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Don't you just hate it when giving a seminar or something similar that the question always comes up like "Whats your opinion of rigid vs soft orthotics?"

I usally just want to scream at them, something like "Get over it! .... we moved on from that dichotomy years ago!

Patients need what they need. If the forces are high, you need high forces to overcome it ....if the forces are low, you only need low forces to overcome it. If you don't get it right, they don't get better. Who cares abou the rigid vs soft debate anymore??? Get over it

__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia
http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________
God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University
This is where I am, where are you?

Other factors that may increase the resistance of the foot orthosis to deformation (i.e. increase the stiffness of the orthosis):

1. Adding a filler material to either the medial and/or lateral longitudinal arch of a shank independent orthosis (thereby making it shank dependent).
2. Using a higher durometer orthosis material in a shank dependent orthosis.
3. Making a longer rearfoot post.
4. Making an orthosis with a higher longitudinal arch.
5. Using a stiffer orthosis shell material in a shank independent orthosis.
6. Using a less compressible rearfoot post material.
7. Fitting the orthosis in the shoe so that the medial and lateral borders of the orthosis are supported by the upper of the shoe.

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

To follow on from Kevin's points...

Adding a plantar facial groove (add a small slug like addition to the positive cast before pressing the shell) should increase the strength. We would usually use this if we were using a 3mm poly shell for an inverted device to add some strength while still having some flexibility for lighter weight patients.

What are your thought's Kevin?

I am with Craig on this. I have been listening for years about the dichotomy: patient weight vs material stiffness. It is nonsense since the amount of force needed for a 10 years child with pes valgus can be far greater than an adult weighting 190 pounds with pes valgus.

You can check the research on the subject, both Craig and Kevin have good examples about it.

I agree except there are still behavioural differences between an EVA device and a shell. EVA will offer very little support or effect on the foot until the plantar surface of the device is in contact with the inner surface of the shoe, and after that the extent of its effect is dependant on the Young's modulus of compression...usually quite difficult to compress..so you get little resistance followed by great resistance.(modified by choice of density and grinding out the medial arch area)
With a shell you get flex across a greater range of positions which offers support to the foot across a greater dynamic range...influencing the foot more consistently over a greater range of positions.

Clearly not a sought after discussion but I'm happy to swim against the current.

Regards Phill Carter

I am not sure if a shell actually flex or not. It is a common argument among flexing shell manufacturers but I do not know if there is some data supporting this claim. The ability for flexing will be based on shoe's design and the forces acting on the shell. It is not the same flexing a shell with your hands than the
shell behavioural inside a shoe.

From my point, it is does not matter what material have been used on foot orthotic manufacturing if it have the property to influence on foot moments.

This modification has been used since at least 1980 at CCPM, when I first saw it being used on orthoses as a podiatry student. In 1990 I wrote that plantar fascial accommodations increase the stiffness of foot orthoses. (Kirby KA: Factors affecting foot orthosis stiffness. February 1990 Precision Intricast Newsletter. In Kirby KA: Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997, pp. 73-74.)

I will tend to decrease the polypropylene shell thickness a little in higher arched feet that need a plantar fascial accommodation in the orthosis to prevent the orthosis from being too stiff for the patient.

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

Phill:

When I teach podiatry students and podiatrists about foot orthoses, I like to emphasize that is important for them to separate foot orthoses into shank independent vs shank dependent types. I first heard this categorization of foot orthoses in a lecture that Dr. Michael Burns (former chairman of Biomechanics Dept. at Pennsylvania College of Podiatric Medicine) gave about 20 years ago. I have used this categorization ever since and think it is critically important for students and clinicians to mentally categorize orthoses in this fashion so that they can better understand about orthosis material selection, orthosis-shoe interaction, and how foot orthoses can be better modified to make them more therapeutic for the patient (Kirby KA: Functional forefoot extensions and accommodative orthoses. March 1990 Precision Intricast Newsletter. In Kirby, Kevin A.: Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997, pp 75-76).

I have used both shank dependent orthoses (mostly plastazote #3) and shank independent orthoses (mostly polypropylene) for the over 10,000 pairs of orthoses I have made for my patients over the past 20 years of practice. The main difference between shank independent (e.g. graphite laminates, polypropylene, copolymers, acrylics) and shank dependent (e.g. plastazote, EVA, cork) orthoses is that the shank independent devices have much greater bending stiffness than their shank dependent counterparts. This mechanical characteristic allows the shank independent material, such as a polypropylene shell, to not experience significant deformation during loading if the arch of the orthosis is not supported by the shank of the shoe. However, the shank dependent materials all have much less bending stiffness than their shank independent counterparts, but still have relatively decent durometer (i.e. resistance to compression deformation or compression stiffness) to allow them to resist deformation of the foot, as long as the plantar aspect of the longitudinal arch area of the orthosis is in contact with the shank of the shoe.

As you have stated, Phill, there are certainly different mechanical characteristics to these materials that allow the clever clinician to use the specific deformation characteristics of these various materials for the therapeutic benefit of the patient. I don't think you and I are swimming in different directions, but that doesn't mean that all podiatrists are swimming in the same direction that we are.

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

Javier:

All materials will flex, given enough force. Certainly, even the orthosis materials with the highest magnitude of bending stiffness do flex under heavy loads. We need to realize that most clinicians can only apply a fraction of the magnitude of bending moment on an orthosis when we bend it with our hands versus when we bend it by running on top of it with our feet.

I do agree that the orthosis materials behave differently inside of the shoe. This is certainly a huge area of research for podiatrists and clinicians in the future.

The bottom line therapeutically with foot orthoses is that they must apply the correct magnitude of force on the correct plantar location at the correct time during gait so that the internal forces and moments within the foot and lower extremity may be altered in a fashion that allows the injured structures to heal, the gait to be optimized and no other pathology to occur.

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

A plantar fascial groove in a pressed shell would make the shell more rigid, but plantar fasical groove in a milled shell (my preference) would make it less rigid.

__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia
http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________
God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University
This is where I am, where are you?

Craig, this is not the case for all milled shells. The scenario you are speaking about is where you have a 8mm shell (or whatever thickness the lab you use manufactures) and then you ask for a 3mm pf groove. This would obviously make the device more flexible, giving a thickness of 5mm in the area of the groove.

If you had a 3mm shell that you prescribed a 3mm pf groove your lab (using CAD-CAM technology) should allow you to have another 2 scenarios. You can have either:
1. A groove that is replicated on the plantar surface, (would appear as a bar) of a thickness of your choosing. This bar is usually equal to the depth of the pf groove, but this may vary.
2. Or a hole in the area of your device as you have milled a 3mm groove into a 3mm shell leaving you with no material in that area. Usually not desirable but used for illustrative purposes.

The example of the "Point 1" I made above then leads to another scenario of shell flexibility. You may not want a pf groove, but may prescribe a bar on the plantar surface to increase the stiffness of your shell. This may be an alternative to using an EVA arch fill in conjunction with a polypropylene shell. You will be able to then grind off a portion of this bar to increase flexibility as required but not have the bulk of the EVA addition (or possible expense).

Basically, one of the main advantages of milling is that you can have a different contour of the device on the dorsal surface of the device to the plantar surface. With traditional manufacturing methods your lab would vacuum press the polypropylene onto the positive cast. The problem with this is that you are stuck with whatever contour the positive cast has for both the dorsal and plantar surfaces of the device.

Your CADCAM lab should be able to alter this in the way that you still have the same dorsal surface, but your contour on the plantar surface can be altered. An example of this may be of you wished to have an area of increased flexibility. You could therefore request that you have a 4mm polypropylene shell with a 2mm thickness at the high point of the arch, the size of which you would indicate either on the cast or the 3D scan of the patient’s foot. This would obvioulsy increase the flexibilty of the device in this area of decreassed thickness. Alternatively you may wish to have the orthotics device 5mm thick at the heel and tapered to 2mm at the distal edge of the device.

The point I am making which although fairly long winded is that the podiatrist has more options than what may have been offered in the past in terms of flexibility/stiffness and it may be best to check with your lab to see what new options are available to you.


Regards
Phillip Hartshorne

Kevin,

Like everybody claim about their products "intelligence", perhaps it will be a time when podiatrist will be able to claim about smart foot orthotics :)

Anyway, you can achieve the same goals using shank independent or shank dependent orthosis. As you have said it is a matter of magnitude of force.

See you on Vancouver.

Javier

Hi Kevin,
I have often thought in terms of shank/footwear dependant or not....same concept as using very different footwear, like walking boots, ski boots or running shoes. Intended use, body weight, force level of activity all effecting the result too of course, plus other stuff I have not thought of just now. The idea of assuming that it is all just forces, is I think, a simplification also.
For example if you have a high cavus foot type where you are trying to transfer load/force from one place under the foot to another during stance you have to reach a long way up from the floor to do it. If you do this with EVA of density high enough to achieve the result and to have a reasonable length of life you will probably end up with comfort/tolerance problems because if you grind out under the device enough for it not to feel like a golf ball it won't do the job. But if you use a shell that flexes you can make a very high device that exerts force on the foot sooner and will flex while the foot can move dynamically more.
The point I am trying to make is that you can apply the forces at different times and for different times using different materials and still have the patient tolerate the device.
Regards Phill Carter

I disagree. I do think that is all about forces. If the orthosis does not apply a force at the right location on the plantar foot at the right time, then the symptoms or gait abnormality will persist. This is true regardless of the longitudinal arch height of the patient.

For the patient with a significant pes cavus deformity with, for example, metatarsalgia, then the goal of the orthosis is to reduce the compression loading forces on the plantar metatarsal heads so that the pain in the plantar metatarsal heads is reduced. All that one needs to accomplish with the orthosis to accomplish this goal is to transfer the ground reaction force (GRF) from the plantar metatarsal heads to the plantar arch and especially to the distal aspects of the metatarsal shaft areas. Now whether one uses EVA, plastazote #3 or polypropylene, an effective foot orthosis can be made with each of these materials to make the patient asymptomatic. However, the problem becomes that if the orthosis is not made in the correct fashion then the orthosis will feel, to the patient, like it is a "golf ball" or "coke bottle" in the arch area.

In order to avoid this uncomfortable situation in these pes cavus patients, I have found that by loading both the lateral and medial columns during negative casting, instead of just the lateral column, as in traditional neutral suspension negative casting, that a more comfortable and effective foot orthosis results. In addition, I have also found that a plantar fascial accommodation is generally required in the orthoses for these patients due to the bowstringing of the medial fibers of the central component of the plantar aponeurosis during the latter half of midstance of gait. I have made very effective and comfortable orthoses using these specific modifications with both shank dependent and shank independent materials over the past 15 years. The first 5 years of practice I was using the techniques that I was taught in podiatry school with miserable results.

Therefore, I am taking the time to write this down now for the members of the Podiatry Arena forum so that other clinicians will be able to save themselves, and their patients, orthosis problems. In addition, this short "lecture" will hopefully make podiatrists also realize that material selection is not the only orthosis design parameter that may need to change as the longitudinal arch height of the foot changes. They need to also realize that, often times, negative casting technique and positive cast modification techniques may need to vary as the longitidunal arch height of the foot varies.

I do agree with you, however, that different orthosis materials require different techniques to optimize orthosis comfort and function. Acquiring a knowledge of the specific physical characteristics of each orthosis material and how it can be used to more effectively treat their patient's symptoms and abnormal gait function is an important part of the learning curve that is required before one can become an expert in foot orthosis therapy.

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

Kevin,
My point was that it is not just about forces, but about how, where, when, what magnitude and for how long they are applied...if it was just about forces...I think, in some situations, you could theoretically, apply twice the force for half the time to achieve the same balance of forces.....but the individual may not tolerate this?....what do you think?
Phill

Phill:

I believe we are basically saying the same thing. The reaction forces that the orthosis exerts on the foot is the crucial mechanical parameter that makes an orthosis work. This orthosis reaction force has the following characterisitics:

1. Magnitude
2. Direction and line of action (i.e. spatial location of orthosis force vector)
2. Location on foot (i.e. point of application of orthosis force vector)
3. Temporal pattern (i.e. pattern of change in magnitude over time)

It is the variance in the above characteristics that all foot orthoses rely upon to achieve their intended goals. This is true regardless of the materials the orthosis is made of, the shape of the orthosis or any other special modifications used within the construction of the orthosis.

Understanding these basic physical concepts of all foot orthoses should greatly help the clinician clarify their thought process when prescribing foot orthoses for their patients.

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

Dear Kevin

The original question was 'what factors affect orthotic rigidity'
I beleive I'm right in saying that there are only two factors, essentially they are;
Mechanical properties of the material (modulous of elasticity) and its moment of inertia about the axis of its thickness.
Changing shape changes the moment of inertia and changes stiffness. Adding material does the same.

The amount of deflection depends on Load, moment arm and stiffness of orthotic structure.
Do you agree?

Dave:

The only problem with your analysis is that in shank dependent orthosis materials (and much less so in shank independent orthosis materials), the plantar orthosis is subjected to loading forces from the shank of the shoe which will largely affect the deformation of the orthosis under load. However, if you are speaking of a homogenous foot orthosis material that is only subjected to bending loads since it is supported only at its anterior and posterior aspects by the shoe innersole, then I would agree with you. However, in reality, the stiffness of most orthoses are affected by their contact with the shoe upper and with the shoe insole, to some extent.

This would be a great application of finite element modelling: to determine the variables in orthosis shape that affect both the deformation of orthoses and the internal stresses within the orthosis material under phsiologic loading forces, both in and out of the shoe.

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

Kevin

In effect wouldn't the shoe materials and the orthotic materials become a laminate which becomes a seriuosly difficult calculation To quote an engineer (whose name I don't have) "All composite engineers need software for laminate analysis. Even simple calculations can't be done on a hand calculator."

This would make sense since the maximum force applied to the foot in stance phase of gait is at around 60% and the maximum pressure is at around 80% of the stance gait cycle. In other words the surface area contact of the foot to the groud reduces more quickly than the force applied by GRF. So the trick is to increase surface area contact of the foot as the forces decrease which I would imagine would be achieved more easily with a more elastic/softer material

Cheers Dave Smith

That's exactly right. In an orthosis made from a homogeneous material, such as an orthosis milled from a block of polypropylene, I would imagine that the calculations for the magnitude of bending of the orthosis under load would be fairly straightforward as long as the shape of the orthosis was not too complex. However, if one were attempting to do that calculation in a tri-laminate of shank-dependent orthosis made of, for example, polyethylene foam and poron, I would imagine that finite element analysis (FEA) would be required to get an idea of how the orthosis may mechanically react under loading conditions.

In speaking to a few engineers who do use FEA in their work, supposedly there are a few FEA software programs that will run fairly well on even a upper-end desktop computer. My understanding is that supercomputers are required for the more complex calculations that result from more refined meshes and in systems that have more components to model.

Supposedly Asics already routinely uses a finite element model of a human foot and lower extremity (that includes all the bones, nearly all the ligaments, and all the muscles of the foot and lower extremity) to determine the mechanical effects of shoe design on the foot and lower extremity, without ever having to physically make the shoe or put the shoe on the athlete's foot!

Pretty cool stuff! Unfortunately, to my knowledge, I am the only podiatrist currently lecturing on FEA at any seminars since it seems that FEA is considered maybe "too complicated" for the clinician to understand?? I mean, FEA has been around for over 50 years so that maybe podiatry will eventually catch up a little to what the engineers see as ho-hum, old-hat type stuff. Hopefully, I see this all changing once the other lecturers in podiatry start to appreciate the great power that FEA has in allowing us to "see inside the foot" and more accurately estimate the stresses and strains on the structural compents of the foot and lower extremity during weightbearing activities.

From: = http://en.wikipedia.org/wiki/Finite_element_analysis

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

What about the fact that orthoses can excert more force at different parts along the shell. A 4mm poly device with a 350 EVA heel post will offer almost no flex under the portion of shell supported by the post (i.e. exert lots of force) but distal to it the shell will flex with minimal force. When do we want different flex quantities at points along the orthotic and when do we want one consist flex quantity(if its possible?)

I often find it difficult to figure the different combinations pods use and for what reasons. 3mm poly with 260 Eva or PPT, 5mm poly with 220 EVA with different grades of fill?? Has any one every done a study on all the combinations used and the amount of force each applies (not easy i guess)?


Tom

Kevin
Referring back to this quote by admin

I'm not sure that this is always true in the case of a direct milled device.
Cutting grooves into a direct milled orthotic for a plantar facia accomodation will give a 'corrugated effect' but will not increase the rigidity of the shell, quite the opposite, it will have less strength.
Reason is; if you take a thin sheet and bend it into a corrugated form (like a moulded orthosis) you have increased its moment of inertia (its effective thickness) and therefore is stiffness increases. If you take a material of certain thickness and cut groves in it then although it appears corrugated and even though the moment of inertia stays the same, because material is removed, the cross sectional surface area is decreased and therefore any load applied gives the same bending moment but increases the tensile stress per cm^2. Therefore the deflection to load ratio will be higher and the shell will bend more (or break earlier) for the same load ie it is less rigid.

What or who are Asics Kevin?

Tom

Although I don't know much about lamination stess/strain and FEM calculations. These are my thoughts;
If you imagine that if you take a material that has a grained structure and make laminates of it but with the grain in differing orientation like plywood for instance to give a more even rigidity in all directions. The structure as a whole becomes much stronger and more durable. To calculate the end product from the individual elements would be quite difficult but fortunately in engineering the modulous of stiffness and elasticity and stress strain for most common laminates (carbon fibre, glass fibre, plywood, for instance) has been calculated and incorperated in software for instant calculation of strength and flexibility etc. However when we put together an orthosis we are effectively making a laminate of unique combination and of widely varying mechanical properties to work out the mechanical properties of the homogenous construct would be extremely difficult and time consuming especialy if you were to factor in the shoe materials.
It is quite amazing, I think, that considering the complexity of the physics required to obtain viable scientific results, it is within the capability of an experienced and skilled clinician to choose a selection of materials and construction that will suit the requirements of their patient sufficiently to give satisfactory results of comfort and pain relief. Even though they wear different shoes with the same orthoses.

Does it? or is it that the foot exerts more force on the orthoses at different phases of the stance phase of gait. Scientifically speaking its the same thing measured differently but I think in this case it is better to imaginge the varying force the foot applies to the orthosis. Since if it were possible to have an orthotic shell with even stiffness along it length (with even flexibility) then although the 'flexibility/stiffness' is constant the amount of deflection would increase with load which may be what we want to achieve if one was looking to reduce peak pressure values.
The whole issue of varying flexibility becomes very complicated when you consider the variables of construct, materials and patient physiology and mechanics.

Have you ever wondered about the ever more weird and wonderful construction of new building in our towns and cities. Well an architect can design his building on computer. Incorporating all the very latest innovations in art and design and inspirartions from the latest Speillberg epic and the computer software will work out the correct values of strength and thickness and for required the materials and laminated and fixings and construction blue print. All he has to do is nip down to 'Do It All', with a wrench and hammer, Get all his materials and by Monday next week he's built an award winning strudture right at the back of your garden and it wont fall down or blow away for at least a thousand years. Well sort of :) Perhaps we could borrow their software. Anyone got a mate in the Institute of architects.

Here's a very nice article that shows how considerations for load and flexibilty/elasticity affect design of materials and structure and I bet the spider can't even count past eight.

Notice how stiffness and flexibility are not linear with increasing load.

--------------------------------------------------------------------------------



Cheers Dave Smith

Dave asked "What or who are Asics Kevin?"
Normally I would presume this is some sort of gee up, but just in case, and i hope Kevin is ok with this i will answer on his behalf. ASICS are a shoe company. http://www.asics.com/ . They make a few different type of athletic shoes. They are available widely throughout the world. Used by a few good athletes, some of which i have raced against and unfortunately been beaten by as well. My PB over the marathon distance is pretty quick if i may say so myself, 4.59, so i am right up there with some of the real guns of the sport. However some of these athletes are just too good for me but i'll keep going and one day may just catch a few if my training keeps going as well it has been lately.

Sorry for talking about myself again. It is so hard not to bring up my athletic career. I am so proud of my achievements. ok, ok, ok i hear you all and i'll get back to the topic of the thread, orthoses. But on the off chance anyone wants me to list my athletic achievements feel free to PM me and if i get enough response i'll start a new topic about my track and field career.

Someone on this thread did mention placing a reinforcement under a milled plantar fascial groove. So for the physics guns and those heavy hitters with engineering theories which make my head spin you seem to have overlooked this. Can you outline your thoughts on why a CAD/CAM system which allows you to incorperate a plantar fascial groove as well as a plantar fascial groove/reinforcement on the plantar surface of the shell would not maintain rigidity? Or if of sufficeint thickness would not increase rigidity? Maybe you guys at PFOLA could have a talk about this and come up with an answer for us. Not too much on FEA as it may be a bit to complicated for my little brain.
I am just of for a run, doing 262meters this morning, so am looking forward to your responses when i get back in an hour or so.
DaFlip

Asics is one of the larger athletic shoe companies in the world. They were formerly called Onitsuka Tiger and are based out of Japan. They make some of the best running shoes in the world. Check out the history of the company at this website: http://www.asicsamerica.com/onitsukatiger/

__________________
Sincerely,

Kevin

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

e-mail: kevinakirby@comcast.net

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

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

Daflip

Oh yes they did, Philip and Craig pointed out that extra material can be added on the plantar surface of the milled orthotic which would increase stiffness, missed that bit, sorry. On my Amfit system, except for overall thickness and heel raises, only the dorsal surface can be modified but these are a shank dependent orthoses.

Cheers Dave Smith

Thanks for reply Dave,
my mind is so fresh today after a wonderful run this morning at training. I finished a killer set of LT runs and got my heart really pumping to 139bpm..ohhh the pain in my legs. Man, the blood was really flowing all over my body especially the last run, the final 10m of the 20m drill was like torture...but once again athletics gets in the way of academia. So....
If there is likely to be a increase in rigidity of an orthoses through the addition of a plantar contour adjustment such as a plantar fascial groove 'reinforcement' i can see only 2 ways of this occurring in a milled device.
1.adition of material post milling procedure
2.a milled device which utilises a cutter capable of producing plantar and dorsal contours
The idea of a bar reinforcement on the plantar surface sounds like a good idea to reduce bulk. It still allows fascial grooves but appears to maintain rigidity of the shell. May also allow us to increase rigidity if thick enough plantar contour change is applied.
Does anybody have access to one of these or any lab dudes here who use one?
Maybe if you could tell us which lab you represent and if this is possible with your CAD/CAM system because this sounds like an awesome idea. I would be interested in seeing a device like this and maybe 'Admin' could allow you to scan an image of the device so we could see what one looks like. Any info anyone?
DaFlip

Mr DaFlip,
Please find attached an illustration that shows not only an increase in shell thickness, but also a decrease in shell thickness leading to varying degrees of rigidity.
The diagrams provided are probaly some of the more common variants that the CAD-CAM orthotic process allows, however both thickness and position can be adjusted to suit the patient's needs. The main notion to keep in mind is the fact that none of these alterations require any change to the dorsal surface of the device.

Regards
Phillip Hartshorne

Attached Images

Shell_Variants-Virtual Orthotics.jpg (96.4 KB, 273 views)

Thanks for the reply. Certainly this provides us with an example of an orthotic with an area which would indicate increased rigidity but no real change in bulk.
This is a great design and well done for posting this on the forum....thanks to Admin for letting images on the post.
Certainly if we as a profession are aiming at controlling rigidity of orthotics through advanced manufacturing processes this appears to be one of the leaders at the moment....virtual orthotics....hmmmm strange name. Keep up the splendid work.
Anyways i am off to ballet tonight to fine tune my physique and allow me to cope with the strains of performing as a self appointed podiatric legend.
DaFlip