Relative Importance of STJ Motion

From the Nestor paper"
"“A rigid functional unit comprise the navicular and cuboid. No other functional units were identified.”

From Kevin's paper:

“…. During many weightbearing motions, the foot may approximate a relatively rigid unit with all the bones of the foot rotating around the central pivot of the talus and the subtalar joint axis.”

The Nester finding does not completely contradict the Kirby statement. Nestor looked at the joints throughout gait. However, at certain times in gait, the rigid body assumption could be a good one. For example, take Ed's drawings at heel contact. Between heel contact and forefoot contact the rearfoot to forefoot rigidity does not effect the calculation of moment from ground reaction force about the STJ axis. Later in gait when the joints are loaded, as well as static stance, the foot is rigid enough to be able to use the center of pressure to calculate a moment from ground reaction force. It will certainly be rigid enough to create a moment about ground reaction force. After heel contact there is little STJ pronation until the lateral forefoot hits the ground, then you get a rapid pronation caused by the fact that at this point in time the center of pressure is much farther lateral to the STJ axis than when just the heel is contact with the ground. How else can you explain the contact phase pronation without examining moments about the STJ axis? (Moment = moment of inertia x angular acceleration. You cannot get a change in motion without a moment) So, the foot must be rigid enough to create a moment about the STJ axis.

Regarding the title of the thread. SALRE doesn't care so much about motion, but more about moments. Even if there were no motion, there could still be moments. These moments will cause stress on anatomical structures. This stress can be reduced by altering the moments about the STJ.

Eric

 

So Ed! Take a "moment" to think!

 

Did someone suggest bracing something?

 

Simon,
Relative importance of one axis as compared to another had to have been done to determine that the Subtalar axis should be the one which must be located and around whose rotational equilibrium we shoiuld concern ourselves.

Relative importance is not directly proportional to size of ROM of a joint.

The timing and functional effect of a joint's motion must also be considered. For the STJ the small rotational motion seems to be used to place the talar head in greater contact with the anterior facet, blocking sagittal plane motion between talus and calcaneus which facilitates propulsion......utilizing the ankle rocker (as Dr. J Perry described).

The relative importance is highly influenced by the relative magnitude of moments produced by forces entering the foot. Axes are placed in different orientations for a reason. If the primary role of the STJ axis were to influence pronation and supination of the foot, it would not be passing through both the force of the momentum down the leg and the force vector of the GRF in the heel.

But what your comments really highlights is the fact that any choice or singular axis is necessarily insufficient. It is a sin of omission. It ignores postural change...... which is simply the consideration of all axes simultaneously by looking at a gross geometric change in the plantar aspect of the foot, soft tissues compressed. It simply yields a shape that can be applied to the foot to act as a starting point for the more even application of a corrective spring force....NOT to brace.....but a calibrated flexible spring to apply a controlled assist to decrease the velocity, acceleration, impact, and aid in resupination in an attempt to make a more functional gait cycle.

Therefore a wiser choice would be ALL AXIS which is also called Posture. In many ways the foot is like a three dimensional puzzle that simply solves itself as the foot assumes a more supinated posture.

So instead of arguing over which axis is more important, shouldn't all be considered.

The only reason therefore to discuss the relative importance of one axis as compared to another is to dispel any false notion that only one axis should be considered......and if one axis were to be chosen.....maybe the STJ axis is not the best choice.

I will continue on as soon as I answer the questions asked.

Ed

 

Ed I think your had better define an axis - as you see it, because it seems different from what I understand an axis to be.

Motion defines an axis not the other way around.

and axis will help explain the influence of moments at the joint.

I made a summary on another thread about the axis in the case below the MTJ,but similar ideas heres

 

Yep nice slides... but I have to say I am more impressed by the giant talus and calcaneus

 

Me too! Although not entirely sure why the talus is wearing a feather in its cap...

 

I thought it was to represent the STJ axis ???

 

No it hadn't. This is a fallacy, it is like saying that Nester assumed that the MTJ axis was more important than any other axis because he published papers on the midtarsal joint. The key is in the title: subtalar joint axis location AND rotational equilibrium theory. It's a demonstration of the principles of rotational equilibrium applied to podiatric biomechanics. I can't say why Kevin initially chose the subtalar joint as the focus of his research, maybe it was an historical hangover from the Rootian focus on the subtalar joint,; maybe he was just interested in the subtalar joint. I do know that in his subsequent writings and teachings Kevin (and indeed others) have discussed the concepts of rotational equilibrium about midfoot and forefoot joint axes.

Do you believe that rotational equilibrium about the subtalar joint axis is unimportant, or less important than that about any other axis? I certainly don't.

I didn't say it was. You made the point that 6 degrees of eversion motion occurred at the subtalar joint, I merely pointed out that sources also suggest that the same amount of motion occurs at the ankle joint at the same time and the proportion of the range of motion employed will likely have implications to the stresses within the restraining tissues.

If range of motion is insignificant, why did you include it in your slides?

You are welcome to speculate upon this. When did you say this was occurring?

Ed, joint axes are artificial constructs defined by the motion of one segment relative to another. Both internal and external moments are significant, Ed. If the GRF vector had no moment arm about the STJ axis, as you seem to be suggesting, then there would be no external moment actin on the STJ during the contact phase.

Ed, to my mind the only person who seems to be focusing on a single axis here is you.

I look forward to reading your answers to the questions asked.

 

So, you are saying that SALRE is based on a valid assumption “at certain times in gait” and the rest of the time it is invalid. A criticism I had not thought of.

See Post # 6 #7 and #8 The Hamel article. You will notice that STJ motion has already occurred before forefoot contact. Maybe that motion is coming from the MTJ axis……and that’s my point, why single out one very questionable axis as opposed to considering every axis. The singularity itself is the primary problem. The choice of the STJ axis in exclusion of all others…..simply makes no sense.
It yields an incomplete solution. Even in relative importance…. The STJ axis may not be a reasonable choice.

The foot creates lots of moments around many axes.

Again, Eric, Why are the only moments that count, those about the STJ axis? Why that axis and not another or all axes? Don’t the moments around all of the joints contribute in some way to the overall kinetics and kinematics of the foot? Would not an axis that experiences many times the moment of the STJ axis be a better focus? But, still why not consider all axes?

What is more, if the STJ axis location were so important, then why not reposition it, cause it to translate to where you want it, by changing foot posture instead of allowing it to fall into its least desirable translational zone and then concern yourself with the distribution of kinematic forces on the bottom of the collapsed foot?

I apologize, we are getting ahead of ourselves here.

I certainly would love to discuss mods and tissue stress theory later. Here I am asking everyone to re-look and re-think the selection of the STJ axis and the idea of singular axis altogether.

Eric,
In this whole post you just pre-suppose the dominant importance of the STJ axis. The purpose of this thread is to challenge that idea.

Ed

 

Ed,

Eric has already pointed out that rotational equilibrium occurs around all axis. Kevin used the STJ as an example and demonstrated an orthoses modification that would affect this axis. Kevin has never said that the other axis in the foot are not important and that the STJ is the ONLY one that is important. He meerly chose the STJ axis as an example of how rotational equilibrium can be observed and altered by a foot orthoses.

 

Volume 41, Issue 7, Pages 1390-1397 (2008)

In-vivo range of motion of the subtalar joint using computed tomography

Lijkele Beimersade, Gabriëlle Josephine Maria Tuijthofde, Leendert Blankevoortde, Remmet Jongesb, Mario Maascde, C. Niek van Dijkade
Accepted 21 February 2008. published online 11 April 2008.

Abstract
Understanding in vivo subtalar joint kinematics is important for evaluation of subtalar joint instability, the design of a subtalar prosthesis and for analysing surgical procedures of the ankle and hindfoot. No accurate data are available on the normal range of subtalar joint motion. The purpose of this study was to introduce a method that enables the quantification of the extremes of the range of motion of the subtalar joint in a loaded state using multidetector computed tomography (CT) imaging. In 20 subjects, an external load was applied to a footplate and forced the otherwise unconstrained foot in eight extreme positions. These extreme positions were foot dorsiflexion, plantarflexion, eversion, inversion and four extreme positions in between the before mentioned positions. CT images were acquired in a neutral foot position and each extreme position separately. After bone segmentation and contour matching of the CT data sets, the helical axes were determined for the motion of the calcaneus relative to the talus between four pairs of opposite extreme foot positions. The helical axis was represented in a coordinate system based on the geometric principal axes of the subjects’ talus. The greatest relative motion between the calcaneus and the talus was calculated for foot motion from extreme eversion to extreme inversion (mean rotation about the helical axis of 37.3±5.9°, mean translation of 2.3±1.1mm). A consistent pattern of range of subtalar joint motion was found for motion of the foot with a considerable eversion and inversion component.


OK, so taking the means we have a ratio of 37: 2 or 18.5:1 In other words, for every degree of subtalar joint frontal plane rotation we have 0.05mm translation, so with 6 degrees of subtalar eversion motion we might expect to see a forward translation of the talus in the region of 0.3mm. I'm sure someone can check if my math is correct for you. How significant is that 1/3 of a millimetre translation?

 

Graham, it's very simple: Ed is attempting to employ a straw man fallacy.

 

Exactly!:sinking:

 

I believe we agree on that point. No one had actually tried to evaluate the relative importance of any of the axes of the foot.

Of course I understand that Dr. Kirby incorporated Newton’s law of Rotational Equilibrium. Admirable. It is true for any axis anywhere. I think we can give Isaac Newton credit for that one. But the SAL is what Kevin added and might lead one on the wrong uni-axial direction.

I agree with your “historical hangover” idea…..but it remains a central and important choice that needs to be considered.

The MTJ axis of Nester only clouds the issue further. Which axis is moving during the plantar palpation technique?

SALRE’s problem is with its singularity. Other axes that are far from parallel to the STJ have more influence. The tissue stress application of SALRE just underlines the singularity of axial consideration. What upward ORF moments lie medial or lateral to the Subtalar Joint Axis?…..ONLY the STJ axis.

Important…… relative to what? It has a function….sagittal plane locking for propulsion. In that capacity it is important indeed. As far as being the solitary hinge around which all foot function see saws….NO. It is one joint in the postural complex that is expressed in overall plantar foot geometry.

I just showed the relative moments around STJ as compared to HRA. The heel rocker’s moments were relatively more important in the collapse of the foot’s structure….. and more relevant to how those using MASS posture biomechanics are attempting to accomplish with foot orthoses.

Range of motion gives us a clue as to what the joint can and cannot accomplish. If you want to use a joint axis to reposition a bone in some way…it is nice to know how much it would, could or should move.

If I was trying to use the STJ axis only to rebalance forces at the end ROM, I agree, extent of motion would have no relevance. No kinematic change desired or required. Seems like the hard way to go about things to me. If you just reposition the axis where it is most functional, balance is a breeze. It takes far less force to do it. It is like moving a refrigerator with a hand truck (a two wheeled single axis ). Balance it properly and it can be moved with very little force.

When the foot is in a more Supinated posture.

By George, I think you’ve got it. I expect little or no external moments acting on the STJ axis during the contact phase due to the placement of the STJ axis in relation to the forces. Do you think that the placement of the axis was random? Of course there is some variation and small moment arms exist on both sides at times…… but nothing like the moments around the heel rocker axis. There are measurable moments but they are small relative to the HRA moments.

 

Graham,

I appreciate your loyalty. This is not a personal attack. No more than criticizing MASS is personal to me. We are discussing the merits of a theory here. We have to accept what the author of the theory wrote as to what the theory states. That is well written in a peer reviewed article. It says what it says.

Please....that's why we went through that whole previous discussion. If Kevin makes one thing clear....it is the dominant importance of the STJ axis. I could belabor this with hundreds of quotes from everyplace Kevin has written. It is in the title of six of his articles, mentioned 433 times in one article. Don't tell me that the Subtalar Axis Location and Rotational Equilibrium Theory is not about the STJ axis. That path leads nowhere. There is more than ample data on that. Strawman doesn't fly here.

Ed

 

Of course it is dominant in his papers because that is what he was looking at. Of course it is about the STJ because that is what he was looking at. If I write a paper on the physical properties and actions of an electron that doesn't mean I don't give a **** about an atom!

 

I need to really read this one asap. This is a very interesting article. I will try to find it in some online journal. A url would be great if you have one, Please? Gotta go....family get together for Thanksgiving.

Thanks,
Ed

 

No, never once led me to believe that the only joint of significance in the foot was the subtalar joint.

Indeed it does. So you agree that rotation about the subtalar joint axis is an important part of gait function?

This is why we try to limit palpation to proximal to the MTJ, I believe Kevin has already spoken about this in later revisions to the technique.

No Ed. There is no problem with SALRE referring to the subtalar joint in isolation. The problem is in people like yourself who cannot see that the subtalar joint was merely an example within this paper and that the application of the "AND rotational equilibrium theory" which the paper discusses can be applied to other joints.

Just run that "locking" past me one more time, Ed. Ed, no-one is saying that all foot function revolves around the STJ axis, other than you in your attempt to build your straw man fallacy against Kevin.

No Ed, what you showed was a slide that you paid someone to draw for you. There's a big, big difference between that and inverse dynamics.

Ed, I'll say again, joint axes are artificial constructs. Moreover, you do not need to reposition an axis or even a bone in order to alter the moments about a joint- kinetics versus kinematics.

Obviously lol.

Like I said, drawing diagrams ain't inverse dynamics Ed. Further, it's not the just the magnitude of the external moment that's important, it's the ability of the tissues to develop internal counter moment. Do you get it?

 

Correct. One of my engineers has a full size McCaw Parrot who occasionally donates a feather.

Ed

 

Singularity of what when discussing SALRE I like to think about the subtalar joint, when thinking about the midtarsal joint I like to think about the midtarsal joint.

If thinking about the Subtalar and Midtarsal joint in-phase and anit-phase motion and I guess moments would be a good place to start.

Whats you point Ed

Explain you last comment

what ORF vectors lie medial or lateral to the subtalar joint everywhere the is contact with the Orthotic that is not inline with the STJ axis at that exact point in time will cause a pronation or supination moment. The orf vectors inline with the axis will not cause a pronation or supination moment.But the important thing to consider is the sum of these ORF vectors which will give us the Centre of pressure and this COP relationship to the axis , which due to the shear medial-lateral or anterior-posterior may confuse the issue.

again you missed my post. From before

Ed I think your had better define an axis - as you see it, because it seems different from what I understand an axis to be.

Motion defines an axis not the other way around.

and axis will help explain the influence of moments at the joint.

I made a summary on another thread about the axis in the case below the MTJ,but similar ideas heres

 

I am trying to sneak in one more post before family arrives.

How many do you draw on the bottom of the foot? The first met cuneiform axis?
The second or third met cuneiform axes? The calcaneo-cuboid axis? The cuneo-navicular axes? Quite a game of tic tac toe. Modern art, I suppose.

Ideally………….. the STJ Kinematic change would theoretically improve gait efficiency. And it did in the article Trotter and Piernowczki published in JAPMA on gait economy.

Good strategy to find a singular axis. I wonder who or what led you draw that particular axis?

The problem is in what you now are taught to do with the data collected on that singular axis. Move kinetic forces to the right or left to be on the right side of the see saw……. That one pivotal see saw…..no others…..the one you drew on the foot….the one you palpated……careful not to affect any other…..like the MTJ for example.
This theory, SALRE is about Subtalar Axis Equilibrium (Which is the title of one of Kevin’s Peer reviewed articles).

I cannot stand back now and say that MASS Posture theory is not about a singular posture…..individual foot to foot but having the same parameters on every foot.

I admit that freely.

When the talar head is on top of the anterior facet sagittal plane motion between the talus and calcaneus is resisted and may even be restricted. The extent of this influence is anatomically and posturally dependant.

I agree. My employees have all the fun of working for me….and then they want to get paid????? The nerve!!! Did I ever mix up inverse dynamics with illustration? I don’t think so. It is just a fabulously executed 3D graphic illustrating a point: that forces being equal…moment arms determine the relative magnitude of moments produced.

Santana Marcum did those amazing graphics. I of course gave him parameters for bone placement based on data from previous studies, cineradiography. Axial placements were according to standard Root, Manter, Hicks, Fick parameters. A best guess was applied to heel rocker axis placement which will have considerable variation step to step and especially between feet both corrected and uncorrected.

But it would be nice if you did reposition the axis. Why not try it?

Tissue stress is important and the strategy of attempting to apply SALRE is equally of concern and will be addressed later. Not ignoring tissue stress….just trying to keep on topic.

Ed

 

Well done Ed!

One aspect of what we look at to determine what forces are acting on the foot to stress a specific structure.

 

How many do you draw? Ed, I'm sure if you can publish some studies which show the techniques and their reliability then we can have a go. The fact is no-one has described these techniques or had them published in peer-reviewed journals. Ed, do you understand the concept of "constraint"?

Just remind me, was that the study you paid for that used a flat piece of foam as a prefab?

Yep, describe the clinical techniques I can use to identify the axis of the talonavicular joint and I'll use it. Do you understand the concept of constraint? You can palpate a projection of the ankle axis relatively easily BTW

No, it's about subtalar axis location AND rotational equilibrium theory. Ed, have you read Kevin's books?

At what point during the gait cycle is the foot in the MASS position?

Oh, OK I thought the stiffness of the bony segments of joints increased towards their ends of range due to changes in the relations of the articular surface geometry and due to soft tissue tension about the joint. I didn't know that joints "locked".

You know when someone is showing guests around their factory and they shout out "what do we do here?" and the people who they pay shout back with the required and prescribed answer? The word "pay" might be significant. The question is, what do the staff say about the boss when he's not there? Just an observation I made when someone recounted a story to me recently. Anyway, I digress.

Because axes are artificial constructs. Moreover, how do you know I don't?


I may be missing from this discussion for a couple of days as someone just crashed into my shopping trolley at the supermarket. Luckily no-one was hurt except that my cucumber did get slightly squashed during the collision.

 

So Ed, do you accept that it is valid some of the time? We can use SALRE to explain pathology when the foot is weight bearing. You are looking at the empty half of the glass and saying there is no water in the glass.

The digrams in posts #7 and #8 clearly show a flat line for angular position for a while before there is a significant change in position. This is consistent with my stated observation that there is a lot of STJ motion that starts at forefoot loading.

As you stated there was very little motion from 25% to 90% of stance phase. There is very little motion between 0-10% which you explained nicely with your diagrams as there was very little moment until the forefoot starts to load at which point, the rest of the foot is still not fully rigid, yet this is when the STJ motion occurs because of the moment created by ground reaction force on the forefoot. (suggestion to other readers, open another browser tab so that you can easily move back and forth between this post and posts 7 and 8.) So, SALRE works perfectly here to explain the observed data.

So Ed, why do you feel the STJ axis is questionable?

The straw man argument is that we do exclude all other axes. We don't

Ed, are you familiar with my windlass paper. Fuller, E.A. The Windlass Mechanism Of The Foot: A Mechanical Model To Explain Pathology J Am Podiatr Med Assoc 2000 Jan; 90(1) p 35-46

In that paper I propose a mechanism of how STJ moments effect moments at the first mpj and first ray. So, I don't exclude other joints.

If you want to explain pathology you have to look at moments and forces. This is the problem I have with MASS theory. There is no examination of moments at any joint. There is no kinetics. You can claim that you look at all joints, but you have not examined the kinetics at any joint.

How do you reposition a joint? What forces do you apply to move a joint to a different position? Is the term "posture" biomechanics without the mechanics?

I see that is the purpose of the thread. However, there has been nothing said so far that questions the importance of moments about the STJ axis. See my windlass paper for an explanation of why STJ moments are important for other joints of the foot. Kevin's rotational equilibrium paper gives an excellent explanation of why posterior tibial dysfunction occurs. How do you explain posterior tibial dysfunction, using posture with forces and moments?

Eric

 

That's gotta be the favourate contender for quote of the year. Would have been proud of that one!

 

How many axes do you draw on the bottom of the foot? The first met cuneiform axis? The second or third met cuneiform axes? The calcaneo-cuboid axis? The cuneo-navicular axes? Quite a game of tic tac toe. Modern art, I suppose.

Ideally………….. the STJ Kinematic change would theoretically improve gait efficiency. And it did in the article Trotter and Piernowczki published in JAPMA on gait economy.

Good strategy to find a singular axis. I wonder who or what led you draw that particular axis?

The problem is in what you now are taught to do with the data collected on that singular axis. Move kinetic forces to the right or left to be on the right side of the see saw……. That one pivotal see saw…..no others…..the one you drew on the foot….the one you palpated……careful not to affect any other…..like the MTJ for example.
This theory, SALRE is about Subtalar Axis Equilibrium (Which is the title of one of Kevin’s Peer reviewed articles).

I cannot stand back now and say that MASS Posture theory is not about a singular posture…..individual foot to foot but having the same parameters on every foot.

I admit that freely.

When the talar head is on top of the anterior facet sagittal plane motion between the talus and calcaneus is resisted and may even be restricted. The extent of this influence is anatomically and posturally dependant.

I agree. My employees have all the fun of working for me….and then they want to get paid????? The nerve!!! Did I ever mix up inverse dynamics with illustration? I don’t think so. It is just a fabulously executed 3D graphic illustrating a point: that forces being equal…moment arms determine the relative magnitude of moments produced.

Santana Marcum did those amazing graphics. I of course gave him parameters for bone placement based on data from previous studies, cineradiography. Axial placements were according to standard Root, Manter, Hicks, Fick parameters. A best guess was applied to heel rocker axis placement which will have considerable variation step to step and especially between feet both corrected and uncorrected. Still it is a pretty good first approximation and makes the point.

But it would be nice if you did reposition the axis. Why not try it?

Tissue stress is important and the strategy of attempting to apply SALRE is equally of concern and will be addressed later. Not ignoring tissue stress….just trying to keep on topic.

Ed

 

I don’t think I would take the time investigating any technique which I believe has no promise of success. I don’t see the advantage of mapping out every axis on the bottom of the foot and then concerning our selves with which side of all of the lines we have been able to apply kinetic force at the end ROM.

I am not sure which meaning of “constraint” you are referring. Enlighten me.

I hope to have Dr. Leslie Trotter’s lecture up soon. She describes our financial relationship with McMaster in depth. If you are implying any bias on the part of Dr. Trotter or Dr. Pierrynowski, I think you owe her an apology and me as well.
If you want to know what materials and methods were used, read the article.
What it did show was improved Biomechanical Efficiency Quotient. It is not my place to defend this article. Leslie and Mike already did that to be published in JAPMA.

Exactly my point. Singular Axial location is useless and multi-axial location is confusing, unnecessarily complicated and in some cases like the TN may be impossible.

Ankle axis location is more interesting indeed. Especially in the design of SMO’s…..an area of great interest to me.

Unfortunately, Yes I have. That is where I got the notion that SALRE could just as well been named; Single Axis Location and Rotational Equilibrium Theory.
I agree that Kevin is credited with bringing the concept of Rotational Equilibrium around the singular Subtalar Axis. He may even talk about the RE around another joint from time to time. Very True. I am not attacking the man. I am attacking Subtalar Axis Location and Rotational Equilibrium Theory. It is a theory and technique that causes us to focus our attention on one singular axis of the foot and use the tissue stress model by applying forces and moments around that axis with various mods on a low arched generic shaped shell sized to the foot.

On a similar note, someone recently brought me a lego like orthotic concept, really. It is a rather generic shaped orthotic that you can snap in place various wedges, bumps, pads, tilts, skives, lumpy bumps…. You know MODS. With a rather simple modification the molds for these devices could produce about any configuration the Tissue Stress / SALRE practitioner would desire and then easily be moved around to gain maximal effect. This could easily be sold in the drugstore….Oh wait. A slightly lesser version is now available at Wal Mart (Always the Low Price, Always) with Dr. Scholls. A formidable opponent.

Anyway…. These molds may be still for sale if someone wants to start a business venture and really believes in offering to the public broadly the advantages of the Tissue Stress / SALRE approach.

You asked that in a previous thread. My answer is the same. We currently have no data on that. Our research at Quinnepiac U. may give us some idea…..but I do not interfere with research. I will read it when it is published.

Although,I can’t wait to get my hands on the raw data.

Semantics…… People understand the concept.

It is called: Core Value. I advise anyone who wants to create a successful organization of any kind. Define Success.

Not in terms of money…..that is a by-product; a result.

Pick a core value that people can adopt easily, that aligns with their basic beliefs. Helping others is almost universal. Sure, we occasionally have to fire someone who is not in alignment with the core value of the company. We did twice recently. People work better, harder, more focused and accurately when they are doing it for a purpose that they strongly believe in. We communicate that core value over and over again. It is our Kool Aid. WE MAKE PEOPLE BETTER. It is our purpose, our motivation, the reason we get up in the morning and fight this fight. We only appeal to customers that share that same desire. Many of our customers use our core value as their own…..and we encourage it. When you walk around Sole Supports, Inc. and ask anyone individually or as a group, “What do you do here” they will answer without hesitation, “We Make People Better” and be proud of it. We make it personal by reading to them the wonderful success stories we receive so frequently.

What you will find anywhere in Hickman Co. TN, about me, personally, is he’s the best employer in the county….possibly the state. I invite you to ask my employees how I am to work for…. Privately…..please do. I received three boss of the year awards in one year. The local TV station awarded me the first on the basis on an essay that one of my employees wrote. Then 30+ of my one hundred employees wrote to the county government and chamber of commerce who awarded me the second award, and the third was most meaningful. Some of my employees felt left out of the other two appreciations and the whole plant, as a surprise to me, awarded me another award: Best Boss Ever…..with a party. I am great to work for…… in fact if anyone, even if it is not their area has any problem with me, I am the first to hear about it because they walk right up and tell me. Execs are encouraged to disagree with me at meetings……on everything. It makes for lively discussion which is fun but it always begins, ends and focuses on our core value.

Another criticism of SALRE I hadn’t thought of: “axes are artificial constructs”.
How do I know you don’t? Good question. If you are practicing the Tissue Stress / SALRE approach you have to leave room between the foot and the orthotic for a layer of Mods. After all that is how orthotics work, right…..mods that move the tissue stresses around the bottom of the foot.

Good luck with that. I am sure we will recover from the separation anxiety.

I hope you got the insurance information from the other cart. Filed a police report. And what were you doing playing with your cucumber in the market anyway? LOL

But you make a point….I have a life besides the arena. The arena is fun sometimes….and I will continue this and a few more threads because there is important information to discuss.

If we are going to spend time here….why not make it pleasant. I will take all personal attacks on me as JOKES……just that.

Maybe you should just start a thread called: Personal Attacks on Ed Glaser.

Then I am sure Kirby himself would participate.

You will probably get a fair amount of contributors…….and that’s fine.

Can we keep this thread on topic? As I hope you can see, my employment practices are irrelevant to this discussion. Neither is my ethics, marriage, dog, deceased hamster, underwear, wardrobe, etc. etc. etc. My personal life is not a biomechanical question.

But thanks for playing.
Ed

 

You might want to edit that post again Ed, it still says the same thing over, P.S. don't worry about the cucumber it's still fully functional

 

Simon,
Thank you. I noticed that and I think I fixed it now.
Ed

 

How does SALRE explain plantar fasciitis? The foot cannot elongate heel to toe in the frontal plane. Which side of the STJ axis should I put my force on to treat plantar fasciitis? What if the plantar fasciae is running parallel to the STJ axial projection?

No, it is a flawed way to examine the foot all of the time.

To really understand what you just stated I took a high speed video, just now, of a stance phase of gait. I brought it into imovie (a Mac application) and measured the percentage of stance where forefoot loading begins. It begins at just over 3/13ths of the stance phase, according to my measurement on one subject. Which is about 24% of the stance phase. The study showed the motion was all but over by then.

On the contrary the study contradicts your prediction.

24% of stance occurs before forefoot contact. Loading occurs over the whole flat foot section of stance. Which begins from 25-27% of stance where no motion is occurring.

Because the relative magnitude of its moment created by the major forces entering the foot are small around the STJ axis in comparison to the HRA for example.

No one is even questioning what you or anyone else does… We are discussing a theory called SALRE. Only the theory…. Not yours or Kevin’s or anyone else’s practice. Heavens…No one would ever want to be accused of using a single axis theory excluding all others. It just happens to be what SALRE is. I have asked how many axes you or Simon draw but that is to show that not even the top Tissue Stress / SALRE docs want to admit that they only draw one axis because you don't want to be pinned as a "single axis" doc..... like one who may have just read the original article on SALRE and uses it as stated in the article.

No but send me a ulr and I will be happy to read it. Stu, as our director of research, has a library of articles. It may be there. I was going to ask him to get me it and the one Simon recommended on Monday.

No one said YOU did. It is not YOU that is being questioned here….it is SALRE. You are not SALRE. Neither is Kevin or Simon. You each practice as you choose....I understand that.

Not true. MASS is the best way of controlling the moments of all axes simultaneously. That is its beauty and simplicity.

The ORF up and Gravity down.
By its very definition MASS Posture biomechanics is far more inclusive than Single axis theory.

The relative magnitude of those moments is more than enough to question the importance of moments around the STJ axis.

PT dysfunction is easily explained using posture. The postural collapse of the foot is what is responsible for the excessive strain on the PT. That is what applies the excessive force. It is postural change that elongates the muscle beyond its anatomic ROM. Re-posturing puts the PT back in an anatomic alignment where it can function more efficiently. Remember the medial cuneiform moves laterally as the foot supinates…giving it additional mechanical advantage.

The truth here is simple:

Single Axis theories like Neutral and SALRE do a poor job both theoretically and practically. They have led to a poor application of the Tissue Stress Model….which we will discuss next.

All Axis or Posture theory is inclusive of all moments, forces, equilibriums etc.
Posture Controls Function.
Whitman stated that, in much more eloquent terms in his 1896 paper.

Ed

 

Who says Ed? You? Where is your evidence to make this statement?

How many times do you need to be told Ed? SALRE was just that but allows those of us with the ability to laterally think to apply the principles of RE and applications of moments to the WHOLE concept of Tissue Stress. SALRE is a part of the puzzle. It is not intended to be the only consideration.

That's because MASS is a splint theory. It fails to consider the actual dynamics of the foot during stance phase. It assumes that if you put the foot in a set posture, at a set point in time, determined by the clinician, then it will work properly! It controls motion by acting as a splint. It will make the foot different but not necessarily better. It does not enhance motion. By it's nature, it can't!

MASS is therefore a temporally flawed theory.

 

I'm talking about the constraint of the joints of the foot.

I just asked if it was the study you funded in which a flat piece of foam was used to constitute a prefabricated foot orthosis; was it? Either it was or it wasn't; why should I owe anyone an apology? A bit paranoid, Ed? Did you fund the study you referred to : yes or no? Was it the study in which a flat piece of foam was used and referred to within the study as a prefabricated foot orthosis: yes or no?

If you are going to put an entire lecture of powerpoint slides up again, can I ask that you just put a link to the file, rather than putting up about 20-30 posts like you did in this thread? Just makes it easier.

Do you think Kevin had to defend his article on subtalar joint axial location AND rotational equilibrium theory to be published in JAPMA? Honestly, why do you believe he hasn't joined in with this thread, Ed?

So if single axis evaluation is useless, looking at the ankle rocker axis is equally useless. Evaluation of the TNJ axis is not impossible, hence we have publications in which it has been done. I thought your whole point here was that the subtalar joint axis was merely one of several axes within the foot? Do you think that the moments acting about joint axes are significant in foot function? Or is it that only the plantarflexion moment acting about the ankle joint is significant, in your opinion?

Ed, for the last time, it's a theory which causes YOU to focus YOUR attention on one axis of the foot. I'll ask again, is rotational equilibrium about the subtalar joint axis significant in foot function: yes or no? Is rotational equilibrium about the "ankle joint rocker" significant: yes or no? I use shells varying in arch height, some probably almost as high in the arch as device produced from a MASS cast. I try and influence the stresses within specific target pathological tissues. Is your theory based around using a high-arched generic shaped shell sized to the foot, what modifications would you use in a subject with chronic lateral ankle instability and peroneal tendonitis? Sorry, I forgot you don't do "mods" everyone gets the same prescription of a high arched device with your idea. :bash:

So we have no idea whether the foot is in the MASS position at any point during the contact phase of gait, yet you would still advocate that this is the best, and only position to cast the foot in? Lol.

Yeah, people understood the concept of MTJ locking presented by Root as occurring because the axes crossed, doesn't mean it was right. We'll come back to this.

or a dictatorship. Anyway, I digress and so do you.

So, if I understand you correctly, your contention is that the ankle plantarflexion moment at the time of heel strike is relatively more important than the subtalar joint eversion moment because it's of bigger magnitude?

Ed, if you only respond directly to one question in this post, then please respond with either a yes or a no to this question: is rotational equilibrium about the subtalar joint axis significant in foot function? That is all I ask.

 

Ed, SALRE is three dimensional. It is wrong to assume that it only works in the frontal plane. (A straw man argument would be to characterize SALRE as frontal plane only.) My windlass paper describes how STJ pronation effects tension in the plantar fascia. But there are some common observations that can be used to verify that STJ motion / moments have an effect on the windlass / plantar fascia.

The push up test of Jack varies across individuals. In some lifting the hallux of a foot in stance causes STJ supination. In others it is more difficult. You can feel the fascia become tight and then you see STJ motion when you lift the hallux. The STJ moves therefore the lifting of the hallux creates a supination moment in most feet. Therefore SALRE is relevant. The supination moment from the plantar fascia is a moment that adds to rotational equilibrium around the STJ. Since, in most feet, a pronation moment from the ground will increase tension in the fascia, then you should increase supination moment from the ground to reduce tension and stress in the plantar fascia. (How does MASS treat plantar fasciitis?)

Why is SALRE a flawed way to examine the foot?? You've tried to characterize it as a single plane model which was wrong. You've said that it's a single axis model and we've agreed and asked why is that a problem. (Even if some haven't agreed, you still haven't said why it's a problem) Well, ok you did agree with me that SALRE doesn't explain 2nd met stress fractures, but there is no reason that SALRE theory should. But within this limitation that SALRE doesn't explain everything, it still can be used some of the time. For example posterior tibial tendonitis and my example of plantar fasciits above. What is flawed about applying it in those instances?

Now we are disagreeing about reality. The graph that you posted in the first three or five posts (came out Root Orien and Weed) has FFL (full forefoot loading) at 27% of stance phase. Full forefoot loading is when the medial forefoot is fully loaded. I have some EMED movies of average gait where the 3rd or 4th frame out of 45 (9% of stance phase) is when lateral forefoot contact begins. So, I question whether your 3/13ths is accurate.

Using the Weed data and the fact that lateral forefoot contact begins about 9% of stance phase we should expect to see pronation begin about 10% and end around 27% just as the diagram you had in post # 7 and # 8 shows. So the study confirms my prediction. What else could consistently produce a pronation motion (seen in the study) than a pronation moment from ground reaction force? A moment from ground reaction force predicted by SALRE and contact phase data. You also aided in this prediction with your diagrams of how force on the heel contributes very little STJ moment. This also is shown in the diagrams as there is little motion before the first 10% of gaint (lateral forefoot contact)

HRA? = Heel Rotation Axis? Well HRA can explain forces in the anterior tibial tendon but are not relevant for posterior tibial tendon. If you want to examine stress in structures you should examine the joint(s) that those structures create a moment about. It's not the magnitude of the moment about the joint, but force within the stressed anatomical structure.

Your description of MASS has not examined the moments about any joints. What forces and moments does an orthotic apply to foot to change the position?

So you are talking about forces, what moments do these forces create? ORF creates a moment at _____? joint. I'm not quite sure exactly what you have claimed about changes in position from MASS orthotics, but I think you have claimed that there is a change in position. So, without an orthotic the foot achieves equilibrium in one position whith an orthotic a more supinated position of the STJ. What moments were changed about the STJ so that equilibrium is achieved at the more supinated position?

You can have a collapsed posture with no tension in the tendon. What SALRE attempts to explain is that in some "postures" the resistance to STJ motion from a moment from ground reaction force will be greater in some "posutres" as opposed to others. So, the reason that you get high stress in the tendon is that the resistance to the supination momnet from the tendon is opposed by a higher pronation moment from the ground. The tendon has to produce more force to get the same motion. So, SALRE explains posture in this instance.

You've made the claim that SALRE does a poor job.
Earlier in this post I said

If it is flawed you should be able to show some error in the prediction of PT dysfunction in feet with medially positioned axes.

Could you provide a bullet list of reasons that you feel that SALRE is flawed. I believe we have addressed all of them in this thread, but I just want to be sure.

The study of biomechanics is inclusive of all joints and postures. You can estimate forces in all anatomical structures crossing all joints using mechanical principles.

It appears that you are using posture as another word for kinematics. You are not analyzing the forces and moments at joints. What is the difference between posture and kinematics?

Eric

 

I was thinking about this and something seemed wrong. When I was using the EMED the time from heel contact to toe off (stance phase) averaged around 650 ms.
So, if your camera takes 13 frames in 650 ms then that is 50ms per frame or 20 frames per second. This is in no way a high speed camera. Regular speed film cameras shot at 24 frames per second. You should take your camera back to where you got it. I think off the shelf video shoots 30 frames per second. How did you get 3/13ths of stance phase as the time from heel contact to the instant of lateral forefoot contact?

The fact that you see pronation from ~10% to ~25% is explained perfectly by the fact that force at the heel has little lever arm about the STJ axis before 10% and then when the lateral forefoot hits the center of pressure is pulled lateral by lateral forefoot contact. This shift in CoP causes the pronation moment that causes the STJ to pronate until equilibrium is achieved at about 25% of stance phase as shown by the graphs in posts 7 and 8. Equilibrium is achieved when the medial forefoot accepts enough load to shift the center of pressure medial enough that there is little moment from ground reaction force, or there is an internal moment (e.g. moment from the end of range of motion of the STJ in the floor of the sinus tarsi.) I really don't see how you can explain the starting and stopping of pronation without using SALRE. I don't see how you can explain how an orthotic can "block the last few degrees of motion" without explaining how equilibrium is achieved in a more inverted position. You may be able to observe a change in position (if it happens), but you have to explain it with SALRE. This is just basic application of Newton's laws. If the STJ has angular momentum in the direction of pronation then you will need a supination moment applied for some time to create a supination impulse to stop pronation.

The other interesting point here is that if the lateral shift in center of pressure is causing the pronation seen then the forefoot is doing this when it is not a rigid body. It doesn't have to be rigid to change the moment from ground reaction force.

I have some images that I would need to place on someones web page showing 1. the CoP for the whole foot. 2. the cop movement before forefoot contact 3. the cop movement at forefoot contact 4. The cop movement a little after forefoot contact. The lateral forefoot contact pulls the CoP laterally.

Eric

 

While lateral forefoot loading provides external ankle dorsiflexion moment to counter the external ankle plantarflexion moment from heel strike, it will often add to the external subtalar pronation moments from strike. So while the initial external ankle plantarflexion moment may be greater than the external STJ eversion moment, the plantarflexion can be decelerated largely through external moment as the forefoot makes ground contact. However, to decelerate the STJ eversion produced by ground reaction forces at strike and then again at lateral forefoot contact, the body is pretty much dependent on producing internal counter moment to bring about equilibrium whenever the projection of the STJ axis is medial to the forefoot. The more medially deviated the STJ axis the greater the external eversion moment (even when the medial forefoot makes ground contact); the greater the internal inversion moment required to bring about equilibrium. Isn't subtalar joint axis location and rotational equilibrium theory great, Ed?

 

3D force diagrams like the ones I presented here. It is interesting that no one, not even Eric and Simon have contested the point that those force diagrams illustrate.

So, Graham if you are thinking laterally maybe you can answer the question that Eric and Simon dodge: How many axes do you draw on the bottom of the foot?
I did attend the debate and Dr. Kirby's workshop. He taught how to draw ONE axis on the bottom of the foot. Case closed. SALRE is single axis. By definition IT, not you or anyone in particular, but SALRE omits the rest of the foot. Ignores the forefoot except as it applies to STJ moment and ignores posture.

I guess we will have to begin the analysis of tissue stress soon because it seems to be the perpetual excuse for the existence of SALRE.

MASS is all about the actual dynamics of the foot during stance phase. Not so much as a splint or brace because those are intended to be rigid and block motion.

MASS delivers a calibrated force and flexibility, so that the orthoses do bend with the application of downward force from the body. You would better describe MASS as a spring theory.

As for the set posture: True…. MASS is the maximal correction that any person can tolerate at Midstance with the heel and forefoot in full contact with the ground.

As for the set time: True…. MASS is taken at Midstance because that is where the maximal downward forces of the human body occur. Toe off shows a slightly higher total force but it is divided at that point between two feet. It is the point of maximum downward force at Midstance that the number and severity of peak gait force events that cross the tissue stress threshold of numerous symptoms occur. That is when micro trauma occurs. So YES there is a single time or event in stance that is of concern to MASS posture users. Proper application of the tissue stress theory should take that into consideration.

Splint theory….talk about a Strawman argument.

As far as making the foot different and not better. Having better posture is usually, considered an improvement. You may find a few contraindications…. That’s fine.
But overall, adding an assistive vertical force to the whole plantar surface of the foot to encourage it generally into a more functional posture is positive.

As I also already said, we do not know because we have no data as of yet as to what posture MASS orthoses put you in at any point in time. Why do you have to map out the location of one or every axis of the foot to consider the actual dynamics of the foot during stance phase? It is just an unnecessary complication. It adds a kind of ‘smoke and mirrors’ level of complexity to a rather simple problem. Supply a corrective force, as evenly distributed, as early in the postural change, and as accurately (calibrated) as possible.

Ed

 

Errrrrr? Actually I did. To reiterate I said: "No Ed, what you showed was a slide that you paid someone to draw for you. There's a big, big difference between that and inverse dynamics." Perhaps if you could cite a study that has actually calculated the moments about the subtalar joint axis during gait (as oppose to the moments about a longitudinal foot bisection).....

Anyway Ed, back to that question: is rotational equilibrium about the subtalar joint axis significant in foot function- Yes or No?

 

Its becoming a bit like late night TV ED soon there will be a voice over and thats not all, as well as with your money back offer we will throw in a full set of...............

How can you claim a MASS type device works with tissue stress when we showed in the last attempt to have a go at SALRE that medial knee O/A pain is reduced with lateral wedges, ie the complete opposite of a MASS type device ie a mass device would add to the stress on the tissue.

It appaers to me that as the importance of tissue stress theory in Podiatry increases you though better jump on this bandwageon , MASS type device the greatest at reducing tissue stress you cry it´s not we shown this already.

 

maybe this study ?

The Short-term Effectiveness of Full-Contact Custom-made Foot Orthoses and Prefabricated Shoe Inserts on Lower-Extremity Musculoskeletal Pain
A Randomized Clinical Trial


Leslie C. Trotter, DC, MBA, MSc, CPed (C)*
Michael Raymond Pierrynowski, PhD†

Background: Foot orthoses are commonly dispensed for musculoskeletal complaints of the foot and lower limb. Few randomized clinical trials evaluate the clinical effectiveness of foot orthoses.

Methods: In this randomized clinical trial with a crossover design, 42 participants wore custom orthoses and prefabricated inserts in their regular footwear for 4 weeks each, consecutively. Twenty-seven participants received prefabricated inserts first and 13 received custom orthoses first. A numeric pain rating scale (possible score, 0–10) was used to measure participant pain.

Results: Statistically and clinically important decreases in pain were reported after 3 weeks by participants wearing custom orthoses first (–1.39 pain units, t12 = 2.70, P = .02). Participants who wore prefabricated inserts first reported no statistically significant change in pain. When the alternative intervention was introduced, participants now wearing prefabricated inserts had greater pain after 1 and 2 weeks (1.1 pain units, t12 = 3.09, P = .01 and 0.9 pain units, t12 = 2.65, P = .02, respectively). Participants now wearing custom orthoses did not demonstrate significantly lower pain at any week compared
with the second baseline but did have significantly lower pain scores compared with their initial baseline scores (–0.81 pain units, t12 = 2.31, P = .03).

Conclusion: Full-contact custom-made foot orthoses provide symptomatic relief after 3 weeks of use for patients with lower-extremity musculoskeletal pain if they are prescribed as the initial treatment. (J Am Podiatr Med Assoc 98(5): 357-363, 2008)

Highlights :
Prefabricated Shoe Inserts. The flat prefabricated insert was a low-density, open-celled, 4-mm foam insert (Tana Sport, division of Sara Lee Household & Body Care, Canada, Cambridge, Ontario, Canada) sized to each participant’s foot. This type of inexpensive cushioning-style shoe insert is representative of those readily available in many retail outlets.

Acknowledgments: Sole Supports Inc for supplying the custom foot orthoses and arms-length financial support to conduct this research and the participants who gave of their time and energy to further our understanding of this topic.


Financial Disclosure: This study was supported in part by Sole Supports Inc.

Conflict of Interest: Dr. Trotter receives a salary from Sole Supports Inc as a technical consultant on product information for Canada.