Has anyone used the Formthotics with or without the heating machine? Can a heat gun be used instead or is the heating machine a necessity?
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Do the Formthotics have to be in shoe when heated on the machine?
Where I work part time (employed) they are thinking of using the Formthotics and just want to know best way to heat them before moulding to the foot.
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Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
I use Formthotics and you do not need to use a heating machine to mould them. I find that a heating gun is adequate for the task.
The heating machine is designed for heating the formthotic in a shoe. With a heating gun I dont think it a matters if you heat them in or out of the shoe.
Paul -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
Turn the heat down and take your time, heat in the shoe but be careful you can melt the shoe. -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
I know Charlie hates it when I say this, BUT you can not heat mold a shank dependent EVA/PE prefabricated orthoses. -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
ie if you increase the arch shape of the formthotic you have changed the stiffness of the device.
if this change in stiffness is significant is a whole other story -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
BUT, how do you change the arch shape of a Formthotic or any prefab by heating it? As they are shank dependent, as soon as you stand on the device, the shape is determined by the thickness of the material and there is no way that heating changes the thickness of the material.
If you do not believe me, get some calipers and measure the thickness of the prefab in a few locations; heat them following the manufacturers instructions, then measure the thickness of the material in the same spots again. Did it change?
You can heat and bend a prefab and let it cool down and it will maintain that shape, but as soon as you stand on it its shape is determined by thickness; heating does not change that thickness; - the only way you can change the shape is by gluing bits on or grinding bits off.
I can't believe people fall for this (and worse, that people can keep a straight face when the teach this).
(Disclaimer: There probably is some benefit to heating the heel area of a Formthotic to facilitate its initial fit into the shoe) -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
Craig l am suprized you took so long to reply to that one;).
Heating in the shoe? brave people, if it gets hot enough to make EVA mouldable:confused: the heel stiffener would also become soft......mind the synthetic linings and the Velcro which both melt at low temps -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
I too have been very confused for a very long time about why I am bothering to heat these things up!
Iv'e concluded it must be for a bit of theatrics, or maybe to make them feel nice and warm?
Acutally, i think its so it takes a bit longer than 46 seconds, which it the resonable time it should take someone to remove the sock liners from a pair of runners and replace them with formthotics.
Because, once you've stood on the things, they're gunna hit the floor no matter what temperature they are. Unless they're molten lava temperature, but then you've got a whole other bunch of problems on your hands. -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
Found the tread where we discussed it - http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=62683
If you change the shape of the device ie bend you will change the stiffness of the device. -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
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Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
And I'd agree that the heating system with formthotics is nowhere near enough to heat the orthotic to the point of malleability all the way through.
Heat moulding shank dependant pre fabs is one of my favourite ways to customise a pre fab, but you have to either add more material or grind some away from the underside of the device to make it practical. -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
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Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
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Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
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Ok, here we go. So lets say we know that foot orthoses work by altering the magnitude, distribution and timing of reaction forces acting on the foot. And that we agree that basically they do this by altering the geometry, load/deformation and frictional characteristics at the foot-orthosis interface. In order for heat molding of eva devices to not alter the magnitude, distribution and timing of reaction forces acting the foot, then the heat molding cannot change the geometry, load/deformation and frictional characteristics at the foot orthosis interface. If it does then the reaction forces will be altered.
So, quick bench test. I started with a block of 10mm thick eva and then did some work on a prefab. If anyone here believes that the heat molding of these has not altered the geometry or load/deformation characteristics, please speak now.Attached Files:
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Loaded upside down, turn your screen over, it'll be quicker than me fannying about with the pictures;)
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Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
The answer you are looking for is no. So even if it does deform back to it's initial shape, the timing magnitude and distribution of reaction forces acting on the foot will have been altered. And since this is how foot orthoses work, we must have changed the way the orthosis works by heat molding it. I hope that helps. -
How significant could these changes be? the higher arch will make the device more rigid, how much is the question? Most likely You could deform the shape with you little finger, clinically significant? I doubt it.
Perhaps the next test could be to measure arch deformation when placed under a various loads?
I think if you are going to modify the arch height by heating, you need to then fill it with Eva. -
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Good examples and pictures Simon
What helped me to get a handle on this was the fact that it was not just the lowering of the arch of the prefab that was possible, but also the raising of the arch of the prefab. Raising the arch increases the stiffness and will have effects on fricition and thus change the magnitude of the forces.
Yes, it can be pushed out by the amount of force from one's little finger. Does that make it clinically insignificant - not in my book.
We have all seen patients with bits of cardboard in their shoes that have been enough to alter the forces enough to reduce tissue stress. Why shouldn't the miniscule change in surface geometry of a prefab be capable of doing the same thing?
Robin -
You've really got to go back to understanding how reaction forces are generated and the factors that influence them. Rate of transfer of momentum is good place to start.
As you know the example I have used is two cars travelling at the same speed, one applies the brakes gently over a longer distance, the other slams the brakes on at the last second. Both cars stop at the same point on the road. But the braking forces (orthotic reaction forces) have been very different. This is effectively what changing the load/ deformation characteristics of the orthoses does.
To better understand how altering interface geometry influences reaction forces, anyone interested should take a look at the paper which Dave Smith, Kevin Kirby and I wrote on in-shoe pressure measurement. I'm told it's helped a few people to get their heads around the influence of orthoses geometry and force vectors. -
One must also understand that in any discussion of both shank dependent and shank dependent orthoses, the orthosis will be signficantly influenced by its contact with the medial upper of the shoe. Just yesterday I had a patient that said that the orthosis felt too high in the medial arch when the orthosis was inside the shoe, but didn't feel too high when the orthosis was laying on the floor, without any shoe mechanical interaction. I simply narrowed the orthosis by 2 mm and he felt the orthosis felt much less high in the arch (the orthosis was sitting flat on the insole of the shoe both before and after adjusting the orthosis).
I agree with Simon on this one....even the simplest flat flexible insole, when now placed into a laced up shoe, can have a signficant affect on foot comfort and foot function since it doesn't necessarily retain its flat shape when it lies against the medial upper of the shoe. These considerations are extremely important when we are discussing orthosis function, orthosis stiffness and orthosis comfort. -
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Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
"rivers rise as the rain descends, don't make that same mistake"- wise words.Attached Files:
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Who was that olympic swimmer who swam about as quick as I did when I was 9 years old, who was at the olympics not too long ago?
Viz. If I lived on the Isle of Man, I could probably be competing in the next olympic 10,000m, if the funding was available. -
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Eric the Eel. I'd forgotten just how funny that was. AWWWEESSOMME!
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As for Australia at the winter Olympics, we would probably be just as crap as great Britain at ski jumping, but we have a few medals. Most infamously is our first gold-
http://www.youtube.com/watch?v=-DHgMiN6Nlc&feature=youtube_gdata_player
I remember listening to a US commentator saying 'that will be the first and last gold medal for australia at the winter olympics'... then we won another the next day in aerials...:DLast edited: Jul 20, 2011 -
Maybe you can bring back the GB tradition in Ice Hockey Simon
GB have a Gold and a Bronze even beat Canada to win the Gold. -
I would agree that you don't need the heat machine, however you will get a much better heel cup shape, arch contour and even heat distribution if you use the formthotics heat machine.
The downside of using a heat gun is time wastage, accidental burning of the shoe, particularly the fabric around the heel counter or nylon mesh within the shoe, and spot overheating of the formthotic, and uneven heating of the formthotics.
I have worked in a number of clinics with high volume formthotic use, by far the best result and use of my time was the clinic with the heat machine, for forming and subsequent modification of formthotic bulk and prescription angular changes (posting) for the device to encourage positive change in foot mechanics.
Heat gun or machine you will get better results with in-shoe heating.
These days I prefer the accuracy of a good lab. -
Simon - I will get my own pictures in response soon..
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Grinding and heating.
I agree with you Craig, there are way too many variables with pre-fabs. -
Re: FORMTHOTICS, DO YOU NEED THE HEATING MACHINE?
Attached Files:
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Simon, out of curiosity what was the density/hardness of the EVA you compressed so easily?
Lower density materials will compress easier and stay that way compared to the higher density materials.
Remember these Pre fabs are ranging in the 4mm-5mm thick in hard EVA's, the percentage of compression available is less in the higher density materials. -
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........Next, I took a commercially available prefab and put it into a materials testing machine (see the picture) 15mm flat disc probe, I added two restraints as seen and measured the height of a point in the medial longitudinal arch section and proceeded to plot load/ deformation data.
Then, I heat molded the device by hand and increased the arch height and repeated the process of measuring load/ deformation
Then, I heated up the device again, this time lowering the arch and repeated once more.
The load/ deformation curves are attached in the .pdf.
The unloaded height of the arch in the unmolded state was: 23.93mm
The unloaded height of the arch after the elevation/ heightening molding was 29.93mm
The unloaded height of the arch after the lowering molding was 18.83mm
Loading was increased on the device such that 1mm increments of deformation were observed. Thus, given that the height of the elevated molding was 6mm higher than the unmolded state, 6mm of deformation and the load required to achieve this should be necessary to bring the height of the arch to the same level that it was at prior to molding (roughly).
So, one way to view this data is to look at the graph, and compare the load at 7mm deformation for the heightened molding and compare that to the load of the unmolded device at 1mm deformation since the device should be roughly the same arch height at this point (Craig's contention that the device returns to the same shape under loading- right?). In other words, in order for the area of the foot which interfaces with this area of the orthosis to occupy the same point in space on the two devices, this area of the foot would need to apply a force of 36N on the device with the heightened arch, but only 10N on the unmolded device. Remember Newtons 3rd law: if the foot is applying a load of 36N to the orthosis, the orthosis is applying a load of 36N to the foot; if the foot is applying a load of 10N to the orthosis, the orthosis is applying a load of 10N to the foot over this area. Thus, the orthosis with heightened arch applies 3.6 times more load to this area of the foot at this point in space compared to the unmolded device.
A simplified example of the potential significance of this difference: lets pretend that this force is the only reactive force at the foot-orthosis interface, lets assume a vertical force vector, lets assume the centre of pressure of this force is 10mm from the subtalar joint axis. Moment = force x distance
36N x 10mm = 360Nmm
10N x 10mm = 100Nmm
It's a bit rough and ready, but hey: what did you do between patients today?Attached Files:
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only slightly less geeky!
Good graph - curious as to why the raised arch showed lower load for the same deformation relative to the others as the deformation increasedLast edited: Jul 21, 2011 -
N.B. this was really just a quick show and tell. A bit of scratch "n" sniff science.:drinks it is obvious though that heat-molding of prefabs is capable of changing both the surface geometry and load/deformation characteristics of prefabricated devices. Thus the timing, location and magnitude of the reaction forces occurring at the foot-orthosis interface can be changed by the heat-molding process. QED
Whether or not these changes are clinically significant is another story.
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