Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?

Agreed, but I think it goes beyond that. The now ubiquitous image of the foot with the everted heel, then placed upon an orthosis with the vertical heel makes the assumption that this is "a good thing", which in a Rootian model it should be because that is what the Rootian model said. But the reality is far from that. How do we know that by bringing the heel to vertical we have not placed one of the tissues outside of it's zone of optimal stress (ZOOS)? We don't. We could show an image of a foot which when standing on a foot orthoses has the heel nowhere near vertical, yet that orthosis may have been highly successful in treating the patients symptoms. The point I'm making is that the position of the heel bisection when a patient stands in static stance upon an orthosis isn't necessarilly predictive of the outcome of that intervention nor of the stresses within the foot and lower limb. So showing a photo of a foot on an orthoses is only key if you are a proponent of the Root model; it is way less important if you apply biomechanics.


We can have vertical alignment of a column, lets say that it is our calcaneus and talus making up the structural elements of that column. Let's clone 4 of these. All of the columns have the same alignment but with different loading across such a column, the stresses may be very different within it- this is understood by architects as the "rule of thirds". I've attached an image of my good friend Ian Griffiths studying this. Perhaps he can describe this while I take Grace to her BMX coaching... The point? Just because we show pictures of various feet standing in orthoses with their heels vertical- doesn't mean the stress within them are the same nor within their ZOOS,

 

I think you just pointed out one problem with tissue stress theory. How do you know how much force is necessary to eliminate the pathological forces you suspect exist and yet does not create other pathological forces at the same time? This unknown amount of force may or may not produce kinematic changes that can be detected by the clinician. So whether or not you are using a tissue stress approach or the Root approach, you are attempting to alter forces to reduce or eliminate pathology, ideally without creating new pathology in the process.

I am willing to bet that if my subject had complaints of medial ankle pain, we could both probably have eliminated his symptoms using two different approaches provided we both reduced the pathological forces sufficiently. In your approach, the heel might have remained five degrees everted and in my approach the heel was about 1 to 2 degrees everted. However, it is possible that I might have over controlled him or that you might have under controlled him. Neither approach has a guaranteed result and either may require us to make adjustments to our treatment plan. You use an approach that you are most comfortable with and I use an approach that I am most comfortable with and unfortunately there are no clinical trials that enable us to compare outcomes.

Jeff

 

But not if the subject had medial knee o/a or chronic lateral instability, in such cases your prescription based on angular measures and holding the foot in neutral would be very different from a tissue stress prescription. And that's the point, Jeff.

 

My point was that although the clinical approach may vary and although the RX may vary, we can't say whose approach is better. We have been treating medial OA with the Root approach for a very long time. We can't objectively compare our results.

Jeff

 

But science and Physics will say that the Root Device ( as I know it ) will/could lead to increased forces acting on the medial knee and therefore being doing damage in medial knee OA patients

Where as Lateral foot wedging in many trails and through the use of Physics to explain why , etc have been shown to improve mobility and reduce pain in these patients

 

Lateral foot wedging for medial knee OA

and from another thread

 

Mike,

If you are using the Root technique in most cases you are posting or balancing the orthotic or cast to support a forefoot valgus condition (i.e. forefoot is supported everted to the plane of the floor), which has an influence that is similar to a valgus forefoot wedge. And if the subject also has a reafoot varus and you use the strict Root criteria to correct the heel bisection to vertical to treat RV varus, then this will create an eversion moment a the STJ because heel vertical would be a pronated position relative to the inverted neutral position of the STJ due to the RF varus. This is another example of why we need to take into account the structure of the individual patient being treated and not just talk about patients in general as if they are all the same. They are not.

Jeff

 

Notice, Jeff...that the "Tres Amigos" never answer our questions? I find that mildly amusing, but ever so telling. Someone really should inform Simon that the technique that he demeans, belittles and vilifies is the answer to successfully treating growing pains in children and RLS in adults. Is it the only answer? I never stated that...I would be allowing myself to be a closed minded practitioner similar in attitude to those that dogmatically post here as having all the answers...and I certainly don't want to be considered like that or included in that "club". I have a LOT more patients now that have been successfully treated, above and beyond that which is written about in my pilot study to draw from...

Confirmed today that the article will be published this month. Yowza!

 

Now we are getting into the assumptions of the Root paradigm that should be abandoned. There is an implicit assumption that the foot will tend to move its heel bisection toward where the heel bisection of the cast is placed. There is a second assumption of the foot always starting in neutral position and compensations occur, because of foot deformities, away from neutral position. We should be looking at where the foot is and not in some idealized position of where we think the foot ought to be.

Specifically, Jeff is discussing about how an orthotic made from a vertically balanced cast will create an eversion moment. Perhaps, Jeff could expand on the logic he is using to say that the orthotic is creating an eversion moment. I feel we should be comparing the foot without an orthotic to a foot with the orthotoic. We don't really know what a heel cup that is symetrical in the frontal plane will do to center of pressure. (A heel cup that is balanced to vertical should, in theroy, be symmetrical in the frontal plane.) But the argument could be made that a vertically balanced orthotic wont do very much. It will certainly do less than an orthotic made from a cast with a lateral heel skive.

Eric

 

I know we disagree on the relevance of population norms. Whilst I agree with you on the uniqueness of each individual, if we evaluate a wide range of criteria / components, then we can build a picture as to any excessive or restricted function and direction of the varying forces which will determine the resultant. More below.

Jeff, I am not quite sure what biomechanical agenda you feel I am trying to fit. I take great care with my posts, drafting them off line and trying to ensure that I give my interpretation of the available data and concepts, specifically without denigrating or ignoring other people’s comments. I noted in my first post on this subject that the discussion was at times an argument and it continues to be so at times. I have specifically steered clear of this aspect.
If you could indicate where you felt I was pushing an agenda I would be most grateful so I can reflect more closely.
For the record, it is clear to me that the Root model of ‘normal’ foot function has been demonstrated not to be the case. However, I still believe that structural alignment has a role to play in determining function and, were I as advanced in my physics as others, I could give a plausible answer. I do not worry about subtalar neutral anymore for the above reasons but also because rearfoot motion incorporates ankle motion and it is not possible for us to distinguish clinically. However, a large tibial varum will have an impact on the moments acting on the foot and the impact will depend on the range of motion available. In the Root terminology, this may be a partially or fully compensated rearfoot varus due to the tibial varum. I think the concerns people express regarding this terminology is, it makes the assumption that the subtalar joint neutral theory is correct.
Similarly, hip rotation can have an impact on load at the foot, as can the degree of hip adduction, pelvic drop, knee flexion, ankle dorsiflexion etc. These motions are all modulated by the relative flexibility, strength and control of the varying muscle groups and this jigsaw puzzle will provide a resultant.

It occurs to me that there is every likelihood that we can consider aspects of the relative theories and make sensible progression. If we are able to assess a wide range of criteria / factors, we could determine whether there is a net pronation or supination moment acting on the foot. However, if the driving force is proximal to the foot, our ability to modulate that function may be less than if the driver is at the foot. This allows for inclusion of some of the structural factors carried forward from the Root theory (although differing terminology would be helpful to move things forward) yet acknowledges that the foot does not function around neutral. The net effect will also be affected by the nature of the activity, footwear, surface etc.

I also have some difficulty with using relief of symptoms with no immediate development of other symptoms as evidence that the treatment provided is correct. However, I like the ZOOS concept because this explains why a range of interventions may all have a positive effect. In some individuals, that range will be smaller than others. This can work well in the hand of the experienced but less so those with less experience. I can stick someone in a walking boot and resolve pain but this will not be good long term function.

I have treated two patients with medial knee OA recently. In both of these cases, they have had excessive tibial rotation yet normal rearfoot eversion. The tibial rotation, in this instance appears to me to be a reasonable potential contributor to the knee symptoms. Given the recent work by Nester and his group indicating that tibial rotation may well be coupled with arch height. I therefore considered their function again and noted that the degree of mid foot motion (in this instance assessed by navicular drop / drift) was relatively greater than rearfoot motion (in this instance assessed by tibial position and relaxed stance). As a result, I provided both with OTS devices aimed at reducing some of the midfoot motion, one with heel raises due to a degree of equinus. Both patients had immediate symptom relief.

Returning to the orthoses paper Simon quoted previously, they noted a significant change in tibial rotation with inverted orthoses, thus it is possible to alter this motion with orthoses. It is not possible to directly compare the orthoses used and I suspect that some people couple tibial rotation to the rearfoot and others to the midfoot but that is another discussion.

I did not have the opportunity with these two patients to re-test the kinematics but I can note that when we do re-test with orthoses, we regularly see a change in tibial rotation and less often a change in rearfoot eversion. The orthoses, without having specific design features will impart a supination motion in an attempt to reduce the arch motion yet have been applied based on some kinematic data – I do not have the ability to measure joint moments so cannot comment on that aspect. I am quite happy that I have taken an evidenced based approach but council my patients that we need to monitor their progress as this is my interpretation of the evidence available based on the information of our analysis which is somewhat different to saying we have direct evidence of the efficacy of the treatment.

 

We also need to hope that the patients with medial knee O/A, peroneal tendonitis, chronic lateral ankle instability etc have not got inverted forefoot to rearfoot alignments.

 

Aren't the successes of the vast majority of medical interventions measured in exactly this way?

 

How the heck would you know? You never measure anything, because you don't believe in that approach. You call it OA instead of it's proper term: DJD. You think that when flexors are firing in order that the patient gain lateral stability, you claim them to be the extensors. You have a patient in your office with obvious uncompensated, (barely compensated), rear foot varus, and you claim by applying an eversion "moment" to the orthotic, (and also abducting the forefoot) you've solved her problem, end-of-story, that's good enough for you....harrumph!

 

Matt, we are not practicing medicine here. We are in an academic debate. So, if I want to make a point in the debate I could refer to the literature. For example, if I wanted to explain to you how center of pressure relative to STJ axis affects moments about the STJ, I could write it all out for you, or I could refer you to my center of pressure paper that has some nice pictures and references. It is entirely appropriate to refer to published literature.

Did you see the Spike Lee movie where this Italian guy who owns a pizzeria and has a black kid working for him. The Italian guy says some stuff to the kid. The kid gets all ****** off and feels disrespected and does something that hurts the Italian guy. The Italian guy says "Why did he do that? I treated him like a son." Matt, I'm going to have to tell you, you are on the abrasive side of the mean. You may not have thought that you offended others, but they feel that you have.

I explained this in post #70. You responded to that in post # 74. You explained why you thought a valgus wedge wouldn't help lateral instability. But, you did not refer to my explanation. In post #85 I asked you some questions about your explanation. You have never answered them. Your response to post #85 is the one I'm responding to now. So, you must have seen the questions.

This is the kind of abrasive stuff that would lead people to want to ignore you. It's not just that you are being critical. It's that you won't say what your disagreement with our stuff is. Why shouldn't you be put on ignore if all you say is your stuff is a bunch of garbage. At least say why you think it is a bunch of garbage.

It should be obvious to you that we are not just reinventing the mouse trap. For the same lateral instability problem the tissue stress approach would use a valgus wedge and you would use a forefoot varus extension. It is different.

On Compensation: Matt, I really want you to go there. If you want to defend the "compensation" paradigm, you need to first define what you mean by compensation. I posted a definition of compensation from the internet. None of those definitions apply. What is the podiatric biomechanics definition of compensation? Matt, if you have an open mind you should be able to question your own beliefs.

No Matt, I didn't really slam them. What I said was that there wasn't anything new there. You kept claiming that the videos were ground breaking and I was just pointing out that the information presented in your video was available years ago. I will actually slam one part of your video. It did not accurately represent what happens at maximal pronation of the STJ. The flourscopic videos showed that the lateral process of the calcaneus hits the floor of the sinus tarsi when pronation of the STJ stops. In your video it looks like the lateral process of the talus is hiding somewhere in the middle of the calcaneus.

I'm still waiting for you to explain the connection between restless leg syndrome and growing pains. Your paragraph above makes it seem that this is also related to biomechanics of the foot. If that is what you intended, what is relationship between biomechanics and restless leg syndrome?

Eric

 

Many aspects of medicine have objective methods for measuring the problem and the effect of the intervention.

I guess, what I am trying to get at here is that, if we can have a cogent theory / paradigm etc., then we should be able to evaluate the interventions and have some process for evaluating why they do not work or potentially cause other problems - or at least have a hypothesis and evaluate it scientifically.

Stopping at they felt better just seems to be part of the story.

Eric, would it be fair to say that the tissue stress approach simply means that you have attempted (and hopefully achieved) sufficiently reduced stress on the tissue to reduce symptoms, irrespective of the method?

The utilisation of the lateral forefoot post is applying one theory (SALRE) to achieve tissue stress relief in this instance. I think there should be some caution in making them one and the same thing as our concepts and theories may well evolve over time and, as yet, there is still a lack of scientific analysis underpinning the academic debate.

 

Here is the only response so far to Kevin's blog on Podiatry Today:

Here is the link: http://www.podiatrytoday.com/prescribing-orthoses-has-tissue-stress-theory-supplanted-root-theory

 

Jeff has made several comments about tissue stress approach not providing an exact prescription for treatment. The above comment is analogous to the question of how hard should you push to pronate the midtarsal joint to get an accurate forefoot to rearfoot measurement. In both systems it's guess work. At least the folks on the tissue stress side will admit it. If you know that you have an "over supination" problem, you do something you know will increase pronation moment. If it is not enough, or too much, you adjust accordingly. As you gain more experience, you will guess correctly more often. However, you should always re-evaluate.

In Kevin's original medial heel skive article he mentioned going up to an 8mm skive. I once heard Kevin say that he never goes above 6. Was it because too much skive caused medial heel pain? Or blanching of the medial heel when it was on the orthosis?

Eric

 

Eric,

Dr. Root attempted to link the examination and prescription process a in computational system so that it wasn't just guess work. That's why he gave formulas for the amount of forefoot and rearfoot correction based on data obtained from the examination process. Although many practitioners don't do a full bioeval anymore because they can't get paid for it and because it is time consuming, many still base their treatment on the concepts that were derived from a comprehensive bioeval.

As far as force to fully pronate the MTJ durning casting, Root recommended ounces of force, not pounds of force. He also said that in many cases of pronation related pathology, it was only necessary to prevent the STJ from reaching the end ROM during propulsion when peak forces acting on the foot were at their highest level. That concept is certainly consistent with tissue stress theory, is it not?

Jeff

 

Eric Fuller-So you posted a definition of compensation from the internet and it didn't apply? LOL! Weak. Compensatory motion in any foot to GRF will probably never be defined by utilizing the internet. Haven't your patients told you to be careful what you read on the IT?

The videos are "ground breaking" because never before has STJ motion been shown in animated format. But you want to nit-pick. I expect that from the Tres Amigos...(in between patting yourself on the backs, that is). The videos are "ground breaking" because never before has anyone thought to overlay the animated bones of the feet over actual video footage of patients ambulating. Valmassy was "blown away" when he saw them for the first time...so was everyone else I showed them to, that doesn't have some underlying agenda. Is that you? Now, I know Valmassy's CV pales in comparison to your lofty achievements, but he still represents a force in our profession.

You continue to mention a fluoroscopic video as the panacea for biomechanics, yet I have never heard about it, before you mentioned it, nor have I seen it. It should be open source. If one is going to blast patients with enormous amounts of radiation, and will never be produced again because of that, it should be made available...don't you think?

Compensation to GRF occurs initially at heel strike in the STJ, then midstance by that joint and the MTJ. How difficult is that to imagine...or describe? The source for growing pains in children was described in my second video...did you miss it? Same as the cause of RLS. It IS biomechanically created. I hand delivered the answer to you in video form, and you STILL can't figure it out? Can't wait for one week to read about it...even after I described it in the last video I offered you? Sheesh!

You can make biomechanics as difficult as you want, if that's what floats your boat, sells your chapters in books, and keeps you relevant. I prefer to solve huge problems...which GP's and RLS most certainly is. Remember, the article you will read is 3K words...pared down from 10K words, 42 pages long, complete with jpegs, illustrations and old pics of those that studied this problem...for 192 years. Now Willis-Ekbom dates back farther than that, actually, and was described in the 1600's. Yet here you are on a public forum, gnashing your teeth about the lateral process of the calcaneus when the fact is NO ONE has depicted STJ motion as accurately in animated form previously. Is there room for improvement? I already admitted that before. My animator had never had an anatomy class and the result of what you saw, not only cost me plenty of money, but many hours of time trying to get the sequencing and motion more correct. My feeling is that you appear to be either an ungrateful nattering naybob or have another agenda for downplaying/minimizing my efforts. Your post does nothing to distinguish between the two...so I'll assume it's a combination of both. You have a LOT invested in promoting the tissue stress theory...so does Kevin. Keep patting yourselves on the back for jobs well done...I'm too busy helping millions of patients by educating thousands of doctors...and doing so in a simplified manner that is easier to understand. Hope this helps.

 

Hey guys,

Ive been very interested in this discussion so far, however i'm a tad lost. As i understand it (i was never good at english at school) Kevin's article is an opinion piece about, his opinion towards the tissue stress model and the root model. is that correct?

My other question is, is the tissue stress model build on the fundamental principles of root's theory or are they two completely independent theories?

Kind regards,
Andrew Devereaux

 

The methods exist, if we look to the Williams et al. paper this is pretty much what they did; they wanted to know why the patients didn't get better with the Root type device, but did get better with the Blake inverted device so they measured the 3D kinematics and kinetics. There are a multitude of studies in the biomechanics literature where joint moments have been measured, we even have studies of strain measurement in individual tissues; the problem is not that it can't be done, the problem is that the cost of the technology required is prohibitive.

 

Agreed and this is sort of my point. We need to go the next stage and use this technology to look at the broader effects of the concepts. As we piece together this information, I believe we will be able to determine additional clinical indicators that will help us guide our assessment / diagnosis and management in the clinical environment that does not have access to the technology and try to remove some of the guess work.

The technology is becoming more accessible and a greater link between the clinicians and researchers would help facilitate this further.

BTW, in your discussion article, you refer to a need for us to determine a method of evaluating the 'dose' of support provided by orthoses. I think this is a really important point.

First blog is up

http://www.biomechanics.completespo...nical-practice/#sthash.69zLoEvI.LZFrzExa.dpbs

 

But it's still guess work. Why? Because tissue injury: "injury is the damage, caused by physical trauma, sustained by tissues of the body"- Whiting & Zernicke: Biomechanics of musculoskeletal injury, Human Kinetics, 1998, is caused by forces; foot orthoses work by modifying forces; yet none of your father's examination techniques nor prescription protocol measured forces. Without measurement of forces, it's all guess work, whether you provide a formulaic link between angular measurements of the foot and lower limb and foot orthoses, or not. I believe this where Trevor and I concur.

 

You could come at it from both ways

But as I said you don´t need to have even heard of Root to understand Tissue stress Anatomy, Physiology and Physics will do

 

Dear Dr Sciaroni,

I have been reading the developments in this discussional thread with great interest. I have always enjoyed and profited from reading what Dr. Kirby writes both in the published literature and on line. In furtherance to this, I have also derived enjoyment and profit from the body of work that Dr. Merton Root had published during his lifetime [along with his compatriots, William Orien and John Weed], and what his son Jeff has written over the years and still continues to write. Indeed, I can also say exactly the same with regard to the published writings and on-line contributions by such clinical academics as Dr. Spooner, Dr. Fuller, Dr. Philips, Dr. Payne, and a large majority of the other contributors to the wonderful repository of knowledge and academic debate that is Podiatry Arena.

The article entitled ‘Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?’ is yet another thoughtful and insightful addition to the literature by Dr. Kirby, which yet again has stimulated a lot of reasoned debate. I sometimes wonder when Dr. Kirby actually finds time to eat and sleep, such is the overall magnitude of his output.

I regularly come onto this forum as a browser with the express intention of learning, and indeed, I have gained much from using this remarkable site over the years. The evolution of clinical models of approach in the domain of podiatric biomechanics has always been a pet interest of mine [e.g.: Root, SALRE, Sagittal Plane Facilitation of Motion, Demp etc.], hence my present posting.

In post 102 [quoted above], you stated the following in reply to Dr. Eric Fuller:

<<I read your chapter on tissue stress in Albert's book. And all I have to write is poppycock and balderdash.>>

This strikes me as both a bold and a bald statement, and as such, I would be extremely grateful if you could elaborate as to why you think the content of Dr. Kirby’s and Dr. Fuller’s chapter from Dr. Albert’s and Dr. Curran’s recent textbook is “poppycock and balderdash”. In addition, it would be a great help to me and others on this forum if you could flesh out your explanation(s) with references from the literature. It appears obvious that you align yourself to the Root model over against the SALRE model, and a referenced account of what underpins your theoretical allegiance would, I believe, be beneficial to this current debate.

Following immediately on from the aforestated, you stated:

<<Trying to re-invent the mouse trap is not helpful, especially in medicine....fine tuning a theory that has been in existence before, tweeking [sic] and defining that theory, certainly is.>>

This does beg the question, and I’d be grateful if you could try and answer it. Why is “trying to re-invent the mouse-trap” unhelpful as opposed to “fine tuning [sic] a theory that has been in existence before”, which you infer to be helpful?

You must, I assume, have firm and resolute reasons behind your statements which I’ve quoted in this posting, especially when dismissing an entire chapter on a specific subject area are mere “poppycock and balderdash”. In addition, I’m also assuming that you must have recourse to some pretty robust references from the literature that serve to underpin and inform your theoretical stance. Giving in-depth answers to what I’ve asked would certainly be helpful to me and would, I hope, prove to be useful in the present thread’s cut and thrust of academic debate.

I must also state that I look forward to reading [as I’m sure do others on this forum] your forthcoming paper on growth pains which you have fanfared in recent weeks. I’m sure that it will be well worth reading.

Thank you in anticipation,

Eric Lee.

 

Franklin-in the opening paragraph from Kirby and Fuller's chapter: "The tissue stress approach is based on the concept that when any of the structural components of the foot or lower extremity are placed under more stress than they can withstand, the structural component will ultimately become damaged."

How is this a new concept, avoiding the obvious question in the readers' mind about structural "damage" or the need to define "withstand"? While there are some nifty drawings included in that chapter, which in my mind at least parallels what Root wrote about years ago, it appears to follow closely precepts that were established 40 years past. Proponents of tissue stress even include bone in their broad definition of tissue, so how is this a paradigm shift away from what we already learned on our own, and/or read about previously? It appears to me that their "all inclusive" definition hedges their bet and is not really a "new" theory, but an expansion of one previously described. While Root didn't live long enough to allow further expansion on his own known entities and further define what he wrote about, (particularly in his second book), does it achieve the desired result for others to re-invent this theory...to design a better mouse-trap? Or does it make more sense to address his work in progress and make it easier to understand for others to follow?

Root was a big advocate of describing the STJ as being the central "theme" of many foot pathologies. Well, guess what? He was right. It has taken me years to reach my own conclusions, through trial and error and my own stubbornness in avoiding his work, but I have come to the same end point. Perhaps I would have determined the cause of Growing Pains in children sooner if I had just paid more attention to his work, or listened more carefully to lectures from John Weed at CCPM.

Remember, too, that Root and Weed only had rohadur to construct orthotics...the advent of polypropylene has allowed us to construct MUCH better devices that can address more encompassing pathologies. Could Kirby have written about medial heel skive additions if rohadur was the only product available? I can't tell you how many times I had to re-make a Blake prescribed 35 degree forefoot inverted orthotic using rohadur while I was a junior student at CCPM. I literally cooked that material trying to make it pliable enough to properly seat on the positive cast. But I digress.

I am not suggesting that Kirby and Fuller's chapter is not without merit...what I am suggesting that it actually represents a continuation of Root's work, with a few tweeks, and definitions thrown in for good measure. Review the header for this thread started by Kirby. He asks has tissue stress theory supplanted Root Theory. Not in my mind.

 

Root's orthotic prescription process was based on the data obtained from a biomechanical examination such as STJ range and direction of motion using the heel bisection as an indicator of the frontal plane component of this motion, neutral position of the STJ, tibial position, FF to RF as measurements as represented in the foot and the positive cast, etc. Root developed strict criteria for the orthotic prescription based on these findings which were taught to students as indicated in CCPM's biomechanics class notes that were written by Drs. Weed and Root and included about 20 pages on orthotic fabrication that was written by me. As a result, two practitioners with the same biomechanical finding should, if following these guidelines, come up with the same orthotic prescription. This system provided a basic roadmap for students and for those practitioners who attended my father's lectures. This is what I see lacking in the tissue stress approach to evaluation, diagnosis and orthotic prescription writing.

You guys are on volume four of your work but you haven't given us the first three volumes (the road map) that serves as the basis of your current work. None of you, Eric, Kevin and yourself has ever to the best of my knowledge, provided a guideline to teach students or practitioners the steps necessary to conduct an appropriate and organized biomechanical evaluation of the patient and the necessary steps that lead to the orthotic prescription. A least Root laid his cards on the table for others to see. You have played two cards but you still hold three in your collective hands.

For example, you and Kevin profess to use the tissue stress theory approach but you have significant differences of opinion about basic examination techniques involved and the benefit of structural analysis. I suspect that tissue stress theory has not been embraced in the U.S. because it is so vague and poorly understood as evidenced by the one response to Kevin's blog on Podiatry Today which I happened to post yesterday. Your examination techniques (at least those of Kevin and Eric's) contain elements of Root theory and yet Kevin claims that Tissue Stress Theory supplants (def: To take the place of or substitute for (another): Computers have largely supplanted typewriters ) Root theory. Perhaps supplant was a poor choice of words. Perhaps augment (def: To make (something already developed or well under way) greater, as in size, extent, or quantity: Continuing rains augmented the floodwaters.) would have been a better and more accurate choice of words in the title but that might detract from the real agenda here, which is to attempt to claim that Tissue Stress is in fact a completely independent and separate entity or theory. It is not and that is the focus of this thread.

Jeff

 

Dear Mr Root,

Please dont think I am being rude but I would disagree with what you said. The tissue stress approach is the medical model taught at universties; identify what hurts, why does it hurt, prescribe an orthotic that helps it to heal. The biomechanical evaluation will differ from one patient to another, because we are unique.

John

 

John,

I would never consider it rude for you to have a different opinion than me and I respect you for expressing your opinion. Are you referring to Podiatry colleges in the U.S. or outside the U.S.?

Jeff

 

Jeff, just answer this question- if we use you father's protocol, are we still guessing? Yes or no will suffice. Yes is the answer you are skirting around because we all know, you included, that it's guess work without force measurement in the equation.

Do we really? And you know this how? Regardless, we are independent thinkers- so we agree on some things and maybe disagree on others as we explore and try to push the boundaries of knoweldge regarding foot and lower limb function. While that doesn't seem to be allowed in a Rootian world (having heard stories of your father's reactions when challenged) I'm quite happy not to agree with everyone and if they can convince me that they are right and I am wrong then my opinion may change, if they can't then it won't- it usually takes good science to change my opinion on a scientific topic, when someone provides me with this I will happilly change my point of view; back to my first question here: if we use your father's protocol, are we still guessing? I think we are; convince me otherwise or concede the moot point.

In the middle of a study at the moment which might negate your assertions here, lets see what the data shows when the study is done, but thanks for that useable quote.

Could I employ tissue stress without mentioning your father or using any of the techniques he developed?- definitely.

 

Without a knowledge of kinetics, a photograph of a heel with vertical alignment of the heel bisection when standing upon a foot orthosis is meaningless. Note how the position of the centre of pressure at the STJ from the orthosis reaction force will influence the stresses across the joint AB. Let's take another look at the photograph in isolation: where is the centre of pressure across the joint- completely unknown because all we have is a photograph; I've just given a number of potentials here as modelled, simplistic examples in the overlays. Note how the rule of thirds applies to the introduction of tensile load on the opposite side of the joint. So, can we predict tissue stress from the position the heel is in during static stance in isolation? Errr, no. But the orthosis held the heel bisection in vertical... Yeah, and, so, what? What if we add in the forces, can we predict which tissues might be under stress now? What if we now add in the position of the rotational axis across the joint?

Giving Root the benefit of the doubt (in that he even thought about this), his assumption appears to have been that we always ended up with #1. Unfortunately, we don't. What can we learn from this? Attempting to place everyone's rearfoot such that the heel bisection is at vertical with a foot orthosis is not the way forward.

Quasi-static free-body analysis solves the problem: when we know where the forces are we can begin to model and predict the stresses, for more info see: Dr. Kirby’s and Dr. Fuller’s chapter from Dr. Albert’s and Dr. Curran’s recent textbook, i had the privilage of reading this chapter when it was first written, several years ago now- I learnt more from this chapter than from anything else I'd ever read. https://faoj.files.wordpress.com/2009/09/lowerextremitybiomechanicsvol12.pdf

 

First question.. yes.

Root's model is based more on position and foot "deformities". You might even say that Root is kinematics. The tissue stress theory looks to examine the mechanical stresses on anatomical structures. You might call that kinetics.

 

Yet we need both kinematics and kinetics to make an accurate assessment.

 

By the way, the more astute of you will have realised that a tensile stress will not be created until the centre of pressure at the joint passes beyond the outer limits of the central third because up until this point there is compression on both sides of the joint between the two elements of the column within the model, this is what architects and structural engineers call the "rule of thirds". F is the vertical component of the orthosis reaction force, in case you needed a key. And Kevin decided that the medial heel skive should be centred on the medial limit of the central third of the plantar surface of the heel portion of the cast because?- lucky guess or genius at work? I'll let you decide- right Boss?

Note also that the foot hasn't changed position in any of these images despite my modelling of changes in the external moment, that is because it is the sum total of both the internal and external moments which determine the joint position, all I have done is change the external moment in my model, provided that the CNS can also modify internal moment, there is no reason at all that the foot cannot stay in the same position when external moment is modified provided that internal moment is equally increased in the opposite direction.

Want to predict how much varus rearfoot post is too much such that it causes the tissues that provide pronation moment about the STJ axis to function outside of their ZOOS? It has to be at least enough posting to place the centre of pressure at the STJ beyond the medial limit of it's central structural third; vice versa is true for valgus rearfoot posting. How's that for predictive modelling Trevor?

This model also predicts the medial and lateral shift in the position of the centre of rotation of the STJ observed in-vivo. At one side of the joint compression is increasing, at the other side it is reducing, the point inbetween is the axis of rotation. In the example I gave, the axis will move more medially as we go from figures 1-4.

Anything new here? No. All I have done is apply well known principles of structural mechanics to the problem at hand, without breaking the laws of physics in the process.

I look forward to your responses.

 

It would be nice to be able to do the study to see if ten ounces of force created a different forefoot to rearfoot measurement than two ounces of force. However, there still is the supinatus problem. Where should the medial column be when you are attempting to measure forefoot to rearfoot relationship. Within the paradigm, there is the condition of supinatus, a positional change in the forefoot to rearfoot relationship caused by high forces under the medial forefoot. So, when you measure the forefoot to rearfoot relationship are you measuring the true forefoot to rearfoot relationship, or are you seeing the influence of supinatus on the measurement. To be able to define the "true" forefoot to rearfoot relationship you would have to describe where the medial column should be when you do the measurement. If you don't consciously choose to put the medial column in a particular position, you would be just guessing whether the value you get is the true forefoot to rearfoot measurement.

I agree with other posters comment about felt better being a good endpoint. That would be what most patients want.

You can reduce stress on anatomical structures using different paradigms. There are many times when I would create the same prescription using both paradigms. However, I feel the major difference between the paradigms is how we arrive at the prescription. The prescription may sound the same, but the thought process to get there is different.

I often find it hard to pin down Root theorists on what their personal belief is about how an orthotic works. Eric Lee's paper is a good place to access the literature on what various people have said about how an orthotic works under the Root paradigm. There are those who believe that the orthosis made from a foot casted in neutral position will push the foot toward neutral position (many believe that it will actually put the foot in neutral position.) And there are those who will believe that supporting the forefoot to rearfoot deformity is how an orthotic works its magic. Note: there is no mention of force in either of these theories. They are directed at changing position and the hope is that changing the position will fix the problem. Regardless, a goal under Root theory is to balance the forefoot to rearfoot deformity that is seen in the measurements.

When I use tissue stress, I model the injured structure and then apply orthotic modifications that I believe will reduce stress on the injured structure. For example, if there is a foot with 1st MPJ pathology that I believed is caused by high medial forefoot loads I will try and shift load to the lateral forefoot. If there is eversion range of motion available, I will make the orthosis have an intrinsic forefoot valgus correction, even if I measure a forefoot varus in the cast. (I will shape the heel cup to get the effect I want there.) So, I am using a Root paradigm tool (intrinsic forefoot valgus post.), but I'm using a different logic in my choice of that tool.

This is my point. Tissue stress is different than Root because the reasons for choosing an orthotic modification are different. Yes, both paradigms can use the same tools. I believe that we should discard the notions of "an orthosis pushes a foot toward because it was made from a neutral position cast, and the notion that an orthosis supports a deformity that cannot be measured accurately. Instead of making the heel bisection of the cast vertical, most of the time, we can choose to modify the heel cup of the orthosis based on where the STJ axis is. Under the Root paradigm, the vertical heel was the most stable position. So, if you start adding medial or lateral heel skives to an orthotic, are you no longer using the Root paradigm? Are you now using tissue stress, whether you think so or not. Root mostly talked about changing the position to change the forces. With tissue stress we are changing the forces to change the stress and not necessarily the position. This is a different approach.

Eric

 

Look at it say, what it is: what you are attempting to measure is an angular relationship between the metarsal heads when an unknown magnitude of dorsifexion force is applied to the 5th and maybe the 4th metarsals such that the metatarsal heads are highly unlikely to form a linear plane from the 5th to 1st metarsal head and a line drawn on the back of the heel which itself has questionable validity and reliability. No problems here then?

 

If all one has is a hammer, then the world looks like a nail. And as long as there are those willing to pay hard earned money to hear lectures from people that can't discern between flexion and extensor contractures while believing they have the answers on biomechanics, then they will make it as difficult as they can, while demeaning those that argue otherwise.

 

There are a couple of interesting comments on the Podiatry Today website at the end of my article. In addition, I wrote a response to one of the comments today.

Anyone else care to comment on my article on the Podiatry Today website?

 

Kevin wrote the STJ axis palpation technique. Protocol from that examination technique. If the axis is more medially deviated than one standard deviation from the mean position then you use a medial heel skive. Lateral heel skive when the axis is lateral.

I've written here on the arena about maximum eversion height. If you want to increase lateral load, you evert the forefoot with an intrinsic forefoot valgus post, but you don't make the post larger than the foot has eversion range of motion.

True we haven't written a book on the prescription protocol. But we have written what to do.

Eric

 

OK, Kevin, read your article before putting my two bits in. I think a better title for the article should be, "Understanding Tissue Stress Principles Enhance Orthotic Prescriptions."

There is one outright error in the article. You state that viscoelastic "means that all the body's tissues will deform under load with the amount of defomation depending on the magnitude of the loading force." This is the definition of elastic deformation. Viscoelasticity is the when Young's modulus is different according to the rate of deformation. This accounts for creep and relaxation (why night splints work).

I'm sorry, after all these years of people espousing a new "Tissue Stress Theory" I'm having a tough time buying that this is a new theory. I see the study of tissue mechanics as a fundamental part of the biomechanics. I was markedly influenced by the book Tendinitis, Its Etiology and Treatment by Curwin and Stanish, c.1984. I was incorporating these principles into my practice before you graduated from residency. Tissue mechanics principles were part of my total teaching package from the moment I entered teaching in 1987. Understanding the concept of viscoelasticity, tells us that rate of pronation is as important as degree of pronation. It is unfortunate that most podiatric biomechanics texts have done such a poor job of teaching basic tissue mechanics and showing how to incorporate those principles. I believe that Paul Scherer's book on foot symptoms guiding us to better orthotic prescription is a good example of better incorporation of the tissue mechanics principles.

I find in your article some very subtle straw-man arguments. You seem to present Root as a one string dogmatic approach to all foot problems. You take the attitude that the only purpose of the Root orthotic is to push the STJ to neutral position and to lock the MTJ. I suppose that is all that many people remember. However I know that you remember that Root discussed many pathologies that should not be treated with STJ neutral orthotics. For example he taught that congenital Achilles tightness, contenital ileo-psoas contracture, and peroneal spastic flatfeet should not be treated with neutral orthotics, but instead pronated orthotics. I find it interesting that Root was quite enthusiastic in helping Rich Blake develop his inverted orthotic. He encouraged innovation and improvement. Fortunately I was raised with a father who believed that Root was basically right, but there are many ways of improvement and refinement. So you may say that I'm really not a Root disciple but a disciple of my own father who was always trying to improve on Root.

One of the problems with using tissue stress is that it has no plans to be quantitative nor predictive. Root envisioned a world of quantitation and prediction of pathology which would lead to prevention rather than just treatment of pathology. The development of link segment modeling to determine the moments around the joints is absolutely necessary to fully take the next real step, and I appreciate those who are now breaking the foot into individual links. I do agree that those who believe that Root was the beginning and the end are destroying the vision that Mert had. Sometimes I think of Mert doing for podiatry what Gene Roddenberry did for astrophysics. He wanted to inspire others to carry things forward. Remember that Root stated in 1994 at the first Weed seminar he was surprised that his 1977 text had lasted as long as it had, that he expected it to be antiquated by 1982.

So, we'll have a lot to talk about in Vancouver next week. Two days just doesn't seem to be long enough.

Best wishes,
Daryl