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Im a podiatry student from Sweden and was just googeling the web for different ways to fabricate orthotics. from the paradigm learned at my uni you should put the stj in neutrual when casting (always non-weightbearing). when using a foam-box or for example the AMFIT system, do u put the stj in neutrual? and how is the patient positioned, sitting, standing? any of you using systems like the AMFIT? and is there any research comparing computurized Vs. traditional POP?

thanks

Björn Englund
student
Karolinska Institute
Sweden

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That is a very valuable resource on this topic

Bjorn

With the Amfit system you can scan neutral, pronated, supinated, semi weight bearing, full weight bearing, any bearing position you like. It up to the clinician to decide the position of the foot to be scanned depending on the patient presentation they are dealing with.

Sub talar joint neutral is just a refrence point, a bit like Magnetic North, - Just because its a refrence point you don't need to end up at the North pole every time you make a journey and like Magnetic North, the position can wander around a bit, which is OK since you don't need to go there. Unless you do need to go there for some reason and then you should ask yourself why.

All the best Dave

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Descartes seems to consider here that beliefs formed by pure reasoning are less doubtful than those formed through perception.

Good point Dave. At the end of the day, once you start adding plaster you change the fot countours and the forces under the foot anyway. I believe that the cast just gives us the correct shape foot from which to work from. The biomechanical assessmnet, understanding and orthotic prescription and fabrication are more critical than casting technique. I've found little (if any) difference in my devices for patients whether casted in subtalar neutral, resting or subtalar neutral with midfoot pronated.

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Adrian Misseri
B.Pod.,M.Hlth.Sci.(Pod.)

You know.. we could just cut it off.....?

Adrian, that is an excellent point.
What casting technique requires the least amount of cast correction, and would you equate this with the best method of obtaining an impression of a foot?

Regards,

Stanley

I use a 2 piece supine cast in subtalar neutral with traction and pressure under the 4th and 5th digits to slightly pronate the midfoot, moreso out of force of habit. I'll also correct for 1st ray elevatus/forefoot supinatus. But honetsly, all the podiatrists at my practice cast differently and we all get good results with our patients.

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Adrian Misseri
B.Pod.,M.Hlth.Sci.(Pod.)

You know.. we could just cut it off.....?

Bjorn, Adrian and Stanley

If you are talking about casting and then using a lab to make the orthoses then there needs to be areference point from which you both can work. By convention this has been the STJ neutral. However in theory any predetermined reference could be used to get the same results as long as the clinician realises the implication of the casting position they use and how it will result in an orthoses precription that will change forces of gait in a way that is benicifial to the patient IE reduce pain and not induce further or subsequent pathology.

However in terms of computerised CAD CAM orthotic production where, to intents and purposes, the evaluation, design and manufacture is in office, then the clinician has greater control and intimacy (not in the carnal sense you smutty boy ) and can use anyfoot position during scan that he wishes.
The point is to reduce tissues stress or achieve ZOOS (zone of optimal stress) and not necessarily a dogmatic repositioning the foot in relation to some arbritary anatomical reference.

Bjorn wrote
Only if this is the requirement of the lab that you use. If they are a good progressive lab they will allow you more leeway as long as they have some reference to work to and they work to your prescription instructions. As opposed to just letting the lab decide the prescription, which is a poor substitute in my opinion. Otherwise if you do your own work you can start of with STJ as your conventional reference and move on to other foot positions and references as you progress.

Cheers Dave

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Descartes seems to consider here that beliefs formed by pure reasoning are less doubtful than those formed through perception.

thanks for all the answers

if you accept the root theory with stj neutral wouldnt a negative impression (from whatever way taken) with the foot in a neutral position make the correction (of the positive cast, computer image etc.) easier? wouldnt a impression from, let say, a foot in a pronated position, force the clinician to make more corrections? isnt this what can happen when using a foam-box, forcing the foot into the foam with little control of its position?

what is the benifits from using a sitem like AMFIT Vs. a foot scan that gives u a 3-D picture?

sorry for all of the questions, its just that there seems to be a dogm, or paradigm, of what is teached at Uni when there is so much more theories and ways to work. I also belive that for one like me, who is intressted in biomechanics, the amount of time for this subject in the curriculumn is to little. but I do have one course in orthotic therapy left during my last term.

I would also like to have your oppinion on what you think about having orthotic engineers (like ortothist) teaching part of the orthotic therapy courses. the problem here in Sweden is that so far no podiastrist excist (my class is the first to graduate with the degree) so there is obviously a lack of biomechanical podiatrist to learn from. during the courses lectur from other countries have, and will, be invited, but still whe have to practice somewhere with supervisors.

thanks for your time

Björn Englund

Bjorn;
AMFIT provides command and control software with its scanner / digitizer. I have yet to see a product anywhere near as adaptable or allowing so much control in orthotic manipulation / prescription.

David is very correct in his descriptions of how to cast utilizing a scanner, any scanner, and what positioning can and may do in regards to the orthosis.

With the AMFIT system I can make an in-house device w/ a built in heel lift, specifically placed adn sized metatarsal pad, groove for a 1st ray cutout or kinitec wedge, FF valgus posting, digital posting ( ala cluffy wedge 1-5 or any combination), Medial heel skive, accomodations, etc.

Learning when to break from STJ neutral takes quite a bit of experience and understanding in what the patient can do and how it may or will affect them once the device is made. Being able to correct for your mistakes is important as well as learning from those mistakes.

Good luck.
Bruce

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Bruce E. Williams, D.P.M.
Breakthrough Podiatry

Bjorn,

Practically, you should use the technique your lab advises. Remember that every lab has their own fudge factors that will allow them to use modify a cast so that the orthosis is comfortable. There are many techniques and many labs. So pick a lab that goes along with your thoughts on the subject.
For instance if you think that a Bergman balancer is the best device for your patient, and you want to use Bergman labs, then you have to use a dangle cast.

Regards,

Stanley

Stanley

Ah! the dangle cast, one of my favourites - But I dont get much time for fishing these days.

Would you say the angle of the dangle is important to consider? Is there a correlation between the 'angle of dangle' and the 'heat of the meat'? If so when is the best time to cast?

Is there any research out there?


LoL Dave

PS Seriously tho I like to use Talar Made for my cast prescriptions.
Like Bruce says Amfit gives you total control over prescription and processing.
The additions and cut out are precise and as variable as your imagination and experience allows. Its quick clean and you have a permanent computer record for future prescriptions should the customer require them. IE no storage space required for stored casts.
There's nothing wrong with Root it's still very relevant but the way you use it has become less dogmatic over the years. Use of anatomical and physiological knowledge, plus application of mechanical principles should underpin the precription protocols. In this way each patient becomes an individual investigation and atrue custom / bespoke orthosis is produced.

Cheers Dave

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Descartes seems to consider here that beliefs formed by pure reasoning are less doubtful than those formed through perception.

Dear all

I would echo Davids opine on the relevance of STJ neutral. It is one of the three reference points of the STJ and very useful in communicating positions. It is not, IMO, the position all casts should be taken in.

I would advise anyone to go to the zoos, (the animals will love it if you do according to S & G). I would also suggest that the principle of Zoos can be applied in 4 dimensions to the timing of gait with judicious use of different materials and posterior - anterior temporal progression. It is a paradigm shift away from the Root dogma (that word is coming out a lot) which most of us trained with but if you can break free of that mindset it opens a whole new world of options!

Simply, no. There is a technique to using a foam box just as there is to using suspension casting (overarm into the weeds near the eddy where eels swim). Its possible to fudge both and its possible to do both well.

Foam has the advantage that you can capture the soft tissues in close to their WB configuration (75 % of change to the foot shape happens in first 25% of body mass loading) whilst still controlling joint position. This, i suggest, is more accurate than the lab adding plaster to symulate a WB soft tissue configuration. It gives a solid reference plane (ie the ground). If you make your own devices (as i do) it also makes it exponentially easier to apply modifications like PF grroves, PF 1st rays, cavities for ulcerating naviculars etc.

I use both, but i admit a preferance for foam. Its not a comprimise, its a choice.

Regards
Robert

Bjorn

I work for am orthotic lab (and have have worked for quite a few in the uk) and would like to add my opinion.
When a cast, either POP, foam or digital arrives, we at the lab have no way of knowing how it was referenced, and even if we are told, have no way of knowing if it was done correctly.
Therefore the only meaningful data we have to work with is our heel bisection if POP or digital (This is very difficult and a whole new thread) and the forefoot to rearfoot alignment (especially the foams box method).
The problem we have, as as Dave mentioned, is the lack of a common reference point. For example, if the foot was done in Stjt neutral and the cast shows a 5 degree fore foot invertus, we have no way of knowing if this is the foot alignment or a poor cast. We regularly have POP casts with 25 degree plus forefoot inverted alignments but I have not yet seen the patient who actually had a foot to match. Even the TEV patient will have some degree of rearfoot invertus to match the forefoot.

The point I would make is that the method of manufacture, CAD, traditional or other, is wholly dependent on the practitioner. Learn how to make a cast that is YOUR stating point for manufacture, teach the lab or technician this method and I am sure you will have success.

Regards

Phil

Robert

Hmmmm! Yes I had a sneaking suspicion about your preferences when I caught a glimpse of your frilly scanties as you walked up the court house steps ahead of me. Dirty boy! go to bed at once!!


Dave

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Descartes seems to consider here that beliefs formed by pure reasoning are less doubtful than those formed through perception.

I fully agree!
Making a pair of orthoses from time to time, even when you do normally lab, is the best way to keep in touch with relevent biomechanics and good prescription of orthoses. You learn so much more hands on!

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Adrian Misseri
B.Pod.,M.Hlth.Sci.(Pod.)

You know.. we could just cut it off.....?

Also look at the time of plastering vs foam vs computerised methods in terms of time-cost. What is the most efficient when it comes to billing the patient?

Plaster is way, way behind...

I work at a second office where there are two other podiatrists. I noticed at the second office I could easily see more patients, so I wanted to know what my problem was at the office where I am the only podiatrist. The difference was that in the office that I was with other podiatrists, foam was used. Both offices used the same lab, and the results were equivalent.
I looked at all the time I was using to make a plaster of plaster impression compared to foam. I had a special room set up for casting that the patient had to be moved to, then there was the time for the staff to set up, the casting and the waiting for the plaster to set, then there was the time in the whirlpool to clean up the patient. There is the time to bring the patient back to the room, and the time the staff cleans up the plaster mess. During this time, the original room the patient was in had to be kept ready for the patient, so I lost the use of this room for 30 minutes, and the patient wasn't happy about all the time they were there. Also, I lost the use of the whirlpool that my elderly patients require before their nail care. I have since switched to foam.
Regards,

Stanley

Stanley

What I don't like about foam box casting, where it is sent directly to a lab, is that it is very difficult to evaluate post impression. I know that Robert prefers foam but he makes a positive cast from the impression that he can then evaluate and build up an intinate knowledge of the negative impression - positive cast relashionship.
He then presses his own orthoses in his lab. I feel this is entirely different. On the other hand if you find there truly is no difference in outcome then that kind of negates this argument. Personally I never feel confident about foam casting and only use it where circumstances compel this.

Dave

__________________
Descartes seems to consider here that beliefs formed by pure reasoning are less doubtful than those formed through perception.

Dave

The foam boxes seem to work really well with the stiff foot type and less with the mobile ones. These issues can be negated by practice but I always have the problem of GRF from the FB being quite significant in some patients who can feel the 'pressure' it causes - they claw the toes and you can end up with a very high lateral arch.
I still prefer semi-loaded techniques and have access to a scanner that allows this - very similar to the Amfit system but with photogrammetry being the data capture method (very useful as you get a photo of the foot as well as the 3d data).
This works really well and allows me to 'play' about with the foot position and then compare the foot contour from each method.

Phil

Many good points made

-The reference the lab has is the heel bisection and not STJ neutral. You should either draw the bisection on the cast or tell the lab the forefoot to rearfoot realationship you want to have in your finished product. This is especially important if you abandon the root paradigm, but still believe in putting wedging in your casts.

-It is difficult to evaluate a foam impression in relation to the foot where it can still be done with a pop mold. If you perform your exam in the same room that you cast in, the only additional time you should have with pop is cast drying time. If you took the time to think about and evaluate the finished product in comparison with the foot you may be able to identify poor impressions. Amfit, same scenario. As was stated earlier, your impression is your starting point in making the orthotic.


Ah, if you accept the root paradigm. Now you have to do a little more thinking than your instructors have led you through.

How does an orthotic made from a neutral position cast alter foot function?
Support the forefoot to rearfoot deformity or "hold" the foot in neutral position? I'd say neither.

The change in arch height from neutral position to resting standing position is variable across people. Some people cannot tolerate orthotics made from minimal fill casts. How do you take that into account when you order from a lab? I tell the lab the arch height I want. Which is the height with a small amount of pressure added to the arch. This is probably very similar to what amfit does.



In theory, I like the amfit system. I like the idea of adding wedges to the "casting" so that you can alter the shape of the device that is made. With any method of making an orthotic there is a learning curve.


There is a lot of additional reading and thinking to do. It will take a lot of time to sort through all of the theories. Time outside of the classroom.

It would be a very good idea to have orthotic engineers teaching in the courses. You need to know how an orthotic is made if you are going to prescribe them. You could learn that from a podiatrist or a technician. The best way to do it is to make a bunch yourself.

Regards,

Eric

Dave,

From my experience most labs will correct the forefoot to the bisection of the calcaneus. This can be seen be done by constructing the bisection on the posterior aspect of the calcaneus of the positive cast (I don’t see how this would be any different from doing it from a plaster impression) Failure to do so will result in a twisting of the orthosis proximal to the forefoot. For instance, if the forefoot has an inverted position relative to the calcaneus, then the entire orthosis will evert (dragging the foot with it). This is how orthoses can increase pronation in midstance. Conversely, if there is an everted relationship or the forefoot to the calcaneus, then the uncorrected cast will invert, and the orthosis made to it will also invert, which will put the foot in an inverted position in midstance.
Regards,

Stanley