Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?

an then to this you have to add environmental factors such as loads etc

which is why Normal can only be N =1

 

Eric,

In response to you and to Mike Weber.

I have to correct you (did ask me to do so). First of all we have to remember that we are talking about the ideal situation, not the average nor of possible combinations that may lead to no pathology. Again the word "normal" continues to be confusing to so many people, to the point that maybe the word should eliminated from the dictionary, or maybe we should use the term only in regards to a line that is perpendicular to a surface. So with the mathematical definition, a normal lower leg would be one that is perpendicular to the supporting surface.

Since you claim to be a tissue stress person, I'm sure that you recognize that bone was made to resist compression. If the lower leg (or even the entire leg) is not perpendicular to the weightbearing surface, then you have introduced an increased element of shear and bending into the leg. Now this may or may not be significant enough to produce pathology within the average human lifespan, nevertheless, I'm sure you would agree that this is not ideal. I'm sure you are well aware of the literature that shows that tibial varum increases the risk of OA in the knee joint. Unfortunately there is little literature that shows the type of feet that combine with the tibial varum to increase the risk of knee OA.

Are you saying that I don't agree with this statement? I believe I was the first person to put some actual numbers to the STJ axis situation in 1992.

Here I believe that Kevin, trying to simplify the foot into one solid mass, is a major mistake. I have made this point many times before, that to not consider that the forefoot has effect on the relationship of the rearfoot to the ground is a major problem. I have a difficult time in believing that the forefoot mobility doesn't have an effect on where the CoP is under the foot. You can't prove that it doesn't. Maybe you can answer this question, what would be the function of the rearfoot and the STJ if you combined a forefoot varus with a laterally displaced STJ axis?

I don't know why your arguments only concentrate on the STJ, like it is at the center of the world. I'm not saying that Root's criteria are the only criteria for normalcy. The list needs to be evaluated one point at a time, and it should be considered open for modification. What points to we want to keep? What points do we need to modify? What points do we want to totally discard? What points do we want to add? I do believe that there needs to be an addition about the normal STJ axis location. I believe there also need to be some additional points added in regards to the forefoot mobility.

I'm a little bit confused by your statement. The literature is replete the effect of genu varum's devastating effects on the knee in producing OA. Now I will admit that we have done a poor job in differentiating the exact place in the lower leg where the bend occurs. So far we have only measured the lower 1/3 of the leg. Maybe we should be measuring the lower 1/3 and the upper 1/3. I don't know why you think that it would be ideal to have the upper 1/3 perpendicular to the ground and the lower 1/3 inverted to the ground.

Your forefoot valgus condition assumes that there is limited mobility of the forefoot to the rearfoot. Yes, it is possible to have these two "deformities" cancel each other out, but we don't see it very often. Also you have failed to consider such Root deformities such as subtalar varus. If the STJ is at its pronation EROM, and the heel is in line with the leg, isn't this still putting increase stress on the posterior tibialis? Isn't the maximum contraction force of the posterior tibialis not decreased with the STJ in this position?

Mike talked about how tissue stress is actual physics. I believe that if he reads the chapter that I wrote for Levy and Hetherington's book over 20 years ago, Principles and Practices of Podiatric Medicine, he will find that I discuss the function of each joint and the function of each muscle, from the hip to the great toe, in terms of understanding the moments produced by the ground reaction forces, vertically, longitudinally and laterally.

In summary, I'm going to fully accept Root's #1 criteria for ideal. That does not mean I'm going to treat every person who deviates from ideal, because that is really the art of medicine, who we're going to treat and who we're not.

Daryl

 

We are evaluating the biophysical criteria for normalcy. I can get behind the idea of ideal as opposed to normal.

Daryl, I still don't understand what you mean when you said that you should treat each of the criteria as singularities. Do you mean that each one should be looked at in isolation from the other criteria? They were presented as one list. Don't you think the authors inteded them to be considered together. Why do you think that they should be looked at in isolation?

I thnk we are in agreement here. What do you think about the comment that I made that looking at the center of knee relative to the center of ankle would be a better measure than lower 1/3 of the leg, to predict the pathology that you discussed directly above?

I have to disagree with you here. There will be some cases where that simplification will produce good predictions. The obvious proof to this is the answer to the question. Can you apply a forece to the foot, distal to the midtarsal joint, and move the STJ. Is the movement of the STJ easier when you have a longer lever arm in relation to the STJ axis?

In answer to your question we need to carefully define the starting conditions. If the foot is resting and there is force on both the medial lateral forefoot then we can ignore the effect of the forefoot varus in relation to the STJ axis. If the axis is laterally deviated in this position of the foot, then it will function as a laterally deviated STJ axis.

If the foot is resting and the forces under the forefoot are high lateral and very low medial, because there is not enough eversion range of motion to significantly load the medial forefoot, then the center of pressure will be "pulled" laterally and there will likely be a pronation moment on the STJ from the ground. Even with a lateral STJ axis. In this situation the CoP will be lateral to the axis, even though there is a lateral axis.

If you started wtih the foot in neutral position.... Then you would have a really hard time figuring out foot function.

The reason that these arguments are focusing on the STJ is that the question that you asked was about the ideal STJ.

Daryl, I'm talking about the whole bone and not a bisection of the soft tissue of the lower 1/3 of the leg. The external frontal plane moment on the lower leg is going to be detemined by the relative location of the center of pressure under the foot and the center of pressure in the knee. I'm just saying that if we are trying to predict medial compartment of the knee pressures then the lower 1/3 of the leg is not as good as a measure as the one that I am describing.

This is my point. You cannot look at the lower 1/3 of the leg in isolation when you are attempting to understand load on the PT tendon. Some of the time, there will be a forefoot valgus that cancels the tbial varum. To say that it doens't happen very often is admitting that it does not happen always and that you know there are times that prediction will fail.

Daryl, I'm not undestanding your point about maximum contraction force in the posterior tibial being decreased when the heel bisection and the lower 1/3rd of the leg bisection are in line.

So, you don't think we should look at the whole tibia, instead of the lower 1/3rd? Do you agree that tibial varum should also be considered in conjuction with STJ range of motion relative to the leg. I feel that these two measurements together can provide some useful information.

Eric

 

Eric, I have only time this morning to reply to a couple of your ideas, and will have to leave the others on the table until I have more time.

If you read the article produced by Eric Lee in Clinics in Podiatric Medicine from 2000, you will find one of the best documentations of the history of the Root methodology, taken from many public as well as private communications between Mr. Lee and Dr. Root, Dr. Schuster, and others. I believe that this article states that there are two definitions of "normal" and it comes quite clearly down on the side that Root used that of the "ideal". So his criteria of normalcy has to be taken as that of the ideal, not of the average. I hope we can lay this one contention to rest for good. If you insist that Root meant the average, then there is nothing more to discuss as we will be in a continuous cycle of disagreement.

I have written to Bill Orien in the last day asking him to make comment on whether the authors of the book intended to let each item in the criteria of normalcy be examined individually, or whether they intended the list to stand as an all-or-none list. Bill sees these endless debates on-line as rather ridiculous, however if he replies, I will pass such on. It is important that we try to get as close to the sources as we can, and right now, Bill Orien is the closest. This is what historians of all types try to do, is get as close to the sources as they can, to try to understand the people they write about. I also believe that the second closest source is Jeff Root. So if they speak about the mindset of the original Root et al. authors, we have to listen.

In regards to your comment about the center of the knee to the center of the ankle, that is open for discussion as to the best methodology for clinical evaluation and documentation. When I first encountered the biomechanical exam that my father did in the 70s, he was using a bisection of the entire leg rather than just the lower third. John Weed explained that they used the lower third of the leg because this seemed to be more reliable. Unfortunately any bisection is open for question as to whether it represents the line of axial load on the lower leg. If you have a better clinical methodology, I will be happy to also consider such. If you look at the lecture I did for Present Resident education, I think I also pointed out very clearly that the plane that you bisect the lower leg in is very important for reliability. That's why I have been very particular in setting up any goniometric exam and in the papers I have published in which I have used goniometric exams, to set forth the coordinate system that I use. I have identified the "frontal plane of the foot" as precisely as I clinically can -- something that I have not seen too many other people try to do in their reliability papers. Whether you like it or not -- we have to have some standard goniometric evaluation so that we can document what is going on, even if we can accept the limitations of such an examination too fully understand everything.

As to the posterior tibial contraction force, please review the active length tension curve of any muscle. This is clearly taught in all basic texts on biomechanics. You'll notice that when a muscle is maximally stretched, its maximum contraction force is decreased. Therefore given two feet, one with subtalar varus and one that fits the Root ideal, and both with equal muscle mass, when both feet are placed with the calcaneus parallel to the lower leg, the one with the rearfoot varus will not be able to contract the posterior tibial muscle with as great a force as the one that does not have rearfoot varus. This is simple tissue-stress mechanics.

Sorry I cannot take more time right now to address the issues further, but will get back to them. As I noted before, some of the Root criteria I can fully accept, some need to be revisited, and there probably needs to be additions as well.

Take care,
Daryl

 

Eric and Daryl,

The authors listed eight biophysical criteria for normalcy. Each one describes an anatomical condition that can be considered independently. For example, the lower third of the leg could be inverted while the heel is vertical, or the leg could be vertical while the heel is inverted. Therefore, regardless of the authors intent, we can consider each criteria for normalcy (ideal physical relationship) individually. For example, what if they had a ninth criteria that said the STJ axis should not be medially nor laterally deviated. Would you argue that we should not consider the merit of these criteria individually?

In terms of what the authors intended, they could not have been clearer in the first half of this sentence when they wrote "The following criteria represent the ideal physical relationship of osseous segments of the foot and leg". Clearly they were talking about the ideal total physical relationship of these individual criteria, not the average position, which clearly would be much different as indicated when they wrote in the same paragraph "Such ideal relationships are seldom seen clinically, and merely represent the basis for evaluation of the degree of deformity".

I believe the authors made an error by including the word locomotion in the second half of the sentence when they wrote "for the production of maximum efficiency during static stance or locomotion". When you read Normal and Abnormal Function of the Foot, they clearly describe supination and pronation of the STJ, plantar and dorsiflexion of the 1st met, supination and pronation of the MTJ and other conditions that contradict this relationship as being normal and necessary for optimal function. So I think they may have meant that in the case of locomotion, there are periods during the gait cycle when these biophysical criteria, when considered individually, contribute to maximum efficiency or are ideal. As a result, I feel the authors should have written that aspect of the paragraph differently as I think some have misinterpreted their intended meaning. This may be why some people mistakenly believe Root et al said the STJ should function in the neutral position. Obviously from reading Normal and Abnormal Function of the Foot, they clearly demonstrated that normal function involved supination and pronation of the foot during the gait cycle.

One of the most important things they ever wrote was the last sentence in the paragraph which says "Only the clinician can determine when the degree of variance is sufficiently great to produce pathology". I know my father didn't feel that minor variances necessarily (i.e. always) contributed to pathology. He used these biophysical criteria and a basis for comparison. During treatment he was much more concerned about producing, to the best of his clinical ability, ideal motion rather than ideal position. Those who heard him lecture, including Daryl and Kevin, will clearly remember how much he discussed the importance of shock absorption and how this mechanism was dependent on active pronation of the STJ, which should then be followed by resupination of the foot.

Jeff

 

I don't see how, Daryl, you could read any of my published papers, books or book chapters and make the statement that I somehow tried to "simplify the foot into one solid mass". Yes, I did use modelling approaches to try and simplify concepts just as does every scientist and engineer that is trying to simplify concepts contained within a complex system. However, I never once advocated looking at the foot as "one solid mass". Please, Daryl, do I need to buy you copies of all four of my books so you will finally read what is contained within them and quit misquoting my work?

As far as the distal third of the tibia being ideal, I have a number of problems with this.

1. Forces are transmitted from the knee to the ankle (and vice versa) through the whole tibia, not just through the distal third of the tibia. I understand that the distal third of the tibia may be easier to bisect, but this doesn't make the middle and proximal aspects of the tibia any less important for transmitting loads from the knee to the ankle and from the ankle to the knee. Eric is right, if you want to have a measurement that is useful for predicting function or pathology, we should be looking at the frontal plane relationship of the center of the knee joint to the center of the ankle joint since just looking at the angular relationship of the distal, middle or proximal third of a long bone to predict function or pathology makes absolutely no biomechanical sense at all. I have been looking at center of knee to center of ankle alignment, and not the distal third of the tibia, now for over 25 years, and it is not that difficult to perform.

2. Clinically, the individuals who seem to have the most stable and normally functioning feet have a distal third of their tibia which is not vertical, but is slightly inverted to the ground. It seems like the "slight rearfoot varus deformity" that the "slight varus distal third of the tibia" imparts to the extremity helps decrease subtalar joint (STJ) pronation moments, from my observations. This seems to be especially true in runners where nearly all the best runners (and soccer players) have a small amount of varus (in the range of 3-5 degrees) in the distal thirds of their tibia. However, a purely vertical distal tibia also seems to work well in most people whereas a slight valgus in the distal tibia does not seem to be so ideal. Therefore, the idea that there is one "ideal" distal third tibial alignment is not based in science or in biology, but is pure speculation with no basis in fact.

No, Daryl, Biophysical Criteria for Normalcy #1, that the distal third of the tibia must be vertical in order for the lower extremity to be considered normal is another one of the ideas that Root, Weed and Orien simply made up using pure speculation that has absolutely no basis in research, no basis in science and no basis in clinical fact. We should therefore make criteria #1 (i.e. distal third is vertical) be first one of the Biophysical Criteria for Normalcy that should be thrown into the trash can since it is neither an ideal alignment nor does it make any sense from a biomechanical standpoint that the distal third of the tibia is any more important from than the proximal two-thirds of the tibia or the middle 1/2 of the tibia, for that matter.

 

Moreover, it is obvious that the loading through vertical columns may vary, as I highlighted earlier in the thread when discussing the rule of thirds. This we may observe a vertical distal third of the tibia in different individuals, yet the loading and tissue stresses in such individuals may vary markedly. How then can a vertical bi section of the distal third of the tibia be seen as "ideal" when in isolation it tells us little regarding the loading nor tissue stress?

 

I guess this rules out "D" from the normal criteria as a non-starter too. Seems to me that Root and colleagues assumed that the only potential here was #1 when they formulated their criteria for normalcy, this just isn't true. Since an "ideal" cannot be variable, the variability displayed here precludes any notion of an "ideal" when it comes to taking such alignment measures in isolation as an "ideal". If Root and colleagues had clarified the location of the reaction forces across the joints... but they didn't, so lets move on.

 

Simon,

I appreciate your drawings, and agree with your analysis. Just because the lower leg is vertical to the floor in all these drawings, does not mean that you have no bending moments on the tibia. The argument is, can you draw a lower leg inverted to the ground and have no bending moments?

Thanks
Daryl

 

I'm going to first say that "your observations" and "my observations" are as valid as "Mert Root's observations". I believe that he was just as good of a clinician as you or I. None of us really have data to back us up, so it's still all conjecture. And as to the word normal, I didn't use that word, I used the word "ideal", which what the Root definition of normal was.

In all seriousness, if you want to publish your center of knee alignment to center of ankle alignment statistics, I would be very interested. I would also be very interested in you or Eric to publish a paper showing the mechanical stresses on the knee and the ankle and within the tibia during weightbearing.

I find the following to be an interesting statement by Tomaro, JOSPT 21:86-89, "
There was a significant difference in the amount of tibiofibular varum between the injured and the uninjured extremities. There was also a significant difference between the measurements of tibiofibular varum when comparing the resting calcaneal stance and the subtalar joint neutral stance positions. This difference in tibiofibular varum between the injured and uninjured extremities may be one example of an asymmetry that can cause unilateral overuse symptoms."

If I read your conclusion correctly, are you saying that you want to replace criteria #1 with a statement that the center of the knee should be vertical to the center of the ankle joint? I have to ask the question, how often do you see the center of the knee directly over the center of the ankle? How often is the center of the knee overlying the center of the ankle joint when the lower 1/3 of the leg is inverted? Is the center of the knee closer to being over the center of the ankle joint when the lower leg is inverted to the ground, or when the lower leg is vertical to the ground? Are you saying that you can have the same bending moment within the tibia when the lower 1/3 is inverted to the ground as when it is vertical to the ground? Are you saying the mechanical forces within the medial compartment of the knee joint can be the same when the lower 1/3 of the tibia is inverted to the ground as when it is vertical to the ground? You've set yourself a high mark to prove. If you want everything that Root said to be proved, shouldn't we expect the same from you?

In regards to an inverted lower 1/3 of the leg condition, Eric did point out that in such situations, the subtalar joint has to pronate more to get the medial side of the forefoot down to the ground. The only way to statically counter this is for the forefoot to be everted to the rearfoot? Can these be off-setting "deformities"? Possibly, but that remains to be proven. Again, such statements are themselves as much conjecture as the conjecture that you accuse Root, et al. of making. In trying to equate a lower tibial varum + forefoot valgus situation to a "Root normal" condition we need kinematic data on the amount of rearfoot pronation and the velocity of rearfoot pronation in both groups of people. When you come up with the hard data, then I'll toss away the criteria #1. Right now it makes more sense to have a lower tibia vertical as an "ideal" condition from which to measure and then use clinical judgement to determine if any treatment is needed.

As can be seen by all who read these posts, there is little real mechanics presented here, but instead only the same old, "Root is wrong" philosophy. What I'm going to call for here, is a lot less pontificating and a lot more research by all. I'll start by spending more time with my current research project and less time writing replies to those who are smarter than Root.

Daryl

 

Nope that's not the argument, the argument is whether the bisection of the distal 1/3 of the tibia being vertical as part of Root's criterai for normalcy is valid? No it is not is the answer you are looking for. Now, can we have a vertical distal 1/3 of the tibia and still have bending moment across the tibia? Yes, obviously. Can we have a non-vertical column without bending moment? Yes providing the net reaction force vectors at either end of the column are in perfect alignment and aligned centrally through the bone, then there will be only compression. Hope that helps.

 

When you look at the maximum force developed versus length of the muscle you usually see a trapazoid, roughly, shaped curve. Most muscles, in the body, will be able to develop very close to their maximum force over the entire range of motion of the joints that they cross. Thinking evolutionarily, the posterior tibial muscle would ideally produce maximum force at the pronation end of range of motion of the STJ and MTJ. Daryl, do you have a study showing that the PT muscle can produce more force when the heel is aligned with the leg. Also the total excursion of the tendon is around a centimeter for the total range of motion of both STJ and MTJ. I did some cadaver work looking at tendon excursion.

As an aside, a rare exception to muscles being able to produce near max force at every joint position is the flexor hallucis longus muscle. It has leverage at the ankle joint as well as the MPJ and IPJ. When the ankle is dorsiflexed, it can produce full plantar flexion moment at the IPJ and MPJ. When the ankle is plantar flexed, the FHL muscle cannot produce as much plantar flexion moment at the IPJ an MPJ.

Daryl, I don't think the length tension relationship is a valid reason for thinking that the heel being in line with the leg is ideal. Or that a posterior tibial muscle in a foot with a rearfoot varus won't be able to produce as much force as a tendon in a foot that conforms to the biophysical criteria of normalcy.

Eric

 

Daryl, I really don't understand why you waste your time trying to support Root when you must know with all your intelligence, that it is just unsupportable. You are so much better than Root.

 

Your comments are funny, Daryl. You want me to "publish" my "center of knee alignment to center of ankle alignment statistics" to support what I say, but you don't require Root, Weed and Orien to have any published papers to support their purely speculative idea that the distal third of the tibia is "normal" and "ideal". Yet you go ahead, and without any published research, based just on their reputation, make the statement: "In summary, I'm going to fully accept Root's #1 criteria for ideal.".

You are missing the point here, Daryl. The big difference between what I am saying, what Simon is saying, what Eric is saying, and what Root et al said when they published their "Biophysical Criteria for Normalcy" is that we are expressing our opinion as to why something can't be ideal. Whereas, Root et al published a list of "ideal" or "normal" criteria and did so without any explanation as to why those eight criteria are "ideal" or "normal", did not provide any references to support their unusual claim and offer us nothing more than their conjecture as to why these eight criteria are ideal.

You can't criticize us for speculating and guessing because that is just what Root et al did, but they published it in book form. If you just say that Root et al conjectured about these eight Biophysical Criteria for Normalcy, had no research evidence to support their ideas and probably should have never even guessed what the "ideal" or "normal" is for the human species, then we can be done with this discussion.

In other words, don't start holding us all up to a higher standard than you do to Root et al when they published their books and what is contained within them. We are saying we don't know what "ideal" is and that we are speculating. Root et al never said that. Root et al said that they did know what "ideal" or "normal" was. If they had been a less dogmatic, then we wouldn't be having this discussion now, would we?!

 

For some reason, I'm getting the feeling this has nothing to do with the truth, but is about who can demonstrate that they are the smartest. Yes you drew a tibia that was not perpendicular to the ground, but you introduced a force that is not a true gravitational force. I already said that you can have an axial vertical force that produces a bending moment on the tibia, however I would still take a vertical tibia rather than a non vertical tibia even with an eccentric axial load. You have just said that vertical forces cannot be introduced into an inverted tibia without producing a bending moment on the tibia, therefore it appears that you and I really do agree, that I with an ideal situation, the tibia should be vertical.
I have already said that the criteria list needs to be examined for modifications, e.g. maybe we need to put another criteria about the center of the knee directly over the center of the ankle. Fortunately, I have quite a few standing bone length studies, full lower extremities, that I have ordered over the past 2 years, so instead of me arguing further (though al the patients have major deformity) I'll try to go through them all and report on the center of the knee to the center of the ankle statistics. Maybe Kevin can give us some statics on the center of the knee to center of the ankle, along with measured lower tibial arum. You want some science about criteria #1? let's start the process instead of everyone just standing on a non researched soapbox.

Take care
Daryl

 

I do hold you to a higher standard because you're still alive, and still publishing. I haven't claimed to have published 4 books. I also hold myself to a higher standard. Every generation should be doing things better than the previous generation. Why should you be content advocating a "new" theory if you're only going to hold yourself to the same standard as the old generation? I just volunteered above to actually do something more than just pontificate. You in or out?

Daryl

 

Daryl:

I do want some science about criteria #1. Please tell me where was the science from Root et al when they claimed that in order to have an "ideal" or "normal" lower extremity, the distal third of the tibia must be vertical?

In addition, how are we "standing on a non-researched soapbox" any more than Root et al "stood on a non-researched soapbox" when they proclaimed that in order to have an "ideal" or "normal" lower extremity, the distal third of the tibia must be vertical?

If Root et al had included some science in their "Biophysical Criteria for Normalcy" before they declared that they knew what the ideal structure was for the human foot and lower extremity, then maybe we could have something to discuss. But unless you can provide some evidence otherwise, Daryl, I really don't see the point in this discussion since none of us knows what "ideal" or "normal" is until the research is done.

We are all just guessing just like Root et al was guessing. The big difference is that we are stating that we really don't know what ideal is while Root et al published a list of "ideal" or "normal" values in his book like he wasn't guessing and just knew it to be true.

Before we proceed any further, Daryl, how could Root et al known that what they were writing about ideal structure was indeed true without any research data to back up their claims? Or were they just publishing these "Biophysical Criteria for Normalcy" because they felt they needed to be published, even though they were just guessing about it?

 

It doesn't matter what they based the ideal position of the tibia on if the current question is, is there an ideal position of the tibia and if so, what is it and why? So if Root et. al. proposed that the ideal position of the distal 1/3 tibia is vertical, simply discuss it based on todays best evidence or conduct research to help answer the question. Why is it necessary to get hung up on the past?

As for scientific process, lets look at Newton's law of Gravity:

Link: http://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation

Let's not dismiss the value of empirical observation.

Jeff

 

Great, Jeff. This will make it much easier since I only want my ideas to be judged just like Root et al's ideas should be judged when they decided to formulate and publish their Biophysical Criteria for Normalcy.

I empirically claim that the ideal position of the distal third of the tibia can't be vertical since many individuals who have asymptomatic gait function and remain asymptomatic all their lives have their distal third of the tibia inverted from vertical.

I have just as much science and research to support my statement as did Root et al when they claimed that a vertical distal tibial bisection was ideal. A vertical distal third of the tibia is not ideal since there are no proven ideal structural parameters within the human species, just ranges of structural variation. To even discuss ideals of structure is futile and meaningless and, to my knowledge, has only been done within the medical profession by a group of podiatrists (i.e. Root et al).

The question then becomes, why did Root et al as podiatrists, out of all the other medical professions that have never attempted such a feat, decide that they needed to speculate as to what the structural ideals of the foot and lower extremity are and then publish it? Has that ever been done before within the medical profession? Not to my knowledge.

Why do such a thing???

 

Jeff:

I find it hard to believe that you would ask such a question when you routinely post up excerpts from a book that was written nearly four decades ago and Daryl routinely talks about what Mert Root thought and what Mert Root would have done if he lived longer, etc, from three to four decades ago.

I'm all ready to move podiatry forward into the future, not getting "hung up on the past". The better question is, are you and Daryl ready to do so also?

 

Kevin,

Root et.al proposed eight biophysical criteria for normalcy. Were these totally original concepts or were they discussed previous to their proposal in volume 1? I don't know the answer to this question, do you? If they were totally original ideas, then perhaps it was an important starting point. We can discuss these mechanical principles all day long but will resolve nothing. Why, because just like Root et. al. we are dealing with theory. My point was, exploring these theories under the light of todays best evidence doesn't necessarily require us to understand their rational but merely to determine if they are valid concepts.

I have seen significant evolution in your thinking about tibial varum over your career. In 1998 you wrote:

and:

Your Precision Newsletter with these comments can be found on the PA at http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=21418

So here in your own words you describe tibial varum as a structural deformity and you also discuss an otherwise normal foot. So what is your definition of an "otherwise normal foot" if you don't accept Root's criteria and have you ever described it so that others know what your idea of an otherwise normal foot is?

You also wrote in this same newsletter:

So in reading this, it does appear that you believe in compensation for "structural deformities" but how can we have structural deformities, if we don't have an understanding of normal values or normal structure?

Jeff

 

No we don't agree Daryl, since even in a vertically aligned tibia the loading may induce bending moments across it and in a non-vertical tibia we may have no bending moment. If the omission of bending moment is the goal, then there is no clear benefit of vertical alignment over non-vertical alignment since either configuration may or may not have bending moments applied. I've re-drawn it so now we only have vertically aligned forces without bending moment. Perhaps we can go back a peg- why aren't we allowed bending moment? And why are we only allowed vertical loading?

 

I have a problem with your drawing. You fixed the rotational moment on the tibia, but now the downward force at the knee joint doesn't pass through the center of the knee joint. Is that healthy for the articular cartilage in the medial compartment? How about the upward force at the ankle joint that you drew? Do you want to have the center of pressure on the lateral edge of the ankle joint? Is that healthy for the cartilage? Seems like the researchers of OA of the knee want to decrease the compression in the medial compartment of the knee.

You asked why we aren't allowed nonvertical forces, and in this situation the argument is to resist gravity in a static situation. Of course, to walk, to climb mountains, etc., you have to have shearing forces, but when it comes to bone, bone was made best to resist compression. Bending moments within bone can cause bone remodeling, and we can always argue which is better. Articular cartilage, in resisting compression forces, stays healthier when the compression forces are equally distributed on the surface with minimum shear. I find it interesting that it has been documented that greater than 20 degrees of genu varum carries with it a 100% chance of developing osteoarthritis in the knee.

Let's face it, the healthiest situation would be to go back to your original drawings, 1-4, and say that #1 represents the most ideal situation. You've got the CoP in the center of the ankle joint upward, in the center of the knee joint downward, and passing through the CoM of the tibia, which produces equal compression forces on both the medial and lateral cortices of the bone. Attempting to create any other condition induces nonideal conditions. Not that the body can't survive these nonideal situations. After all, people survive all types of non ideal situations, like breathing the air in Los Angeles, and still live a normal life span.

I find it interesting that everyone trying to convince me otherwise (and I have given serious consideration of the arguments) causes me to be more convinced that mechanics dictates the most ideal situation as one in which you have the CoP in center of the knee joint and in the center of the ankle joint, and through the CoM of the tibia. Any other condition becomes less than ideal. So thank you Simon for taking the time and effort to produce diagrams that are more convincing to me that criteria #1 is correct for the ideal situation, though I am open to additions to criteria #1 to include statements about the upper 1/3 of the leg being vertical and the CoP being in the center of the ankle and knee joints.

Best wishes,
Daryl

 

Kevin,

I am ready to move to the future when the past has been proven to be the wrong direction. I believe I wrote the first non-Kirby paper on the axis of the STJ, adopting your basic ideas and trying to better quantitate such, giving you the first independent and quantitative evidence that you were correct. Seems like I introduced other clinical measures of STJ movement such as transverse plane angular measurement and linear translation of the heel when the STJ moves. If you listened in Vancouver, you found that I am deeply into diabetic biomechanics which requires me to try to read the latest literature on the biomechanics of the soft tissues. I think that you will find my diabetic orthotic is an evolving entity, as I try different ideas and test them with pedobarograph. I went to Howard Dananberg's office many years ago, soon after his first publication, and did a project there, in which I gave him data that showed his concept of how the hip joint sagittal plane motion was restricted in FHL, and increased when the Dananberg orthotic was put in the shoe. I believe that I wrote in Levy & Hetherington's book a chapter that discussed the moments on every joint though the gait cycle. You know that I have introduced publically the idea of the type I and type II medially displaced STJ axes, which is of great importance in flat foot surgery. I presented at ACFOAM last year a poster on the results of my further research on the contribution of the plantarflexion of the medial and lateral columns to creating an inverted or everted forefoot deformity. I gave a paper at one Weed seminar on how the twisted plate concepts could dictate such things as whether the pronated foot could induce genu varum or genu valgum deformities. You know that I have presented posters at ISB on STJ axis and also on body COM movements. I am doing a project right now about torsional stiffness of orthotics. I have designed already future projects once we get the money. These are just some of the things that should demonstrate that I continue to move forward and am not "stuck in the past."

What I fail to do is rush to judgment on how unenlightened those in the past were. Just because research is recent, doesn't mean that it is better than research and ideas of the past. Truth is not age dependent. At the same time, I don't hold Thomas Jefferson up to the standards of today in regards to humans as property, and I don't hold Root up to a standard of scientific scrutiny that exists today, and I can accept the great ones of the past with their warts. Yes I do hold you and me to a higher standard, and I do constantly question whether past assumptions by Root are correct. I continually ask such questions as, "Should there even be a neutral STJ position?" and "How should we define an inverted/everted forefoot deformity?" and "How much tension should exist in the Achilles tendon at heel lift?" and "Of what value is any bisection?"

For you to characterize me as archaic and nonprogressive is indeed disingenuous. I find it interesting that I seem to be able to find agreement and interlocking of various theories whereas so many on this forum seem to think that you have to be on one side of the boxing ring or the other. I seem to be able to find agreement between the work of Nester and the Hicks model. I can accept STJ moment theory and incorporate it with twisted plate theory. As I noted in Vancouver, it's time we quit talking about Root theory and Tissue Stress theory, and sagittal plane theory, because they all are contributions to our understanding of biomechanics. Finally I can't help but believe that Mert is smiling somewhere, knowing there are some podiatrists who still care enough to try to push the understanding of the mechanics of the foot forward.

Since Simon was kind enough to provide us with the drawings that convinced me that criteria #1 is basically correct, though some additions may be needed, are we ready to move on to analysis of criteria #2.

Take care
Daryl

 

What Root and colleagues actually said was: "The distal third (1/3) of the leg is vertical"
and that "The following criteria represent the ideal physical relationship of osseous segments of the foot and leg for the production of maximum efficiency during static stance or locomotion".

We have already demonstrated that when "the distal third (1/3) of the leg is vertical" this can still have several different loading pattterns acting through it, which you accept. Variation in loading means variability in the mechanics of the lower limb even when the the distal third (1/3) of the leg is vertical - "ideals" don't have variability: they are either "ideal" or not. So in isolation Root's criteria is invalid. It doesn't matter what we think they might have meant, or would have said, we can only judge Root's criteria on what they did say.

What Root and colleagues didn't say are all of the caveats you are now willing to put in place in order to make Root seem right: that the whole of the tibia needs to be vertical, not just the distal 1/3; that the loading force must act vertically downwards at the proximal end of the tibia with a centre of pressure positioned exactly at the centre of the knee joint; that the loading force must act vertically upwards at the distal end of the tibia with a centre of pressure positioned exactly at the the centre of the ankle joint; both the downward directed and upward directed forces must pass through the centre of mass of the tibia; that this "ideal" only applies to static stance; as soon as one wishes to move, it is no longer ideal.

What you you end up with is a criteria which bears very, very little resemblence to the criteria Root and colleagues published, but you are still willing to say that Root and colleagues were right? :deadhorse:

 

We'd probably be a little more successful in arguing about what the Bible means on this one.

I see this debate now as more philosophical than academic, i.e. you want Root to be wrong, and I want him to be right. This isn't about what the ideal should be, it's only about Root being 100% right or 100% wrong. Egos seem to be more at stake here, not the truth. Just as I'm not going to rubbish Dudley Morton or Royal Whitman, or John Manter, but instead try to extract from each the truth and apply it, so I'm not going to get on the bury-Root-train.

I told you that what I stated was static state, not dynamic. I never maintained that the Root dogma was the entire or whole dogma, that it was closed forever and couldn't be amended. I maintain therefore that the criteria #1 is correct, and that you cannot get ideal condition if the lower 1/3 of the leg is not vertical to the ground. Yes you're going to see people with medially displaced subtalar joint axes and with tibial varus go their whole lifetime w/o problems (Lynn Staheli has spent a lifetime showing that his flat feet are not pathological).

So again, I was wavering, but then you did convince me, not the other way around. This discussion is should not be about whether Root was 100% right or 100% wrong, but whether the criteria for normalcy (or I should say idealistic) should be amended and the development of a consensus for criteria that can be taught in the school setting.

Thanks for your thoughts,
Daryl

Daryl

 

Daryl, this section of our discussion began when I asked you directly for a yes or no answer to the question: do you think Root's criteria for normalcy is valid- you didn't provide me with a yes or no answer, but I can see now that you know that it is not valid.

I want the truth as much as you or anyone. I couldn't give a toss about Merton Root as an individual, never met the bloke- no personal baggage. As a scientist, I'm only interested in whether that which is held up as gospel by some, stands up to the scrutiny of science. In my view as a scientist, it falls short again and again, this being just another example. Does that mean "I want Root to be wrong"? No, it means I have read the works of Root, critically evaluated them in a scientific manner, reviewed as much of the experimentation as possible which has been done both before and after the work of Root, and have drawn the reasoned conclusion that much of what he wrote was wrong.
Why do you want him to be right, Daryl?

What anoyes me most is when the disciples of Root are presented with evidence which demonstrates errors in the reasoning of Root, they then start to try to bend what was actually written to try to make it seem right! To quote Bill Hicks on discussing fundamental Christianity: "They believe the bible is the exact word of god, then they try to change the bible, pretty presumptuous huh? “I think what god meant to say…” I’ve never been that confident. They actually have a new version of the bible out called ‘the new living bible’ and it’s updated version in modern English I guess so it’s easier to understand, but it’s really weird when you listen to it “and Jesus walked on water and Peter said “awesome” suddenly we get Jesus hanging ten across the sea of Galilee, Christ’s bogus adventure, you know? Deuteronomy 90210 it’s such a weird belief."

Should it be amended? No, because it is meaningless in populations of real people and clinically has no real worth.

If I was asked to design a bipedal robot that just had to stand statically upright would I make the leg vertical- of course I would because it's easier that way. But I wouldn't bother with a knee joint or any other joint for that matter. The human body's design wasn't optimised (idealised) to just stand statically upright though was it?

 

I think that is a fair statement, Jeff. My opinion is that, during the time the Biophysical Criteria for Normalcy was written (Root ML, Orien WP, Weed JH, RJ Hughes: Biomechanical Examination of the Foot, Volume 1. Clinical Biomechanics Corporation, Los Angeles, 1971), probably in about 1970, Root et al they felt they needed a set of ideal structural values about which they could then establish their foot and lower extremity classification system which relied on being deviated from that ideal. They were trying to create a morphological classification system which allowed better communication of structural parameters among health professionals which they hoped would move the profession of podiatry forward in their knowledge.

For it's time, I think Root et al's Biophysical Criteria for Normalcy made sense and was valuable. However, now 45 years later, I think the Biophysical Criteria for Normalcy is hindering progress for our profession since it is too simplified, is not based on research, does not take into account the range of variability within the human population that allows "normal" gait function, and is based on clinical observation and personal opinion and not on science.

The big question is do we need a set of singular values for "ideal structure" (like Root et als Biophysical Criteria for Normalcy) in order to be effective clinicians for our patients and understand the biomechanical function of the foot and lower extremity. I don't think so.

Rather, I believe we should be teaching the normal range of variation (i.e reference range) in foot and lower extremity structure and the effects of variation in structure of the foot and lower extremity on biomechanical function. We should not be so bold and unconscious of our intellectual limitations to assume that we know what the ideals are for the human foot and lower extremity.

Here is what Root et al wrote in 1971:

With the knowledge of hindsight, here is what I think Root et al should have written in 1971:

 

I know that you weren't there, but Kevin was, in 1994, at the first John Weed Seminar, Mert made some interesting statements. He stated that he really was very afraid to ever publish a book because if he did, then people would hold his feet to the flame of those printed words forever, that people would never let him change his mind nor modify any of his writings. Seems like he was right, as to your reading. I'm willing to let what he wrote be part of the whole. You want what he wrote to be the whole, so it's all yes or all no. You would have been a good barrister, for you would indeed be the one asking the defendent whether he still beat his wife and demand only a yes or no answer. For some unknown reason you choose to be as inflexible and dogmatic as you want Root to be. Guess I knew the person, you only know a book. Makes a big difference, doesn't it?

As to your statement that it has no worth, you seem to be ignoring a lot of literature on the ill effects of genu varum (which almost always translates into lower leg varus).

However, back to the academics, I am attaching a picture (one of over 60 I have ordered in the last 2 years) of a radiologic study that I ordered for limb length discrepancy, with the patient standing in the normal relaxed standing. I would appreciate if you would give me your analysis of which side is closer to the ideal, and why. This is a chance for you to show us what a great analyzer you are or to convince us that it doesn't matter which tibia is more inverted. (Don't forget that you are facing the patient, so the right is on the left.)

Looking forward to your analysis on the bending moments on the leg, and the forces within the ankle and the knee.

Thanks
Daryl

 

BTW, There is no problem with my drawing, or drawings.

First off you said:

So, I drew a lower leg, inverted to the ground, that had no bending moment.

But then you moved the goal-posts and said:

So, I drew a lower leg, inverted to the ground, that had no bending moment with only vertical forces acting upon it.

But then you moved the goal posts again and said:

So I've drawn you another one, it's a lower leg, inverted to the ground, that has no bending moment with only vertical forces acting upon it and the forces are well within the central third, Daryl. Hope this meets your criteria.

 

You seem to be allowing your personal feelings for Merton Root to cloud your scientific and academic judgement and you clearly are unable to answer a question which only requires a yes or no answer with a yes or no answer. Rather you woud rather divert from the question. I'm not asking you if you are still beating your wife Daryl. I was asking you if you think Root's criteria for normalcy is valid or not?

Now, do I understand modeling and the influence of the position of structural elements within a system? I think we can take it as read that I do, don't you Daryl since by your own admission it is the modelling I have performed here which has helped you to understand this? Will any of this prove that Root's biophysical criteria for normalcy is valid? No it won't. Do you know where the centre of pressure at the joint surfaces are in any of these radiographs? That the magnitude of loading on each leg is identical, etc. Since we need to know these things to form accurate models- don't you think?

 

Straw-man Daryl, I didn't say it didn't matter if one leg is more in varus than the other- did I now? As for convincing you, I doubt anyone could convince you of anything you didn't want to believe unless it was "Mert" himself.

Here you go Daryl, some suggested loading that might exist here, let the arrow length be proportional to the magnitude of the loading. Which has the bigger bending moment? Left or right? The point is this, looking at structural alignment in isolation, without knowledge of the loading forces acting across the structure is a very blunt instrument indeed, as I have previously demonstrated in this thread. This is the very reason why statements such as "the distal third of the tibia is vertical" can never be taken as valid criteria for a biomechanical "ideal".

Edit: I'd already drawn this and replied before you moved the goal posts again! But the point remains, and your guess at what the magnitudes and locations of the forces should be are only as good as mine. Which one has the bigger bending moment Daryl? Left or right will suffice.

I'm not the one introducing more and more caveats in an attempt to prove the Root's theory that "the distal 1/3 of the tibia should be vertical" is correct though Daryl; see those pre-Copernicus folks- they'll be you then. "I think what God (Mert) meant to say"...

Anyway-which tibia has the biggest bending moment?- the word "left" or "right" only as your answer please.

 

The reason that it is important to examine the past is that what we currently believe comes from the past. What we currently believe influences where we will go in the future. The criteria for normalcy was something that I was taught in podiatry school. Should we continue to teach it. As Jeff points out we should examine each in terms of current knowledge and make the decision of whether to accept it and move on. I think we can all agree that tibial varum can have some influence in pathology. Daryl may be correct that lower 1/3 of the leg may be a more reproducible measurement clinically. However, if get back to thinking clinically, we need know the importance of tibial varum has on clinical decision making. So, if tibial varum is normal, do we ignore it? If it abnormal, how do we change what we do? I'm still trying to get an explanation for why we need a definition of normal that is other than circular. "If we don't know what normal is how can we know what abnormal is?" With a high degree of tibial varum there is an increased chance for medial knee OA. Why pick a normal?

Anyway, I'm ready to move on to the next criteria.

Eric

 

B. The knee ankle and sub talar joints lie in transverse planes parallel to the supporting surface. (Figure 31)


Does anyone have figure 31 so that I can figure out what this means?

Eric

 

I'm guessing it means that those wavy lines which represent the joint spaces at the knee, ankle and subtalar joints that we can see in Daryl's radiographs above, should be straight lines which are parallel to the supporting surface.

 

Simon,

Do you see a difference between the left and the right ankle joints in the radiographs? The left (as pictured on the right) trochlea of the talus is inverted as compared to the right leg. Which ankle appears more normal to you?

Jeff

 

Jeff, I see a lot of things in those radiographs. What I don't see are the point of application, direction nor magnitude of the net loading forces acting through those bones in the radiograph.

Which of these ankles "appear more normal" to you?

 

Daryl, how do you get them to stand with their center of mass located between their feet. A lot of people, when standing, will put more weight on one foot. Is that normal?
Eric

 

So should Root et. al. have drawn the trochlea level as demonstrated in the right leg or inverted as demonstrated in the left leg of the radiographs that Daryl posted? Perhaps much of this debate centers around the use of in office radiographs by podiatrists here in the states. Root, Weed and other DPM's routinely used X-ray to help in their diagnosis and treatment whereas clinicians who don't use X-ray can't see the underlying osseous structure and relationships.