too is the concept of normal and abnormal.

For example, today I had a podiatrist send in a patient for casting in order to fill their Rx for their orthotics. The doctor's diagnosis was metatarsalgia/capsulitis and the patient also complained to me about pain along the plantar fascia. The patient brought in their X-rays which I reviewed. The patient has a very low calcaneal inclination angle, especially on the right. I did a brief bio eval prior to casting. The patient has about 30 degrees of dorsiflexion of the hallux B/L on open chain examination and demonstrated an apropulsive gait, functional hallux limitus and medial arch collapse during weightbearing. They demonstrated a good range of ankle dorsiflexion with the stj in or near the neutral position. I observed the open chain rom of their stj and they exhibited little to no calcaneal eversion relative to the leg. They also have a history of right knee replacement. I didn't take a single measurement but I was able to observe several things that appear to me to be contributing to their symptoms.

Notice that I did not mention the word normal or abnormal when talking about this patient. I was probably able to paint a picture in your mind with some of the descriptions I used in spite of the fact I did not measure anything and only estimate one angle (the hallux). So I agree we are not well served by the over and/or incorrect use of the terms normal and abnormal. But in order to make this process more scientific and to paint a more accurate picture, some actual measurements might be beneficial. So how can we improve our terminology and examination techniques so that individuals can better communicate about patients? I think we both agree that their is a problem and that is at least a start!

Jeff

 

The bottom line is that what "normal" and "abnormal" means to each podiatrist, in regards to foot structure and function is quite variable. Therefore, to use these terms meaningfully, they first need to be defined.

What does normal mean?

Does "normal" indicate the Root et al definition of an ideal structure?

Or does "normal" indicate an average (i.e. mean) structural value, and how many standard deviations from the mean should "normal" be?

 

Maybe Normal should = Pain free of something like that.

So a foot can go from Normal to Abnormal to normal again all depending on Pain or maybe we should include structural changes such as Hallux Valgus as well.

But the issue comes back to what the reader read or wants to read.

So Maybe we should not use normal at all, just painful and/or a foot undergoing structural changes deemed to be of a negative nature.

Maybe

ps tbh I wrote abnormal and normal being more a smartass than thinking, well that showed me

 

I am going to agree very much that Root did leave out some basic classifications. I'm of the opinion that Root influenced me not so much as to trying to classify feet but as to looking for etiology of function that creates problems. I view the opportunity to do a goniometric exam as the opportunity to look for reasons for abnormal function. While Root did expound a little more on earlier work by Russel Jones on the abnormal declination of a STJAxis, and which was further explained by Don Green, You, Kevin, took the next big step by identifying abnormalities in projection of the STJ axis on the transverse plane which then led me to finish earlier work to find an actual mathematical equation for the axis. Besides abnormal STJ axes, I believe that we need to know more about any abnormal linear translations of the os calcis. Root hypothesized a little about abnormal MTJ axes, however I believe we have hardly scratched the surface of this important topic. I believe that Root never took into consideration abnormal length tension curves for the triceps surae, and there are a host of other things he never addressed or considered. As I've listened to you over the years, I know that you feel the same frustration as Root did with a large number of foot professionals who are not interested in learning more math and engineering science, only in learning how to get bigger fees.

You will notice that Root's actual definition of normal had nothing to do with subtalar joint neutral. It basically said that a normal foot was one that could function during a lifetime without creating angst for its owner. So if Dr. Lyn Staheli can function his entire life with feet as flat as pancakes without ever suffering a twinge of pain, "um so besser". Sometimes, when reading the various posts of others, I think of the similarlity of so many Christian religions all basing their beliefs on one specific book and arguing about the interpretation of that book. Everyone has their own interpretation of what Root said and what his theories were and how those theories are implemented in their practice. When someone brings in a very-non-Root orthotic and tells me what a wonderful thing is is for them, I can accept that. I always want to know, though, why it works. And when a "Root-orthotic" doesn't work I always want to know why. Was it my lack of knowledge or my lack or application. These are the people that are so valuable and become what Dr. Weed called, "My seminar expenses."

So Kevin, I echo your call for common ground to move us forward on. While many accuse me of being only a Root apologist, I do continue to study and research, never satisfied that I, Root or anyone else knows it all, or even a good proportion of it all. As to the calcaneal bisections, I hope that you do have a copy of the paper "LaPointe et al. - Reliability of Clinical and Caliper-Based Calcaneal Bisection (2001)" If you don't, I'll send it to you. I do believe we all need to come together on defining some type of calcaneal reference lines that we all use for goniometric examination. If we don't, then we need to say that goniometry of the foot should be left for physiotherapy voodoo examinations.

Best wishes,
Daryl

 

In regards to making measurements of the foot and lower extremity, I have long wondered why we don't use the maximally pronated position of the subtalar joint (STJ) as the reference position by which to measure many of the structural parameters of the foot. It seems like the maximally pronated STJ position would be far more reproducible from one examiner to another and if we needed a mark on the posterior calcaneus this "calcaneal bisection" could simply be drawn on the foot while standing in the STJ maximally pronated position to eliminate another source of inter-examiner error.

Since so many people stand in the maximally pronated STJ position, the "vertical calcaneus" would therefore become the baseline position for maximally pronated STJ position. The maximally pronated STJ position should work better for reproducibility since it is a rather "hard stop" that defines the end range of motion to STJ pronation due to bone-on-bone contact forces within the sinus tarsi and should be easier for less experienced examiners to reproduce.

On another note, I think that one of Root's main failings with his classification system is that he totally ignored talar head position relative to the three-dimensional relationship of the rest of the foot skeleton. Root focused on calcaneal bisections in his measurement system. Why? I don't know why.

I believe Root must have been thinking that the posterior surface of the calcaneus which we bisect when using the Root system had a great deal to do with the function of the foot, when, in fact, it has very little to do with the overall function of the foot. The posterior surface of the calcaneus does not necessarily tell us where the medial calcaneal tubercle is in relation to the STJ axis (where most of GRF is focused on the plantar calcaneus). The posterior surface of the calcaneus also does not tell us where the insertion of the Achilles tendon is relative to the STJ axis (where Achilles tendon tension force is focused on the calcaneus).

Not only did Root not try to identify the STJ axis location posterior exit point on the posterior calcaneus (which would have at least allowed him to start considering the magnitudes of STJ supination moments coming from the Achilles tendon and the medial calcaneal tubercle), but he didn't consider the very important anterior exit point of the STJ axis through the dorsal neck of the talus. He seemed so locked and focused into this "calcaneal bisection", a measurement that really has little functional significance to foot biomechanics, that I believe this prevented him from looking at talar head and neck position more (like Schuster did on the East US coast) where he probably would have hit more "pay dirt", in regards to foot kinetics and, therefore, foot biomechanics.

Another big problem with Root's classification scheme is that he used the word "normal" to mean what he felt was "ideal" structure. Root did not use the term "normal" to indicate a range of structural variances which would allow optimum gait function. Rather, by using the term "normal"to mean "ideal", he set the stage to create his system where any measurement that wasn't exactly what Root said was "normal" would be abnormal. This was a huge mistake.

No laboratory test used in this day and age uses only one value to be "normal". Rather, labs use a "normal range" to account for the variability of the human species, their different blood chemistries, physiological makeups, etc. Root would have done much better to give a "range of normal structure" rather than one value for his ideal "normal" in each of the parameters he suggested measuring. In that way, a "3 degree forefoot valgus deformity" would no longer be considered "abnormal" but would rather be considered within the normal range of frontal plane forefoot to rearfoot relationships. I think this one change, by itself, would have made Root's system much more palatable to many of us in this day and age.

This is not a personal condemnation of Mert Root but rather is my retrospective look at the history of podiatric biomechanics with the knowledge I have now, in 2015, that Mert Root could never have possibly had. We must identify the problems with evaluation systems of the past, find better solutions, and then do the research it takes to see if a new evaluation system is indeed an improvement on the older systems. This is our best way forward.:drinks

 

Kevin,

Merton Root was extremely aware of the clinical significance of differences in the spacial location and differences in the anatomical location of joint axes between individuals. He wrote and spoke extensively about how joint axes influence motion relative to the cardinal body planes and why this is important clinically. He did not limit this to just the stj and mtj although he did concentrate on these joints because of their significant contribution to motion of the foot.

He felt that heel bisection was a good indicator of stj motion but he recognized that there was no actual way to clinically measure stj motion. He used heel bisection to measure the frontal plane component of stj motion and he discussed how changes in the anatomical location of the axis of the stj would influence frontal plane motion of the heel between individuals. Below I have attached an excerpt from Normal and Abnormal Function of the Foot in which some of these concepts are discussed.

Jeff

 

Normal and Abnormal Function of the Foot was really good at explaining how when a hinge like axis is not in any single plane that motion will occur in all three planes. However, the picture of the hinge, in those descriptions, may have mislead many people into thinking that when you describe an axis, motion must occur about that axis. When in fact a joint axis is just an imaginary line the describes motion at one particular instant in time. Too many people think that motion must occur about imaginary lines.

Eric

 

Kevin,

I think we need to look at all this in the context of the time. Merton Root has been described by many to be way ahead of his time. His books were books were really text books that attempted a comprehensive explanation of the function of the foot, including an explanation of the physics of motion and stability, a complete description of muscle and osseous function throughout the entire gait cycle and resting stance, structural and functional anatomy and theories about causes of pathology. It has proved to be a tremendous resource for many readers, especially given the void of this type of text book at the time.

I do not agree that Root "totally ignored talar head position relative to the three-dimensional relationship of the rest of the foot skeleton". Here is one section that addresses it:
Normal and Abnormal Function of the Foot, page 45 Figure 1-77
"The foot with an excessive range of transverse plane motion at the midtarsal joint undergoes a medial shifting of the distal aspect of the rearfoot when bearing weight. The center of the talus shifts to the medial side of the longitudinal axis of the foot and more weight is born by the medial side than by the lateral side of the foot. An excessive medial loading of the foot causes the foot to pronate excessively.

The adducted position of the rearfoot causes an abnormally large abducted relationship between the forefoot and the rearfoot. The head of the talus and the navicular also budge medially because of the adducted rearfoot position. Therefore, this foot has many of the characteristics of a pronated foot even when the subtalar joint is in a neutral position."

And on page 306:
"In stance, the forefoot is fixed against the floor by friction, and no forefoot abduction can occur as the midtarsal joint pronates. Therefore, the transverse plane motion, associated with midtarsal joint motion, occurs in the rearfoot by adduction of the calcaneus (Figs. 9-12 and 9-13). Medial shifting of the ankle and leg results from this calcaneal adduction and causes medial displacement of the mechanical axis of the leg (Figs. 9-14 and 9-15). Weight from the leg is supported by the medial side of the calcaneus and produces a significant lever arm for subtalar joint pronation. Attempts to control abnormal pronation in patients with this type of problem have met with limited success and a mechanical device different from those presently in use, will be required before effective control
of pronation can be established".

Here you see that recognition of the significance of talar or talonavicular adduction was just beginning to be recognized. After the book was published, Root began to appreciate this all the more and as he predicted, many of us worked to develop devices that proved to be more capable of controlling this type of foot due to deeper heel cups, inverted orthoses, higher arched devices, medial heel skives, etc.

Who will write the next Biomechanics 101 book for tomorrows students and practitioners? Perhaps others are afraid to put their money where their mouth is and invest the time and money to create a better alternative. Yes, there are books of news letters, books with chapters written by different contributors, but who will make a comprehensive effort to tech lower extremity function with a book or series of books like Root et al did from basic terminology, examination technique, and from functional theories to treatment? Personally I believe that is what is required to take the next step forward in biomechanics. And if anyone does step up to the challenge, they will be judged by the same test of time as new information inevitably becomes available.

Jeff

 

Eric,

I agree, and as I just said, whoever writes the next book should explain it that way!:drinks
Jeff

 

Jeff:

Thanks for that quote from Dr. Root's book. I don't remember him ever talking about talar head position in his lectures but certainly he probably considered it as you have shown in your quoted passages. I would explain it differently, using subtalar joint axis location, but the essence of the mechanics of this foot type seems to have been appreciated by Dr. Root.

Like I said earlier, we have learned a lot since Dr. Root quit publishing over 35 years ago. I feel that Dr. Root did more for podiatric biomechanics than any single podiatrist ever, that I am aware of. However, Jeff, I think you will find that my four newsletter books and my five book chapters are fairly comprehensive in the subjects they cover and certainly, at least according to many, serve as a valuable resource for the evaluation and treatment of mechanical disorders of the foot and lower extremity, for the detailed prescription of custom foot orthoses, for the troubleshooting of foot orthosis and shoe issues and for the biomechanics of the foot and lower extremity.

However, if I was to write that "Biomechanics 101" book for podiatry that you mention above, I would certainly spend a lot of time getting podiatrists up to speed on proper terminology used within the international biomechanics community (along with proper definitions and meanings for appropriate engineering terminology and concepts) so that I would be teaching real biomechanics, and not what many of my classmates and students called the "voodoo biomechanics" that we were all taught in podiatry school.

 

Kevin,

If you wrote that Biomechanics 101 book I would think you would have to provide definitions even for "common" terms like stability and instability and also explain how the context of such terms is important. It almost seems silly by today's standards how basic some of Mert's first book was (like explaining the cardinal planes of the body) but he needed to make sure the reader really understood him. I can see the need for a modern day version of a book like his where the author explains the basic concepts of joint mechanics (moments, lever arms, etc.) and how standard biomechanical terminology should be used with respect to the lower extremity. I think there are elements of tissue stress in Root's work just as there must be structural considerations in tissue stress theory. Maybe you need a Bill Orien type to motivate you to assemble a team of writers to write a book that could serve as a text book for podiatry and other students such as PT's. I really think the lack of a standard text in the podiatry schools is contributing to the lack of consistency and perhaps interest in basic biomechanics by modern students.

Jeff

 

No, I don't need anyone to motivate me. What I do need is more hours in my busy days of seeing patients, running a business, writing a newsletter every month, writing about five articles a year for Podiatry Today, staying on top of the current literature, reviewing papers for five different journals and preparing and giving three international lectures a year plus about 5 lectures in the States per year. I simply don't have the hours available in the day to take on such a task currently.

 

I would be interested to see the documentation in the referring physician's chart. I would put my bet that your documentation is better than the physician's documentation. This is bet is based on the type of documentation that on-site residency evaluators see in charts that residents write.

I agree that we need to be very careful in our use of the word normal. The term is defined by the needs of society (see Root's definition of normal). I really don't think it is normal for anyone to want to run 26 miles. Yet I have one patient who isn't happy unless he does it at least 20 times/year. Is that normal? I think that the only true definition of normal is the mathematical one, a line that is perpendicular to a given line or plane.

Best wishes,
Daryl

 

I always appreciate the thought you put into your posts. I never object to someone asking questions. Only if we are unafraid of truth can we hope to find it. (I hope that Simon has had time to listen to Rupert Sheldrake point out how we created a circular definition in defining the speed light) Just this one post that you made could be the basis for a complete symposium, and I'm not sure I can really address adequately the issues you raise with just a short reply.

Believe it or not, I have questioned these ideas as well. What is your opinion of the LaPointe, et al. paper (2001) that was able to get good intertester reliability of calcaneal bisections just using a good caliper? I'm not sure why you say that the STJ maximally pronated position is more reproducible? Are you talking about about the ability to put the STJ in a maximally pronated position? If you are talking about the ability of examiners to measure the degree that the calcaneus is everted when the STJ is maximally pronated, then you bring in two variables - the problem of defining a common calcaneal reference line, and of defining a tibial reference line. Any goniometric examination of any body part requires definitions of the reference lines. It also requires clear definition of the plane that the angulation of those lines will be measured in. One of the problems I found in my early days of doing goniometric examinations was that the Root-Volume I book did not fully define the frontal plane of the foot. That is why in my 1992 paper I took special care to define this plane, in much greater detail than Root. I am not aware of another paper that has defined the frontal plane of the foot in such detail. One of the big problems with Root and every other reliability paper has not addressed precisely the plane that one measures inversion-eversion in. The way I see it, thousands of clinicians have no problem investing $5K in a quantitative vascular testing unit, but they have big problems in investing more than $5 in decent goniometric equipment. If your previous description of Root saying that anyone can bisect a calcaneus is correct, then this would make me very disappointed in such an expression of naivety.

The vertical calcaneus was certainly the definition of neutral by Wright & Desai (1964). Levitz & Sobel's contention that Root misread the Wright & Desai paper in defining neutral forgot cannot be true because Root's 1964 paper on an approach to foot orthopedics was published in February and Wright & Desai's paper was published in March of that year. Oops!

Now if you only want to measure the total ROM of the STJ, you could start at STJ fully pronated position, call it 0 deg., and measure the available ROM in the supination direction. But is that really enough information? The idea of a neutral STJ position is much older than Root. You'll remember that Lovett & Cotton in 1898 put forward the idea that there was a position in which the STJ was neither pronated or supinated. My question to you has nothing to do with reliability studies, but instead -- should there be a neutral position, in which the foot is neither pronated nor supinated? I have made the argument before that trying to define a neutral position of the STJ is not unsimilar to a mathematician trying to define the number "zero."

Relying on a "hard stop" idea is a nice thought, but I haven't found the PEROM to be necessarily as hard as one would think it should be. If it was, disruption of the spring ligament wouldn't be as devastating for increasing the pronation of the STJ. Certainly the position of the ankle joint affects the EROM of the STJ in both directions, not just one. I think I have addressed this problem before, that in any goniometric examination of any joint, in the foot, hand, knee, etc., one has to really define what it means to be at the EROM of any joint. How much tension should be on any of the ligaments that restrain that joint? As I mentioned before, if you want to throw away goniometry of the STJ, you have to then make the same argument for throwing away goniometry of any of the body joints.

I would like everyone to think about what the changes would be in clinical practice, that would have to be addressed if we started measuring STJ from its PEROM. Some of the issues that would have to be addressed include:
1) How do we determine what position we want to push the foot toward in correcting pronation of the foot? I'm not saying that a person stands on an orthotic in the position that the foot was casted in, but it pushes the foot toward the casting position until equilibrium is reached between the foot changing position and deformation of the device.
2) How do we determine if the patient has an inverted or everted deformity?
3) What position should be foot be in when it is casted?
4) How do we define whether a patient has an abnormally supinated foot?

Maybe you've already got answers for these questions. But they do have to be addressed.

I know I've been criticized previously for trying to get into Root's mind. I think Jeff adequately addressed the talar head. As I mentioned above, if you want to measure anything, you have to have reference lines. So are you saying that we should or we should not be trying to measure the available ROM of the STJ? As you read my papers, you'll see that I define a sagittal plane of the calcaneus, by drawing both a posterior and plantar calcaneal bisection. Unfortunately Root really did not define the plane that his bisection lines were made -- you are correct that he somehow thought it was a natural skill. Now Chris Smith tried to redefine calcaneal bisections by saying that it was a line that was parallel to the medial posterior border of the calcaneus. I'm not sure that anyone has tested yet that this reference line can be drawn by those w/o calipers more reliably. Since no one is now recommending clinicians buy calipers, maybe we should all use Smith's idea.

I never felt that Root thought that the posterior calcaneal bisection was what determined the function of the foot, but instead it was a way of measuring and documenting the function of the foot. Again, maybe it's that same old argument of two people reading the same religious text and having two very different ideas of what it said. Again, I ask, should we be documenting the kinematics of the foot? Now I would love to have a 6 camera biomechanical lab for all my patients to have full kinematical evaluation, but are there relatively easy ways to try to document the function of the foot, even if it is a static stance state?

I think you are a little tough on Root here, because he certainly inspired me to do the work that resulted in my first STJA paper (1985), in which I defined how to find clinically the direction cosines of the axis, and I know that he inspired Don Green to publish his theoretical paper on the angulation variations in the STJ. I agree that Root accepted the Manter and Hicks drawing of where the STJ axis was relative to the posterior calcaneus. I proved to myself in 1980 that the STJ axis exit point on the posterior calcaneus was superior to where it was drawn when I went to Ellen Kreigbaum's biomechanics lab (one of those PhD type of labs), we took pictures of me moving my wife's STJ, with the outline of the posterior calcaneus on the skin, and then digitizing those pictures. We found that there was a point on the posterior lateral edge of the calcaneus, about 4 cm above the most plantar point that did not move. I still have those pictures if you ever want to see them. I have put them in a few of my lectures in the past. You'll notice, Kevin, that in my 1992 paper, I made the mathematical argument that the axis of the STJ intersected the floor at a point that was an average of about 5 cm behind the calcaneus? Are you aware of another paper before that that found such? Also, you must realize that in my first chapter of Hetherington and Levy's book I drew the STJ axis as passing through the proximal neck of the talus. I find it interesting that if one looks a sagittal plane projection of the STJA and the ankle axis, that they seem to intersect.

I'm not going to disagree with you that Root did not try to define well a variable range of normal. I think he may have understood it, but he was at times very dogmatic (maybe he felt he needed to be at that point in time). I think it's easy to see it as a mistake now because of the way that the biomechanics evangelists seized on his ideas and preached with rigidity that there was only a fixed normal. Unfortunately, students are of such a mind that they have a difficult time in accepting variations of normal -- call it academic immaturity. The answer to any question has to be either (a), (b), or (c) and nothing in between. The question I have to ask is have you defined the STJ axis normality as being one specific position, or do you accept a range of normal?

I will agree totally with your last paragraph. I am the first to point out that Root didn't have all the answers, and he left a lot of things unanswered and some things poorly argued. That's why it is important that we find what we need to keep, what needs to be modified and what needs to go. I believe that we need an iFab meeting that could focus just on some of the more controversial Root ideas. We could spend an entire session just discussing whether there should be a neutral STJ position? What are the advantages of keeping the L&C 1898 concept and what are the advantages of throwing it away? What would happen if we did throw it away? What would you teach students?

I am all in agreement that the vast majority of our profession are not even familiar with common biomechanics terms, especially here in the U.S. That's why I spent so many pages in my first book chapter discussing these terms. (One of the best books I found was Cochran's "A Primer of Orthopedic Biomechanics.") That's why I used to ask such questions as, "Given all other factors equal, Which type of foot is easier to pronate, a narrow foot or a wide foot?" I agree that in our schools, first year biomechanics should never mention the STJ neutral position, and that goniometric examination should be introduced in the 2nd year. I still remember clearly in my ears, Milt Wille saying to Mert in 1975, "Mert, your biomechanics is all bio, it has no mechanics." That one line has been my inspiration since entry into podiatry school in 1976, and continues to guide me.

Best wishes,
Daryl :drinks (ginger beer)

 

Kevin,

I know you are very busy. My father actually rented an apartment so he could work on the book without being disturbed. He spend a lot of evenings and weekends there. He made enormous sacrifices to get the book written, including taking weeks out of the office at a time so that he and the other authors could get together and write. One of those times was our "family vacation" in Lake Tahoe where the moms and kids went skiing and played in the snow while the authors sat around all day working on the book.

What I feel is missing today is a book or series of books that attempts to explain structure and function of the foot (The Structure and Function of the Foot would be an excellent title for the text), including an explanation of the cause of pathology, and a book or section on examination, diagnosis and treatment. You know, an A to Z approach to examination, diagnosis and treatment. You have written and lectured extensively, and I commend you for that but unfortunately all this work is fragmented and isn't organized in a manner that makes it easy to follow like an A to Z approach.

We can only imagine what lower extremity biomechanics might be like today if Root et al hadn't written their books. I'm sure it would be much more difficult to understand their theories and approaches. In spite of the flaws, it has created a fertile environment for discussion and debate. Perhaps some day you will assemble a dream team to help you write the next book on foot function.

Jeff

 

I listened to that a couple of years ago whilst I was lecturing in Spain; have you read his ideas of "morphic resonance"?


I'd like to play Devil's advocate in addressing these questions:

Well if we want to correct pronation, we should push it toward supination, away from it's end of range of pronation position. A better question though is why do you want to "correct pronation"? Surely a better approach is to identify the injured tissue, realise it's biomechanical function and provide an orthosis which relieves the stress on this tissue in order to assist in it's healing? Otherwise, you could end up increasing the stress on an already injured tissue just because you are trying to "correct pronation".

Question: do foot orthoses "push the foot towards the casting position"? I can certainly take a cast of the foot and design two very different foot orthoses from the same cast which "push" the foot in very different directions depending upon how I modify that cast/ orthosis.

Is this important? Why not identify the injured tissue, realise it's biomechanical function and provide an orthosis which relieves the stress on this tissue in order to assist in it's healing? Patient with osteoarthritis in medial compartment of the knee, everted bisection on the heel- which way do you want to "push the foot"; patient with inversion injury at the ankle, with "everted deformity" which way do you want to push the foot?... I could go on.

That really doesn't matter, what is important is designing an orthosis which modifies the external moments such that the stress on the injured tissue is relieved to within tollerable levels. It can only do this mechanically in 3 ways: by changing the surface geometry; changing the surface stiffness; changing the frictional characteristics. One could start with a cube of material and still achieve the same aim and same shape that any cast could provide.

See 1) above. Positions of the foot are not "abnormal" (OK, so you got a transmalleolar fracture, the position your foot is in might be abnormal, but talking about basic variances here), the stresses within the tissues may be. Lets take two individuals with identical goniometric measurements from their feet and lower limbs, which one gets injured? You don't know right? Unless it's one of the few pathologies that we have predictive models for, for example, MTSS and navicular drop (althought technically this isn't a goniometric measure). Which takes us back to the premise of the "normal foot" being based upon goniometric data. If it isn't predictive of pathology nor of patient outcome, it isn't worth performing it. If foot orthoses work by modifying forces why are we measuring angles, when angles in isolation don't predict forces?

I disagree too with the notion of "normal" being based on averages.

 

Can't agree that certain positions of the foot are not "abnormal". Is a floating toe from an over-shortened metatarsal a normal toe position? No, it is abnormal. Is an excessively short Achilles tendon/gastrocnemius/soleus complex which doesn't allow the foot to be plantigrade during standing so the individual can't be get the heel on the ground during standing normal? No, it is abnormal. Is a 15 degree hallux varus deformity normal? No, it is abnormal. I do believe we can agree to a range of goniometric values which are within a range which most podiatrists and orthopedic surgeons could agree to as normal. We do measure angles on plain film x-rays when we evaluate for foot pathology or foot surgery and have a range of "normal" for these measurements? Yes we do. Why should we then not also have a "normal" range of motion and position measurements for the foot and lower extremity? I see no reason why not.

I believe that podiatrists who do surgery are trained to and need to rely more on "normal and abnormal" measures when evaluating feet and lower extremity abnormalities for possible angular or linear bone and joint corrections than do those podiatrists who do not do osseous surgery. However, regardless of whether the foot is being treated surgically or non-surgically, position of joints, shape of the bones and structure of the joints are all important in determining the forces and moments acting across the structural components of the foot and lower extremity. The problem is we will never know whether these measures are important or not until we investigate each of these measures thoroughly, which we definitely have not done yet as a profession.

The problem is, with the current research available to us, I don't think the subtalar joint neutral measurements advocated by Root et al are the way forward for us. My gut level feeling is that someday we will have studies that will start to allow us to have either old or new reproducible measures that can predict some of the forces and moments acting across the foot and lower extremity during weightbearing activities. However, for now, I believe it is best to keep an open mind and stick to the principles of Newtonian mechanics and known physiological mechanisms to try and determine which measurable parameters have the greatest potential for us to better predict pathology and then design research projects to study those parameters and if they correlate to pathology.

There is much more work that needs to be done.

 

Simon, I agree. Tooth decay is normal process and the average person has cavities. If the average 20 year old white male has 3.75 cavities, dentists wouldn't be encouraging 20 year old white male patients with no cavities to stop brushing and flossing in order to make them more "normal" now would they! Ideally we want to prevent all cavities. There are things that the patient can do to help prevent cavities but some will get cavities regardless of how well they practice good dental hygiene. In this case, medicine shoots for the ideal condition as the goal, not the average.

Jeff

 

What is it about the British and Americans and their teeth?

Are these British teeth "normal"?

 

How about these American teeth? Normal, average or is it just Mike?

 

Steve Buscemi's "abnormal" teeth have landed him quite a few good acting gigs....or are his teeth "normal" for a bad-guy/eccentric guy in the movies....?

 

I think we can talk about foot structure and how it can be associated with pathology. For example, how a plantarflexed 1st ray can be associated with excessive supination in the rearfoot contributing to inversion ankle sprains. If you treat it with an orthosis, it is not necessary to measure the plantarflexion angle of the 1st met or ray but if you were doing surgery, you would probably want to measure it on x-ray pre-surgically. I don't know that foot structure normal ranges are necessarily as valuable as say normal ranges in blood work, but certainly as the subject gets further away from an ideal or baseline structure, and when we can associate that structural condition with pathology, it can be very valuable clinically.

Jeff

 

He'll never land a gig playing agent 007. If he wants to play a bad guy, then that's normal for him. Put those teeth on Sean Connery and see what happens.

Daryl

 

So someone with a 14.9 degree hallux valgus angle is "normal" but someone with a 15 degree angle is "abnormal", and these two feet are completely different? No. That's the problem of artificial delineation of "normal" from "abnormal". Another patient has an angle of 13 degrees but complete errosion of the intersesamoidal crista- "normal" though right? Two patients both with hallux valgus angles of 15 degrees, one is is congruous by Piggott's (1960) definition, the other "subluxed", both "abnormal"?

Back to goniometry of the rearfoot- lets say we have two calcaneii that we can accurately bisect and we see that they are both 6 degrees everted, will these two patients have the same forces acting across their subtalar joints? Not necessarilly. Lets make it easier, lets say the patients are the same mass, will these two patients have the same forces acting across their subtalar joints? Not necessarilly. Lets do a free body analysis: we add in gravity and ground reaction force, both bisections of the calcaneii have the same angulation, but one is 4 cm long and the other is 4.5, do both calcaneii have the same force couple acting on them from these two forces? No. We could go on.

I'm not saying that structural data isn't important, I'm saying that measuring the angle of a line on the back of a heel or anywhere else is no where near enough information in isolation to predict stresses. Just because surgeons draw lines on plain film x-rays, doesn't mean that this is a valid gold standard apporach, it just means that's the way it was done given the limitations of the day.

 

The goal of agreeing to delineation between "normal" and "abnormal" within any structural parameter of the human body, or in any branch of medicine, is not to "predict stresses" or to "predict pathology". Rather, the goal of classifying one structure as "normal" and another as "abnormal" is to give a general categorization of that isolated value relative to the human population as a whole.

The term "high normal" and "hypertension" are used in this article to delineate values of blood pressure.

http://www.nejm.org/doi/full/10.1056/nejmoa003417

The term "normal" range of motion of the knee after ACL reconstruction is used in this article to describe knee range of motion values.

http://ajs.sagepub.com/content/40/1/108.short

The terms "normal" and "abnormal" are used in this book to describe development parameters in the infant and child.

http://books.google.com/books?hl=en...v=onepage&q=normal and abnormal ankle&f=false

I could go on and on.

The bottom line is that these terms "normal" and "abnormal" can be valuable descriptors used for communicating basic health-related parameters to the lay-public and in a clinical setting, but need to be well defined in scientific research where more precision is required and where it will be understood that any categorization process of a parameter into "normal" and "abnormal" does not necessarily indicate impending pathology.

 

Ignoring the obvious problem with the argument that just because other branches of medicine use the terminology of "normal" and "abnormal" doesn't make it right, blood pressure measurements do have predictive models associated with them. If your podiatric goniometric measurements don't predict stress nor pathology in a clinical setting, then what's the point of performing them? I guess you could argue that you might use before and after measures of say range of motion to monitor the effects of an intervention, but here we are more interested in the intra-subject change, not necessarilly a comparative to the average; comparing such measures to the average is fraught with potential biases and problems without first developing multi-variate models to partition the variance and identifying potential sub-groups and elements of co-variance.

In other words, compare to the average. I felt Jeff gave a good example of one of the potential problems of doing this last night. I'd question the value of giving categorisations of "normal" or "abnormal" for the sake of it, with no predictive value to pathology; history tells of a number of European chancellors attempting something like that... amongst other things, we had cucumbers which were too curved. Should we create sub-groups, or just look at "the human population as a whole", which do you think?

Then we have the situation in which your patient is classified as "normal" by your categorisation to the "human population" but has pathology, and your patient who is catergorised as "abnormal" by your system who is happy and healthy... remember that you weren't interested in predictive value...

 

Measurements whether they be for limb length discrepancy, subtalar joint (STJ) axis location or maximally pronated position of the STJ, are simply objective parameters that allow the clinician to better assess one individual's structure and function relative to others and what a range of ideals should be. Simon, I don't know why you think measures need to only predict stress or pathology to be worth performing since, at times, until you measure something, you won't know if it is pathologic or not.

Take the example of measuring STJ range of motion. Do I measure STJ range of motion just to "predict stress or pathology"? No. However, I do measure STJ range of motion to rule out tarsal coalition, rule out a peroneal spasm, rule out spasm of other extrinsic foot muscles, rule out pain with range of motion, rule out crepitus with range of motion and assess whether the patient has a medial, normal or lateral STJ axis location including quality or range of STJ motion. In other words, it is not just the number of degrees of range of motion I am only interested in when measuring STJ range of motion. To the experienced clinician, the clinical measurement itself will rule out pathologies which may be present that, otherwise, may not be detectable.

This is analogous to the primary care physician testing cranial nerve function on a physical examination. Are they doing it to "predict stress or pathology"? No. They are doing it to rule out pathology that may not be able to be detected without performing these tests. What if for 19 patients in a row, this primary care physician found nothing in all the cranial nerve tests, would he quit doing them just because they "didn't predict stress or pathology"? No. Because on the 20th patient, he just might detect a cranial nerve abnormality that leads him to order an MRI scan that then leads to the early diagnosis of a brain disorder that needs early detection to be treated successfully. I want to see that type of primary care physician for my own health care: the one who does these tests because they should be done to rule out pathology, not because the tests being done will change my doctor's treatment plan or not.

In other words, clinical tests and measurements are not done solely to "predict stress and pathology", but are also routinely done to rule out pathology and ensure normal functioning of the neuro-musculoskeletal system of the individual, as a whole. This is what we do as foot-health care providers, not just fix mechanical problems of the foot and lower extremity, but be the foot-health care clinician that has the ethical responsibility to alert the patient and their other treating physicians regarding to potential health issues which may affect the life and health of the individual over time.

I believe a good start for the international podiatry profession would be make it very clear that Root et al's "normal" meant "ideal" and also that Root et al's ideas of "ideal" have no research evidence to support them as being "ideal". In other words, I don't believe that any of Root et al's 44 year-old Biophysical Criteria for Normalcy (see below) are either ideal or represent what we currently understand as being "normal" (Root ML, Orien WP, Weed JH, RJ Hughes: Biomechanical Examination of the Foot, Volume 1. Clinical Biomechanics Corporation, Los Angeles, 1971, p. 34).

Rather, we need research from large groups of asymptomatic individuals who function normally during walking and/or running gait to determine what the clinical characteristics are regarding foot and lower extremity geometry, range or motion, muscle strength, etc before we can even begin having a good idea as to what is "normal" and what is "abnormal" is for the human population. Then, I believe, we will be able to move forward for our profession, and the patients we all treat on a daily basis.

Good discussion, Dr. Spooner and everyone else who is joining in.:drinks

 

When we identify or define ideal or optimal biophysical criteria it can then be used as a guide for the clinician. For example, when we say that we need a minimum of 10 degrees of ankle joint dorsiflexion for "normal" function, it is not an absolute value but is does serve as a guideline and limitations of ankle dorsiflexion, be they structural or functional, can contribute to pathology. However, just because some individuals have less than 10 degrees of ankle joint dorsiflexion doesn't necessarily mean it is pathological. The clinician must assess the individual patient and must make a judgment as to whether or not the limitation of motion is contributing to the patient's symptoms or pathology.

Jeff

 

As Root et al said on the page describing their biophysical criteria for normalcy that Kevin just posted, "only the clinician can determine when the variance is sufficiently great to produce pathology".

In spite of the problems associated with defining normal, average and ideal values and in spite of some of the inherent problems with measurement technique, we seem better off having these imperfect guidelines than we would be trying to function without them because they have proven to be clinically useful. It might be an interesting exercise to redefine the ideal biophysical criteria for "optimum function" (not normalcy) with todays understanding of foot function. It would be interesting to start with a very general and broad description and see how much we can narrow it down.

Jeff

 

In other words, you are using these tests to predict stress/ pathology or the lack of it. N'est-ce pas, Kevin?

 

No, I don't buy that logic. I present some guidelines: everyone with a cough must drink arsenic- I get rid of everyones cough. Are these not the best guidelines ever? No.

Here's how we begin to define it: we define optimal function as a quantitative variable, we can then say the phenotype "optimum function" = P, then we get: P = Genotype + Environment + (Genotype x Environment), which tells us what? Then we partition the variance in the Genetic and Environmental components. Go ahead, make a start... The first base you should get to is that "optimum function" is unique to the individual and to the environment.

 

Agreed, and the research we already have from large groups of asymptomatic individuals show large amounts of variation between them. The best data we have up to 2015 tells that variation from the mean is to be celebrated not condemmed as "abnormal".

 

So, we should never use the word "abnormal" to describe any pathologic and highly unusual structural variation within the foot and lower extremity? Then we would be the only branch of the healing arts to appear to have so little confidence in our knowledge that we don't feel comfortable using "abnormal" to describe an obvious pathology. No thanks.

 

It's "abnormal" if it's predictive of pathology, Kevin. That's the point:drinks But that is not the same as this which you said not so long ago:

 

Say what? More than one force acting on the foot other than gravity? OK...let's assume for a moment that the force of friction is eliminated from the discussion. What other forces are at play beyond the 9.8N of force applied from GRF? Perhaps my POINT to all of this, is not necessarily to simplify everything but to make it more practical to the independent Podiatrists working in their offices attempting to solve problems. While academics tend to make these concerns so OVERWHELMINGLY difficult, (non-practical), I'm trying to bring a 'voice of reason' to this discussion. One only needs to read through this blog to understand my frustration with academics. Yes, once GRF is applied to the foot, that external force is distributed internally by the bones of the foot, (and above), in multiple ways. But then we come to the treatment of that external force. Considering that a piece of rohadur, now replaced by polyprop or graphite, is our treatment, most Podiatrists are at the mercy of the labs we use to construct these orthotics. Given the built in "fudge factors" inherent with computer scanned casts, construction of these orthotics are most times, best guess scenarios for many practitioners. Yes, we fill out the Rx sheets, but there are many more problems with orthotic devices that are not necessarily a problem with casting or practitioner prescription. Perhaps Jeff can comment on that from his perspective.

To draw lines on the back of the calcaneus at least allows the independent practitioner a starting point of reference, whether, or not, that line is accurate. To dissect axis of motion of the STJ and MTJ ad infinitum, ad nauseum is, IMHO, an exercise in practitioner futility. Perhaps my more basic, practical approach is the reason I have connected the dots in not only determining the source of pain in growing pains in children, but have made the connection to resolving the mystery of RLS in adults. Each and every day, I'm seeing these problems and resolving them, much to the delight of those patients that have suffered with these maladies, some for decades. My patient base has expanded greatly since I concluded the project and wrote the pilot study...my hypothesis supported as my success rate grows.

 

Simon,

The other day I describe a patient with a low calcaneal inclination angle on his right radiograph as compared to his left. He has greater symptoms on his right foot than his left. Hypothetically, if we use these values for calcaneal inclination angle as our guideline:
low: less than 20 degrees
medium: 20-30 degrees
high: over 30 degrees
and when I describe his foot as having a low calcaneal inclination angle, it allows us to communicate even when we don't actually measure it because the trained eye appreciates the difference. If I did measure it, and even given some reasonable margin of error, this allows clinicians to communicate in a far more meaningful manner and it does without it.

Now if I had said:
abnormally low: less than 20 degrees
normal: 20-30 degrees
abnormally high: over 30 degrees
it would create an unnecessary value judgment. So I favor descriptions that can be used to identify structural or positional variances that don't impose value judgments whenever possible.

I dispensed this patient's orthoses on Friday. He immediately felt like there was too much pressure in his right arch. His right cast and orthosis demonstrated a lower medial arch than his left side but he felt pressure in the right arch. His radiograph suggests some collapse of the medial and lateral longitudinal arches, especially on the right side. Had I not seen his x-rays, I could have observed increased pronation and foot abduction on the right but the films gave me an even better understanding of his structure. I ground out some of the EVA plantar fill under the medial arches and he reported that the devices were tolerable. This is a patient who will probably require a more gradual break in period given his foot type.

Another interesting thing about his case. I reported that he demonstrated about 30 degrees of dorsiflexion of his hallux B/L and functional hallux limitus during his apropulsive gait. He commented that he felt like he was "pushing off his big toes more" and he also commented that his right foot "wasn't turning out as much".

Jeff

 

But P= G + E + (G x E), Jeff, so tomorrow you might see a patient with a low calcaneal inclination angle on his right radiograph as compared to his left who has greater symptoms on his left foot than his right... And that is the reality, which over the last 25+ years I have seen on countless occassions, end of story.

Let's not deflect the question because it's really, really important: what does the equation: P= G + E + (GxE) tell you, Jeff? Here's what it tells me: it tells me that your dad's "biophysical criteria for normalcy" with it's "one size fits all" inferences cannot ever be valid; that really is the end of it's story. I doubt that you'll ever concur with that, even though it's patently obvious.