Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?

Daryl:

Thanks for your comments. I believe we have gone around this stump many, many times before. Therefore I will keep my comments brief.

What I remember being taught at CCPM in biomechanics and from my attending many of Dr. Root's lectures, which I now call "Root Theory", was a very specific protocol on how to prescribe foot orthoses. It is possible that if Mert Root lived longer, he would have modified the way he thought foot orthoses should be prescribed. Maybe Mert Root would have invented the medial heel skive, or lateral heel skive. Maybe Mert Root would have started encouraging putting forefoot extensions on foot orthoses. Maybe Mert Root wouldn't need Rich Blake to teach him about how well his inverted orthosis worked at treating runners versus Root's standard vertically balanced foot orthosis that Root taught should be made for most "foot deformities". However, Mert Root didn't live that long or do any of those things. I know. I was there. I taught his material to students and went to his seminars with his followers. Let's accurately report history, not change it as time goes on.

Please let's keep the discussion to what actually happened and what was taught to generations of podiatry students and podiatrists. Let's not speculate about an individual who is worshiped by many and then imagine what would have happened or what they thought he wished would have happened if he had lived many more years. That is not science.

Looking forward to Vancouver.:drinks

 

Did I miss something? Has Kevin quantified what one standard deviation is?

As those who have heard me speak over the last few years (I haven't put this in writing) have heard me talk about two types of MDSTJA. I call them type I and type II. Type I has a normal location at the posterior aspect of the calcaneus, but a high deviation from the sagittal plane. Type II has a medial location at the posterior aspect of the calcaneus and a normal angulation with the sagittal plane. The question is, which of these types of MDSTJA does Kevin refer to in defining what a standard deviation is? It is important to define these two types of MDSTA when considering flat foot surgery. They require different types of procedures.

Daryl

 

To all of you that have patiently waited for the article to be released...thank you.

http://www.podiatrym.com/Current_Issue2.cfm?id=1632

 

Jeff:

After all this debate, I thought I owed you an explanation about this article. The editors of Podiatry Today Magazine asked me to write this article for the April 2015 issue of Podiatry Today back at the end of 2014 after I suggested that such an article might be worthy of inclusion in their 2015 cover articles. The editors of Podiatry Today like controversial articles so they wanted my article to stir up discussion. I wrote the article with the idea to stir up some controversy and discussion. It seems, so far, that the article has produced some good discussion which is exactly what Podiatry Today, and myself, wanted from the article: Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?

As you know, here in the US, interest in biomechanics is dying within the podiatric profession since the increasing emphasis on surgery at our podiatric medical institutions and podiatric residencies has largely reduced the time of exposure of podiatry students and residents to biomechanics and foot orthosis therapy. Because of this, at every opportunity I am offered, I try to write and/or lecture to podiatry students, podiatry residents and podiatrists on biomechanics topics, in an attempt to increase the level of interest in biomechanics and foot orthosis therapy within my, and your father's, profession. With my current article, I was hoping to stimulate more interest in biomechanics and foot orthosis therapy within the US podiatric profession by producing a controversial topic that challenged some previously held beliefs. I don't know if the article accomplished that goal, but at least it appears that over 1,900 people have read the article, now about a week after it was placed online.

I agree with you, Jeff, that Tissue Stress Theory is imperfect. I wish it was a perfect, fully developed theory that explained everything, but it isn't. In fact, many of your comments about its imperfections hit the nail squarely on the head and, believe me, I already know about them. Eric Fuller and I, in our chapter in Albert and Curran's book (which we actually finished writing in May 2004, or about 11 years ago) had many long discussions about Tissue Stress Theory. We felt that there was so much more to discuss when we wrote the chapter but, at 60 pages already, we couldn't make it any longer, even though we wanted to. We left out detailed discussions on examination techniques and, instead, tried to focus on theory, concepts and provide a few examples of treatment using Tissue Stress Theory. I like the chapter as it is, but it certainly isn't the last word on the subject (Fuller EA, Kirby KA: Subtalar joint equilibrium and tissue stress approach to biomechanical therapy of the foot and lower extremity. In Albert SF, Curran SA (eds): Biomechanics of the Lower Extremity: Theory and Practice, Volume 1. Bipedmed, LLC, Denver, 2013, pp. 205-264).

Simon Spooner and I have also had many discussions on Tissue Stress Theory. Simon has many good ideas that I have learned a great deal in my discussions with him. In addition, his lectures are always very educational, thought-provoking and entertaining. I have probably argued more about biomechanics topics with Simon over the past 15 years than anyone else on this planet. However, I don't know where I would be without his valuable input into my thinking process.

One thing that Simon and I don't always agree on is the value of the foot and lower extremity measurements that Dr. Root and colleagues taught and wrote about. I think they have more value than Simon does, but I think this reflects my training with Ron Valmassy, Chris Smith, John Weed, John Marczalec, Bill Sanner, Les Jones and Rich Blake at CCPM and also reflects Simon's independent thinking process. I think the Root et al measurements help me better assess the feet that I see. However, I'm not so sure that I can communicate with others well on how a foot is structured using these measurements due to the large errors between clinicians when using the Root et al measurement system.

I agree with you, Jeff, that we need to have a way of measuring the basic structure of the foot and lower extremity and don't think we should eliminate Dr. Root and colleague's ideas on foot and lower extremity measurement. However, they do definitely need improvements or new measurements need to be developed.

I also don't think we need to stop teaching the idea of subtalar joint (STJ) neutral position since I find it a valuable idea when discussing and teaching foot and lower extremity biomechanics with students and residents, even though it does have some problems associated with it. I just wish there was better reliability in all these measurements.

From what I see now, nearly none of the third year surgical residents I train in my practice from Kaiser Sacramento have been well-trained at performing foot and lower extremity measurements, compared to the surgery residents I trained 20-25 years ago. I don't think this is a positive thing and makes me worry very much about the future of biomechanics and foot orthosis therapy here in the US since I probably won't be around to train them any more 10 years from now in my practice.

As I've told you many times publicly on this forum, and privately in our personal discussions, I think your father, Merton Root, and his colleagues, John Weed, were great men. Drs. Root and Weed, along with Bill Orien, did more for podiatric biomechanics than any group of men in history, to my knowledge. I never felt that they wanted podiatric biomechanics knowledge to stop with the writings of their books. But rather, from what I heard and observed from them over the years, they wanted others to build on what they had already accomplished and discovered.

And now, in my 30th year of practice and 31st year of teaching foot and lower extremity biomechanics and foot orthosis therapy, I feel that I have been doing exactly what Drs. Root and Weed had taught me to do. I have been simply exploring and presenting alternative ideas on foot and lower extremity biomechanics and foot orthosis therapy over the past three decades since it is has been my hope that these new ideas, new tests, and new techniques will provide younger podiatrists increased knowledge that will allow them to make further improvements in theory, clinical examination techniques and tests, and foot orthosis modifications to achieve my goal of improving the lives of more or our patients. Nothing more, nothing less.

Hope this explains myself better. Looking forward to seeing you in Vancouver at the PFOLA meeting next week. I think you'll enjoy my lecture on "History and Evolution of Foot and Lower Extremity Biomechanics and Foot Orthoses". Your father plays a prominent role within my lecture.:drinks

 

Only question I have is: How do you know that the blue rectangle is always lined up with the green rectangle? What if the calcaneus is translated laterally?

Thanks
Daryl

 

Why does it have to be Kevin to define what the standard deviation. The standard deviation of variation of the STJ axis is in the literature. I don't have access to my CoP paper at the moment, but the article is cited in there. It may have been in Inman's book. Daryl, I was trying to find a way to describe what I do. When I assess STJ axis position, I get a sense of whether I feel the axis is Extremely deviated from average, moderately deviated from average, or close to average. It's qualitative and I needed a way to describe what close to average is.

Eric

 

Matthew:

I moved your new article on The Myth of Growing Pains to a new thread so that we can discuss the subject of growing pains in it's own thread. http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=102039

By the way, I read your article and I think it has many good ideas in it that hopefully will stimulate further research on this important subject.

Good job to you and Doug!:drinks

 

Oh! it's that old standard deviation you're talking about. I thought that there had been some new numbers put up to define the average and standard deviation.

BTW - how do you document the STJ axis location in your medical records? Do you put any numbers to it? It would be nice if we had a stard nomenclature to recommend to ABPM or the Federation.

Thanks
Daryl

 

It isn't- I made the simplest model possible to make it easy to understand for those attempting to get their heads around the concepts. That said we could do away with the rectangles altogether and just discuss the joint line, which of course isn't a straight line in-Vivo either. However, this is a model, so I've simplified things to make it easier.

I'm away with my family at the moment since my daughter is racing her BMX at a national meeting this weekend. I'll draw it out with offset when I return, Daryl.

 

Daryl:

The paper I coauthored in the Journal of Biomechanics back in 1992 along with members of the Department of Mechanical Engineering at the University of California at Davis, and Dr. David Jenkins, described the method by which we quantified the subtalar joint axis plantar projection in our research project which studied the lower extremity measurement parameters which correlated most closely to knee joint loads during seated cycling (Ruby P, Hull ML, Kirby KA, Jenkins DW: The effect of lower-limb anatomy on knee loads during seated cycling. J Biomech, 25 (10): 1195-1207, 1992).

Here is a diagram of the quantification method for STJ axis location, which I created 24 years ago, from our cycling research paper which used a pedal "force plate" to determine the pedal reaction force vector in the twenty three cyclists we measured and studied.

 

Daryl:

I like your idea of classifying medially deviated subtalar joint axes. It's something I've recognized for many years but have never written on. Maybe we can discuss it some in Vancouver next week since it may be worthy of a paper.:drinks

 

It was picture 4 I was interested in seeing. The others are standard. So you document the angle theta as being the deviation from your long axis of the foot? and then you the point where it crosses the long axis of the foot in terms of the truncated length of the foot. Those two measurements would certainly work.

I personally document theta, but then put a qualitative description of where it crosses the metatarsal head region, or it went medial to the first metatarsal head where it crosses the medial outline of the foot. My purpose was to see if there is a consensus out there. Like I said, it would be nice for an organization like ABPM, or i-fab or some other official group to issue a recommendation for documentation that payers could then rely on.

I'm sorry I don't have this particular article of yours, but will grab it.

Thanks
Daryl

 

I disagree with the predictive part of the comment. So, to be predictive you have to have a measurement that is repeatable across examiners. The measure has to be show to be correlated with pathology. The treatment for the predicted condition has to be shown to be effective. There was a study showing STJ axis location was repeatable. The theory predicts that people with a highly medially positioned STJ axis will be much more likely to develop PT tendon dysfunction. We could prescribe orthoses for people with highly medially positioned STJ axes with medial heel skives before they develop PT dysfunction.

I am not aware of any pathology predicted by Neutral position theory. Daryl, you and I will have agree to disagree on the ability to accurately measure forefoot to rearfoot relationship. We can even choose to ignore that problem and there are still other problems. Theoretically, what pathology is predicted by forefoot to rearfoot relationship? What pathology is predicted by heel bisection position in stance? So, if we wanted to prevent both lateral ankle instability and posterior tibial tendon dysfunction would we use the same neutral position theory protocol for writing the prescription for the orthotic for both conditions? I think the way that the different paradigms would be used predictively shows that they are distinctly different paradigms.

Eric

 

As I said in the post...

I will put a lateral or medial in front of extreme or moderate.

Eric

 

I'll send it to you, check you inbox.

 

My concern is related with the fact that I'm not sure the long axis of the foot is always the best reference. This axis, when designing shoe lasts, is defined as a line which passes through the most posterior point of the plantar contour of the footprint and the tip of the second toe -as it can see from Kevin's diagram also. This comes from an unsuccessful experience with designing a shoe last for a C-shaped foot [a Charcot-Marie-Tooth foot]. Traditional reference system for the lasts is based on this long axis of the foot which, in the case of C-shaped feet, doesn't work for me. One reason could be that the most posterior point doesn't have the same position as in the case of a straight foot. Attached it is an article and an image which are explaining better this problem. The question is: it remains the definition of the theta angle the same no matter how the foot shape is ?

Sincerely,
Daniel

 

Dan,

Thanks kindly for the article.

The long axis of th foot has always been a tricky thing due to the wide variation in the degrees of forefoot adductus. That's why, when I wrote my 1992 paper, I didn't use the long axis of the foot, I used only the plantar bisection of the heel as my X axis to define the sagittal plane direction, and I measured the STJ axis deviation from this axis. I used theta as the deviation from the transverse plane and phi as the deviation from the sagittal plane. I used the posterior bisector of the heel as the Z axis, and then the Y axis was the perpendicular to these two axes, using the right hand rule for thed right foot.

One of the things I heard Mert Root lecture about many years ago was not wearing too straight of last for an adducted forefoot. So I stared looking at this, and started trying to match the adduction of the forefoot of the shoe with the foot. I put a foot on a piece of paper, and outline it, when the STJ is in neutral, and then draw two lines, one is the long bisector of the heel and one the line from the 2nd toe to the midarch, and mesure this line. I tell the patient to look for a shoe that matches this angle. People find much greater comfort with their shoes when they do this. I haven't done a formal study on this, it just made common sense, and the clinical results seem to match.

Best to you,
Daryl

 

Daryl, why do you choose to do the outline in neutral STJ position as opposed to resting STJ position? Wouldn't you get a better shoe fit in resting position?

Eric

 

Kevin,

Sorry for the delayed reply. I have not had time the past two days to contribute to this ongoing discussion. We both agree that there are aspects of Root theory that need to be challenged and ideally replaced with a more accurate model of function or treatment. I can appreciate why you feel the need to stir things up. Many podiatrists give very little thought about the cause of the patient's pathology and simply use somewhat generic type orthoses with the expectation that the devices will solve the patient's problem, which in many case they do. Unfortunately we also know that there are too many treatment failures as a result of using an approach that lacks an adequate evaluation of the source of pathological forces or fails to consider how to best address these pathological forces with the orthotic prescription.

Both Simon and Eric have stated that they make their own custom orthoses. As a result, they can treat their patients in a different manner than those who order their devices from a lab. In the lab environment we need concise standards, techniques and terms in order for the practitioner to be able to convey to the lab exactly how they want the device manufactured. For many labs, including mine, this means using heel bisections and other generally accepted techniques to orient the cast and to determine the amount of forefoot and rearfoot correction that will be placed in the cast and the resulting device. These and other prescription factors then determine the nature of the forces that will act on the foot in an effort to reduce or alter the patient's pathological forces.

Part of my frustration in these PA discussions comes from the suggestion that we abandon these examination and orthotic fabrication techniques like heel bisection without offering a practical alternative to those practitioner who use commercial labs. I believe there are many reasons why biomechanics may be dying within the podiatric profession. Perhaps controversy will help to inspire further research or motivate the profession to work to develop a more accurate and efficient approach to treatment. I have witnessed a lot of change in how my lab functions over the years, so we are not stuck in some 1970's or 80's version of biomechanics or orthotic therapy. However, I will continue to argue in favor of the methods that I have seen create great treatment success until I see better alternatives, like those that have resulted in the changes in how my lab functions over time.

Jeff

 

There are positives and negatives for both methods. It's easier to do with the STJ neutral, and then the shoe also assists a little in preventing too much forefoot abduction. Most of the time (not always) I want a little bit of error on the adduction rather than the abduction side. Try it yourself and then we can compare notes.

Daryl

 

Hello Dr. Phillips,

I've tried a similar thing when I've started to design a last for a C-shaped foot [see fig.1]. I've found general information about C-shaped lasts, especially related with sport shoes but not technical details about principles involved in the design of this kind of lasts. The problem is somehow similar with difference between some indices calculated based on the footprint and Foot posture index : modifying only the last bottom doesn't imply a proper modification of the 3d shape of the last in order to obtain a "perfect" fit. The intersection between long bisector of the heel with the line from 2nd toe to the midarch gives us a point which could be considered a "center of the rotation" of the forefoot relative to rearfoot. But this point should be the intersection between an axis and the transverse plane. The question is: which is the orientation of this axis ? Could be related with midtarsal joint ? I think knowing this orientation could be of help when modifying lasts using CAD solutions for designing C-shaped lasts [see fig.2]

Sincerely,

Daniel

 

It is important to think about how our "treatment" (shoe recommendation) is going to push on the foot to create our desired change in moments applied to the foot. An adducted shoe will tend to push from lateral to medial at the distal lateral aspect of the foot. Specifically at the the 5th toe where we commonly see that corn a lot of patients complain about. I've been noticing a trend that you tend to see that corn be a problem in feet with more abduction of the forefoot on the rearfoot. It would be nice to do the study to see if foot abduction was related to the complaint at the dorsal lateral aspect of the fifth toe.

I'm trying to envision how you do the tracing in such a way that it is easier in neutral position. Do you do the tracing weight bearing?

Daryl, would you do the tracing in resting STJ position if the patient complained of peroneal tendonditis?

Eric

 

Having looked at a lot of positive casts of feet in my life, I think we need to differentiate those with an adducted forefoot that demonstrate a very laterally prominent styloid process of the 5th met from those that don't. The laterally prominent styoild process often needs to be accommodated in the orthotic device but this also causes the OD to be wider in the styloid area, making shoe fit even more difficult.

Although the bulk of the forefoot adduction probably originates at the MTJ, there seems to be adaptive changes at the 5th met-cuboid joint that contributes to the enlargement and prominence of the styloid process.

Jeff

 

Dear Jeff,
Are you taking in consideration the shape of shoe lasts in this case ? Do you recommend C-shaped lasts in these situations ?
Sincerely,
Daniel

 

Googled withstand. Standard definition applies.

with·stand
wiTHˈstand,wiT͟Hˈstand/Submit
verb
remain undamaged or unaffected by; resist.
"the structure had been designed to withstand winds of more than 100 mph"

There is also a discussion of materials testing in the chapter that illustrates what we mean by withstand.

Eric

 

Daniel,

Yes I do because if you don't, the shoe will adduct the orthosis within the shoe because the orthosis has a C shaped lateral border.

Jeff

 

If I casted the patient with the STJ neutral, then yes!. I don't want the shoe trying to abduct the forefoot against the rearfoot more than my orthotic is designed to do. Most of the time, the secret to treating peroneus brevis tendinitis is to pronate the LAMTJ. Sometimes you can do it only with a felt everted forefoot onlay added to the insole of the shoe. Only if I had to cast the patient with the STJ pronated would I then try to fit the patient into a shoe that had the shape of their pronated STJ+OAMTJ. Yes, there are cases, but most are not.

Again, there's nothing like doing an exam on a patient before I decide exactly what to do.

Daryl

Again, start working with patients and see what you find out before you start nit-picking every possible situation. Try it with your friends and family first. I have found that this little system works with a vast majority of people, whether they are seeing their podiatrist or not for any foot complaints.

Jeff, If you're reading this, this would be a sample of something that I discussed with you doing in a simple study.

 

You bring up several points in a short post. And I am not just nitpicking. The title of the thread implies that we should be discussing the difference between tissue stress and neutral position theory. I'm trying to see what exactly the logic is in neutral position theory. If we can state that logic and the logic of neutral position theory then we can help discern if there is a difference. If there is a difference we can also discern if one theory is more plausible than the other.

I still don't understand how you draw your picture to compare with the shoe. That is why I'm having a hard time seeing why it is easier to draw the picture when the foot is in neutral position. Is this a weightbearing or non weightbearing measurement?

I would agree that forces that pronate the midtarsal joint would tend to help peroneus brevis tendonitis. I have my explanation of why that would be. I'm interested in why you think pronating the midtarsal joint would improve peroneal tendonitis. What is the explanation under neutral position theory?

So, if a patient's problem is peroneus brevis tendonitis, and if a shoe that abducts the forefoot on the rearfoot does increase pronation moment at the STJ, then why would a shoe that abducted the forefoot on the rearfoot be worse than a shoe that did not?

Eric

 

It appears to me that you're still making biomechanics a lot more complicated than it should be. Sure, I can see value in furthering our knowledge of "how things work", but not at the expense of leaving 90% of those in our profession behind in order to prove your correctness. By the sentence you/I referenced above, one would get the impression that everyone with a forefoot varus deformity, for example, would either have stress fractures and/or walking around with a continual limp. We know that is not the case.

What Podiatrists world-wide need and want to know, is a consensus opinion on:

1) Making biomechanics easier to understand...more palatable.

2) How to write prescriptions more accurately so re-order cost expense is minimized.

3) Agreement among the academics on how to best deal with 1 and 2 above.

4) More problem solving research to direct the profession on how best to treat the problems we face in our offices/clinics, with the end result resulting in successfully treating patients and furthering the cause of Podiatry.

I see nothing here that accomplishes those goals. Instead of attempting to re-invent the mouse trap, we should be focusing on simplifying the task of successful treatments. When I see/read page after page, post after post of those arguing their points, it means we're failing our patients by confusing those in our profession. If your "new" theory was solid, easy to understand/comprehend and allowed for widespread usefulness by those in our profession, there wouldn't be the need for hundreds of posts attempting to prove that point.

 

I have to say that I really think this has been a very good discussion.

Kevin, forgive me for paraphrasing your response so much but could not agree more. Your article has stimulated the lengthy debate and I really believe this has been one of the most useful I have seen for a long time.

I also agree with your comments on the limitations of the model, the potential relevance of structural alignment, the need for reliable measures and the need for an understanding of what was meant by STJ neutral in addition to the limitations and the need to move our thinking forward.

I would add that I suspect most people agree with a tissue stress approach, it is the method of achieving the tissue stress relief that still causes much of the discussion. Perhaps we could consider an approach where we agree tissue stress relief is the way forward, factoring in the need to try and predict / prevent negative effects and then evaluate the differing approaches there are to achieving the aim.

Agreed and, like Kevin I believe that some of the structural alignments have a role to play.

So, just so I am sure I am responding accurately to the concept you are relaying, as you increase the degree of posting, the axis will move more medially as does the CoP. If this exceeds the central structural 1/3 of the start position, this will tilt the balance such that we move outside the ZOOS.

This is effectively the concept I have considered when looking at how pressure patterns will alter with increased medial / lateral loading. If for instance, we wanted to move the CoP medially, we can apply a medial load up to a certain point, Beyond this, either the intrinsic factors will start to overload or we will have a physical shift of the position of the foot such that the CoP will now start to move laterally again (or more) accurately, not transfer medially during dynamic function.

This provides predictive modelling but how do you determine how much post is required to cause that without considering the foot and, as importantly, what is happening proximally to the foot which will also direct motion?

There is so much in this post and again is a real point of clarity. In particular the ability to reduce stress but by differing means, as I alluded to above. Divorce tissue stress from SALRE / Root etc., then we are not arguing about tissue stress but the means to the end.

Out of interest, you used the 1st MTPJ example – how do you determine that the problem is caused by increased load? I ask, because from your wording, there will be situations where you do not feel this to be the case?

Eric, do you have the reference for the repeatability study?

Another question: If we can accept that, as the foot moves, the position of the many axes within the foot (including STJ) alters, then deformity will have the same effect.

Given that many people with TPD have ligamentous changes as well, this will have a profound effect on axis location. Thus, is it the deviated axis that causes the TPD or vice versa? I am unaware of any prospective studies that have followed people with medially deviated axes and seen how many developed TPD but that does not mean they are not out there.

Out of interest, if you had a patient with TPD symptoms, a medially deviated STJ axis with adequate rearfoot motion but OA of the midfoot such that the forefoot was fixed in inversion, how would you manage that foot with an orthosis? Just interested and with a wry smile, because I almost said, how would you control that foot…..

 

Trevor and Colleagues:

I hope that you know, Trevor, that I respect your opinion very much since I know your clinical experience is considerable and that you also stay current with all the latest developments in mechanically-based treatments for the foot and lower extremity. It is good to see that we can agree more with each other and possibly see a way forward to improve our methods of foot orthosis prescription.

In addition, I believe you have hit the nail squarely on the head with your statement which I will quote again:

If we can arrive at a consensus that relieving tissue stress on injured structures should be the primary goal for foot orthosis therapy with the additional goal being that the foot orthosis therapy instituted for the patient does not cause pathological stress on other structural components of the foot and lower extremity, then I think this will certainly allow us to start to move forward together. I think that we can all agree that if we can put our heads together to come up with a model of evaluation and treatment that accomplishes the goals of Tissue Stress Theory without making it too esoteric and difficult for the average podiatrist to understand, then then this would, indeed, be a very positive step forward.

Matt Sciaroni's last post struck a chord with me when he wrote:

Maybe Matt is right....by our using modern engineering and biomechanics terminology to teach tissue stress principles we may actually be "turning off" many podiatrists that want to use tissue stress principles in their practices. My thought has always been to try to teach these modern engineering and biomechanics concepts to podiatrists so that they can then better understand the treatment principles of Tissue Stress Theory. However, maybe I've been wrong and there is a better way to teach these principles in a fashion that facilitates the transfer of knowledge more effectively.

I know that getting someone to understand concepts such as forces, moments, stress, strain, elastic modulus, modelling and viscoelasticity may be too much to ask of a podiatrist that doesn't have a strong background in physics and engineering. I don't know what the answer is but, certainly, I think Matt's point is valid.

I will give this all some consideration in the coming weeks, especially when I attend the PFOLA meeting in Vancouver next week. I will listen to the lectures and ask those attending how they feel they should be taught in order to better understand the more advanced biomechanics and engineering concepts that may be required to fully utilize the concepts of Tissue Stress Theory. There is always room for improvement in anything we teach and I'm open to new ideas if the end-goal of better patient care is the result.

I would especially be interested in everyone else's opinions as to how these tissue stress concepts should be taught or have been taught in the past. Are we teaching them at the best level? Are they too simplified, too complex or just right? Any suggestions for improvements?

Thanks to everyone for a cordial, educational and meaningful debate on this very important subject. It's been one of the best discussions we have had in years.:drinks

 

Trevor, I agree, this has been a very good discussion. You asked several questions. I have time for one now.

Here is another difference between tissue stress and neutral position biomechanics. In neutral position biomechanics the assuemed starting position is neutral position of the STJ and a deformity will cause movement away from neutral position.

In tissue stress we look at the foot where it is in stance. So, in stance, the bones won't be moving. The effect of the deformity has already taken place. Then we look at the forces applied to the foot in stance. For example a partially compensated varus foot will have a high load on the lateral forefoot and a low load on the medial forefoot. In this situation, the vast majority of the time there will be a fairly high pronation moment on the foot because of a lateral location of the center of pressure. So, the deformity is having an effect on the moments applied to the foot, but there is no range of motion of the STJ available to allow the STJ axis to move.

Eric

 

Thanks for the comments Kevin. I think divorcing tissue stress relief from the method allows us to evaluate different methods and thus develop concepts. I started my contribution to this debate noting that I had not articulated my concerns regarding tissue stress relief well. The debate has crystallised this for me – simply relieving stress in itself may not be a good thing and needs the qualification of minimising the negative effects and whatever approach you take to achieving the relief, you need to be able to try to estimate the general effect. It has also just occurred to me that when I have presented and provided a brief over view of the varying concepts / approaches, I have always separated SALRE and tissue stress relief just because of what we have discussed above. Not because it was particularly smart thinking but more because the tissue stress concepts were published post many of the management approaches. Your first sentence above summarises that well.

In terms of teaching, I could not agree more, the principles are key. In order for people to be able to employ concepts and review practice, they often have to be able to apply this within the frame work of their clinical experience / comfort zone. I wonder if explaining how the structural alignments that people are familiar with i.e. tibial varum, partially compensated rearfoot varus etc. would result in increased forces/moments in certain areas / on certain structures etc., would help to develop the concept (see below). This can then be developed to look at the differing concepts. Outlining the strengths and weaknesses of the varying concepts will then help people be more appraise more critically.

I also wonder if we need to consider modifying the name applied to the approach. It is clear that your work on STJ axis location / equilibrium has been pivotal in the development. However, as Daryl has noted, the location of the stj axis to the other planes is important, we have not discussed the ankle axis and relevance to function, there are instances in gait that the rearfoot is not in ground contact, the midtarsal and forefoot axes are significant, the position of the axes change through stance etc. Rotational equilibrium on its own does not seem sufficient. I suspect that, if what you have suggested above can be achieved, the refinements of the process may lead to a new descriptive for an approach to achieving tissue stress relief which can then be evaluated.

Just for clarification, when I referred to deformity here, I was not talking about the Rootian type deformity, more the pathological problem such as the adult acquired flat foot, even the case of someone with trauma to the ATFL will alter the range and direction of ankle and thus rearfoot motion so effecting any axis position.

That said, I assume by your comments that you feel that structural alignment can contribute to loading pattern and the example you have provided above is exactly what I was referring to in the teaching aspect in my response to Kevin above. Use a positional alignment most can understand to explain the principles. If I take this example one step further, we can demonstrate how range of motion is relevant to function. The partially compensated rearfoot varus has, by the theoretical definition, utilised its available rearfoot motion, hence the lateral load / pronation moment. If however, the foot had more motion and greater rearfoot pronation can occur, the location of those forces will alter and thus the moments will alter. It then becomes easier to explain the effect on different structures.

One final thing I need to clarify with you is the last paragraph – I assume when you say the tissue stress relief applies to stance and the bones are not moving, this is conceptual to try and understand the principles? This is actually a good reason why we should separate tissue stress relief from the assessment / management approach. As I allude to in my response to Kevin above, the dynamic factors are key as I know you are aware all too well.

It is interesting that we have not considered sagittal function. If, for example, we can agree that the maximum foot contact area should occur around the middle of midstance (i.e. when the two medial malleoli are level), then one would expect the CoP to be somewhere near the middle of the foot.

Whilst we have discussed medial / lateral deviation, what about anterior / posterior? I often see a forward shift which indicates some sagittal alterations which, in turn, will affect the pronation / supination moments but also my approach to management. I accept you may have discussed this on the arena before and apologise if this is the case.

The golf course beckons.

 

Simon

Considering Kevin’s comments about making things easier to understand, I wanted to see if there was a way of describing what you discuss here. I therefore did a quick search and started with the rule of thirds – actually, this is a term used in photography which, in itself is interesting and will help my daughter with her graphics GCSE, so that was a bonus.

To get information on your topic, required a search on the middle third rule for anyone else interested.

So from what I can see (and happy for you to correct me where appropriate), this has been applied in architecture because materials such as concrete perform poorly when pulled / or stretched (i.e. placed under tension).

Thus, concrete needs to be compressed (the opposite to tension). If the resultant force is within the middle third, there will be compression. As the resultant moves out of this zone and reaches your figure 4, there will be tension at the opposite side (laterally in this case). Now, as we are not made of concrete but have many tissues which are able to withstand tension (concrete has poor tensile strength), these structures (skin, ligament, tendon and bone) will all have increased tension applied a percentage of which would be friction at the skin / orthosis interface.

Logically, they will be able to withstand some force outside of the middle one third and some tension may be beneficial but there will be a ‘failure’ point with injury / symptoms. The point at which this occurs will vary between individuals but also with the point of application of the resultant force. In the example you provide, this is the rearfoot post – if this is wide (i.e. traverses across the width of the heel) compared to narrow (i.e. is just on the medial side), the position of application and thus the resultant change.

Would this be an accurate interpretation of the process?

 

Kevin-thanks for the post, but let me expound on my points. It's not that Podiatrists are "turned off" to TST, but perhaps the concept has been made too unwieldy for real and prudent problem solving in our practices. The concepts of moments, stress, strain, viscoelasticity and forces are not beyond our comprehension, but how does your theory solve the problems we see in our practices and make our job easier? The sign of REAL intelligence, IMHO, is taking more complex problems and simplifying them for distribution to others. Consider that when you reassess the presentation of tissue stress. Further, consider how your approach differs from Root Theory in simplifying our task in our offices and then discuss that, in future presentations. For instance, I don't believe Root advocated the use of forefoot extensions to the orthotic, (how could be, given the paucity of materials during his time?), but now we\I seem to believe it is a worthy addition. I don't disparage Dr. Root for this, nor do I advocate dismissing his long held, time tested techniques...I simplify modify them to suit my patient's needs. As a 3rd gen doctor, I have been surrounded by physicians all my life, and one lesson that experience taught me is that docs tend to make medical conditions much more complicated than they really are. Perhaps this is the lesson I learned that allowed me to "see" through the dust to resolve the issue of GP/RLS. Just some thoughts.

 

Matt:

Thanks for the post. I believe that possibly the way forward here is to provide examples of specific orthosis prescription modifications used for each specific pathology seen in a podiatric office. Eric Fuller and I have been calling it the Tissue Stress approach for years. Paul Scherer, DPM, has instead been calling virtually the same concept Pathology Specific Orthoses in his relationship with Pro Lab.

Whatever the name used, the concept is the same. The orthosis should be modified to treat the specific anatomical structure which is injured. The orthosis should not specifically be modified to treat any measurable "foot deformity" that may, or may not, have any biomechanical relationship to the patient's specific symptoms.

In this regard, I did write a series of 13 newsletters several years ago that was published in my last book where I detailed the biomechanics and specific orthosis modifications I use to treat a variety of common pathologies including proximal plantar fasciitis, metatarsalgia, distal plantar fasciitis, plantar plate injuries, Morton's neuroma, posterior tibial tendon dysfunction, lateral-dorsal midfoot pain, tarsal tunnel syndrome, sinus tarsi syndrome, sesamoiditis, peroneal tendinopathy, knee osteoarthritis, patellofemoral pain syndrome (Kirby KA: Foot and Lower Extremity Biomechanics IV: Precision Intricast Newsletters, 2009-2013. Precision Intricast, Inc., Payson, AZ, 2014, pp. 81-108).

I believe that by teaching the treatment of one pathology at a time, using the concepts of how that pathology may have occurred, what abnormal forces/stresses likely caused the pathology and how the use of specific foot orthosis modifications may best reduce the pathological forces on the injured structure, that this may be a possible way forward...keeping it relatively simple and very practical for the clinician. I would be happy to send a few of these newsletters your way if you wanted to read them and see if you feel that I have done a satisfactory job at making the concepts we are trying to put forward here more practical and helpful for the clinician.

 

Trevor:

Thanks for the post.

Actually, what you are suggesting, Trevor, is something I have contemplated doing for the last few decades, but never got around to writing specifically about it. In other words, why shouldn't we be able to take the concepts taught by Root et al about specific "foot deformities" and then apply the more recent concepts of medial and lateral deviation of the subtalar joint (STJ) axis, Nester's moving axes of the midtarsal joint, joint stiffness and rotational equilibrium to try and "bridge the gap" between the Root et al theories and our more current thinking.

Certainly much of what Mert Root and his colleagues taught was very valuable but some of what they taught makes no sense when applying more recent scientific theories and research. Is it possible to somehow marry the concepts taught by Root et al with more newer biomechanical modelling concepts to make the theory even better? I think it can.

However, it will require a lot of work and will require many people to change some of their preconceived notions of how the foot works, but I believe it can be done. One of the problems with such a marriage of theories is the known inter-observer errors in the Root et al measurements including determining STJ neutral position, calcaneal bisections, forefoot to rearfoot relationship and ankle joint dorsiflexion, to name a few. This problem has led many experienced clinicians to simply abandon many of Root's measurements due to their known errors and try to come up with better ways of understanding foot function. I don't know if that is the best approach either.

I feel that we should be able to all accept the fact that such "deformities" do exist in some form or another since we all see a wide range of foot structure within our patient populations. If we can then come up with a more reliable and consistent method of measuring these structural variations in foot morphology [maybe using the maximally pronated STJ position as the reference position for STJ rotational position?], then possibly we can also correlate these structural variances to the ground reaction forces and their specific locations, magnitudes and temporal patterns relative to the joint axes that are the cause of many of the pathologies we see in our practices.

Anyway, Trevor, thanks for your thoughtful responses. You are making some very good points that, I believe, are helping us move forward in our mutual goal of providing better foot orthosis care to our patients.

 

Here are some comments taken from a 2006 thread on the subject of tissue stress which can be found at http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=1559:
I have bolded a few sentences to highlight them. It is interesting to see these nine year old comments and how they relate to this thread today. We can see some evolution in the Tissue Stress theory/thinking process but many of the fundamental concerns still exist. I believe that in order for podiatric biomechanics to progress, we must consider the ideal educational process for students. They must first have a good basic understanding of physics. They must have a good understanding of anatomy and physiology. They must be taught how the basic concepts (laws) of physics can be applied to the body and how living tissue might respond.

My son is finishing up this third year of biomedical engineering at a California University. His first two years were almost entirely dedicated to math, physics, chemistry, circuits and things other than anatomy and physiology. In other words, the engineering aspect of biomedical engineering is the foundation of his education. He could easily go into a different branch of engineering as a result of his foundation.

Do today's podiatry students have an adequate foundation in physics or do they get it in podiatry school? If not, Tissue Stress will have limited success. If so, then how should tissue stress be taught? Biomechanics is a branch of biomedical engineering. I see a dramatic difference in how biomedical engineering is taught as compared to biology or premed. If the podiatry education or pre-education path isn't aligned with biomechanics, then what does that say about the role of biomechanics in modern day podiatry schools?

What I do like about the recent discussions is the realization that we need to look at the success and failure of tissue stress and Root theory in an effort to find a better path forward.

Jeff

Kevin Kirby:

Craig Payne:

Kevin Kirby:

Adam (user name Berms):

Adam:

Simon Spooner:

Craig Payne:

Kevin Kirby:

Kevin Kirby:

Robert Isaacs:

 

I'm not too optimistic ! I don't see in the near future for the bioengineers to be directly implied in the clinical activity as the podiatrists are. If we are looking at some aspects of the characterization of this profession ( http://en.wikipedia.org/wiki/Biomedical_engineering ) as:
-...Much of the work in biomedical engineering consists of research and development, spanning a broad array of subfields ...
-...Clinical engineering is the branch of biomedical engineering dealing with the actual implementation of medical equipment and technologies in hospitals or other clinical settings...

then we'll see that its activity doesn't assume a direct contact with the patient. I don't see finite element analysis [FEA] studied in the podiatry school as I can't see an bio-engineer managing a foot pathology as a podiatrist!
Just studying physics, mechanics, math, chemistry,.... doesn't make you able to understand pathology. It should be studied that part of physics/mechanics which are of help in a treatment process. Which is that ? Some bright minds from podiatry and bioengineering schools should stay around the same table and define the intersection between these professions ! Otherwise, I think, there will not be any progress.
How many bioengineers are on Podiatry Arena ?
How many articles from bioengineering which can be of direct help in clinical practice can be mentioned here ?

Sincerely,
Daniel

 

Let's give an example of a study from bioengineering field, made on a healthy woman which "did not present congenital or acquired deformities of the feet or any other disability that might affect her gait " How this work should be read, understand and used in clinical practice ?
Sincerely,
Daniel