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Think vectors, i.e. you can have a point of application of a force that is medial to the STJ axis, but still cause pronation moment due to the direction of the force vector. Robert Isaacs gave a very nice explanation of this elsewhere. I'm sure he'll link us to it.

__________________
Who? What? When? Why? Yeah? And? So? What?

"My mission drive is to open up my eyes, 'cause the wicked lies and all the sh!te you say..." http://www.youtube.com/watch?v=V4NW5S1UTPQ

"Science is the antidote to the poison of enthusiasm and superstition."

It comes from the variation in the surface geometry and the variation in the "packing" of the articular surfaces as they rotate and translate relative to each other throughout the range of motion. Also, to an extent the tension in the soft tissues surrounding the joint will have a role. I've probably missed something, but that's my quick answer after a couple of minutes thought. Which I think is kind of what you are saying.

This study demonstrates how the contact area changes as the joint is moved:
http://www.ncbi.nlm.nih.gov/pubmed/18701029

This is an interesting view:
http://www.ncbi.nlm.nih.gov/pubmed/1...ubmed_RVDocSum
"Recent studies have described the subtalar joint as a structure with no degrees of unresisted freedom, i.e., motion from the single neutral position is attained only by deformation of the ligaments and of the articular surfaces."

__________________
Who? What? When? Why? Yeah? And? So? What?

"My mission drive is to open up my eyes, 'cause the wicked lies and all the sh!te you say..." http://www.youtube.com/watch?v=V4NW5S1UTPQ

"Science is the antidote to the poison of enthusiasm and superstition."

1. I realize where your focus is (The STJ) but what about the midfoot axes (The Vault)? What about the forefoot axes? What about balancing one foot to the other?
2. Dr. Kirby's valgus orthotic (I'm trying to include a copy and hope I figured it out) is so unprofessional and cheap looking. How can he dispense it in good faith as representative of an orthotic to patients and the medical commuity?
3. His device has a rearfoot valgus post, no vault conformity(is lower than the patients high arch), has a 3-4 mm forefoot bar post with an aggresive first ray cutout. It's similarities to my prescription as per my posting on this thread is more than coincidental.
4. I am trying to download a similar Centirng for this rigid/rigid type. It has a varus post instead of a bar post (different foot type) but it is a first strike, professional looking product. I can understand why sarcastically Dr. Kirby turned down my challenge to evaluate and produce an orthotic for the same patient. I would win for esthetics/cosmetics/professionalim, even if his device IS better (and its not!).
Dr Shavelson

Attached Images

	Kirby Orthotic.jpg (76.7 KB, 130 views)
	rigrigCentring.jpg (126.9 KB, 131 views)

Hi Phil,

Some of the variation, I believe is genetic in that the articular facets are angled differently in different people. Some people are tall, others are short. Some variation is from "Forefoot to Rearfoot" relationship. Even though I find this measurement very unsatisfactory in terms of repeatability, there is some merit in the extremes. A forefoot to rearfoot relationship with a high degree of valgus will behave different than one with a forefoot varus. In the average foot, the foot will tend to pronate until something stops it. To some degree one of those things that stops the foot from pronating is the medial forefoot hitting the ground. If, you started in neutral position, then as you pronate the STJ there will be internal rotation of the talus and since the axis position is determined by the articular facets of the talus the axis will internally rotate as well. The axis will internally rotate until the pronation is stopped. With all else being equal, the forefoot valgus foot will have the medial forefoot hit sooner (in a more supinated position) than the forefoot varus foot. So, the axis will not have internally rotated as far in the forefoot valgus foot as compared to the forefoot varus foot.

The above tells you why it is important to assess the location of the axis when the STJ is in the position seen in static stance as opposed to neutral position.

Phil, I believe you asked about the foot that seems to pronate no matter where you push it. Tthere are some feet that have everted so far that the vast majority of the plantar surface of the foot is lateral to the STJ axis. These feet will often have abduction of the forefoot on the rearfoot. There is usually a small sliver of surface area on the medial calcaneus that wont cause pronation. If you invert the foot you can increase the area in which you will see supination in response to plantar pressure.

I hope this helps.

Eric

Dennis, I believe we discussed some of these, but could explain why midfoot and forefoot axes are important, and why one should balance one foot to the other.


Dennis, did you notice in his post that he described that modification as a temporary modification?


Dennis, did you know your tone is very confrontational? Is it necessary to call someone unprofessional when you disagree with them?

You point out the dfferences between yours and Kevin's devices. Why do you think your modifications are better?

Regards,

Eric

Phil:

I just so happened to give a lecture on this subject this morning at the California School of Podiatric Medicine to the second year podiatry students.

The variability in subtalar joint (STJ) axis spatial location can be due to a number of structural variations with the human foot or may be due to changes in rotational position of the STJ or midtarsal/midfoot joints. For example, a metatarsus adductus deformity will tend to make the STJ axis be more laterally deviated relative to the forefoot whereas a metatarsus abductus deformity will tend to make the STJ axis be more medially deviated relative to the forefoot. In addition, a maximally pronated STJ will always have a more medially deviated STJ axis than the same foot when it is supinated at the STJ.

Once the forefoot is loaded by ground reaction force (GRF), the plantar ligaments and plantar fascia tighten, the STJ, midtarsal and midfoot joints all compress and basically, the foot becomes relatively more rigid than when GRF is not acting on the plantar forefoot. Then, if, for example, the center of pressure (CoP) is moved laterally on the forefoot, then either the STJ pronation moments will increase or the STJ supination moments will decrease, depending on the spatial location of the STJ axis relative to the GRF vector. In other words, the GRF acting now on the forefoot is transmitted directly back to the rearfoot, from the forefoot, so that either increased STJ pronation moment, or increased STJ supination moments, and/or increased STJ interosseous compression force results from the mechanical action of GRF on the plantar forefoot. Even if the patient only has GRF acting on the forefoot, such as during the propulsive phase of walking, the GRF is still causing a direct STJ pronation or supination moment due to the relative rigidity of the forefoot on the rearfoot. In physics and biomechanics, this is called the "rigid body effect".

A chapter of my third Precision Intricast Newsletter book is devoted toward explaining how forces are transmitted through the foot with ligamentous tensile forces causing joint compression forces, joint stability, etc. These are basic mechanical concepts that, unfortunately, are not taught thoroughly in most podiatry school biomechanics programs. These concepts need to be understood before one can fully appreciate the subtalar joint axis location and rotational equilibrium (SALRE) theory of foot function (Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. JAPMA, 91:465-488, 2001).

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

Eric:
I called his DEVICE unprofessional, NOT THE MAN!
but here we are twisting and avoiding the issue. Let's close another thread editor.

I seriously think his device is a shabby, patched-up, created on the fly, UNPROFESSIONAL looking orthotic. Can you really argue that it does not!

But look at how skillfully The Arena avoided my suggestion for an orthotic casting and prescription to solve the thread and look how skillfully you changed the topic and made it personal.

Why wouldn't one of you open minded blokes say "I'll try this other method just to prove Shavelson wrong", espeically the bloke who posted the question in the first place.

“Every clique is a refuge for incompetence. It fosters corruption and disloyalty, it begets cowardice, and consequently is a burden upon and a drawback to the progress of the country. Its instincts and actions are those of the pack.” Madame Chiang Kai-Shek
dennis

Dear all

Thanks for all of your excellent work in answering my questions. I now feel as though it has filled the gaps in my knowledge in relation to rotational equilibrium approach.

Onto Dennis's comments about device cosmetics etc.
I run an orthotic lab that makes orthoses to customer specifications and consequently see over 200 different style and approaches. Some are similar approaches to your 'Vault' approach and others are very different. Therefore I have no axe to grind in any direction.

The technology I use is VERY advanced resulting in my devices being much prettier than yours so consequently that makes me a better person, practitioner and all round hero.

I hope you see how ridiculous my comment seems and maybe how your similar comment is to it.
Lets try and be a bit more professional or I will post piccies of orthoses that are so pretty you will weep with envy!

Phil

Phil:
I appreciate your genuine words but I hope you realize that away from The Arena, I have a different personna. The Arena members are probably more civil to "those that don't work with STJ axis theory" away from the Arena, I am sure.
My theory and work is denergrated before inspecting it (I know that none of you has taken a serious look at it )
I simply implied that Dr. Kirby's device when seen by other patients in a gym or at a doctors office or at a conference or seminar would have less importance, impact and marketability because they (to use your sarcastic term) aren't pretty.
Dr. Kirby is a fine person (as is the editor) whom I respect, quote and monitor, he is an excellent practitioner and the hero of The Arena. That doesn't make his orthotics any more digestable as eye candy.
Phil: As a lab director, I am sure I can talk you through my suggested casting and prescription for this patient (or another) so that you can make a Foot Centring to compare to the one rotational equilibrium will produce and I believe we will both learn something by the process, come what may.

Please visit www.foothelpers.com and maybe you can share your website with me so we can get a foundational feel of where we are coming from.

"The bend in the road is not the end of the road unless you refuse to take the turn". -Anon.
Dennis

For those who missed the earlier discussion of Dennis' theories, can we get a link back to that thread?

Link

Personally, I try to never judge a book by its cover http://en.wikipedia.org/wiki/Don&#39...k_by_its_cover.

I spent many years working with undergraduates in the manufacture of foot orthoses, some of the devices they manufactured and dispensed looked terrible (I was often embarrassed for them, but allowed the process of learning to take place), yet this did not appear to influence their efficacy. Strangely enough, the way they "sold them" to their patients did. Make of that what you will.
Wouldn't Phil be violating your patent if he did that?

__________________
Who? What? When? Why? Yeah? And? So? What?

"My mission drive is to open up my eyes, 'cause the wicked lies and all the sh!te you say..." http://www.youtube.com/watch?v=V4NW5S1UTPQ

"Science is the antidote to the poison of enthusiasm and superstition."

Dennis

Thanks for the offer of making a pair of Foot centering orthotics.
However I think the sample size etc wouldn't be large enough to allow me to make a fair comparison. Also a Rotational Equilibrium (RE) orthotic is not a fixed entity. As I am sure you are aware, RE is not just applied to the Stjt but any segment of the foot so it would be hard to compare one device against another.
As a clinician the issue I have with the your approach of foot typing is that it does not seem to make the link between cause and effect. The matrix you use is created using assumptions that do not take into consideration more proximal gait influences and alignments e.g. the effect of weak glutues medius on shank rotation during gait. If an orthotic applies a counter force to the internal rotation forces being driven by the leg, the potential for injury is quite high.
The idea of linking the MLA and LLa isn't that new. We often apply a Carlton saddle modification to orthoses that creates the Vault that you speak of. Nothing wrong with the but it just another part of the varied prescription armory that we have - 'horse for courses'.

Regards

Phil

Phil:

You are correct in ascertaining that I am less involved in cause and effect than most of The Arena Seniors.
I am more involved in effect and solution.
Medicine is an Art as well as a Science and where I am biased in Art, you seem biased in Science. As clinicians, I think the common ground is where the well rounded greats live.

I am not skilled in the gluteal effect of my orthotics but in 38 years no patient or consulting physician or therapist has accused my orthotics of “promoting a pain in the A_ _". Many patients proclaim postural performance and strength as well as symptom reduction in the superstructure as a benefit of my orthotics as they are attended by consulting specialists more knowledgable than I in gluteals.
I maintain that while you are focusing energy, funds and time finding cause, I am finding (unproven but some of which may prove valuable) cures that you won’t research or try until proven.
The Tenets of Neoteric Biomechanics are (currently):
1. The Vault of the Foot must be prevented from collapsing in closed chain
2. The rearfoot must be balanced to the three body planes
3. The forefoot must be balanced to the three body planes
4. The rearfoot must be balanced to the forefoot
5. The left foot must be balanced to the right
6. Extrinsic and Intrinsic musculotendonous units must be encouraged to work with power and in phase in closed chain.
What do you have against that?
Functional Foot Typing profiles all feet into one of ten FFT’s and then produces Foot Centrings (FFT-specific orthotics) that utilize foot type-specific orthotic casting and prescribing techniques (utilizing your “prescription armory” as well as some new ones that I have developed in an organised way). No one Foot Centring is the same as any other (not even a right/left for a given patient.
This reduces complications and failures as it increases positive outcomes and makes Foot Centirngs the most custom orthotics available.
What do you have against that?
Furthermore, Neoteric Terminology is more understandable, teachable, reproducible and even more defining then your difficult engineering and physics terminology.
For example, Maximally pronated rearfoot (the flexible rearfoot types) and less than maximally pronated rear foot (the rigid rearfoot and stable rearfoot types). Which is more understandable?
Furthermore to give an example of where Neoteric strategy would be of benefit, in reviewing Dr. Kirby’s recent important researched article, I believe the authors would have come up with much more impressive data if they profiled all of “the less thans” into rigid and stable types using Functional Foot Typing, dividing the "less thans" group.
I think the unfortunate difference between us as clinicians is that although I try to keep up on SARLES Literature, you pay no attention to mine or any others, yet ooze apparent knowledge on these foreign subjects with the same confidence that you do about STJ Axis Theory.
“The authority of those who teach is often an obstacle to those who want to learn”. Cicero

Dennis

Dennis

Why the confrontational statements?
I was hoping that you may be able to stay away from personal assumptions about me and worded my comments as neutrally as possible.
FYI, I am not a SALRE 'disciple' but a Tissue Stress model advocate. SALRE, Root, Sagittal plane etc all have their place and I was hoping for a constructive conversation with you as your methodology may have had some merit.
Unfortunately your attitude has had the effect of closing my mind to your approach - nothing to do with your theories but everything to do with your attitude.
I will refrain from name calling and will keep things professional , something you seem incapable of doing.

regards

Phil

In any debate, there are challenges of discussion that when answered further the knowledge of all involved.
The dictionary defines confrontation as:
1. an act of confronting.
2. the state of being confronted.
3. a meeting of persons face to face.
4. an open conflict of opposing ideas, forces, etc.
5. a bringing together of ideas, themes, etc., for comparison.
6. Psychology. a technique used in group therapy, as in encounter groups, in which one is forced to recognize one's shortcomings and their possible consequences
Isn't that what we are doing?
Must I only agree with what you say?
What names did I call you (as you infer)?
When I said:
I think the unfortunate difference between us as clinicians is that although I try to keep up on SARLES Literature, you pay no attention to mine or any others, yet ooze apparent knowledge on these foreign subjects with the same confidence that you do about STJ Axis Theory.
I said I THINK!!! that calls for a reply from you so that I can know your fiber better. I did NOT name call.
Have you ever read any information on Neoteric Biomechanics is a fair question, I thought.

Please either answer one or more of the questions/points I raised or suggest an online course for "attitude repair while visiting The Arena" which I will subscribe to and then return softer and more user friendly.

Dennis

Sorry to bring back an old post. Was just wondering how to dorsiflex the medial column when casting?

Ben:

While holding the foot in the standard supine neutral suspension casting position with one hand, I will use the contralateral thumb to apply a variable magnitude (about 2-5 lbs) of load to the plantar aspect of the first metatarsal head while simultaneously applying a variable magnitude (about 2-5 lbs) of load to the plantar aspect of the head of the proximal phalanx of the hallux with my index finger. This negative casting modification produces an elongation of the arch of the foot, a pre-tensioning of the plantar fascia, and a minimal change in the forefoot to rearfoot relationship within the resultant negative cast. This is the first time I have ever described this procedure publicly, but have been using it for the past 20 years in my practice. It is one of the many negative casting modifications I use to optimize the orthosis morphology for my patients.

Hope this helps.

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

Hi Kevin,

So I guess this is similar to the function that plantar flexing the 1st ray has? Benefits would be possibly less forefoot manipulation when casting and possibly a more 'natural' capture of the dynamic MLA?
I try this out.
Thanks for sharing your knowledge, it’s very much appreciated.

Kind regards,
Ben

No. The technique I described dorsiflexes the first ray.

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

sorry misread that. Just wondering when applying force to the plantar 1st metatarsal head would you risk creating an artifical forefoot varus?

edit: just had read your previous post a couple of times again. Guessing the force applied to both the metatarsal head and the hallux comes to an equilibrium, leaving the hallux realtively straight and windlass primed. I will stop asking (stupid) questions and try it for myself.

thanks again

When I've used this technique, I've often wanted, and gotten, a fairly large change in the forefoot to rearfoot relationship in the cast.

I usually use the technique when there is very little eversion range of motion available when the patient is standing and there is a large amount of forefoot valgus in the foot. If you did not modify the cast, and balanced the cast vertical there would be a large amount of intrinsic forefoot valgus correction, which could lead to excessive forces on the lateal side of the foot. If you balance the unfodified cast severel degrees inverted to reduce the amount of intrinsic forefoot valgus post then you will tend to be inverting the heel cup of the device. Often these feet, with a large amount of forefoot valgus will often have a laterally deviated STJ axis. You don't want to invert the heel cup in these feet. This problem is solved by dorsiflexing the first ray to decrease the amount of forefoot valgus.

Kevin, when do you dorsiflex the first met when casting? When do you try not to alter forefoot to rearfoot relationship?


Cheers,

Eric Fuller