Research parameters for evaluating casting methods

Re: Research Parameters

Neil:

Thanks for taking the time to post here on Podiatry Arena about your casting system. Certainly, I appreciate the time and effort that you have taken to create such a device. I have to say that the testimonials on your website are not appropriate for a medical device unless you either had testimonials from patients who did not get these great results with your orthoses or had a disclaimer that your testimonials are not meant to be representative of all those patients that have had foot orthoses made using your casting machine.

It seems that Sheldon should have, initially, fully explained why he wanted to know about negative casting accuracy and validity before he embarked on a fishing expedition here on Podiatry Arena to find out what our thoughts are on the process. He has handled our initial questions well which he should be commended for.

Maybe now, after the dust has settled some, the two of you can now get this discussion going in a positive direction as to how important it really is to have reproducibility in negative casting for foot orthoses. What research have you done so far on this subject and has it been published anywhere yet??

 

Re: Research Parameters

Gosh what a passionate bunch we are! What a healthy thing that we care so much about what we do. The disease of apathy has no hold here so:drinks to all of us.

Steve. You said:-

__________________

I think this was a good point well made!

Whilst it is wonderful to see so many podiatrists willing to stretch their understanding and challenge themselves i fear these bold souls are in a minority. I know many more who practice biomechanics based on what many (myself included) $consider to be an outdated "pure root" model. This is not a situation i like nor applaud and certainly not one i would defend. It is, however, very sadly one i beleive exists.

This is only my view based on my personal experiance. Perhaps it is unfair, i certainly hope so. But i have to say i agree with Steve.

And that brings us to what i beleive to be the nub of the present debate (and many others we have had). What is the defining characteristic of an orthotic which makes it more / less comfortable / effective.

The root model, still taught as gospel in some institutions (beleive it!) speaks much of the importance of angles. Calcanei posted one degree more this way or that, forefoot / reafoot angles. If we take this model to be correct then i can see how a system like this could make a huge difference. I can imagine how the foot could be more objectively positioned like this than with the vaguaries of suspension neutral casting (for eg).

However.

I am increasingly of the view, as time goes on, that these elements are of lesser significance. The traditional model of positive cast prep calls for a fairly arbitary addition of heel expansion and arch fill, in practice i wonder how much of the so carefully derived foot capture survives the process and makes it to the finished orthotic.

I think that gross "macro" variables such as material choice, type of device, footwear, and substantial modifications such as skives and 1st ray cutouts are of far more significance.

The research comparing orthotics made to a standard last (pre fabs) to those casted to the foot give, IMO some credance to this view.

As has often been observed these studies are flawed in comparing truly custom orthotics to pre fabs. Truly custom orthotics are not simply cast to a common formula but designed to fit the actual presenting pathology. And this inevitably defies our attempts at inductive research because such design is so influenced by the practitioner's expertise and experiance. Far more so, i contest, than it would be to the practioners ability to cast.

So how important are the factors detailed in sheldons list?

In my opinion, and it is only my opinion, not greatly. They hark to a time when such things as precise angulation of the calc in casting were considered significant and critical to orthotic success. IF, as Steve inferred, the foot could be relied upon to stay in exactly the position in which it was cast when using the insole and IF as Simon pointed out there was a single "optimal" functional position then this system would indeed be a breakthrough. But it can't and there isn't. So in my opinion, its not.

So this, for me, is the orthotic equivilent of a 4 tape deck. An improvement on the old system to be sure, but ultimately one which has come too late, after systems which in some way are simpler yet more elegant (tissue stress model) have become available.

Kind regards
Robert

 

[Check4SPAM] RE: URL Attempt

www.apodc.com.au/AJPM/information/reviewed_paper.pdf

Kevin

Thanks for the reply. I was expecting a bit more biifo in the reply from someone like yourself :boxing:so thanks for that!

The research is attached for you to look at, but remember when you read it, the FAS had no MLA Curve or Cuboid Curve to manipulate the MLA or Lateral aspect of the foot. I'm sure that if a new study was done the result would be much better. The study done on comfort and control (also by CP) was only sent to me by fax and wasn't published and I will put it up on the web site soon.
Let me know what's not kosher and I'll change it.

The testamonials were all written by people who'd been cast and issued orthotics from the FAS at the clinic. Have we got it wrong sometimes? You bet! and thats why we give their money back if we don't fix the problem.
That's where it would be fantastic to have some great minds (like yourself) to reseach and test some of the theories out there. Like I said before. It's up to the practitioner as to what position the foot is placed in with the forces applied which will be in the negative, positive and orthotic.

I would be prepared to fly to your practice in the US with an FAS to show you what it can and can't do and see if it passes any tests you may like to put it through. After all these years, if the only thing on my mind was money I'd have thousands of FAS's out there, but there are only 21 and so far to do this, it's cost a bomb.

I'm at home at the moment and don't have the letter handy written by Craig Payne after our first meeting with the FAS, before the 1st lot of research.

He basically said that the FAS could be the only machine to measure the amount of force needed to be applied to the foot to produce an orthotic.

Whoever wants a machine to try out, research or test just let me know and I'll do my best to organize it. If I wanted to be secretive about it I certainly wouldn't put it out there like this.

Regards

Neil

 

Re: Research Parameters

On the reading of the article I do not believe it supports your sweeping statement that "if you look at the origins of qualitative research it was developed as a backlash to the perceived masculinity of science."

Simon I understand that you see yourself as the self appointed thought police of Podiatry Arena.
However consider this:
Does your overly aggressive, contemptuous and condescending reaction to opinions other than your own help to foster participation on the forum or does it stifle discussion?

I have no doubt that you are a superior clinician than most. It is obvious just from reading most of your posts that your depth of understanding and grasp of the truth behind the words of the research is outstanding. 90% of the time I love your work.

We have hijacked this thread into something else but I believe it needs to be said if this website is to be everything it can be to all podiatrists. If everyone is too scared to state an opinion then where will that take us?

I obviously have not been on your radar before now. However if you had read any of my previous posts in other threads then the meaning behind my too subtle comments would have been clearer.

IN MY OPINION it is an unfortunate but self evident truth that many podiatrists believe in the validity and reliability of their measurements and create orthoses based on those measurements alone.

"Now back to your research into global trends in casting and orthoses fabrication protocols, Steve...." If you are so keen on this research then I suggest you do it yourself. It was certainly never my idea. If every opinion stated had to be backed up by research then again there would not be much discussion.

Was Pink singing about you?

You, Yes You, Stand Still Laddie!

When we grew up and went to school, there were certain teachers who would hurt the children anyway they could
by pouring their derision upon anything we did
exposing any weakness however carefully hidden by the kids.

Out in the middle of nowhere they were home at night
their fat and psychopathic wives
Would thrash them within inches of their lives!

ooooooooooooo, oooooooo, ooooooooooo, ooooooooo, ooooooooo, ooooooooo,oooo.

We don't need no education
We don’t need no thought control
No dark sarcasm in the classroom
Teachers leave them kids alone
Hey! Teacher! Leave them kids alone!
All in all it's just another brick in the wall.
All in all you're just another brick in the wall.

(A bunch of kids singing) We don't need no education
We don’t need no thought control
No dark sarcasm in the classroom
Teachers leave them kids alone
Hey! Teacher! Leave us kids alone!
All in all it's just another brick in the wall.
All in all you're just another brick in the wall.

Spoken:
"Wrong, Guess again!
Wrong, Guess again!
If you don't eat yer meat, you can't have any pudding.
How can you have any pudding if you don't eat yer meat?

Pink Floyd "The Wall" - Another Brick in the wall.

P.S. I played this song for the kids before they started their first day of school on Monday. I also love yelling the last two lines at my kids for fun.

 

Re: Research Parameters

When I first read Craig's paper on this system, back when it was published, I thought that it was a significant breakthrough. It was able to simplify casting and prescription for orthotics which is something that all podiatrists must struggle with. However in practice I found that the significance of the casting and measurements was not valid to dealing with the pathologies I was seeing. Rightly or wrongly I also resisted giving up any control of my orthotic construction to a lab much less a machine.

Karl Landorf's study on the effectiveness of different orthoses on plantar fasciitis is a good example. It is arguably the best study done on orthotic effectiveness. However for it to be quantitatively acceptable it needed to reduce the variables which included that everyone received the same prescription to their cast. Unfortunately this also reduces its validity because few podiatrists do the same thing in their own practice. Perhaps orthotic research needs a more qualitative approach to be valid.

 

Re: Research Parameters

Robert: :good:

I think you have made many good points, Robert. I mostly agree with your analysis. Considering Root et al's subtalar joint neutral theory, just a few weeks ago I finished writing an article for the April 2009 issue of Podiatry Today magazine titled, "Are Root Biomechanics Dying?" In that article I discussed why I thought that "Root Biomechanics" was falling out of favor in podiatry schools around the world and why I thought other theories were coming more to the forefront.

Neil's machine certainly seems like another acceptable method to make a negative cast of a foot. Whether it is the "best" or "most repeatable" method by which to make a negative cast, we may never know. In addition, as time goes on, my opinion is that a machine such as Neal's will not be considered as being necessary for the clinician to make excellent and therapeutic custom foot orthoses for their patients.

In regards to the relative importance of an "accurate negative cast" in producing optimum custom foot orthoses, here is the answer I wrote in response to a question that I was asked for an "orthotics roundtable" in Podiatry Management magazine last year:

Therefore, my opinion is that obtaining an accurate negative cast is only one of the critical steps that must be performed by the clinician in order to produce optimum custom foot orthoses for their patients. I don't believe that any "casting machine" will help a podiatrist make better orthoses if they don't also have a good understanding of the other seven steps that go into making better custom foot orthoses for their patients. However, poor negative casting will certainly ruin an orthosis that would otherwise have worked very well for the patient. Hopefully, this discussion gives a more comprehensive analysis of the relative importance of "negative cast repeatability" in the making of effective and therapeutic custom foot orthoses for our patients.

 

Wow you guys are a passionate bunch!
The spectacular "casting machine" sure seems to have got the adrenal glands pumping. I wonder if this clinically measurable....the effect of the magic casting machine on lowerlimb kinematics kinetics and adrenal production amongst health professionals.

Lets get back to the point: WHAT ARE THE BEST RESEARCH PARAMETERS AVALIBLE TO MEASURE THE EFFECT OF AN ORTHOTIC ON A PERSON WEARING ONE VS NOT WEARING ONE,OR WEARING ANOTHER TYPE? Or should we use pain scales....
In my humble clinical practice internal rotation of the knee and hip during midstance seems to affect the myofascial control system the most. Pelvic posture , quadriceps ,glute ,tib post peroneal (etc etc) firing do change with this observable and measurable parameter.
Is this a good research parameter?
What do the academics and the foot soldiers of this profession (and lets act like professionals) think?
The outcome of positive discussion may improve the sucess rate of orthotic prescription for us all, whether the magic "casting machine" or the "2D magic foot mat" or tracing the foot onto a piece of paper or otherwise is used.
Kindest Regards
Gavin Johnston

 

Have the magnitude of forces causing the problem been reduced?

 

Can we measure the magnitude of the forces and compare them?

 

Tanks Craig
Call me stupid but... how are these forces measured in the clinic and or in the lab. Im used to emg activity,ROM,function and pain perameters.
Ive got a pressure plate from the "Diasu Diagnostic Support" with video and stills which I use to measure L/R loading (a very interesting guide to structural and pain compensation patterns) Fore/Rear foot loading, Metatarsal pressure, bipedal and mono pedal balance responses ....At the moment thats limited to static but as I get more data miner savy I can look at some of these parameters in the gait cycle.
But still at a loss of how I can measure forces received in the leg?
Thanks
Gavin Johnston

 

There are modeling systems that are trying to create accurate measures of internal and external forces. They are close to getting a reliable level of accuracy.

As the original question was "Research parameters for evaluating casting methods" the ability to measure them in the clinic is perhaps another question and a lot further off.

 

External forces acting on the foot can be measured quite accurately with force plates, pressure mats and in-shoe pressure insoles. Measuring internal forces, however, is another story and can only be estimated using inverse dynamics and/or modelling techniques unless you are in a country, such as Sweden, where they allow you to implant strain gauges or force tranducers into live research subjects. Every year, the technology is improving but, for now, we can only measure external forces, such as ground reaction force, reliably.

 

Go Sweden. Maybe send the FAS to europe Neil???

Can the external orthotic reaction forces be measured ie between the foot and orthotic?

 

I always had a feeling Sweeds did it better...or Dainish??

 

Re: Research Parameters

www.apodc.com.au/AJPM/information/reviewed_paper.pdf

Kevin

Thanks for the reply. I was expecting a bit more biifo in the reply from someone like yourself :boxing:so thanks for that!

The research is on the web site for you to look at,(I was unable to send it as an attachment!) but remember when you read it, the FAS had no MLA Curve or Cuboid Curve to manipulate the MLA or Lateral aspect of the foot. I'm sure that if a new study was done the result would be much better. The study done on comfort and control (also by CP) was only sent to me by fax and wasn't published and I will put it up on the web site soon.
Let me know what's not kosher and I'll change it.

The testamonials were all written by people who'd been cast and issued orthotics from the FAS at the clinic. Have we got it wrong sometimes? You bet! and thats why we give their money back if we don't fix the problem.
That's where it would be fantastic to have some great minds (like yourself) to reseach and test some of the theories out there. Like I said before. It's up to the practitioner as to what position the foot is placed in with the forces applied which will be in the negative, positive and orthotic.

I would be prepared to fly to your practice in the US with an FAS to show you what it can and can't do and see if it passes any tests you may like to put it through. After all these years, if the only thing on my mind was money I'd have thousands of FAS's out there, but there are only 21 and so far to do this, it's cost a bomb.

I'm at home at the moment and don't have the letter handy written by Craig Payne after our first meeting with the FAS, before the 1st lot of research.

He basically said that the FAS could be the only machine to measure the amount of force needed to be applied to the foot to produce an orthotic.

Whoever wants a machine to try out, research or test, just let me know and I'll do my best to organize it. If I wanted to be secretive about it I certainly wouldn't put it out there like this.

Regards

Neil

 

Sorry, It already sent before!

Neil

 

In-shoes systems (fscan, pedar rscan) can do that.

 

Can they measure force and direction of force?

 

Re: Research Parameters

I don't consider myself to be anything more than a contributor to this forum so your understanding is wrong. Analyse your statement above and re-read our exchange of posts in this thread; who here has turned this into a personal attack and taken the aggressive, contemptuous and condescending tone? People who live in glass houses shouldn't throw stones, Steve.

Do I help to foster participation in this forum? Well a quick look at the stats suggest that I probably do: I've started 50+ threads which have received > 760 responses and I've been thanked a number of times for the responses I've given. Is this stifling discussion? I don't know. To be honest Steve, it is you who will ultimately stifle discussion here because rather than participate in this thread any further, after this little encounter with you I shall probably take some time away from the Podiatry Arena.

Steve, you are welcome to form any opinion of me that your mind desires. Frankly, I don't really care what you think of me.

You're still not.

 

No. In shoe systems are Vertical only, they measure in only two dimensions.

Anyone who doubts the significance of the other 2 should not attempt skiing

Regards
Robert

 

Re: Research Parameters

Don't forget your ball.

 

Re: Research Parameters

Noir desir 666.667 track 7 all yours sunbeam.

 

Re: Research Parameters

Dear Simon,

I will pray for you as requested.

Here is a better song from "The Smiths" I know it's over

"If you're so funny
Then why are you on your own tonight ?
And if you're so clever
Then why are you on your own tonight ?
If you're so very entertaining
Then why are you on your own tonight ?
If you're so very good-looking
Why do you sleep alone tonight ?
I know ...
'Cause tonight is just like any other night
That's why you're on your own tonight
With your triumphs and your charms
While they're in each other's arms..."
It's so easy to laugh
It's so easy to hate
It takes strength to be gentle and kind
Over, over, over, over
It's so easy to laugh
It's so easy to hate
It takes guts to be gentle and kind

 

Remember this question?

If a clinician has a repeatable and reliable method of casting for the manufacture of orthotics, what would be the best research parameters, to prove or disprove whether the method is valid

Seems pretty difficult to get some direction.

Would comparing vertical forces with an F-scan be usefull?
Comparing static supination resistance forces whilst weightbearing in an orthotic?
Comparing windlass forces?
Broader comfort study?
Send to sweden for bone pin study in walking or internal force measurement?
Other forms of kinetic assessment?

 

Sheldon:

Here is a simple study for you: have one clinician that is experienced in making negative casts using the neutral suspension casting method and another clinician that is experienced in making negative casts using Neil's machine take negative casts on the same 20 subjects. Now, have an independent orthosis lab make orthoses from both casting methods for all of these subjects with the same orthosis prescriptions and then choose one or all of the following types of orthosis assessment techniques that will allow you to compare the two types of orthoses:

1. Comfort
2. Kinetics (force plate, pressure mat, in-shoe pressure insole, inverse dynamics)
3. Kinematics (3D video gait analysis, bone pin study)
4. Relief of symptoms

I think you will find that both orthosis casting methods will produce very similar, if not nearly identical, results to each other. Now that you know how to do the study, when are you going to begin??

 

Sheldon:

Here is a simple study for you: have one clinician that is experienced in making negative casts using the neutral suspension casting method and another clinician that is experienced in making negative casts using Neil's machine take negative casts on the same 20 subjects. Now, have an independent orthosis lab make orthoses from both casting methods for all of these subjects with the same orthosis prescriptions and then choose one or all of the following types of orthosis assessment techniques that will allow you to compare the two types of orthoses:

1. Comfort
2. Kinetics (force plate, pressure mat, in-shoe pressure insole, inverse dynamics)
3. Kinematics (3D video gait analysis, bone pin study)
4. Relief of symptoms

I think you will find that both orthosis casting methods will produce very similar, if not nearly identical, results to each other. Now that you know how to do the study, when are you going to begin??


Kevin:

It's Neil here. I rang Sheldon and because the research will be done from Sydney Australia I figured it best I reply.

Firstly, thanks for helping with the research protocal. Having someone like yourself give advice is a real help.:drinks

If you don't mind, can I ask a few questions to finalize the protocal?

1) For the person taking the 20 pairs of suspension casts: what sort of script should they fill out ie: Inv./Evert/ skives/flanges/additions/shell material thickness ect... Or just a standard root device and same material for all participants. Because there aren't any modifications done to the FAS casts the scripts would be different exept for additions to the orthotics.

2) Should each subject have the same foot posture and symptoms or varied?

3) Who would be the best person/people to review and check that we're doing it right?

To answer your question, we would be ready to go ASAP.

Thanks again,

Regards

Neil

 

Re: Research Parameters

Appreciate your comments and understand your thinking in regards to your machine design. Sounds like with all your experience you would have the right to call yourself an expert in the field:drinks

All the best Dave

 

Sheldon,

.

At the moment, and reasonably for clinical and research purposes, F-SCAN. It's all we have to date that analyses multiple temporal and pressure parameters.

 

As Simon pointed out a while back there are many definitions of valid. So, the questions becomes how do you measure valid? Now if you changed your question to ... which method provides greater relief of symptoms or which method produces the greatest kinetic change, then it would be much easier to design the study.

I also feel that is a better research question to compare on method to another. The question does this casting method reduce symptoms is not as good as does this method reduce symptoms more than placebo, or another method. Also, if you studied kinetic changes, then you should know whether those changes were associated with positive outcomes.

Regards,

Eric

 

Nice design. A few points.

1. You'd need to blind the person who issues the orthotics so they don't know which is which (and obviously the patient). Simple enough. Randomise a number for each set of orthotics with the numbers not correlated to the method til after data analysis

2. You'd need to be aware of the issue of which pair the patient tried first. The L Trotter paper in which a casted orthotic worked less well if used after a simple cushion springs to mind (the Trotter effect?). In a large enough study this would be ironed out but could skew the data. Would need to make sure which pair was tried first was randomised.

In terms of what to test:-

3. Comfort is not necessarily the same as efficacy. As Dave said I could make a device with megasoft porons and latex which would be comfortable but might not do much for symptoms.

4. Kinetics is a better idea i think, but still flawed because of the missing dimensions

5. Symptom releif would need a much bigger study group to iron out variations in pathology!

(i'd go kinematics myself)

I guess this would depend on your hypothesis. If you were asking "is this system better" then certainly. If you are seeking to disprove Kevins null, that they are the same" then any difference would be adequate!

Love it. Who's doing it?

Regards
Robert

 

Hi Robert

Missing dimensions? What do you mean by that?

Rebecca

 

Dave,

thanks for the reply:drinks and I'll try to answer your questions.

1) Why was there so much vagueness and secrecy in the OP and replies.
2) The 'Kinematic V's Kinetics effect of orthoses and which of these can be achieved or are desirable' argument.
I think it looked like there was secrecy because I never gave permission for the posting on the FAS and questions were asked in a round about way. Now that I'm involved you can be sure it's all open.

Because there are vertical, translational and rotational forces applied to the plantar surface of the foot and you can feel the supination resistance or pronation resistance and see movement, hopefully we can measure both and see at what point the forces/movement make a difference to symptom relief (if any).

Wow! 80,000 hand jobs in the industry, when did you change over to podiatry?

(my 99 yr old grandmother has nicer looking hands than me!) OMG! Does she work in the industry too? Can I book --- no no no slap my wrist for even thinking it -- (sorry Neil they were just sitting there - to good to resist, naughty me!)
I did a couple of years at uni but dropped out! Should've finished and still regret it but maybe wouldn't have come up with the idea for the FAS. Good or bad, that's just the way things turn out.

NO! she doesn't! I know you didn't mean anything bad by it, but no need to take a stab at my Nan's expence.:boxing:

What about the internal forces and the GRF and the foam reaction forces and the manual forces applied by the clinician
There are still no vertical, rotational and translational forces applied to the plantar foot when someone stands on foam, (from my understanding) and lets say the patient needs a lot of medial rearfoot control ie: Kirby Skive to take away the agressiveness of the MLA. I'm pretty sure you can't do it, unless say you left the First in a dorsiflexed position and modified the F/F of the cast. I cant say. I haven't done enough with the foam to comment too much. Maybe in the reaearch we should test against the foam boxes too!

Robert Isaacs runs Footprint orthotics and uses 'soft and squishy' technology to make comfortable insoles and they are excellent for many patients. I see your thinking but comfort does not neccesarily equal good outcome. A peice of flat 6mm pink poron as an insole might be very comfortable but it probably wont change internal forces very much.

I get your point here but you have to remember that both types of casts and orthotics were done for each person. ( FAS-WB and NON-WB )
All jobs were 4mm poly with R/F posts and vinyl TC.
Because the control and forces applied to the foot were evenly distributed from the FAS orthotics I believe this is the reason for the increased comfort. If aperson needs a lot of control and force applied with an orthotic it not a problem with tolerence because the weight and pressure the orthotics exert should be evenly distributed over the foot. Making it more comfortable and easier to tolerate ie: Blisters, hot spots...

Regards and thanks

Neil

 

Neil

OK so now we've got the real McCoy on line, things make more sense.

So now I understand what you are trying to achieve.

I.E. Using the FAS a certain change in kinematics, or at least of static foot position, will result in a more comfortable foot orthosis, when compared to other casting and fabrication methods where all other parameters of construction are the same.

This premise does not make the assumption that positional changes are optimal and that they are achievable during ambulation. However this does seem to be the major premise of your FAS. Are these assumptions reasonable?

Furthermore when repeating the cast and fabrication any clinician using the same prescription parameters will achieve the same result with high precision and only minimal variation between each set. This will apply to both inter and intra clinician results.

Query

Is it impossible to have two different kinetic conditions but only one kinematic result? I.E. Can force be applied in different ways to obtain the same foot position?

Two questions under general headings here

1) COMFORT
Comfort can be extremely subjective.

What are the parameters or criteria of comfort?

Can they be defined in objective terms?

Would it be reasonable to assume that even distribution of pressure equals one criteria of comfort?

If force per unit area can be used to define comfort is there a cut off value. IE A point where a decrease in the force per unit area does not increase comfort?

What range would this value have across a population of interest?



2) FORCE

Can even distribution of pressure or force per unit area across the foot - orthosis interface be an obtainable criteria if a kinetic or kinematic change is required?

Does your FAS know anything about the forces and force vectors applied during foot alignment correction?

How does the force applied by the FAS relate to the force applied by the foot orthosis?


Cheers Dave

 

Sorry. Should have clarified. Did'nt mean to be obscure.

In shoe systems are vertical loading systems. They measure only vertical force. They measure lots of bits of vertical force which sometimes gives the impression that they measure in 2 dimensions but in truth it is only one dimensional data. They measure Y-, that is downward force. The do, however, measure it through time making them technically a 2 dimensional system.

What they cannot mesure is Z+/- force (medial / lateral) or X +/- (forward or back.) These things are really quite important especially when considering the function of insole.

Consider a hypothetical frictionless surface at a 45 degree incline. If you put a weight on it that the surface will exert a purely lateral force. The weight will slide off instantly. Now change that surface for, say, laminate board. The weight will still slip off but more slowly, the board will exert both a lateral and vertical force. Now glue the weight to the board....You get the idea.

Try this. Take your shoe off. Put your thumb under your navicular and push straight up. Foot probably supinated. Now without moving your thumb push at a 45 degree angle or so so that the force is aiming at somewhere around the cuboid. Foot probably pronated. Now a VLS placed under your thumb would detect a similar straight up force in both cases, yet the two forces caused completely different effects! Why? Because in on the force was pure y - and in the other it was y - AND a bit of z (lateral). But the VLS can't detect Z. Thats the flaw.

This is one of the answers to the eternal dilemma of how an orthotic modification place medial to a STAxis can still exert a supinatory moment. Because the force exerted will not be simply vertical but triplanar. A VLS cannot pick this up.

Does this explain what i meant or am i rambling incomprehensible gibberish again?

Regards
Robert

 

Bravo! Bravo! :good:

Dave

 

Neil:

In giving your potential research project some more thought, I think it would be most helpful to first establish how your machine's negative casts are different than other methods of negative casting. What I mean is that we must first establish what the differences in the three-dimensional shapes are in the negative casts produced by your machine and by more traditional methods of negative casting since you are claiming that your machine is a superior method of casting.

I would prefer to have at least three different methods of negative casting being analyzed. Here are the most likely candidates: neutral suspension plaster casting, foam bed casting, your machine. The feet to be casted (probably at least 20, better at 40) should have raised line of material adhered to their posterior calcaneus that would then, on negative casting, produce a posterior reference groove that would allow a calcaneal reference line to compare one cast to another. Then positive casts would be produced from each set of negative casts and dimensions/shapes of the cast would next be analyzed.

Here are some parameters one may consider for positive cast analysis:

-Heel width
-Angulation of forefoot to calcaneus in frontal plane
-Posterior calcaneus to first metatarsal head length
-Posterior calcaneus to fifth metatarsal head length
-Lateral arch height
-Medial arch height
-First metatarsal head plantarflexion/dorsiflexion relative to lesser metatarsal head plane
-Lateral foot border shape
-Radius of curvature of plantar heel in frontal plane
-Radius of curvature of plantar heel in sagittal plane

This would be an initial paper that would establish the basis for future comparisons in later research studies that would investigate foot orthosis kinematics, kinetics, and comfort in subjects casted with your machine. If done well, it could easily be published in the Journal of the American Podiatric Medical Association.

Hope this gives you some ideas. Good luck.

 

http://www.staffs.ac.uk/isb-fw/LITPDF/muendermann31 doc.pdf
http://www.acsm-msse.org/pt/re/msse...WyL3jvLCM5hD0Gnv!1321082991!181195629!8091!-1
http://www.humankinetics.com/jab/viewarticle.cfm?aid=2677

Worth reading the other published output of this team in relation to this topic: Anne Mündermann; Benno M. Nigg; R. Neil Humble; Darren J. Stefanyshyn

 

1) Take casts using techniques outlined above.
2) Scan casts
3) Overlay them within CAD system
4) Observe and measure ALL differences.

Piece of cake.

You'll need to show variation within as well as between casting techniques.