MASS Discussion

Simon:

Isn't the supination resistance test (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) simply measuring the dorsiflexion displacement stiffness of the medial longitudinal arch (MLA) at the plantar-medial navicular?

One of the problems is that we really don't know whether the supination resistance, or the MLA stiffness, is due to only passive factors or are possibly due to active resistance/assistance from the extrinsic and intrinsic muscles of the foot. Possibly this problem can be solved by EMG or certain experimental testing protocols?

Certainly it would be nice to see some data on MLA stiffness in the foot as it correlates to subtalar joint axis spatial location and to resting MLA height in relaxed bipedal stance. My guess is that we would see higher MLA dorsiflexion stiffness in feet with more medial STJ axis locations and increased MLA height in relaxed bipedal stance. What do you think, Dr. Spooner?

 

Simon:

I believe the research has shown that the central nervous system will likely need at least one foot strike on the surface before it can determine the optimum leg stiffness for that surface. So, leg stiffness is determined at the time of foot strike, as long as the person has been already running on that surface with some steps before.

Also, didn't one of Irene Davis' recent studies use the term "leg stiffness" as a term to measure the change in knee moments versus change in foot loads? Is there one accepted definition for the term "leg stiffness"? From my reading, it seems variable.

Good to be closer to your time zone, Simon.:drinks

 

Exactly what I was thinking. Here's where my money is: as we limit knee joint extension (increase knee flexion), foot pronation will increase. Bet ya'.

 

Yes, the test you outlined is a qualitative assessment of dorsiflexion displacement stiffness, but neither load nor displacement were quantified in this test. The jig I've developed to quantify both of these may have use clinically. However, looking at dynamic function, during the first half of stance the MLA should be displacing downward (plantarflexion not dorsiflexion), so is it not the pronation (plantarflexion) stiffness of the navicular that is important? As I said previously: "if we have a joint that is functioning near end of range it will be relatively stiff in the direction towards that end of range and more compliant away from that end of range of motion, i.e. a STJ which is near maximally pronated will have a high degree of pronation stiffness, but will have lower supination stiffness (assuming it's not fused)", Given this, is it not equally plausible that while the supination resistance might be high, the pronation resistance might be low.? So if we measure MLA stiffness as change in navicular height under a given load, then the supination stiffness of the medial longitudinal arch may be high, while the pronation stiffness of the medial longitudinal arch may be low. It depends where within the range of it's potential heights the MLA is functioning; where within the zones of optimal stiffness the navicular's articulations are.

During dynamic function it will be due to a combination of passive and active factors.

I think I get your message Kevin. But the question is, does supination resistance measured statically correlate to dynamic stiffness of the MLA?

 

I already owe you a beer and a pound from previous bets. I recon your on the money as well.

 

And this is what has been driving me mad this evening: if an orthosis is stiff enough to overcome the supination resistance of the medial longitudinal arch, i.e. it displaces the navicular dorsally and lifts the medial longitudinal arch, this orthosis must be stiffer than the medial longitudinal arch in order to achieve this, i.e. it must overcome the supination resistance. If the navicular is supposed to be displacing downward during the first half of stance, any device which increases the height of the medial longitudinal arch during the first half of stance will also be too stiff to allow downward displacement of the navicular and medial longitudinal arch.....:bash:

Unless it increases the force derived from the active structures....
I need to sleep on it.

 

I started thinking about the leg as a series of springs ( the muscle) with the joints acting at the switch to load up spring or allow for the energy to be returned, with the knee the over all switch. A bit like those diagrams and projects with lights and switchs AC v´s DC we all had in science at school. But the realised that it still does not help the problem above....

What I did think is that if the device has give and will also return energy the stress on the device will load the orthotic which will also return energy as the heel starts to leave the ground, maybe ??? The only problem will be if the device is too stiff, ie no give no energy return ??

say we it takes 5 mm of Navicular drop (ND)as "normal" and X is the energy return provided from the plantar muscles and fascia.

we reduce the Navicular drop to 3mm and the energy return from plantar muscles and fascia now become X-2. Could the deformation of materials ( the orthotic) make up for the -2.

IE ND(5MM) * foot intrinsic Muscle and fascia loading = X (energy return)

ND (3MM)*foot intrinsic Muscle and fascia loading+ orthotic loading = X energy return.

I just putting it out there to see if I off on one again.

The problems will be if the material is too stiff or if the muscles do not get enough load we will lose vitial energy return during gait.

What did sleep bring you ?

 

Kevin, I missed this post you made last night- I guess that's what happens when our time zones are too close together

The paper Ian linked to here shows the variety of approaches used to calculate leg stiffness and evaluates them: http://www.podiatry-arena.com/podiatry-forum/showpost.php?p=141816&postcount=52

If Irene was measuring change in knee moments with foot loads she was measuring knee stiffness, not leg stiffness? But since stiffness is deformation and load, unless she measured deformation(angular change) and not just moment I don't see how this is a measure of stiffness- do you have the paper, Kevin? Perhaps you could ask her on our behalf?

 

Simon:

While wandering around Rome again today....see the magnificent Pantheon below....I did some thinking about this problem you were pondering last night.

First of all, some thoughts on "combined stiffnesses". When object A is being analyzed for its load-deformation characteristics (i.e. stiffness), then object A will have a different stiffness when in physical contact with object B that has either the same or a different stiffness than object A. Now, when a load is placed on object A while in contact with object B, then they will, together, have a different load-deformation curve and a different "combined stiffness" than either of them when tested individually.

Imagine a oak board of higher bending stiffness being layed on top of a pine board of lower bending stiffness. Even though the oak board has a higher stiffness than does the pine board, the addition of the lower stiffness pine board will increase the "combined stiffness" of the oak-pine board combination. This is the nature of engineering mechanics: any external applied force, no matter how small, can change the stiffness of an object as long as the external force that is applied acts at an area of deformation of that object and in the direction that is opposite to the direction of deformation of the object.

Secondly, some thoughts on your specific example of medial arch deformation of an orthosis and supination resistance. Supination resistance is a measure of an upward directed external force acting on the medial half of the plantar navicular relative to the upward movement of the navicular (causing the medial arch of the foot to rise) in response to that external loading force. However, medial longitudinal arch (MLA) stiffness of an orthosis is a measure of a downward directed external force on the MLA of the orthosis relative to the downward movement of the MLA of the orthosis in response to that loading force. Since the stiffnesses measured with supination resistance and with orthosis MLA loading are in exact opposite directions, then any force applied by the orthosis to the plantar MLA of the foot will be in an equal and opposite directions to the force applied by the plantar foot to the orthosis.

Therefore, the stiffness of the orthosis and foot can't be combined to form a "combined stiffness" [as I mentioned earlier in the first section of this posting] since the directions of applied force and object deformation are opposite to each other. However, for a given applied force X acting on the dorsal aspect of the orthosis that deforms the orthosis MLA downward a distance, Y, then that same force X can also be assumed to be deforming the foot MLA upward a distance, Z, due to Newton's Third Law of Motion.

Now, given that X/Y is the orthosis stiffness, T, and X/Z is the foot stiffness, U, then we will have the following equation that determines the mechanical relationship between foot MLA stiffness (acting in an upward direction) and orthosis MLA stiffness (acting in a downward direction):

YT = ZU.

The above mathematical relationship of orthosis stiffness to foot MLA stiffness can then be used toward developing a better understanding of the mechanical interactions between the orthosis and the foot during weightbearing activities and how foot orthosis design may be modified for various pathological conditions of the foot and lower extremity.:drinks

 

I think I follow you, let me check my understanding:
So, we don't have a combined stiffness because the forces are opposite in this example. What if the the foot + orthoses were deforming in the same direction, i.e., the navicular is moving downward (inferiorly) and the orthosis is being compressed in a downward direction beneath it and is thus being deformed inferiorly too? Then do we have a combined stiffness?

I was thinking about it today as two springs in series (spring 1 = orthotic , spring 2 = MLA), with each spring having a different stiffness K1 (orthotic) and K2 (MLA). If we placed the springs end to end, on top of each other, on a surface and compressed the springs with a load (lets say, body weight), mg, the spring with the lower spring stiffness would compress more than the spring with the higher spring stiffness- right? But they would both deform in the same direction and have an effective net spring stiffness. http://scienceworld.wolfram.com/physics/SpringsTwoSpringsinSeries.html

This is perhaps of interest here:
http://www.ncbi.nlm.nih.gov/pubmed/11415628

Nice photo BTW.

 

´
I´ve read your last 2 post Simon and Kevin and some of my random ideas may not be so off the mark but defintly not well expressed.

Question how does device compression(ie EVA) OR plastic flex (ie poly) effect stiffness of the MLA and my idea about elastic energy return have any merit ?

 

When the navicular moves downward along with the orthosis during weightbearing loads acting on the foot, then we do have a "combined stiffness" of the medial longitudinal arch (MLA) foot-orthosis combination that would be greater than either the flattening stiffness of the foot MLA (load acting on the dorsal apect of the MLA pressing downward) or the flattening stiffness of the orthosis MLA (load acting from the dorsal aspect of the orthosis MLA pressing downward).

However, for the specific example of the supination resistance test, the loading force is acting upward, instead of downward, on the MLA of the foot. Therefore, the "combined stiffness" concept would not apply if we were trying to describe the mechanical relationship between the supination resistance test and orthosis MLA deformation from the foot pressing downward on the orthosis.

This might be a better mechanical analogue if one were trying to combine a "pronation resistance test", where the examiner added a vertically-directed downward external loading force onto the navicular to see how much the foot's MLA displaced downward (i.e. flattened) under a given load, along with the orthosis MLA resistance test, where a vertically-directed downward loading force acted onto the dorsal MLA of the orthosis to see how much the orthosis MLA collapsed under a given load. In this case, if the foot had little "pronation resistance" (i.e. low compliance to arch flattening under downward-directed arch loading force) but was then placed on top of a stiff orthosis, the same load that once collapsed the MLA of the foot 5 mm, for example, may now only collapse the MLA of the foot-orthosis combination by 1 mm due to the increased "arch flattening stiffness" of the foot-orthosis combination.

From my last posting, I believe the equation I described is a fundamental principle of the mechanical interactions between the plantar foot and dorsal orthosis at the MLA. The equation is based on the fact that the force required to deform the foot's MLA into a higher arched position will be the same force that deforms the orthosis into a lower arched position. For example, even if the foot has a more stiff MLA with the supination resistance test (force acting on plantar MLA of foot is directed upwards and requires more force than normal to raise the MLA of the foot) and is standing or walking on a more compliant orthosis (force acting on dorsal MLA of orthosis is directed downwards and requires less force than normal to lower the MLA of the orthosis), then the amount of force required to flatten the arch of the orthosis and the amount of force required to raise the MLA of the foot will always be the same due to Newton's Third Law and the mechanical requirement that the same orthosis-foot contact force in the MLA area of the foot and orthosis must always exist, but in equal and opposite directions. Hope this all makes sense to you and the others trying to follow along.

Good stuff, Simon. Thanks for one of the best discussions ever on Podiatry Arena!

 

Simon,

I think you are right. Here is one of Irene's papers where she defines the types of lower extremity stiffness. Her paper on high and low arched runners measured both leg and knee stiffness.

 

Firstly, Mike I haven't forgotten your question; I am thinking about it and trying to answer it for you in my conversations with Kevin- keep reading and asking...

Kevin,
I think in general we concur.

So given that the navicular should be dropping during the first half of stance, if we want to optimise the downward displacement of the navicular )i.e. MLA stiffness) during this part of the stance phase, a better predictor of the orthotics ability to achieve this might be a "pronation resistance test" with the orthotic in situ, than the "supination resistance test" And, in this situation we have 2 springs acting in series, which will result in an effective net spring stiffness for the foot + orthotic- right?

In this situation, the orthotic can only add to the net spring stiffness i.e., foot stiffness + orthotic stiffness must be greater than foot stiffness in isolation. Therefore, orthotics can only increase the net spring stiffness- not reduce it when the foot spring is compressing during this part of stance- right?

The equation you outlined is the spring equation for 2 springs in series: f = -K1X1 = -K2X2 which I linked to earlier, of course it is of fundamental importance to the foot- orthosis interaction when we are modelling both the foot and the orthosis as having varying degrees of spring stiffness, which is why we are discussing it now, and the reason I have been spending way too much time thinking about it and tinkering with it for the last too many years.

So we have two springs of different stiffness: the foot spring (k1) and the orthotic spring (k2), as we have both now said: the force acting upon both of the springs is the same. Yet the deformation that occurs in each will be dependent on the spring stiffness in each. So lets assume K2 > K1 = more deformation in the foot than the orthosis so net decrease in navicular downward displacement? K1 > K2 - more deformation in the orthosis than the foot? So net increase in navicular downward displacement? Right?


Loving it and Learning.:drinks

 

Simon and Kevin,

It seems to me that the orthosis acts like a spring that is activated by vertical loading. The distal edge is free floating and the posterior aspect is essentially anchored by the heel of the foot. As the orthosis is loaded, the distal edge slides anteriorly as the arch is compressed because the device elongates.

The foot is more like a truss and as it is loaded the foot elongates which results in increased tension in the plantar tissue structure (i.e. fascia, etc.). The foot bears load on the orthotic shell and anterior to it. The more the orthosis is compressed, the more pressure there will be under the met heads, anterior to the shell. So I think a lot of this has to do if you're talking about a static loading condition or a dynamic situation. Right???

Regards,
Jeff

 

Jeff, I wasn't happy with my final paragraph that you quoted above and so I had edited it out while you were posting. I'm trying to straighten my thoughts on that bit, I'm not convinced what I had written was correct.

The anterior edge of the device is something I have battled with in finite element modelling- whether to fix it or not. In the end I sided with you that the anterior edge should not be fixed in the models. Really it depends on how much it digs in to the shoe.


In our discussions were are accepting the foot and orthosis to be modelled as springs. If you like, the foot could be two ridged segments hinged together at the top and with a spring connecting the two free ends., i.e. a sprung truss. The behaviour of this sprung truss under load will depend on the stiffness of the spring and the initial geometry of the triangle that the elements form. The point you make means that the load on the two springs (orthotic spring and foot spring) will not be equal to the total ground reaction force. I think this point is well made. However, if we are only considering the portion of the foot in contact with the orthosis then the loading on the two springs has to be equal if they are in series. It should only be the portion of the load acting at the foot-orthosis interface that should be included in the calculation of stiffness.

Kevin, the model we spoke about in private the other day comes into play here.

 

Very Interesting discussion :drinks

I may be trying to make this more complex than it needs to be here but is does the finite element model Simon mentioned only work in the Sagittal plane?

The reason I ask is that it strikes me that viewing the insole / arch as the spring truss takes no account of planal dominance, nor the resistance to pronation from the transverse plane stiffness of the orthotic + the shoe.

For example, Take two insoles with the same sagittal plane stiffness. One has a high and curved medial flange, a high friction top cover and is in a shoe which resists expansion. The other has no medial flange, a slippy top cover and is in a shoe with little or no resistance to medial expansion. Will they behave the same way and have the same effect?

Crazy notion. When the foot pronates in stance the anterior and posterior points of the truss stay pretty much fixed in the transverse plane (barring, perhaps, a little bit of anterior movement Jeff and Simon alluded to). The navicular travels down and medially. We can test the stiffness of the down component as Simon has been doing. Would it be possible to also test the resistance of the shoe + Orthotic resistance at various angles? So if for EG the planal dominance is such that the navicular has a 1:1 ratio of drift drop and the navicular therefore travels at a 45 degree angle one measures combined resistance at 45 degrees but if it is 1:2 on a frontal planal dominant foot one measures the resistance at 22.5 degrees?

Or, still brainstorming, could one mark the point of navicular contact with the orthotic and measure the medial expansion resistance and the sagittal plane resistance and do the Maths to work out the vector?

Or am I completely missing the point?

 

No, FEA is 3 dimensional. I should also add that you can manipulate the direction and magnitude of loading, either to discreet areas of the model or as a whole.

As I said earlier in the discussion: if for example we wanted to look at the medial longitudinal arch stiffness we need to look at both the vertical stiffness- navicular drop and horizontal stiffness- navicular drift (See post No. 97 in this thread). At the moment we have focused our discussion on the vertical component. I am sure you could do the same thing with the horizontal component too. However, since it is the vertical leg stiffness that has been identified as a risk factor for running related injuries, it makes sense to me to try to unravel this topic by focusing on the foot and orthosis vertical stiffness for now- it's tricky enough, Robert- don't you think?

However, if you replace the words "downward" and "upward" in our discussions with medial and lateral displacement- you won't be a million miles away Robert if this is your interest.

 

This discussion is interesting. It is simply a restatement in more complex terminology what I have been saying all along. Orthotics deliver a force back to the foot in the opposite direction from gravity and the magnitude of the force should be calibrated. The orthotic should flex evenly while applying the force and allow enough pronation to adapt to the terrain but not enough to enter the pathologic zone. More information can be found in my lecture at the Miami College at:

http://www.youtube.com/user/solesupportstv#p/c/623AEEF0A18E246D/0/FA8cOI_fd0E

Still NOT ONE person has been able to Quote Whitman as saying anything like MASS. Yet you acuse me of reintroducing his ideas.

Then you restate my ideas and make believe you have come up with them. That's fine. To me it is more important What is right. than Who is right.

Put on your ZOOT suit and ZOOM to the ZOO.

Adding skives to slightly higher than RCSP orthotics even with "minimal arch fill" and inverted pour (which does not change the height of the MLA) is just combining two minimally effective approaches to attempt to rival a full contact, MASS posture approach. The reason why your patients are experiencing pain with orthotics that do not combine skives with slightly higher arches is because you are, for the first time, leaving the Pathologic Zone and entering the Dysfunctional Zone where high orthotic impact forces are rampant. The Postural Zones were introduced at the Western Congress an are in the lecture referenced above.

Mapping distance against pressure is exactly what I have been describing on this arena since 2006(when I first posted) and been lecturing on for 14 yrs. and doing for over 20. I have not only thought of it, I have done it. You are just catching on.....finally. Good luck re-creating my work and restating my theories as if they are original. As the Sole Supports team of engineers and biomechanical theorists continue to pioneer new approaches to calibration you are welcome to follow behind restating these ideas in more complex terms to confuse everyone.

I remember (and I am not sure if it was in Kevin's newsletters or a post on the arena) when Kevin stated that he believes that orthotics should be shaped either at RCSP or just a few degrees above RCSP. All that mattered was tissue stresses and the kinetic redistribution of forces around the STJ axis shadow. Now suddenly he has been using MASS like orthotics for years (of course only on children). When you get it right you can also use it on adults. We do 6000x per month and growing rapidly.

Imitation is the highest form of flattery.

Thank you,
Ed

Clearly if the spring effect of orthotics were important to anyone they would immediately see that the best POSTURE to apply the spring is MASS. Rather than having the arch fall onto a flat spring that begins applying its force at or near the end ROM of pronation, it would be better to begin the dampening effect with minimal impact and shearing by posturing the foot in the Maximal Arch that a person can accept at midstance with the heel and forefoot on the floor: MASS. As I have stated many times, this causes a time delay in the onset and therefore decreases the total extent of pronation.

Now its your job to restate those ideas. And don't forget to restate soft tissue compression as well. Maybe you can call it soft tissue stiffness.

BTW, the supination resistance test does not measure or quantify anything. It is a subjective qualitative test.

Complicating the language makes it harder for doctors to grasp and less usable. The message becomes "I am smarter than you." instead of "Here is a simple way to Make People Better."

When I deliver substance, you just change the terminology and restate my ideas.

Also, shoe resistance is minimal. I deformed about 100 shoes, even hiking boots, and found that I only one hiking boot had any significant resistance in the MLA area. Shoe makers purposely leave extra room in the MLA to accomodate the wide range of pronators that will be wearing those boots. The one pair of hiking boots that had any resistance were the ones I use when I am carrying a heavy backpack and the extra resistance is justified and helpful.

Thanks again for accepting MASS,
Ed Glaser, DPM
CEO Sole Supports, Inc.
www.solesupports.com

 

Well done, Ed. Any chance you might answer the questions I asked of you?

 

I wrote this response to Simon about a week ago but was interrupted before I could post it. Then the discussion changed completely to become one about ZOO's and stiffness (which is another way of saying calibration...when it is applied to orthoses).

Getting back to MASS discussion, which is the title of this thread, I thought I would post it. The other stuff should be in a thread called ZOOS or Stiffness.

Problem is: as the tip gets smaller and the downward force is more concentrated the shell deforms differently. Internally the plastic delivers more of the force horizontally because the plastic-tip interface is perpendicular. This tends to bulge out proximal and distal to the tip.
As the tip gets larger, the macro curvature of the plastic varies and unless the tip geometry can vary with that of the shell you end up with inconsistencies between orthoses. It’s easy to get it to work for one.
We have tried spring tips, rubber tips and metal of various shapes and sizes.

We got past that with the full contact approach. Although it is not perfect, it more closely approximates the body’s forces when the shell is the shape of the foot with soft tissue compression.

Remember it is only when these venn like ranges (with fuzzy boundries) loose sufficient overlap as to cause enough singular events outside of their therapeutic range to add up to symptoms that a patient complains. That is the tissue stress model…which I agree with. There is a threshold damage to elicit symptoms.
Injury rates (with a large enough n) are a less subjective measure especially in athletes because of the repetitive motion in some sports, even more can be gleaned from that.
Worker’s compensation injuries might even be better in that sense.
I don’t like our n yet. We need more teams, for more years with more control years. Early anecdotal evidence looks good.

We worked too long and hard on this formula to just give it away. Another lab might work out a win win deal with me on that but I have considerable financial interest in that intellectual property. I will gladly show you the path I have walked. Then it is up to each lab to come up with their own formula. In walking down my path they will no doubt see better ways than I have come up with…and so are we looking for better ways. What you have told me in this thread is very valuable…you have pointed out that the data that we have been collecting for the last 4-5 yrs will be invaluable in the implementation of FEA because it is needed to point at the correct range of forces to make FEA applicable. We have a 4-5 year headstart…..a window of opportunity. We will use it wisely. We are nearing completion on the beta testing on a new data collection device that will be one day be in thousands of offices giving us a huge publishable study.

I am married to PAmelda Marcos. We have about 100 shoes here. I went up and pushed on the medial side of each of them and found something very interesting. They all have considerable play in the MLA area. I guess that’s because so many people pronate a lot. I thought, certainly my hiking boots would have a rigid medial wall. One did. That is the one I use when I am carrying a heavy backpack.
All the rest, to my surprise, including my workboots were relatively soft in that area. When we are calibrating for a 150lbs person, the 2lbs of force is inconsequential. In fact, I can tell you what is. Our experience is that if a person gains or looses about 30-35 lbs (about 15% of body weight might be closer) they either pronate right through their orthotic and loose the effect or they are intolerably stiff and have to be recalibrated. Your reward for loosing weight is free recalibration for life. Your punishment for gaining is new orthotics. For causal weight lifters we do have a buttress that fits under the arch molded to the shell which can be taken in and out. That option is not on our forms, but it is offered. I really don’t know if we charge for it or not.

I really don’t get it. If Kleg is CNS moderated then it should adjust.
I really don’t see how the orthotic contribution to Ksurf is anywhere near the contribution of the shoe. Build in an optimally cushy heel shock absorber as part of the shoe with optimal geometry to encourage a better preferred pathway of COP, would be a better approach.

I could sell you a titanium device but the price would be prohibitive. When you take things out of the scientific lab and try to provide them in the real world there are serious business realities you have to overcome.
Thomas Edison is my hero. He was able to take invention after invention out of the lab and into production. He was a great salesman. Became very successful in business while bringing the world 1097 patents. Synthetic rubber, wax paper, the battery, phonograph ,movie camera and projector, improvements in electricity generation, cement (he owned the Portland cement company). He was wrong about DC current and Tesla won out on that. I admire him as well.

I agree the orthoses does have an effect on Kfoot, and to some degree, through external rotation of the leg affect kleg but then the CNS and muscles have to work in concert….which they do.

The optimal stiffness for a foot orthoses is dependant on body weight, foot flexibility and momentum. If you want more than that you just have to do the math for yourself. I think you are one of the few who could recreate what we have done…and probably go farther…..if you had enough money, staff and time.

Beyond simply predicting….if form follows function you should be able to reverse deformity. Dr. Dock Dockery is one of the giants in our profession. 110 peer reviewed articles, three textbooks, numerous chapters and he has no dog in this fight. You should listen to what he is has to say about reversing injuries:

http://www.youtube.com/user/solesupportstv#p/c/CE901224FEE3B973/3/F2JPxd9q6r4

Or Dr. Guido LaPorta’s comments on patient tolerance of high MLA:

http://www.youtube.com/user/solesupportstv#p/c/CE901224FEE3B973/5/CwzTR39EIG4

Or Dr. Mary Crawford analysis of the theoretical concepts:

http://www.youtube.com/user/solesupportstv#p/c/CE901224FEE3B973/4/ASPuH4nrBu4

These are people who I personally look up to and whose scientific minds far exceed my own.

I have discussed having pins implanted in my talus and calcaneus with a local surgeon and he has agreed. We just have to get it scheduled.

And this is probably where a postural orthotic is more effective than a purely tissue stress orthotic that acts near the end range of pronation. It certainly will have a greater kinematic effect on the superstructure. We are almost done with a one year, 60 subject, prospective study at a university on this issue. I cannot comment on the results prior to publication as you know. Anyway I was only given one small piece of data. With just under 70% of one year data collected, 23% were still in the skived orthotics while 87% were wearing the MASS posture orthotics.

Think of it this way. You want to control a motion that starts in one posture and moves to another. You want to restrict the motion in that one direction. How early in the movement should you begin to apply your controlling or limiting force? As early as possible, especially if deceleration as a function on time is important. MASS is an individual posture for each person whose geometry is taken with the soft tissues compressed, and which is a model of the geometry of the foot when it is in the highest posture attainable at Midstance without lifting the medial side of the foot off the ground and while maintaining full compressed contact with the heel. Midstance is chosen because it the point of maximal stress. Where the downward force is vertical, and where there is single leg support in walking.

Good. We agree.

Nope. When I am ready to share the formula…I will. Until then everyone will have to do the work themselves.

Our cycle time is 30 sec. for a measurement. Three taken only holds things up 90 sec. It could get better and our new measurement device, when it is done….I am always pressuring engineering, they think I am like a little kid in a car, “Are we there yet?”…The new measuring device will be a one trial measurment with more data points and more accuracy.

I hope this is helpful.

Ed

 

Come on people, Where is that Whitman quote??? or Roberts????

Schuster and I certainly share a common path.
If anything, Kevin has just gone further down the same path as Root. The bigger post.
And I have gone further down the same path as Schuster. The higher arch.
Only I, like Root, have defined a corrective posture, come up with a casting technique to achieve it. Then I've gone full contact with soft tissue compression and calibrated. The most exciting development is yet to come....we are just weeks away from release.
Time will tell.
Ed

PS: A little trig will tell you how much a 3-6 degree inverted pour might raise the MLA (if it did at all). Even in a very wide foot it would be between 3/16ths and 3/8ths of an inch. About the same amount that is attained just by soft tissue compression alone. It is no where near MASS.....not even in the ballpark. So you tilt your pancakes a little more and add a tiny arch....so what.

 

Robert,

No, you make an excellent point. In those feet that functionally demonstrate an increased ratio of talar adduction or talo-navicular adduction as compared to average during closed chain pronation of the stj, this is a very important issue. This condition use to be described as excessive verticality of the oblique axis of the midtarsal joint, for us “old timers” who can remember that far back. Forefoot abduction is relative adduction of the rearfoot. Transverse plane motion is more difficult to resist than pure sagittal or pure frontal plane motion, so we need to address this in our orthotic Rx.

Closed chain rearfoot (i.e. talar or talo-navicular unit) adduction can be resisted with the following orthotic modifications: 1) inverting the positive cast increases the slope of the heel in both the frontal and sagittal planes and increases the height of the medial arch, 2) decreasing or eliminating medial arch fill on the positive cast increases the slope of the orthotic shell in both the sagittal and transverse planes, 3) adding a medial heel skive increases the slope of the medial heel in both the frontal and sagittal planes, 4) using a deeper medial heel cup especially when extended into the medial arch increases the surface area of the shell under the talar head and the navicular area, 5) using a wide arch profile (i.e. medial flange) increases the medial surface area and height of the medial arch of shell, 6) using an extrinsic rearfoot post because it significantly stiffens the orthosis, especially the posterior aspect, which resists deformation of the shell when under greater load.

This thread was essentially started because of claims that "functional orthoses" don't adequately support the medial arch of the foot and as a result, a new treatment paradigm is needed. And only the messiah of orthotic labs can save us because they miraculously "calibrate" the orthotic shell to give us the magical, ideal shell stiffness. If calibration is so special, why does the lab need a no questions asked return policy? My customers don’t need one because our products are well tolerated and clinically efficacious.

Your point about viewing the arch in the frontal plane is well taken by some. I'm still wait to hear why we should cast the foot with the arch in an abnormally elevated position for the first two thirds of the stance phase of gait, unless the device doesn't actually support the arch in this out of phase attitude.

Respectfully,
Jeff

 

That's why you need to understand the spring equations which Kevin and I were discussing last night. If you did, you'd see exactly how the orthotic contributes to the Ksurf, Ed.

Your statement that you "really don’t see how the orthotic contribution to Ksurf is anywhere near the contribution of the shoe" suggests that "calibration" of the orthotic is less important than calibration of the shoe, so why do you bother to "calibrate" the orthotic, Ed? Indeed, like I said, how can you calibrate an orthotic to optimise biomechanical function unless you are assessing the footwear in terms of its stiffness as part of the orthotic calibration process?

Yeah, you may well be right, but wouldn't that put you out of business?

I'm glad we agree. The question is whether the foot drives the leg or the leg drives the foot?

I created foot orthoses of various stiffness in an attempt to optimise orthoses deformation characteristics based on the body weight, foot stiffness characteristics and estimates of dynamic loading a long time before I'd even heard of you Ed. I began using finite element modelling of orthoses about six years ago. I'm not trying to recreate what you perceive you have invented. The optimal Ksurf values for running are freely available within the literature. I read a couple of papers to find them out, so I don't know why you think it's a big secret? For you, it's your business, for me its a hobby.


What is your interpretation of the bipedal spring mass walking model described by Hartmut Geyer, specifically the implication of this model with regard to foot orthosis design and "calibration"?

 

For the first time in ages, I agree with Ed

This is a brilliant discussion about stiffnesses and such. Its not really a discussion about Mass, the only real link is that Sole supports claim a calibration mechanism. If MASS refers to the Position it is not really relevant.

Would it be too herculean a task for admin to split the thread? I Know its a lot of posts but we have a really schizophrenic thread here between a fantastic discussion of a FEA of stiffness, a discussion on Ed's claims of calibration and a discussion on the MASS position.

As Jeff said

Me to. :good:

As I have said 3 or 4 times in this thread, If we are talking about the relative virtue of a MASS orthotic Calibration is irrelevant if The MASS position is not shown to be the prefered one.

Regards
Robert

 

As always with these discussions, we are all correct within our own paradigms.

The point is perojative. How much will a rearfoot wedge raise the arch? Not a lot. This suggests that the object of a rearfoot wedge is to raise the arch. Its not. The point of both raising the arch and posting the rearfoot is to acheive a desired mechanical effect. To judge the effect of either one must consider them against the desired outcome not against each other. Logical fallacy.

One might as well ask how much a higher arch will invert the rearfoot.

 

"I'll get me coat".

 

Its a BETTER discussion.

Be a shame for people to not find it because its in a thread about mass!

But what do I know?

 

OK, MASS position of the foot
1. When during the gait cycle is the "normal" foot in a mass position?
2. When during the gait cycle does a foot on top of a foot orthosis produced from a MASS position cast adopt the mass position?
3. If the foot is ever in the MASS position during gait, what is the duration of time that the foot is in this position on top of the MASS produced device?
4. How much deformation occurs in a MASS produced orthosis from heel strike to toe off?
5. When the foot functions on top of a device produced from a MASS position cast, is the pressure distribution at the foot-orthoses interface uniform across the entire interface?
6. What evidence is there that a device produced from a MASS positioned cast is more efficacious than a device of similar stiffness characteristics produced via an alternative casting technique?

There are more, but that'll do for starters.

MASS produced device? Anyone else ever wondered if the MASS produced device might be just that, MASS produced? It's not is it, Ed?

 

Which Question? I get bombarded with questions to the point were I loose track. That is why I usually do not get involved in this discussion. It is too much of a time sucker.

How about the question I keep asking? Kevin, David and Robert keep ignoring it.

Quote Whitman describing Mass, please? Or admit that it is new.

Thanks,
Ed

 

No Ed, I was trying to continue the discussion we were having last Sunday, you subsequently responded to that, for which I thank you. Unfortunately, the thread has now moved on and I've just lined up another half a dozen questions for you., see my post above.

Whitman described high arched foot orthoses, not MASS casting. A better question is are the arch heights of the devices described by Whitman comparable with those produced when a device is produced from a MASS positioned cast?

 

Maybe we should optimizing both the downward (during early stance) and upward displacement of the navicular (during late stance) with the foot orthosis? I do think that possibly making a "pronation resistance test" could be helpful but we must first remember that, when the orthosis is in place underneath the foot, the starting position of the medial longitudinal arch (MLA) height is higher than when barefoot so the stiffness results may be using different origins of MLA position between barefoot versus barefoot with orthosis which may affect our interpretation of a "pronation resistance test". I do agree that the effective net spring stiffness of the foot/orthosis combination would be best measured with some type of "pronation resistance test."

I agree. Orthoses will increase net spring stiffness of the foot/orthosis combination to arch flattening deformation.

Thanks for the better 'look" to the equation I described yesterday. Certainly this idea makes complete sense to me. As the orthosis become stiffer (k2 increases) then it will deform less for a given downward loading force on the MLA of the orthosis. As the orthosis becomes more compliant (k2 decreases) then it will deform more for a given downward loading force on the MLA of the orthosis.

If the foot spring (k1) [which is measured as the amount of force required to raise the MLA of the foot a given distance with an upward directed loading force on the MLA of the foot] is more stiff then the MLA will deform less for a given upward loading force on the MLA of the foot. If the foot spring is more compliant then the MLA will deform more for a given upward loading force on the MLA of the foot. The foot spring k1 could be measured using the supination resistance test. I believe we are in agreement on the above two paragraphs?

Now, since the force, F, is constant in magnitude but of different directions (one is + and one is -) for the foot spring and orthosis spring, then as long as our equation accounts for this difference in direction of the F value (+/-) then we should have a workable equation that predicts how foot stiffness and orthosis stiffness may interact with each other mechanically in our model. This would be a great paper for publication since this type of modelling, with appropriate examples and illustrations, would greatly enhance the mathematical modelling of foot orthosis therapy. I believe that such a paper could also be made practical by describing examples of clinical situations where such a knowledge of the mechanical interactions of orthosis stiffness and foot stiffness might become very valuable for the clinician in prescribing foot orthoses and troubleshooting foot orthoses.:drinks

On another note, Pam and I toured the Vatican Museums and St. Peter's Basilica today....simply amazing is all I have to say!!

Here is a photo of the inside of St. Peter's Basilica with Bernini's baldichin in the center under the great dome designed by Michaelangelo.



[/QUOTE]

 

Kevin,
Another fantastic photograph (we really do need a jealousy smilie here)

Agreed. So the elastic modulus of the orthosis is important and the frequency of the oscillation too.

Agreed,. The orthosis deformation test you described perhaps goes some way toward this. However, and this is the problem, we need to either physically produce the orthosis in order to test it- or we need subject specific FEA models of the foot and orthosis- which creates real issues. However, Ed says he's got this process down to a few minutes

The starting point of the marker in the MLA is key- which is why my brain turned to Jam the other night.

Yep.

So, are we actually going to write this one or just talk about it? Your turn to start I believe...

 

I have uploaded one of SoleSupports own documents that demonstrates that this orthotic design is based on the propulsive phase of gait, not the first two thirds of the stance phase of gait. This is not a fuctional arch height that occurs anytime during contact and midstance. Take a look and see for yourself.

 

sheesh.

Ok, before mass nobody else had thought that insoles with very high total contact arches would be a good plan. It's a completely new idea. Have you seen Kyle? (he's about this tall).

Perhaps we could move along to whether it's a GOOD idea rather than your rather annoying obsession with being feted as a visionary. Then if we all decide it's ace we'll join in a rousing chorus of "how great thou art".

Simons list is a good place to start.

 

Robert:

It's amazing how ignorance, combined with a desire for fame and fortune, gives some people great hope that their ideas are totally new.

 

I think you'll find I made that point in a thread 3 years ago! Don't you go taking credit for it!

 

And fame is highly overrated, just ask Tiger Woods. At least Tiger's answers are truthful and concise!

 

Ouch!!! PMSL

Lets be careful. Ed is poised to address the questions Jeff and I have been asking all thread which Simon neatly and concisely potted for us. Don't get all passive aggressive Ed, Its all in the nature of good hearted fun.

 

For the record, I have had some excellent conversations with Ed Glaser and Dennis Shavelson. I do get frustrated, given the out and out assault on Root type orthotic therapy, when my simple and direct questions about the potential flaws in MASS orthotic therapy are routinely ignored. Criticism is a two way street. I was hoping a little gasoline on the fire might get it roaring again!

Respectfully,
Jeff