Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?

Nope, what we should be thinking about is that the positon and motion of the rearfoot might not be as significant in pathology as was once thought. Did you read the most recent meta-analyses on foot posture and it's relationship to pathology both in static stance and dynamic function?

We should also consider that foot orthoses DO NOT NECESSARILLY WORK BY ALTERING REARFOOT KINEMATICS.

You ludites can carry on in your dillusional states denying the science and attempting to flog your wares (see Kiper)... I got better things to do on a Saturday night.

 

Simon

Nope, what we should be thinking about is that the positon and motion of the rearfoot might not be as significant in pathology as was once thought

Herein lies the distorted thinking about biomechanics. POSITION& MOTION are NOT the issue in pathology (although it may be the direct cause in some cases). It is the INSTABILITY MOMENT (you know, like in “STJ moment”).

Combined with the various biomechanical data and individual architecture of the lower extremity human frame. Depending on where the person is biomechanically WEAK and vulnerable to repeated stress.

 

What the devil is an "instability moment"???

Dennis... The way you take technical terms and morph them into completely meaningless and fancy sounding language is hilarious. Probably impresses patients, but round here I promise you it has the opposite effect...

 

Griff

Dennis... The way you take technical terms and morph them into completely meaningless and fancy sounding language is hilarious. Probably impresses patients, but round here I promise you it has the opposite effect...

If you took my meaningless terms and thought more about it as a patient, you'd be a better doctor.

If you were a better doctor, you'd understand my meaningless terms.

 

Griff

What the devil is an "instability moment"???




As for an instability moment, how did you understand Dr Kirby article, where he described a STJ moment? What was he talking about?

 

Trevor:

I'm sitting at the airport getting ready to fly over the pond to your wonderful country, so I have a little free time to reply to some of your thoughtful comments.

After all is said and done, I do believe that structure is important and should be considered by anyone treating foot and lower extremity pathologies. I still use the Root measurements when examining my patients since I think, in my hands, they are good for screening patients as to joint ranges of motion, basic foot morphology and organizing my thoughts as to what is going on structurally within their foot and lower extremity. I also closely examine the patient to determine the anatomical structure that is injured, determine subtalar joint (STJ) axis location and also determine where the patients stands within their STJ range of motion in relaxed bipedal stance. Finally, the gait examination is very helpful at putting it all together and making certain there are no obvious gait abnormalities that could indicate muscle weaknesses, reduced joint range of motion, painful gait (antalgic) compensations or central nervous system (CNS) abnormalities.

Unlike you, I have never used in-shoe pressure analysis but certainly this technology seems like it could be helpful in some cases. Unfortunately, since my practice is so busy, and I have somewhat limited office space, there is no way I could use this technology regularly without significantly reducing the number of patients I see in a day and hiring more staff to run the machinery for me. It does look like a nice tool, but for my practice situation, it isn't worth the extra expense and time that I currently require to make my patients better.

Using the Tissue Stress Approach to foot orthosis therapy, I believe, is essential to providing our patients with the best conservative treatments available for their mechanically-based foot and lower extremity injuries. In reading the comments of many of those who are still infatuated with the teachings of Mert Root and colleagues in this thread, it appears to me that either they don't want to understand the biomechanics and engineering concepts that are required to fully comprehend the Tissue Stress Approach, or that they are just too old to learn any new tricks. Unfortunately, these individuals are all from my home country which I am not very proud of.

Certainly, if we are to move ahead as a profession, we must throw out the bad ideas and keep the good ideas, and not be so locked on to our past beliefs that we prevent ourselves from becoming better clinicians for our patients. I sincerely believe that some of the concepts and techniques that Root and colleagues championed are still useful and hopefully we can incorporate some of their techniques, along with the Tissue Stress Approach, to further improve the therapeutic effectiveness of foot orthosis therapy for our patients.

When I am in Manchester next week, I will be spending a full two days discussing the concepts of Tissue Stress with the other lecturers at Biomechanics Summer School 2015. It should be a great seminar and I'm greatly looking forward to it. I likewise had a great time lecturing with you a few years back at BSS 2011 and hope you will be able to attend the conference also. Thanks again, Trevor, for keeping this thread helpful and thoughtful, since I believe, other than the occasional nasty comments, this is one of the better threads we have had here on Podiatry Arena for quite a bit of time.:drinks

 

"I still use the Root measurements when examining my patients since I think, in my hands, they are good for screening patients as to joint ranges of motion, basic foot morphology and organizing my thoughts as to what is going on structurally within their foot and lower extremity."

Bingo. Again, Kevin answers his own question as the blog header.

 

We have anatomical and mathematical standards for our Rx options.
Standard forefoot width: We bisect the 1st interspace and the 1st met head in the sagittal plane. Our standard forefoot width is the mid point between these two anatomical landmarks. Wide=bisection of 1st met head, extra wide is 3/4 of the distance from the 1st met interspace to the tangent of the most medial aspect of the 1st met head, etc.

Our medial expansion extends to the 1st interspace and the depth is governed by the sagittal plane contour of this line and tappers out anterior to the medial aspect of the rearfoot post. We have incremental increases or decreases in the amount of fill relative to this line and the depth of the arch is then governed by the sagittal plane contour of the foot along this line. Minimal arch fill is essentially a wash in the arch to smooth out any irregularities but does not add any real fill to the medial arch.

The length of the rearfoot post is based on a percentage of the length of the orthotic shell. A long and short post are mathematically determined and correspond to rearfoot post lengths derived from shorter and longer devices. As with all of our Rx options, the clinician can call and ask for our standards. Once familiar with them, these relative changes are easily incorporated in their Rx.

And I do. That is why we need to be exacting and have developed clear standards for our clients. No wonder you never had good success with the Root type functional orthoses.

 

Dennis,

I have a reasonable handle on internal and external joint moments yes. Please do explain to me what an "instability moment" is in this context...

 

Trevor,
I'm out of town without a keyboard, so I will try to respond best I can. How do you determine that a foot demonstrates great pronation moments. In some feet, the cause of the pronation moment is the personal muscles. When there is a lateral stj axis is lateral the ground will tend to cause sublimation. Inresponse, the peroneals need to activate to prevent a sprained ankle. The peroneals may be creating so much eversion that, after heel off, the lateral forefoot will be off of the ground. All of load will be on the first met head and hallux,

I don't recall ever seeing a poorly advantaged pt muscle causing increased peroneals activity.

What do you mean by loss of windlass mechanism? What do you see when this occurs?

Eric

 

Kevin

Thanks for spending the time to reply and I fully understand your reasoning regarding technology. I have colleagues and a sports scientist who record the information for me as, like you, I could not afford the time to do so myself. I also appreciate that it is not necessary in order to manage the majority of our patients but I have found the technology to be a very useful adjunct and, as much as anything, keep my mind open – I often see things I did not expect.

I think your first paragraph is extremely important and perhaps one of the most pertinent that has been written. The assessment approach you take shows how some of the some of the concepts outlined by Root et al (i.e. structural alignment rather than STJ neutral function) can be combined with the SALRE approach and thus tissue stress relief. I would like to see proximal function introduced to the approach as the primary driver for loading can originate outside of the foot and greatly effect loading.

Examination of function comes more easily to some than others but I do believe this approach can actually make understanding function easier to understand.

Unfortunately, I am unable to attend BSS this year due to family commitments and am disappointed as it looks like an excellent programme.

I don’t suppose you are coming to London at any stage whilst you are over?

Trevor

 

If I see a foot that has more of the features of pronation than supination during gait, then I will make the assumption that there are greater pronation moments. Thinking on this as I answer, as the foot moves towards its end point of pronation (whenever in gait that occurs), the pronation moments will be greater and there does not need to be an alteration in position for these to continue exerting load on the tissues (aka sinus tarsi syndrome). At the point that motion begins to reverse (assuming it can), then there is a relative change in the moments - could either be a reduced pronation moment (i.e. less firing of the peroneals) or an increased supinatory moment (i.e. external leg rotation) but the net result may be the same. I am not sure I have quite explained what I mean but…

For want of a better description, a more pronated foot type but not necessarily a deviated STJ axis on the clinical examination (may be deviated dynamically but that’s another discussion).
[/QUOTE] In some feet, the cause of the pronation moment is the personal muscles. When there is a lateral stj axis is lateral the ground will tend to cause sublimation. In response, the peroneals need to activate to prevent a sprained ankle. The peroneals may be creating so much eversion that, after heel off, the lateral forefoot will be off of the ground. All of load will be on the first met head and hallux,

I don't recall ever seeing a poorly advantaged pt muscle causing increased peroneals activity.

What do you mean by loss of windlass mechanism? What do you see when this occurs?

Eric[/QUOTE]

I get the laterally deviated concept. However, if I have increased load on the first met head which prevents 1st MTPJ dorsiflexion / 1st met plantarflexion (i.e. functional hallux limitus), then there will be a loss of the windlass mechanism. This has the potential to place load on the peroneals as the mechanical advantage of longus is affected and I have seen some instances of a functional instability with this foot type.

Regarding tib post, there was a degree of theoretical surmise in that, if the relative strength of Tib post was reduced, then there is a potential for an imbalance with the peroneals – we certainly see an imbalance with classic tib post dysfunction.

Trevor

 

In some feet, the cause of the pronation moment is the personal muscles. When there is a lateral stj axis is lateral the ground will tend to cause sublimation. In response, the peroneals need to activate to prevent a sprained ankle. The peroneals may be creating so much eversion that, after heel off, the lateral forefoot will be off of the ground. All of load will be on the first met head and hallux,

I don't recall ever seeing a poorly advantaged pt muscle causing increased peroneals activity.

What do you mean by loss of windlass mechanism? What do you see when this occurs?

Eric[/QUOTE]

I get the laterally deviated concept. However, if I have increased load on the first met head which prevents 1st MTPJ dorsiflexion / 1st met plantarflexion (i.e. functional hallux limitus), then there will be a loss of the windlass mechanism. This has the potential to place load on the peroneals as the mechanical advantage of longus is affected and I have seen some instances of a functional instability with this foot type.

Regarding tib post, there was a degree of theoretical surmise in that, if the relative strength of Tib post was reduced, then there is a potential for an imbalance with the peroneals – we certainly see an imbalance with classic tib post dysfunction.

Trevor[/QUOTE]

Trevor, we have a chicken v egg question. I'm saying that the high loads on peroneals are causing the hallux limitus and you are saying the hallux limitus is causing the high loads on the peroneals. The lateral stj axis is what is causing the high loads in the peroneals.

Eric

 

Trevor:

We arrived safely in London only a couple of hours ago. We only have a few short vacation days here before we head over to Manchester for the seminar on Thursday. Here's the view from our balcony of the flat we rented about 300 meters from Hyde Park. The London vacation begins!!

 

Griff

You call my terms meaningless, what you fail to grasp is that we are in different technologies, therefore “terms” can take on a new more descriptive meaning.

So what the devil is an instability moment? To understand that you have to go back to the beginning.
Root, defined Overpronation (op) as: the entire range of motion of the MTJ in any gait cycle, which results in maximum instability during locomotion of the kinetic chain. This statement of op however is for a bare foot, not a foot with some support like an orthotic. Because of that the statement has to change,



So, overpronation with an orthotic is due to instability not compensated for the orthotic. Would you agree? That instability becomes op with an orthotic.

When, all the wt bearing and pronatory forces are driving thru the kinetic chain into and throuout the foot, IT MUST BE STABLE. It cannot op, be unstable, sublux, deflect or whatever term you choose to give it. Because if it is unstable or op, it will “unlock” the foot to pronatory and wt bearing forces, that unlocking, becomes the instability moment.

That force repeated through out a lifetime, potentially causes biomechanical inflammation.

Traditional orthotic technology allows for for two areas of op/instability during the gait cycle.
First in the rearfoot, then at propulsion.

This technology, while it has helped many, is not helping as many as it should.

 

Trevor:

If a foot has increased subtalar joint (STJ) pronation moment during gait then that foot will either tend to undergo increase STJ pronation motion during gait or will be maximally pronated at the STJ throughout the stance phase of gait. In addition, as the STJ pronates further, the STJ axis becomes more medially deviated which may further increase the magnitude of STJ pronation moments.

As you noted, it is not necessary for excess pronation motion to occur during gait to have pronation-related pathologies occur such as sinus tarsi syndrome since the excessive tissue stresses caused by excessive magnitudes of STJ pronation moment are sufficient to cause symptoms to occur. In other words, it is the excessive STJ pronation moments that cause the pathology, and not necessarily the presence or absence of STJ pronation motion that causes pathology.

Any time the foot begins to supinate at the STJ during gait, either from a maximally pronated position, or from neutral position, we can assume from Newton's Laws that this STJ supination motion has been caused either by an increase in magnitude of STJ supination moments and/or by a decrease in magnitude of STJ pronation moments. In addition, the alteration in moments which produce this STJ supination motion may either be from external sources (such as the increase in external STJ supination moment from a medial-heel skived foot orthosis) or from internal sources (such as from an increase in contractile activity of the posterior tibial muscle or from an increase in contractile activity from one of the external hip rotators).

One of the beautiful things of understanding foot mechanics with the foundation of Newton's laws and with basic physics and engineering principles is that many clinical problems may be solved by simple application of these laws and principles. For example, if one knows that the principle of rotational equilibrium will apply to all structures with axes of rotation (e.g. the foot), then when one sees a foot that is in a static standing position (i.e. in relaxed bipedal stance), then even this non-moving foot can tell us plenty about the forces and moments that exist within It. We should be able to, with good predictive ability, say what types of forces need to be present within the structural components of the the foot and lower extremity to allow it to remain still, with all the toes plantigrade on the ground, and with the medial longitudinal arch maintaining its arch height without flattening completely.

We must continue to fight against those individuals who claim they know how the foot works just because they can sometimes make patients better with custom foot orthoses. The rest of the medical profession is watching us closely and respects those professions who have done their own research to advance their own profession.

 

"We must continue to fight against those individuals who claim they know how the foot works just because they can sometimes make patients better with custom foot orthoses. The rest of the medical profession is watching us closely and respects those professions who have done their own research to advance their own profession."

And those that are on the "ground floor" must: 1) counter the academics that have agendas that include self-promotion, and 2) not dismissing the successes and failures of treating patients but learning from them, in spite of the plethora of articles written that suggest otherwise. The medical profession is not watching us closely...they couldn't care less, and have long since started referring patients elsewhere because of what this blog thread alone, represents.

__________________

 

Dr Hunt

You don't have to ask me twice, I second that.

 

Matt,

Which begs the question, is TST just a podiatry biomechanics/orthotic thing or what? Are orthopedic surgeons talking about or using TST in their practices? I would be interested to see any examples of where TST has appeared in any orthopedic journals or literature. I think that would demonstrate some awareness outside of the current circle of interest.

Jeff

 

Tissue Stress Theory is now 20 years old. There will be about 200 podiatrists and other foot-health clinicians from around the world attending a two-day seminar devoted to Tissue Stress Theory this weekend in Manchester. I would hope that anyone who has a great interest in foot orthosis therapy should have known about Tissue Stress Theory many years ago.

http://www.physicaltherapyjournal.com/content/82/4/383.full

http://jan.ucc.nau.edu/~cornwall/FandA/Vicenzino_2004.pdf

 

Dennis

"Different technologies" or not, scientific terms are standardised and have well documented universal meaning. You can't just make them mean something else because you fancy it. What is pretty clear from your post is you have no idea what a 'moment' is. Hence you are happy to use it in a nonsensical phrase such as "instability moments".

Over the weekend I've been practicing my lecture for the aforementioned Biomechanics Summer School in which I will put forward a case for why clinicians should move away from the 'overpronation model' when assessing and treating their patients. I had one of those jittery periods yesterday where I suddenly worried that this was all too obvious and no one was actually still practicing this way anymore anyway. Thanks for putting my mind at rest on that one.

 

Jeff-no orthopedic surgeon I know is discussing TST, or even knows about it. Remember, though, that orthos, while being pretty sharp, are more like very well trained mechanics that are well versed in general medicine. The co-author of my GPs/RLS article is a DPM that was trained by one of the premier orthos on the west coast, so he has the surgical approach/skills of an orthopedic surgeon, with the biomechanic aptitude of a Podiatrist....a pretty good perspective.

Note also, that at the Manchester meeting where Kevin is lecturing, it appears that there are no MD's in the curriculum. That's pretty telling. The debate that rages within our own worldwide community, Root Biomechanics vs. TST, only hurts our cause. It appears to me that the TST adherents should've made TST as adjunctive information to bolster your father's work, instead of portraying it as a "new approach". Kirby, himself, admitted above that he still uses Root based biomechanics while initially examining patients, which answers his own blog header question.

While Podiatrists worldwide are arguing about these topics, orthos are sending their patients to orthotists with prescriptions that defy logic and principle. We have lost our seat as premier LE biomechanical specialists and, IMO, this blog should elucidate why.

 

From 1979, http://jbjs.org/content/61/2/159.abstract etc to 2015: http://www.bjj.boneandjoint.org.uk/content/97-B/4/492 , I'm sure there will be earlier examples, but you get the idea.

 

Griff

Leave it to you, to deflect the issue.


The facts are that thinking like an engineer to resist pronation on a dynamic structure that loads and unloads, should be engineered by wedges, skives, medial buildup etc, etc.--That doesn't make sense to me!

The foot is a dynamic “bridge”--the engineering you describe is for a static bridge, like the Golden Gate in San Francisco.
Root was very clear: “an orthotic should “compensate for abnormal motion while allowing the foot to move in an unrestricted and natural way.”


unrestricted and natural way.” do you really not think that wedging, skiving and medial build up are restrictive? After all you are trying to resist pronation, ??? Otherwise, what else are you doing? Can you possibly think this is accurate enough? I see balancing the planes of motion in thousandths of a degree. Anything else is less efficient to bio-mech efficiency.
It is to that degree that an orthotic does what it's supposed to do!

 

Matt,

We have a semantics issue. Personally I think it would be far better to use a term like Pathological Force Analysis and Management to describe what we do. Pathological Force Analysis is a term that is broad enough to describe the wide array of theories, techniques and approaches that are used to asses the patient, including structure, function, tissue stress, etc. Then we can have an intelligent debate about the theories and techniques that provide the best explanation for the pathology in question. Pathological Force Management is a term that can be used to describe any and all mechanical interventions. Under Pathological Force Analysis and Management, elements of different theories can be employed without the all or none mindset that we are seeing as a result of the question "Has Tissue Stress Theory Supplanted Root Theory", which creates unnecessary division and detracts from the goal of improving patient care?

Jeff

 

Actually bridges are not static and are designed to give under load. This help prevent structural failure.

 

Here is a video that talks about the dynamics of the Golden Gate Bridge. Functional Orthoses are not rigid structures either.

https://www.youtube.com/watch?v=dxoB5dYZg_Y

Jeff

 

Jeff,

I'm well aware of that, I was making a point and giving an illustration. Why don't you talk to me about what's important in our orthotic technologies?

Instead of finding a moot point.

 

Jeff:

I agree with you that we all need to work together to improve the theory and techniques for future generations of podiatrists. Endless debate really does not move us any closer to our common goal of improving patient care.

I do believe that there may be a way for all of us to work together to move forward. However, I would rather it not be a public discussion since it would be much easier and less confrontational to discuss this with you and a few others in a smaller group. When I get back to Sacramento next week after the seminar maybe we can discuss these ideas further.:drinks

 

When does a force become pathological? How do we measure this clinically? etc... I look forward to the outcomes of your discussions with Kevin.

 

I was attempting to talk about importances in technology. Orthotic flexibility is an important component of orthotic design. My point was, many things that may look rigid, are in fact not. You have attempted to paint traditional functional orthoses in a certain light and it is not consistent with my own experiences and observations. We are not trying to lock the heel in the device or to hold it in any one position. We are using the device to create reaction force on the plantar surface of the foot and that reaction force is determined by the manner in which we cast the foot, the manner in which we modify the positive model of the foot, the material type, thickness and the shape of the orthotic shell, the density and configuration of any extrinsic posting and the nature of any top coverings and additions that we might add to the shell. There are many factors we must consider when writing the prescription.

I am always looking for ways to improve outcomes. Last week a doctor ordered a gel based top cover material that looks similar to Spenco on the outside but is actually a gel sandwiched between nylon on the top and bottom. Our cost for this top cover material was almost $60 per pair. It has great anti-shear characteristics but is too expensive for most applications (this was a diabetic patient with a TMA on the other foot and long history of ulcers so the cost of the material in this case could be justified in an effort to reduce future treatment costs).

When I hear people report very poor results with traditional functional orthoses, I typically think to myself why? Why, if the theories and techniques are so bad, do so many people get good to excellent results. I think I would be more inclined to be interested if you told me you got good to excellent results with traditional orthoses and that you had found a way to improve on your results with a new or different technology.

Like others, I have issues with your terminology. That aside, I think the only way to evaluate your product would be to test it. However, I don't really see a good quality example of your product on your website and I don't understand the methodology of your prescription process. As a result, I would hesitate to spend a lot of money on a product if I had a hard time understanding just what it is and how it actually functions. I get it that the fluid moves away from high pressure points and moves to lower pressure points. But functionally, based on my understanding of how the foot functions, I don't see how it can improve function. It seems like an accommodative type of device, which might be fine for that purposes.

Jeff

 

We deem it pathological when we find symptoms that are consistent with the forces that would appear to cause the pathology in question. For example, many things can cause or contribute to plantar fasciitis. We can evaluate the individual in question and attempt to design an orthoses to address the pathological forces such as functional hallux limitus. If we reduce FHL and the symptoms resolve, we can assume that we have reduced the pathological forces.

In TST, the goal is to reduce the stress on the injured tissue. How is that any different? How do you know when you have reduced the stress on the injured tissue?

 

Kevin,

I would be happy to! I'm not totally rejecting TST although I really don't like calling it a theory or a treatment paradigm. I just don't think it can function independent of some of the techniques and practices that fall under what has come to be called "Root Theory" (a term I detest!). I think you and I agree on the value of many of these techniques yet we both recognize that they are poorly understood and not easily teachable. Have a good time on your trip and enjoy the conference.

Jeff

 

No different, which is why I asked the question. The difference is in how we think the foot orthosis works. However, we fall to difference in the realms of pathologies associated with excessive supination moments, where many would have us increase the supination moments further to treat the pathology. When pain levels reduce and/ or functional capacity increases are the outcome measures I generally employ. And for the record, your dad didn't discuss functional hallux limitus, nor the windlass mechanism- I guess the ideas of someone working in Brum in the 1950's didn't cross the pond back then. I take it that they have now.

 

Repeat post

 

There is something to structural alignment. As Jeff has pointed out, at the extremes a foot with a forefoot valgus will function differently than a foot with a forefoot varus. The difficulty comes when you try to differentiate two feet with measurement differences of less than 5 degrees (and possibly more). STJ axis location is part of the structural concerns.

It is not the motion of pronation that is the problem. It is the stopping of pronation that is the problem.

Eric

 

Certainly tissue stress theorists are saying that orthoses work. We use some of the same orthotic prescription variables that are used in neutral position theory. There are only so many variations that can be done to that piece of plastic that is sitting under the foot. Tissue stressers may use a particular orthotic variation for a different reason than Neutral position theorists. So, in that sense, I would agree that we can't function independent of Root theory. We both use plastic to alter forces under the foot.

Eric

 

Jeff




Instead of stating that scientific terms are “standardized”, maybe you can give an eample of which terms I used that go against that standardization, and if my terminiolgy is an issue, it's a minor issue

We are using the device to create reaction force on the plantar surface of the foot

What then would you want to see on the outcome of a scan for it to look like? Please describe a generalized picture of what you'd want and expect the pressure forces to show for the FF.
Or the MF or even RF.

When I hear people report very poor results with traditional functional orthoses, I typically think to myself why? Why, if the theories and techniques are so bad, do so many people get good to excellent results

No one using traditional orthotic technology is getting “excellent” results. I practiced for 17 years using the same technology, I was as good as anybody, and I did not get excellent results. In fact I probably got better results than most of my colleagues, but I did not consider them excellent results.

With the fluid technology I use now, I get excellent results. I am able to help 100% of pts with a biomechanical problem. Many of my pts have been with me for as long as I've been doing this.

But your bound to have some good to excellent results with some individuals. With a better technology you'd have much better results with everyone with a biomechanical issue. The essence of any orthotic is to minimize and reduce wt bearing and pronatory forces. Trad tech does do that, but look at the clinical trials with generic orthotics—50/50 most every time.



I don't understand the methodology of your prescription process.

That's not a problem. I'm not keeping secrets, but that's not even important. That can be explained, it's just a different technology.


As a result, I would hesitate to spend a lot of money on a product if I had a hard time understanding just what it is and how it actually functions.

Do you mean as a pt or a dpm?


I get it that the fluid moves away from high pressure points and moves to lower pressure points.


No Jeff, maybe you really don't get it enough to understand how it works, Fluid is not moved to a pressure point, it moves away from a pressure point and moves to an area of lesser pressure.

The fluid is not under the met heads, it is just behind the contact of the met heads to the floor.
The fluid is hydrodynamically equalized by the pressure of each met and supports each met in its natural alignment position, neutral as it were.

The resultant pressure under the forefoot for example, ideally would be spread out evenly. This would mean in order to get that picture that the peak force of each met was peaking more uniformly at the same time. If the GRF were not spread out evenly it would indicate something else.


But functionally, based on my understanding of how the foot functions, I don't see how it can improve function. It seems like an accommodative type of device, which might be fine for that purposes.

You really don't see that?? Then you didn't read my article as you said you would. That said, it also is an excellent accomodative device. You should see how well it biomechanically redistributes pressure over pressure ulcers.


Isn't it time for podiatry to come into the 21st Century. The improvement in patient results would be dramatic (especially for the many, many failures that are walking around.

Fitting is a matter of technique, just like casting, but modifications are made in grams and mg of fluid, rather than wedges and skives. And if you truly know biomechanics, then you know what to expect to hear from the pt.

Read the article.

 

Eric

It is not the motion of pronation that is the problem. It is the stopping of pronation that is the problem.



When the forefoot is just about to touch the floor, just prior to midstance—is the STJ still pronating? Or have you stopped it, before the deceleration of the 1st met (before it reaches peak force) and MTJ?

 

The STJ is still pronating before the medial forefoot hits the floor most of the time. The exception is when the STJ has used all its available range of motion before the medial forefoot hits the floor.

Dennis, your second sentence is not clear. Are you referring acceleration of the metatarsal itself. Or, are you referring to ground reaction force on the first met decelerating the pronation motion of the STJ? Which peak force are you referring to? Whole body or force on the first met head? One needs to understand how forces are applied to the foot to understand how orthotics work.

Eric