Why do traditional orthotic shells end proximal to the MTPJ's?
Members do not see these Ads. Sign Up.
-
-
Re: Orthoses length
Why do i think this is a trick question?
Ok i'll bite
Because traditional orthotic shells are primarily designed to exert force on the rear and midfoot. Unless you are using a forefoot modification to exert force under the mpjs extending the orthotic to this point will merely take up room in the shoe and if you extend the actual shell, affect the sag plane function.
Interestingly all the orthotists i have ever worked with use only full length orthotics. Possibly to do with the fact that they tend to work in piedros or bespoke footwear.
I pause with baited breath to have my head chewed off...
Regards
Robert -
Re: Orthoses length
I don't buy the sagittal plane thing see here:
http://www.podiatry-arena.com/podiatry-forum/showpost.php?p=20460&postcount=1 -
Re: Orthoses length
It would not be a difficult to set up and experiment in which foot orthoses are made "too long" and measure function and comofrt in subjects; then repeat the measures with the orthoses shortened. -
Re: Orthoses length
-
to add an extra element of stiffness to the shoe both through torsion and flexion moments that was not there to start with.
The level of this effect is going be directly related to the material/substance used for the forefoot extension, Poron, EVA?
As to how or why this lessens the effect of mid/rearfoot functional orthosis, l didnt know it did? but then again thats why l am here:)
although l would imagine it would slow the flow midfoot to propulsive stageLast edited: Nov 29, 2007 -
The reason I was given when I asked the same question some years ago was to not interfere (or to facilitate) on MPJ dorsiflexion during propulsion phases.
Regards, -
bionetz
Janvier wrote
>The reason I was given when I asked the same question some years ago was to not interfere (or to facilitate) on MPJ dorsiflexion during propulsion phases.
That was my understanding too and to illustrate this I would take the cast and draw a bisection line of the proximal phalanx of the great toe and fifth toe, proximally, then join a line across the broadest aspect to the metatarsal heads (defined by the medial and lateral prominences of the respective metatarsal heads). Where the lines intersect identifies the centre of the 1st and 5th heads respectively . The length of the orthosis should not extend distal to that point and finish proximal to the area otherwise it will interfere with the leverage function of the mpjs. Once heel lift takes place and weightbearing is over the met heads (mid propulsive phase) the traditonal 3/4 orthoses ceases to function (other than provide arch integrity). I have always used silicone props in conjunction with 'functional' foot orthoses to engage the lesser toes.
Full length inlays of accommodative materials provide added comfort (if required) and most shoes should have approx. 3/16 " dead space to work with. At one point smaller sized functional foot orthoses were popular whereas now there seems greater acceptance of 'buttress style" foot orthoses (not sure why this is as there appears to be no physical advantage from the bulk). Some shoe manfacturers now claim to have shoe fittings suitable for foot orthoses, which to me seems rather an anathema since foot orthoses should fit the foot (and not the shoe), suffice anything the foot gets into the orthoses goes comfortably too.
This may mirror the increased reliance practitioners put upon orthotic services, where minor adjustments made by the practitoner may negate product warrenty and therefore it is easier to have the supplied foot orthoses fitted to a larger shoe. (?)
But hey. what do I know?
toeslayer -
The same can be said of some Orthosis when it comes to midfoot fit to say nothing of the inappropriate style choosen by the client:bash: -
Boots n all
>.....there is slip/traslation at the back of the shoe.
As a mimimalist I would argue if the foot orthosis causes the heel to slip out of a standard shoe, then the bulk of the orthoses is at fault.
toeslayer -
l would love to say that to some of the reffering Pods but l tend to break out in a rash at the thought of "tar & feathers":eek:
Yes sometimes they are a bit high but sometimes the shoes they try to fit them into are far from right, its about balance, you cant spend $450+ on an Orthosis and try to make it work in a low cut $25 shoe:bash: -
Boots n all
Certainly sympathise.
toeslayer -
Re: Orthoses length
-
Re: Orthoses length
Don't buy it. :pigs: -
Last edited: Nov 30, 2007
-
A good portion of our patients are elderly and its a sod of a job trying to get a 80 year old to wear trainers or decent shoes with a removable lining. They think that it makes them look old!:hammer:
Regards
Robert -
Polyprop or Carbon Fibre is a completly different topic, l dont know if you could call them " traditional orthotic shells " as you stated in the initial post but thats cool.
"I have a pair of trainers on today, the thickness of the sockliner at the forefoot is 2-3mm, If I remove this and replace it with a full length orthoses made from 2mm material how will this effect the room in my shoe?"
No l agree with you, you have changed nothing much in this case, pending the stiffness of the replacment compared to the original, if you replace it with Polyprop or Carbon Fibre it changes everything (excluding the space issue), especially if the shoe does not have enough "rocker" effect to the sole shape or you have bought a plate that does not match the contours of the shoes sole, heel height, toe pitch, thinking of those your 8 inch stilettos at the moment of course:)
As l stated in my earlier reply, poron and EVA were given as a few examples, add
Polyprop or Carbon Fibre to the examples and you have the same statement working just fine for your discussion
"The level of this effect is going be directly related to the material/substance used for the forefoot extension, Poron, EVA?".......Add them here:cool: -
-
Hi all, especially Mr Toeslayer,
I'd like to add some thoughts clinical/lab perspective and having been involved in this stuff for a while. There are just too many quotes to acknowledge that I'll just have to miss them all.
So we're talking about the rigid shell extending beyond the 'normal' length of finishing just behind the met heads.
I've got three real threads to outline.
1. I have made them longer and to the end of the shoe.
For sprinters I have made rigid full foot orthotic shells (called them RFFO's)
These were made on casts taken with the forefoot dorsiflexed against the rearfoot. The amount of dorsiflexion was a variable. It was impossible to sprint in flat or low angled forefoot and an angle of 25-35 degrees seemed to work well - possibly enhancing performance if not at least improving stability. The higher the angle got the more difficult it was to walk with them. These devices were mostly made using real carbon shells with a thin soft EVA cover.
2. From time to time we had a few clients ask for shells to be extended, so that they extended under the met heads in the form of Morton's extensions, Reverse Morton's, 2-4 extensions or with cutouts for particular met heads and extending under the rest. I don't think we were unique in doing that and we were rarely asked to remove the extensions.
3. In my clinic, patients usually arrive with a couple of pairs of orthoses at least.
One of the things I check on these old devices is the length which if long enough to interfere with dorsiflexion of the mpj's can be the cause of unresoved problems and the development of new ones either at the mpj itself or back at the bases of the mets. I have seen 1stmpj ROM improve more than 20% after wearing a shortened (from being 'too' long) device for a week. Often this was not the presenting problem.
I'd say that you could extend many shell if you wanted to but would need to have some 'spring' or dorsiflexion angle built into it. Personally I like soft extensions if at all possible to keep devices more stable in shoes and so that I can add extra bits under the forefoot wherever I like very easily.
Cheers
Shane -
young Shane et al
Absolutely no arguement from me and would suggest a "conditons apply" clause to specific managements. It would however be the exception rather than the rule, correct me if I am wrong.
In a previous existance I taught the manufacture of foot prostheses and would set students the laboratory task of devising a foot prosthesis for post Symes amputation based on Root biomechanics. (Yes, I was once a devotee.) The best examples always included an distal extension of the three middle metatarsal plane with a moulded prosthetic toe block set to a pre-calculated angles to give the prosthetic extension, toe spring. Similar I think to what you are suggesting?
When is out next coffee date? On me this time.
Hav a good one
toeslayer -
netizens
Something which I have not seen discussed on the forum is when the use of balanced foot orthoses are contra-indicated because the physiological age of the joint. As I understood the situation as suggested in Root et al was there was a time when joints were no longer able to adjust to realignment (without further limitation of movement or osteoarthrosis) and at that point 'function foot prescriptions' were contra-indicated. This situation occurs as part of the normal aging process and was not uncommon in the thirty something group. Interesting aside the demographic is one to which foot orthotics are most frequently prescribed. Can we expect further foot morbididty as this demographic ages caused by foot orthotic intervention ?
What say you?
toeslayer -
could you elaborate on the above statements please? Possible post a picture or diagram.
I'm a bit confused in your statement that you cast with the forefoot DF'd against the rearfoot. Can you describe this technique? It sounds like you are flattening the medial arch with this technique.
You also describe a 25-35 degree angle of the forefoot. I'm trying to visualize all this but am a little slow tonite I guess?
Thanks
Bruce:wacko: -
Mr Toeslayer,
I'm back from Adelaide next Sunday (9th), so perhaps later that week - the Friday?
and:
Hi Bruce, you said:
Imagine if a cast was taken semi-weightbearing with the heel about 4cm off the ground but the forefoot in contact. Then round off the forefoot a bit more in the positive cast so that it has a very mild curve in the sagittal plane.
This is a sprinting device and you definitely do not want the device to be high in the medial arch. We want to enhance movement in the sagittal plane and reduce movement in the frontal plane as beyond a certain amount occurring as part of a recoil any excess is a waste of time and energy.
So you have a basic shell. There are more variables possible and one of these days perhaps it can all be researched.
I hope this helps.
Cheers
Shane -
This is based on the idea that shank independent materials, such as polypropylenes, acrylics and composites, have enough intrinsic stiffness so that if they extend past the metatarsophalangeal joints (MPJs) the orthosis shells would not only interfere with normal MPJ dorsiflexion but would also tend to produce uncomfortable excessive loading forces plantar to the MPJs during late midstance and propulsion. Of course, the shank dependent materials, such as EVA, plastazote, and cork, can easily extend past the MPJs since they do not possess the intrinsic stiffness that will prevent them from being deformed at the MPJs as the propulsive phase of gait occurs. -
thanks for the reply, I understand much better now. Essentially you are pre-loading the mpj's for dorsiflexion transition from midstance toe-off.
Will you add a 4mm heel post to the devices since you cast that way, or not?
I'd be curious to see any research you have on those?
Be well.
Bruce -
Hi Bruce,
Only got to an early stage in the research and can say that these devices enhanced velocity but it was harder to start.
The casting angle was over 20 degrees and could be calibrated with an angled platform, and were obviously more than 4cm at the heel. Heel raises on the orthoses seemed logical up to a point to reduce the time taken for the heel to be dropping into weightbearing.
I wouldn't mind taking this project up again sometime!
Cheers
Shane -
Shane
>Definitely, as have regards to pass on from another of your comrades splattered around the globe. I had a chat with this one in Brisbane - just to get you thinking.
I'm back from Adelaide next Sunday (9th), so perhaps later that week - the Friday?
Would you believe, I earn a modest living on Friday and seem to be busy up to the 20th. Will give you a ring tho' and arrange something.
Meantime, I bet it was AC in Brisbane. That girl could do a tango with me anytime. :morning:
.... and I would like to acknowledge the benefit of Yeastvite tablets and Senatigen Wine as a perfect combination for the older more discerning adult.
toeslayer -
It was AC, so that wasn't hard at all, Mr Toeslayer,
We'll have to make it a WEDNESDAY!
Cheers
Loading...
- Similar Threads - Foot orthoses length
-
- Replies:
- 1
- Views:
- 790
-
- Replies:
- 6
- Views:
- 1,594
-
- Replies:
- 1
- Views:
- 1,612
-
- Replies:
- 1
- Views:
- 1,324
-
- Replies:
- 0
- Views:
- 972
-
- Replies:
- 19
- Views:
- 3,498
-
- Replies:
- 0
- Views:
- 1,281