When custom orthoses?

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pods, i've already entered this query in a post under the "dc wedges" thread, however apart from a response from mr spooner, whose contributions i always "highlight" when i browse the biom threads (along with messr's payne, kirby, and "atlas") it hasn't seemed to raise much concern ... i realise mr kirby likes to 'ruminate' for 24 hours or so on a subject before always entering a well-thought out, informative response ... so i repeat (if that's legal admin?)

"why wouldn't a combination of rearfoot, forefoot, and lateral column support wedges? adhered to the sock lining perform as efficaciously as a custom orthoses in altering the CoP, reducing tensile and compressive forces, and reducing symptoms", mark c

 

Use custom made when the design parameters needed can not be provided by other means (ie prefab; footwear) after a compromise has been made for environmental considerations.

 

sorry craig, i can be as "thick as a brick" .. so is that a "no"

 

What I try to do and try to teach is not the prefab vs customisable prefab vs custom made (vs all the different ways of making a custom made) debate - they are all orthotics and they all have different design freatures and characteristics.

A foot has certain characteristics that need these design features (or variables or parameters) that it must get to get better, after a compromise has been made for environmental issues (ie footwear type; occupation; sport; etc). Does it really matter where those design features come from? A custom made or premade?

There are only some features that can generally come from a custom made (eg shank independent)
Custom made can generally be made less bulky
Custom made can generally last longer (which is cheaper in the long run if orthoses are indicated in the long term)
Custom made can generally be made more comfortable.

It all depends on just what the foot needs and what is the best way to achieve it.

 

Mark:

Since I do not have the multiple stomachs that my bovine friends are blessed with that enable them to optimize the rumination process, my cud-production process is now significantly shorter than 24 hours.

Now, on to your question.......

There is no reason that a combination of wedges placed onto a sockliner or aninsole could not be contructed to provide therapeutic results for many patients with mechanically-based pathologies of their foot and lower extremities. However, to do it as precisely as a custom foot orthosis would be quite difficult to do without somehow taking a 3D image of the foot. In addition, these "multiple wedge orthoses" would likely deform much more rapidly over time than a custom foot orthosis, would be much more bulky, would be less likely to fit in a large variety of shoegear as a well-made custom foot orthosis would, and would probably be less comfortable over time.

It is neither the casting technique, nor material, nor the orthosis lab that allows the optimal production of custom foot orthoses. Rather it is the clinician's knowledge of foot and lower extremity biomechanics and the clinician's knowledge of how foot orthoses may be best designed to alter the external and internal forces in the foot and lower extremity that allows the optimal production of therapeutic custom foot orthoses.

 

thanks kevin, what i meant by the bovine / 24 hr reference was that you don't seem to rush in and charge like a "bull at a gate" .. apologies if taken anyother way ..
.. i can certainly appreciate "and would probably be less comfortable over time", and "these "multiple wedge orthoses" would likely deform much more rapidly over time than a custom foot orthosis" .. but i'm unable to comprehend why ... "do it as precisely as a custom foot orthosis would be quite difficult to do without somehow taking a 3D image of the foot", and "would be much more bulky, would be less likely to fit in a large variety of shoegear as a well-made custom foot orthosis would" .... as surely any (frontal plane) angle of wedge would be identical to frontal plane angle of orthosis to achieve equable effect (with no difference in bulk?).... and doesn't casting provide difficulties in that it captures the plantar soft tissue shape .. the gun biomechanists don't need a cast to calculate what's needed? .... how am i going? thoughts appreciated, mark c

 

Mark:

Briefly....shank independent orthoses, such as polypropylene, can be made very thin to fit many shoes, last for 10-15 years and fit the plantar contours of the foot perfectly. Can any customized pre-fab orthoses claim the same abilities?

 

fair enough, but why does the orthoses / wedges / whatever have to ..

.. for the ENTIRE proximal 2/3rds of the plantar foot


.. and ..

..i never mentioned pre-fab's .. i was referring to additions to a sock lining or adhered to a flat (thin) template .. thanks again

 

Mark

I think I know where you are coming from so will offer my opnion on why the fitting of an orthoses to the 3D contours of the foot may be more ideal than a 2D wedge.
The bespoke shell should be in close contact with the calcaneus - as an example - the shell can then be 'propped up' or 'supported' by a rearfoot post. Any triplanar motion within the calcaneus should meet resistance via the shell. How the shell reacts to this force/motion is dependant on lots of things - i.e orthoses design.
In the case of the sock liner with multiple wedges, this type of orthoses interaction would not be possible due to them being 2D in design.
The question is always how much forces are required to effect a positive clinical outcome?

Does this make sense?

Cheers

Phil

 

No evidence that it does.

If we use sticky wedging applied to a sock liner there are a finite number of positions this can be placed in: 18 in total-

No forefoot + No rearfoot
No forefoot + rearfoot varus
No forefoot + rearfoot valgus
No forefoot + heel lift
No forefoot + heel lift + rearfoot varus
No forefoot + heel lift + rearfoot valgus
forefoot valgus + No rearfoot
forefoot valgus + rearfoot varus
forefoot valgus + rearfoot valgus
forefoot valgus + heel lift
forefoot valgus + heel lift + rearfoot varus
forefoot valgus + heel lift + rearfoot valgus
forefoot varus + No rearfoot
forefoot varus + rearfoot varus
forefoot varus + rearfoot valgus
forefoot varus + heel lift
forefoot varus + heel lift + rearfoot varus
forefoot varus + heel lift + rearfoot valgus

Given varying degrees of wedging this provides a large number of possible wedging options.

Phil has suggested that these wedges are effectively 2D and that when we use an orthotic shell we have a complex series of 3D planes. Given that force and therefore pressure are vector quantities, the orthotic reaction force vector (ORF) produced at any given instant in time during contact phase is, to a large extent dependent upon the angulation of the orthotic shell. But it is also dependent upon the angulation of the terrain (external environment) and upon the position and accelerations of the body segments above the orthotic. In other words, just because a wedge appears 2D, the vector produced is still 3D; viz sticky wedge has a 3D effect. further if a heel lift is used in combination with a rearfoot wedge we have a bi-plane post.

David Smith and I began discussing the interaction of orthoses with terrain a while ago and both came to the conclusion that it is amazing that orthoses work when often the magnitude of variation in terrain is greater than the magnitude of the post added.

Also worthy of note here is that this means that when we use pressure plates to see whether the CoP is medial or lateral to the STJ axis and we observe that it is medial to the axis, we cannot automatically assume that this is creating supination moment as the vector may be angled such that it passes laterally to the joint axis.

My own observation here is that when using sticky wedge, because of the lack of contoured fit, the pressure beneath the wedges feels a lot higher than from an equally sized post applied to a shell. This may be a good or bad thing. Moreover, does this make a difference to the outcomes? Anecdotally I achieve a great deal of success with sticky wedge and so too with casted devices.

 

Mark:

Perfect contour: decreased plantar pressures in weightbearing areas of foot
Imperfect contour: increased plantar pressures in areas where wedges are too thick

Most experts in foot orthosis therapy agree that one of the things that make a custom foot orthosis so comfortable is its excellent 3D conformity to the plantar foot. If we accept that fact to be true, Mark, how long would it take you to construct a bunch of wedges added to a sockliner or insole that not only fit the foot as well as a custom casted foot orthosis but would also maintain its shape under weightbearing load for longer than 1 year? I'm sure it could be done, but at what time expense to you?

I would bet that I could construct a more comfortable and more therapeutically effective customized insole for patients than could 75% of podiatrists by adding multiple pieces of adhesive felt to a flat insole, as you suggest, Mark. However, this device, which would take me about 20 minutes to construct to make it work best, would probably work well for 2-4 weeks, within a month or two would eventually compress, become less comfortable and less therapeutically effective. Then I would need to reapply wedges again to make it the correct shape which would also need to be adjusted for each shoe type depending on the shank contour of the shoe.

Alternatively, I could take that 20 minutes to perform an evaluation, gait examination and casting for prescription foot orthoses and make an orthosis that will last the patient 10-15 years and not need to be modified for years. As a consumer, which one would you want? In addition, what is the equivalent monetary value to the patient to not have to take time off of work at least twice a year to have their wedged orthosis modified to keep them working correctly? How much value to the patient is it to not see their orthosis degrade and their discomfort increase every few months?

I think that once you do cost-benefit analysis of the custom casted orthosis vs the multiple padded insole, you will not only find that a correctly made custom casted foot orthosis is a significant bargain for the consumer, but it is much more convenient time-wise for the patient and allows the patient to wear a wider range of shoegear. However, custom-casted orthoses are not the only way to make patients better since the in-shoe plantar reaction forces required to make the patient asymptomatic may be made with virtually any solid material, as long as it has the optimal shape and stiffness.