Prescribing Orthoses: Has Tissue Stress Theory Supplanted Root Theory?

But the casting technique does, in reality, influence the shape of the resulting orthoses. Labs don't take weightbearing, semi-weightbearing and non-weight bearing casts and simply turn them into identical shapes. It just doesn't happen. And if they possibly could, they would need exact specifications. It would require knowledge (data) of the intended shape, which the lab or CAD/CAM system has no way of knowing. If I gave you a full weightbearing cast of a subjects foot and asked you to carve it into the exact shape the same subjects non-weightbearing foot without you seeing the subjects foot, could you do it? No.

I stand by my contention that TST lacks orthotic fabrication standards and protocols. There are several books that explain orthotic fabrication and none of them address the tissue stress approach. Why no standards in TST? How is any study going to attempt to replicate the practitioner's approach when there is no orthotic fabrication protocol? They can't even begin to study it because there are no standards.

This is not relevant to my point. I don't want to veer of in another direction at this point in my effort to better understand the methodology behind TST.

 

Just to add my two cents, I believe that both Jeff and Simon are making good points here.

Personally, since I use a modified version of Root negative casting method, and have had great success with this approach for three decades, this is what I teach to my students/residents. We need a baseline model from which to start to teach young clinicians, but this baseline model isn't the only one that can be used to make comfortable and therapeutic foot orthoses. So, in this regard, I believe we need some sort of systematic approach to the prescribing of foot orthoses, especially for less-experienced clinicians.

However, Simon also makes a good point in that the final orthosis can be arrived at in a multitude of ways, without even ever having to cast, mold or scan the foot. The clinician does need to understand the mechanical principles of how foot orthoses perform their kinetic, kinematic and therapeutic effects and then can decide on how to best make that orthosis to accomplish the goals of foot orthosis therapy.

Personally, I believe there are many good things about the methods advocated by Root et al and I still use many of them and teach many of them. Yes, many of these techniques taught by Root et al were described earlier by others, but Root, by publishing his textbooks and lecturing extensively on them, set the standard for his era in how the foot and lower extremity can be evaluated and foot orthoses can be prescribed for patients with overall good results. At this is what occurred here in the US and probably happened to a lesser extent in other countries, even though the influence of Root, Weed and Orien was undoubtedly worldwide.

However, I also believe that many of the things that Root et al taught are erroneous and need to be recognized and replaced with more accurate/better techniques/information. Root theory, as it was taught to me at CCPM, was unbending and, for that reason, many of its concepts which were once thought to be gospel by a whole legion of "Root disciples" need to be publicly debated, which we are doing now. Hopefully all this discussion will allow us to all move forward for our common goal of improving the care for our patients.

Kuhn wrote a whole treatise on the concept of changing paradigms and we are in the midst of it. Here is what Eric Fuller and I wrote over ten years ago on this subject:

 

I'll say again, the casting technique does not necessarilly influence the shape of the resulting orthosis. Lets say I follow your dad's book on casting and create a negative cast how they advocated, I then pour a positive cast from it with the heel balanced to vertical, I then create a puddle of plaster in a box and stick the positive cast into it to create a cube. I then press an orthosis shell over this cube. In what way has the original casting technique influenced the shape of the orthosis shell?

What if I do have the subjects foot in front of me, and I was Michelangelo, could I carve my cast exactly then? Rhetoric. What if I have two different plaster technicians doing my arch fil, will they get it exactly the same? You're making the assumption that it needs to be the exact same shape as the subjects foot- it doesn't. How do OTC devices work, Jeff? And we know they do.

We got a study ongoing at the moment which should highight some of the issues you hold dear to.

And I stand by my contention that "standardised protocols" are unnecessary when humans aren't standardised. Moreover, it is obvious that your "Root standardised protocols" are inherently flawed. Let's use a series of measurements which have poor inter-rater reliability, then we'll use a casting technique which has poor inter-rater reliability, then we'll send the casts taken by multiple practitioners of the same foot to a lab and ask them to apply a standardised protocol, they have a couple or three plaster technicians interpreting the "prescription". Guess what, you'll get variation in the shape of the orthosis at the foot-orthosis interface.:bash:

Yeah? And? So? What?

Let me type slowly so you might understand.. there are no standard protocols because when we take a patient centred approach we realise that every individual is unique so we must design a treatment strategy for that individual as an individual.

This is quintessential to the point, Jeff. That you, as president of PFOLA, don't recognise this is somewhat worrying. How do foot orthoses work?

 

Question: could we make efficacious foot orthoses without any knowledge of, or ever using the casting technique outlined by Root and colleagues? Yes.

So, the question becomes: what advantage does this technique offer, if any? We know it is less reliable than ground referenced techniques.

 

I really don't think the Root et al casting or prescribing techniques offer any advantage to any other. However, since we don't know which technique is best, and until the time we have the research which shows which technique is best, then I will continue to use and teach the techniques that have worked well for me and my patients.

I believe that this is what most clinical instructors do with students and residents. They teach the skills that they have found to work the best in their own hands, while acknowledging that there are other methods that may work equally as well, or better. This is how I have been teaching for the past 30+ years.

In other words, for the podiatry student, podiatry resident and young podiatrist that has little clinical experience, I believe it is best for them to have a certain set of skills that will allow them to function independently in a clinical setting. Once the student/resident/young podiatrist has gained more clinical experience and confidence in their foot orthosis skills, then they can branch out and use any orthosis production method that they feel best suits their needs and their patient's needs. I encourage orthosis and clinical experimentation in all the third year surgical podiatry residents I help train.

All in all, I have changed the ways I teach biomechanics and foot orthosis therapy multiple times over the past three decades and expect I will change again before I retire from practice. The bottom line is that we need much more research before we can say what orthosis production techniques are best and, until that time, we must keep an open mind to new ideas so that we don't get left behind as a profession when a better idea and/or technique comes along.

 

I tend to agree. Yet the podiatry student, podiatry resident and young podiatrist need to be empowered to make critical evaluation of the knoweldge base and not need to feel that they have to comply with their mentors preferred technique in the face of lack of evidence to prove one technique any more more superior to another,

That said, I honestly don't think that any casting technique will ever be proven to be best because casts don't treat feet, foot orthoses do.

 

I don't teach that the student, resident or young podiatrist must do things my way.

However, I do remember, as a young podiatrist, that I just wanted to become proficient at one technique, and wanted to learn that one technique from the clinician that had the most clinical experience and that I most respected.

I think that this is what most young students/experienced clinicians want. They want to initially learn enough clinically to become proficient at one or two a techniques so they can function independently and get their patients better. As they mature into more experienced clinicians, hopefully they will start to explore other techniques to see what works best for them and their patients.

My philosophy? Teach a few skills well, but encourage the students and young podiatrists to explore and experiment on their own as their confidence grows. I believe this is the best way to teach students, residents and young clinicians and encourage their personal and intellectual growth.

 

Say we have a foot with a medially deviated STJ axis 1st mpj pain and is able to lift the lateral forefoot 3mm off of the ground when attempting eversion range of motion. In relaxed stance I'm able to slide my fingers under the lateral forefoot. I think the problem is too much medial forefoot load. I want to decrease the load by attempting to supinate the STJ (increase supination moment) and I want to increase lateral forefoot load with an intrinsic forefoot valgus post.

Jeff, if I sent your lab a foam box or a plaster cast impression and asked you to add a 3mm high intrinsic forefoot valgus post and I asked you to make the heel look like a cast that was balanced vertical with a 2mm heel skive, could you make me an orthotic with those specifications?

If someone gave me those instructions I would be able to produce an orthotic. That orthotic would be made without the need for heel bisections or awareness of forefoot to rearfoot relationship. It also wouldn't matter how the impression of the foot was obtained.

Eric

 

I have had a lot of experience of making non-Root protocol based functional orthotics for clinicians and must say that I can't agree with Jeff comments about TST not having a protocol in place.
When a clinician took a cast - using any method - I would then ask them what they want the orthotic to do to the foot. This is a simple protocol that harmonises with TST.
It reduces the blind reliance on the lab that has been cultivated by some manufacturers (This is not aimed at any lab in particular) and reduces things back down to clinician culpability and capability.
The type of cast used did become a important aspect of the process as the foot geometry/shape could vary a lot from method to method. However once a clinician understood this then the results were excellent - at my last lab we had managed to get RFT (Right first time) to 99% compared to the first lab I worked at being closer to 85% - this included returns for adjustment/tweaks.

Maybe now is the time to write the book on prescription protocols for TST based orthotics - might be more of a pamphlet.

Cheers

Phil

 

maybe my question was missed due to my poor way of asking

when or what makes a device a modified Root device? and when do the modifications to a script that have been mentioned mean that a device is just a shaped piece of plastic which said modifications ?

 

It should be pointed out That I doubt there are many who adhere to the strict Root negative casting method anyway

I was taught how to find " STJ neutral " at Uni only to discover that that was not the way Finding " STJ neutral " was described by Root et al

and then comes back to my questions to Jeff re modified Root devices when does taking a foot impression stop be a modified Root Casting technique ?

Because I honestly believe not many people use the Root et al techniques for Casting or making devices in the true definitions anyway

 

Phil,

I don't see this ("When a clinician took a cast - using any method - I would then ask them what they want the orthotic to do to the foot.") as a protocol.

Does TST have any specific rules or procedures for manufacturing orthoses? In a technical manufacturing environment, in order to manufacture products in a consistent manner, you need clear guidelines. For example, when manufacturing a Root type functional orthosis, we establish a heel bisection and can measure the angle of the forefoot to the rearfoot. If the subject cast had 10 degrees of forefoot valgus, and if the RX called for the heel to be corrected 4 degrees inverted, we know that the heel would be 4 degrees inverted to the the floor and the plane of the forefoot would be six degrees everted to the floor. Our default correction is to heel vertical but knowing that, the practitioner can alter their RX in a specific manner and that protocol could be applied at any lab that uses the Root protocol.

In your example, I see no rules, guidelines or standards associated with TST.

Jeff

 

and I think you will find that many people and labs who claim to be using or producing Root or Modified Root devices and biomechancial theory are not

So where does that leave us ?

Well I think we can all agree orthotic foot devices work

so my suggestion is if we can agree to a definition of how foot orthotics " work " as step 1

Simon has defined how orthisis work

Altering the magnitude of the reaction forces
Altering the vector of the reaction forces
Altering the temporal patterns of the reaction forces

and I would personally add which will result in Kinetic and possible kinematic changes in foot mechanics

if we are agreed on the above, which will then define the language of any further biomechancial discussion

why does we correlate a list of every know orthotic modification and break them down in how they work of the foot? not when to use them but what they " do "

Jeff I am sure you have a list

ie Medial skive - when used will pull the Ground force Reaction medial and under the heel, the roll of the medial skive is to increase the magnitude of the Ground reaction force acting on the foot medial to the Subtalar joint, The direction of the Ground reaction force Vector can be altered by adjusting the depth and angle of the skive. The stiffness of the skive can also be adjusted by adding EVA or other materials, which will also increase the surface area of the heel skive etc etc



or something like that

met domes/ met cookies , increased arch fill , decreased arch fill/ no arch fill , cuboid notches etc etc etc etc

this way the 1st step we get away from Root verse Sagittal plane verse Tissue stress verse .....

it would also be of benefit to many

and then the next step would be when used for what conditions ( and this is where is might get ugly again )

and of course this list would include a Root and Modified Root device ,

before we started of course there would need to be agreement re bisection lines , we may never get anywhere but maybe Daryl we need to talk about Bio-Mechanics

yes I also know this was started but never got going

but it should not be that hard to get going

if Jeff could provide a list ( it could be expanded on later) we then make sure each item has a universal name or names attached ie met dome/met cookie

and start a new thread

Define what a Met Dome/ Met Cookie does ( not when to use it )

then once agreed the definition gets added to a data base

but we would need to 1st define the language used ie the language of mechanics ( forces, moments and of course the bits which make it body related Dorsiflexion moment) If this could be agreed on then I think we could get started if people are willing

 

Jeff:

I don't know that trying to establish a specific set of rules is best for teaching the correct prescription of custom foot orthoses. Let's take the example of how John Weed, DPM, for years, taught podiatry students to prescribe foot orthoses at CCPM using the specific set of rules laid down by him and Mert Root, DPM.

Dr. Weed, one of Dr. Root's most trusted colleagues and coauthor in all of his books, taught over a thousand podiatry students at CCPM the rule that foot orthoses should be prescribed based on "foot deformities" and on how the heel bisection we drew on the posterior heel aligned to the ground while the patient stood in relaxed calcaneal stance position (RCSP). He never taught us to change the orthosis prescription based on the anatomical location of pathology since he was teaching us what was then called "Root Theory".

Dr. Weed taught the rule that if the patient has a "fully compensated rearfoot varus deformity", where the calcaneus could "pronate to vertical", then the orthosis was prescribed with a vertically balanced heel, regardless of whether that patient had medial knee OA, posterior tibial tendinitis, patellofemoral syndrome, peroneal tendinopathy, sinus tarsi syndrome, a Morton's neuroma, sesamoiditis, ilio-tibial band syndrome, etc.

Dr. Weed also taught the rule that if the patient has a "partially compensated rearfoot varus deformity", where the calcaneus couldn't "pronate to vertical", but, rather, was at the heel inverted position when the subtalar joint was maximally pronated position, then the orthosis was prescribed with an inverted heel, regardless of whether that patient had medial knee OA, posterior tibial tendinitis, patellofemoral syndrome, peroneal tendinopathy, sinus tarsi syndrome, a Morton's neuroma, sesamoiditis, ilio-tibial band syndrome, etc.

So, we had rules coming down to us from Drs. Weed and Root, but was that a good thing? No. It created the impression that these rules were set in stone and, as we know now, they were not in fact the "best rules" to get patients better with foot orthoses since the rules of Drs. Root and Weed regarding the prescription of foot orthoses did not take into account the anatomical location of the foot and/or lower extremity pathology in their orthosis prescription. In fact, their orthosis prescription protocol probably did more harm than good in a certain subset of patients since it ignored the fact that sometimes, pronating the foot is the best way to heal pathologies.

Therefore, I wouldn't be so sure of yourself that having a "set of rules" is always a good thing, especially when this "set of rules" is wrong and erroneous. Rather, it is better we teach concepts of how foot orthoses work and how foot orthoses alter the temporal patterns, magnitudes and plantar locations of orthosis reaction forces on the plantar foot which, in turn, alter the internal forces acting within the foot and lower extremity. Then, with this knowledge, we teach how foot orthoses can be made to alter these external and internal forces for the benefit of the patient.

In fact, in regard to how foot orthoses mechanically function, I believe that myself and Don Green first described the concept of orthosis reaction force (ORF) and how foot orthoses worked to alter the subtalar joint pronation and supination moments in our chapter in Steve DeValentine's book from 23 years ago (Kirby KA, Green DR: Evaluation and Nonoperative Management of Pes Valgus, pp. 295-327, in DeValentine, S.(ed), Foot and Ankle Disorders in Children. Churchill-Livingstone, New York, 1992):

 

I would agree if we were mass producing a product. However, by their very nature bespoke, custom foot orthoses are effectively just that: bespoke and for all intents and purposes uniquely designed for the individual. Sure we may need to perform repeat prescriptions, but with modern systems it's not too hard to store a digital profile of either the finished orthoses or the casts, we can even store the casts for that matter.

 

Not me, that was Kevin. I said that the foot orthoses can only directly alter forces at the foot-orthosis interface by modifying:

1) the surface topography at the foot-orthosis interface
2) the load/ deformation characteristics at the foot-orthosis interface
3) the frictional characteristics at the foot-orthosis interface

Hence, I am interested in Jeff's intepretation of exactly how the surface topography influences reaction forces at the foot-orthosis interface so that we might begin to explore the need to cast all feet in "one, ideal postion"...

As for the biomechanical effects of your met dome: it depends on what it's made of, its shape and where you put it...

 

Excellent point, Simon.:drinks

 

Ahh right google and some articles had it as you

re the met dome of course, I was just putting a few examples on paper

 

Mike:

I think Simon and I are basically saying the same thing. However, Simon added the frictional characteristics factor which I really hadn't considered before and we discussed quite a bit over a few beers at the pool at a conference in Orlando back in 2011.:drinks

The bottom line is that foot orthoses modify the temporal patterns, magnitudes and plantar locations of ground reaction forces acting on the plantar foot by altering the surface topography, load/ deformation characteristics and the frictional characteristics at the foot-orthosis interface.

I first mentioned my definition of a foot orthosis on the Podiatry Mailbase in January 1998, which included a few of these concepts:

https://www.jiscmail.ac.uk/cgi-bin/...-3&J=on&d=No Match;Match;Matches&z=4&P=194905

Reading this Podiatry Mailbase post makes me remember Graham Curryer, God rest his soul.

 

Jeff

This is the point I am trying to make. The protocols employed by labs are there for their benefit to ensure that the output from the manufacturing process is reproducible and repeatable.
However a lot of the protocols do not relate to the required foot mechanics. For example soft tissue expansions around the heel are purely arbitrary and there are far better methods for defining this that I won't go into at the moment.
One of my biggest irritations was the forefoot to rearfoot measurement you highlighted. If a practitioner took the time to create an accurate cast using whatever method they deemed necessary rather than relying on the lab to 'correct it' the quality of devices would improve significantly.
So is you need a protocol for TST it is as simple as helping clinicians take an accurate cast, explain simply what they want the orthotic to do and the restrictions that the orthotics may have on it e.g. pt compliance, footwear, durability etc and then use a variety of flexible protocols to get the desired end result.
I am sure if we questioned a group of practitioners who make their own orthoses and use TST, they would have this protocol - I just 'engineer' the cast and orthotic to reduce the pathological stresses that are the underlying cause of the foot pain.

I have made a lot of orthotics for members of this Arena and have seen no fixed protocol other then the above with remarkably high success rates - the common theme being that they use a TST approach to the Rx.

Phil

 

I just explained the "how" by performing the FEA and some other experiments. I also just thought of another experiment for me and Griff, when we get the current one finished- my bad, but cool, I'm on it now.

 

I'll take Dr. Spooner on my team any day of the week!:drinks

 

I see Jeff's point here. He runs a lab. People mail him casts and he is expected to make an orthotic, from those casts, and send it back. The lab does need to know what to do with those casts.

Which brings me back to the question that I asked Jeff a few posts back....

I can add something to the above instructions. Medial arch height at the navicular tuberosity. If I send a lab a cast and tell them give me 22mm arch height at the navicular tuberosity, a heel cup that looks like a vertical heel cup with a 2mm medial heel skive, and a 3mm forefoot valgus intrinsic post, I think the lab should be able give me what I want. I would expect no plaster added to the plantar lateral aspect of the forefoot between mid calcaneus and the neck of the metatarsal.

Eric

 

well we could just measure the heel width non-weightbearing and on weightbearing, but this only tells us the expansion on a flat surface as oppose to within the finished orthosis/ shoe... right?

Eric had a pop at this problem many years ago: http://www.japmaonline.org/doi/abs/10.7547/87507315-88-1-12?journalCode=apms

 

Nail, squarely on the head. The problem lies in the practitioners ability to tell the lab what to do. The formulaic recipes of Root approach negated the need for any real thought by either party: the practitioner nor the lab. If only life were that simple. Practitioners need to re-establish themselves in telling the labs what to do, as oppose to the vice-versa. All comes down to practitioner education and labs having a tick box saying "lab's discretion": Lazy old crap. But that is what the Root approach encouraged: practioners didn't need to think, nor understand biomechanics, all they needed to do was perform "the measurements" and send a "neutral cast" to the lab and let the lab produce a device for them. They could dispense it to the patient and blame the lab if it didn't work, in the same way that the lecturers blamed the casting technique if it didn't work at CCPM. Been there, seen it, done it; look at it, say what it is...

 

Another criteria that I include on my prescription writing protocol. A weight bearing measurement of the width of the fat pad. I don't remember ever having any heel cup irritation when I made the fat pad expansion as big as the width of the weight bearing heel.

Which brings up another Root teaching. The lateral expansion plaster should not be greater than a certain amount 1/4 or 1/8" (I can't remember which) or you will lose control of the heel. We can toss this factoid. The heel cup of the orthotic does not put the heel of the foot where the heel of the bisection of the cast was balanced. (I know some Root disciples claim they don't believe this, but many people who were taught Root biomechanics do believe this. It is implied in the teachings.)


Eric

 

Simon

On a practical level it is the room in the heel counter that really matters - if the orthotic is too small it moves in the transverse plane and if it is too wide it won't fit the shoes.
Its a lot easier to measure the inside of the heel counter and then make the insole fit it exactly (you have to include the thickness of the shell as well)
This method was 100% successful at eliminating any heel cup pinching - that is until the pt tried to fit their orthotics into a radically different shoe.
The other confounding factor is when the heel counter of the shoe is too flexible but you can't expect miracles from your orthotics.

Phil

 

Great discussion

I agree with you Eric and to the part I bolded from your post Eric:

I suppose the heel would be placed in the position of bisection if you only look at the foot as a cast sitting in your orthosis on the benchtop.
Position of the heel is then is determined by ones frame of reference I suppose.
I feel a better frame of reference is the body COM and how that is positioned in dynamic walking rather than what happens in static stance. I am not a fan of looking for sub talar neutrality in all my foot orthoses mainly because that position in normal human motion is only achieved twice and in a very instantaneous way during stance in the gait cycle. There is no "one way" to achieve a well functioning foot orthosis. There is also no one solution for the same issue. When we begin to look at this work that way we remove the opportunity to "think outside the box". Humans are far from consistent and far from being "the same" why would I treat them as if they were?

 

As GRF and ORF are vectors ( http://en.wikipedia.org/wiki/Euclidean_vector ) I believe it should be mentioned in the orthoses' definition another one essential property of a vector, next to the point of application and magnitude ! This is "direction" ( http://en.wikipedia.org/wiki/Direction_(geometry) ) which will give us information about moments around specified axes

Sincerely,

Daniel

 

"The theories an explanations of normal function of the foot presented in this text are coherent. Each explanation must be consistent with the known facts of every applicable basic science. No fact of any basic science must conflict with the logic leading to a conclusion, or else that conclusion cannot meet the standards of coherence and must be discarded as incoherent and, therefore, unreliable."... Merton Root in Introduction of "Normal and abnormal function of the foot"



So, according to Root, when the conclusion cannot meet the standards, the "conclusion" should be discarded and not the "known facts of every applicable basic science". In this sense I'm understanding Root's work, so I believe "Root Theory" only "involuntary" has encouraged what Simon is mentioning. In the same time TST or other theories discussed on PA could "involuntary" encourage a lot of different personal approaches in the absence of a general accepted and objective "validation" tool [as for example Sackett's "Rule of evidence and Clinical Recommendations"]. But who can determine a practitioner to assume a theory AND a "validation tool" ? At the end "All comes down to practitioner education..."
Sincerely,
Daniel

 

Aloha,

Theories are only theories until they are proven fact. To claim that "the tissue stress theory is currently the best method by which to design prescription foot orthoses" without significant evidence seems hopeful. Very little evidence has been brought forward in this article to prove that the "Tissue Stress Theory" is more effective than the "No Dah Theory".

Claiming to reduce the tension or compression of certain body parts/tissues is great but how do you measure it? Where is the evidence that adding a 1/8 inch soft top cover will help reduce ground reactive forces (GFRs) more than the hunk of wedged foam it is sitting on? And will that 1/8 of extra top cover be enough to mitigate the very large impacts our very large patients produce? Are they placing probes in the tendons and fascia of walking people and measuring the effectiveness of their prescriptions vs Root-based or other newer gait systems?

If we really want to develop a new system for orthotic prescriptions, perhaps we should look closer at how we make orthotics and the shoes (midsoles and soles) that support them. Are we just rehashing the same plastic orthotic-insert on the same bed of deforming foam with a new slick pitch? More solid science is needed before making the big claims of uber superiority.

Mahalo, Steve - See more at: http://www.podiatrytoday.com/prescr...y-supplanted-root-theory#sthash.ySZhBr5T.dpuf

 

Matt this might seem like a stupid question, but how does an arch based orthoses control excessive heel motion at midstance??
when the heel strikes the ground no matter what position it is in, inverted or neutral/ vertical or everted, then quickly accelerates into a severe or maximum pronated foot type, as soon as that heel leaves the floor as the foot enters mid-stance - terminal stance how is the arch going to change the direction, when this has a very small lever acting across the STJ??? I'm somewhat lost!

 

cpoc-Perhaps a definitional problem exists...so let me begin by clarifying my terms. Mid stance is when the foot is in complete contact with the ground, just prior to forefoot loading as the patient enters the propulsive phase of gait. At full contact with the ground, the orthotic imparts maximum control over not just the rearfoot, but the fore foot as well. It's when said patient enters the propulsive phase, ie., when the heel is off the supporting surface...that's when/where/how we, as a profession have failed to demonstrate better foot function. In other words, if the foot collapses again, (re-enters a pronated position), once the heel is off the ground and the only orthotic contact is the distal parabola, then we can't make an argument for their effectiveness, can we?

 

cpoc103,

In order for the foot to pronate at the subtalar joint during stance, the calcaneus must evert and the talus must adduct and plantarflex. When the talus adducts and plantarflexes during closed chain pronation at the STJ, the navicular also adducts and plantarflexes with it, but not to the same degree as talus. So during closed chain pronation of the STJ the talus and navicular both adduct and plantarflex but there is relative abduction and dorsiflexion of the navicular on the talus.

In order for the talus and navicular to plantarflex relative to the ground during closed chain pronation of the STJ, the medial arch must become lower. The medial arch of the orthosis is very effective in resisting lowering of the medial arch of the foot and as a result, can be used to help resist STJ pronation. If you only look at the STJ axis relative to the plane of the floor and the long axis of the foot, and if you only think about forces medial and lateral to the STJ axis, you're missing the important triplane orientation of the STJ axis and your not considering the simultaneous motion that must occur at the MTJ in order for the STJ to pronate. The forefoot has a profound influence on the rearfoot, and visa versa. The orthosis acts on the MTJ as well as the STJ and on the foot as a unit. Although functional orthoses are far more than arch supports, we should not dismiss or minimize their important role in supporting the medial and lateral arches of the foot and how this support influences the overall function of the foot.

Jeff

 

Cpoc103:

I think this is a very good question.

Foot orthoses "control" subtalar joint (STJ) pronation and closed kinetic chain (CKC) heel eversion by creating external STJ supination moments. External STJ supination moments are, by definition, those STJ supination torques that are applied externally onto the foot, such as from ground reaction force (GRF). Internal STJ moments, on the other hand, by definition, are those STJ supination torques that originate internally within the foot and lower extremity, such as from posterior tibial contractile activity.

The way a foot orthosis generates an external STJ supination moment is by shifting the GRF more medially on the plantar foot so that the net STJ supination moment is increased or the net STJ pronation moment is decreased. One way to generate external STJ supination moment is to shift the GRF more medially on the plantar heel. This is commonly accomplished in custom foot orthoses with the medial heel skive technique (Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992). Another way to generate external STJ supination moment is to shift the GRF more medially on the plantar midfoot and/or the plantar forefoot. This is commonly accomplished by increasing the height and/or stiffness of the medial longitudinal arch (MLA) of the foot orthosis.

Therefore, if one wants to maximize the "control of excessive STJ pronation" with a foot orthosis, then it is necessary to customize the foot orthosis in such a fashion that GRF is shifted medially on the rearfoot, midfoot and forefoot so that the medial heel skive, for example, may work synergistically with the increased MLA height/stiffness to redirect GRF more medially under not only the rearfoot but also the midfoot and forefoot.

However, to complicate matters, too large a magnitude of STJ supination moment from a foot orthosis has the potential to also cause such a large increase in STJ supination moment that the central nervous system (CNS) perceives this in STJ supination moment as being potentially harmful. The result is that the CNS will alter the efferent neural activity in the extremity muscles to prevent lateral ankle instability and a potential inversion ankle sprain, especially during late midstance and propulsion. As a result, my theory is that the CNS will not only decrease the contractile activity of the gastrocnemius-soleus complex (GSC) during late midstance and propulsion and will also increase the contractile activity of the peroneal muscles.

The result of this change in efferent neural activity from the CNS during late midstance and propulsion during walking to the GSC and peroneals is not only an increase in STJ pronation motion during late midstance but also a shortening of the propulsive phase and the overall stride length due to a decrease in ankle joint plantarflexion motion. Therefore, when the stride length appears shortened and late midstance pronation occurs with an inverted orthoses, I will commonly add a forefoot valgus extension and/or decrease the varus shape to the foot orthosis. My hypothesis is that by increasing the valgus correction in the forefoot and/or decreasing the varus correction in the rearfoot, I am adding sufficient extra external STJ pronation moment (and/or decreasing external STJ supination moment) to the foot during late midstance and propulsion which, in turn, allow the CNS to sense that it can now activate the GSC fully during late midstance and propulsion. Allowing the CNS to activate the GSC fully during late midstance and propulsion will increase the internal STJ supination moment and internal ankle joint plantarflexion moment which will, in turn, allow more active STJ supination and ankle joint plantarflexion motion during the propulsive phase of gait.

Hope this helps.:drinks

 

“The basis for designing optimum foot orthoses for patients is understanding what the abnormal forces and moments are which are causing the pathology and then use the foot orthosis to modify the reaction forces “

The very nature of any orthosis does minimize some pronation, therefore the opportunity for some anecdotal success. Trying to modify the reaction forces is just guessing without the technology itself lacking scientific backing.
An orthosis Rx is that which decelerates the motion of pronation, starting at heel contact, then minimizing and reducing instability of the balance of the natural pronation movement thru midstance and propulsion.

 

If she's already fully pronated at static stance, how does any further pronatory device solve this problem? It doesn't

Correct, because at this moment in time, the plantar surface of the foot has halted (against the shape and position of the orthosis), but the transference of the forward motion and momentum of the intrinsic structures carries forward. This allows for further pronation -which I would call overpronation or simply “instability”

. I've asked Kevin this same question several times above and he either has me on ignore, or refuses to answer such a simple question. Instead, many of the proponents of tissue stress theory are using terms like "moment"...and I'm assuming it's to appear more like engineers, then Podiatrists. Oh well. Why not just discuss "motion"? Orthotics are very good at limiting excessive motion and/or redirecting GRF's.--

the problem here is that the excessive motion being limited is not very accurate, because there is no scientific technology that supports it.


Excessive calcaneal motion is best controlled at midstance when the orthotic obtains full purchase...less so at heel strike.

At this point, the calcaneus has everted further, based on the continued momentun and instability at midstance. A proper dynamic biomechanical orthosis should begin decelerating pronation starting at heel contact.

But once the heel comes off the ground as the patient enters into forefoot loading and propulsive phase of gait, that's where we, as a profession, have not provided useful data. I aim to change that.

Hydrodynamic technology can demonstrate maintaing the proper momentary stability at heel off.

 

One way to generate external STJ supination moment is to shift the GRF more medially on the plantar heel. This is commonly accomplished in custom foot orthoses with the medial heel skive technique (Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992). Another way to generate external STJ supination moment is to shift the GRF more medially on the plantar midfoot and/or the plantar forefoot. This is commonly accomplished by increasing the height and/or stiffness of the medial longitudinal arch (MLA) of the foot orthosis.

If using static angles/skives and and increasing or decreasing height and stiffnes for the control of a biomechanically fluid dynamic gait cycle is your idea of engineering, you better go back to the drawing boards.

 

Although functional orthoses are far more than arch supports

I don't think so. A well fitting arch support that minimizes the ROM withing the confines of the planes of motion and allows the foot to move thru a gait cycle optimizing joint congruency is very functional.

In fact in various clinical tests between custom functional and generic orthotics, it almost always seem to be a tie in the outcome.

 

Dennis-BINGO! I must admit...post #515 is one of the most convoluted, rambling and stretched leaps of faith I've read in quite some time. CNS? Really? Wow.

But you are correct, Dr. Kiper...we have not managed to provide practitioners and patients with the necessary information to conclude that orthotics work like we would like to believe they do, particularly after the heel comes off the ground and the patient enters propulsive phase of gait. If you have a method using hydrodynamic technology that will achieve this, then go for it...please. I'm taking a different direction...much simpler yet with, hopefully, reproducible results. It will mean less of a leap of faith, but will require digital productions of information. Medicine in general, and Podiatry in particular needs to move away from analog presentations and information distribution. We are like dinosaurs...but that's a discussion for another day.