Recent debate over pre-fab dispensing by DPM’s and complaints about a lack of biomechanical education, practical exposure and EBM from the DPM community prompt me to try to define my position regarding Modern Biomechanics for debate starting with custom shells.

Custom Orthotic Shell Position Paper   

The literature referring to casting methods for creating a custom foot orthotic shell show some work better than others.  There are from Kia to Mercedes orthotic shells that although made from similar materials, have different performance and outcomes. 

Many Podiatrists have not acculturated to the protocols suggested by research and practice EBM’s to be most effective for custom orthotic shells.  They may not review the literature, they want a faster, neater or cheaper way to make their shells or they are too busy in their practical lives to stay current with biomechanics.

The casting method shown in the medical literature to be most effective in producing a quality functional custom foot orthotics is a three dimensional nonweightbearing cast or image of the foot.  Plaster or foam box casting where the patient sits and the foot is placed down on the floor to produce the cast, standing on a force plate or standing on a digital imager of the foot too often produces nonfunctional or harmful orthotic shells.

Furthermore, the medical literature is proving the common casting position called Subtalar Neutral Position does not produce excellent shell outcomes.  New, yet unproven casting positions are surfacing for investigation. 

Like surgery, the more education, technical skill and experience of the person taking the cast, the better their outcomes.  A skilled podiatrist and not an assistant, a chiropractor, a physical therapist, a pedorthist or a shoe store clerk is the best educated and experienced to cast for custom orthotic shells.

In summary, a skilled podiatrist monitoring the literature, taking graduate courses, utilizing a three dimensional nonweightbearing cast and advanced casting position represents the state of the art for generating custom orthotic shells and should have the best outcomes when compared to others.

References upon request.

I agree on many statements made however, I just want to comment on one thing.  In terms of the casting method it is true that there are new and improved techniques emerging and of that I am an advocate.  But in my practice I have heard so many opinions about the casting method and of course mostly from non-professionals. Things like plaster casts are the best way to make an orthotic versus foam boxes.

The reality of all of this is neither one is better over the other because neither method are necessarily indicative of the end product.  The casting method is just a means of obtaining a three dimensional image of the foot while in the desired position.  What is important is that position.  I can use a plaster slipper cast and place the foot in pronation.  This does not produce a better orthotic than one that was casted with a foam box in neutral position.

Let’s end this redundant debate over casting methods (force plate excluded) and focus on what is really important; the casting position of the foot.  As mentioned there are new casting postures in practice that are producing great results over the former.  Let us focus on that.

The methodology of how a cast is taken determines what orthotic one obtains. There are times you want to utilize different casting techniques when evaluating patient age, disease being treated and the clinician's goal for that patient.
In the case of a neutral non-weightbearing cast impression taken with a subtalar joint neutral position, I would consider this to be a "functional" orthotic. This I would tend to use where I want maximal control of pathobiomechanical factors that are contributory to a patient's symptoms. In my practice, this would probably account for approximately ">90%" of orthoses that are made in my office. Improper technique in casting to obtain such a device leaves little "gray" area in casting errors and may lead to intolerance of patient being able to tolerate such a device. Orthoses laboratories may compensate for this by placing a larger amount of medial plaster fill to lower the orthotic edge if you are getting a "hand corrected" device and placing a plaster rearfoot buildup in width to accomodate for an increase in heel diameter with patient weightbearing.
However, there may be times where one may want to provide a partial weight-bearing cast technique. I view this as an "accomodative" orthotic. This is especially useful with geriatic patients who have never functioned in a subtalar "neutral" position in years and probably would never tolerate such a device. In addition, I would consider utilizing this casting technique with a stage III - RA patient where foot joint subluxation is maximal, incongruity of foot structure/contours due to excessive osteoarthritic processes or in some geriatric diabetic patients with an ulceration history. This casting technique has a larger "gray" area for patient acceptance/tolerance if the casting technique is not optimal. When I use this technique, care should be taken to maintain the stability of the first ray by applying slightly more dorsal compression over the first ray while the patient applies partial weight into the cast foam.
 I find sometimes patients who have not responded with orthoses to their symptoms (ie, metatarsalgia, plantar fasciitis, posterior tibial dysfunction) may have received an "accomodative" orthotic and NOT a "functional" orthotic from other clinicians. We as "foot specialists" need to evaluate each patient and utilize casting techniques that are best for the patient. 

I do not know Dr. Scotti and therefore I debate his biomechanical paradigm and nothing personal.

In general, feet are not flat, they flatten in closed chain. 

In open chain, most feet have a higher vault, a higher CIA, a healthy looking sinus tarsi and 1^st ray on the sagital plane and there is no impact of the foot upon the posture.

When impacted by ground reactive force (GRF), some feet do not change much (The Rigid/Rigid, the Flat/Flat and The Stable/Stable FFT's).  However, most feet collapse in the rearfoot (The Flexible/Rigid FFT), the forefoot (The Rigid/Flexible FFT) or both (The Flexible/Flexible FFT) in closed chain.

Most feet, depending on type, tone and muscular engine function when opposed by GRF collapse the vault of the foot, lower the CIA and dorsiflex the 1^st ray in opposition.

In addition, when the posture is weightbearing on a collapsed pedal foundation, the ankles, the legs, the knees, the thighs, the hips and the low back deform, degenerate and weaken on all three body planes.

The only casting method that does not allow this to happen is a non weightbearing cast and semi or weightbearing casting methods produce a collapsed orthotic shell.  Admittedly, they may have positive effect on pain and overuse syndromes but they are actually harmful long term to most feet and postures.

Root gave humanity an open chain biomechanical evaluation that impacted closed chain function and developed an open chain casting technique that controlled the foot and reduced GRF better than any methods in use at his time.  The need for a non weightbearing cast has not reduced to this day. 

I agree that “a plaster slipper cast in pronation does not produce a better orthotic than one that was casted with a foam box in neutral position”.  But I strongly counter that both are failures when compared with a non weightbearing plaster or fiberglass cast.

Rigid/Flexible Functional Foot Type Open Chain
 

 






Rigid/Flex Functional Foot Type Closed Chain

Very concise and eloquently put.  No offence taken, in fact I do, should I say, we do agree on most everything that you said.  The variation sits in the medium.  I too agree that the casting method has to be one that emulates the patients non-weight bearing or corrected position.  Your article about "Beyond Root" in, in my opinion, right on the mark and I could not agree with you more.  However, this casting position that you speak of can also be obtained with a foam box.  Simply by supinating the hind foot, dorsi-flexing the hallux to incorporate windlass and plantar flexing the first ray will produce a very corrected position that best emulates the non-weight bearing.  This will vault the arch and shorten its length.  By supinating the hind foot makes medial skives unnecessary.  Again I want to stress that it is not the medium in which the cast is taken, but the actual posture of the foot.  Just because I use a plaster cast, does not produce a better orthotic and visa versa.

I am also a Pedorthist and as a result I personally manufacture all my orthotics in the clinic.  By using the foam box I need to make less adjustments which means arbitrarily adding plaster to this precise cast that you just made in order to balance the foot to the ground.  In fact, most labs with do this as well as adding plaster the arch, they call it "cast dressing"  making all your efforts to be accurate redundant.  By using the foam box with my casting method mentioned above I can capture the foot in the ideal posture, one we both agree upon.  I can do so and make sure the heel, 1st and 5th MPJs are plantar grade and balance without having to add material.  The less you need to add to a cast the more true to your ideals it is.  This method also proves to be very reproducible.

Again I agree with everything you say, but it can be done in a foam box too.  Can we agree on that?

Dr. Scotti:
It is a pleasure to debate with you.  I'm pleased we are not obscuring the discussion with supinatory moments and sagital plane block language that can be confusing to Residents and practitioners alike.

 
Sight unseen, you are casting foam beyond Root and until proven otherwise, your devices deliver better outcomes when compared to STJ Neutral plaster casted devices routinely.
 

The fact that you control the lab portion of the process eliminates defaults that many DPM labs use to produce shells that are safe, dispensed without rejection and inferior to the potential of the casts being sent to them in order to reduce returns.

I debate that loading the windlass in order to get additional vault into an orthotic shell exaggerates the metatarsal heads plantarly, stretches the plantar plates unnecessarily and may encourage 1-2 lesions, neuromata, etc. to form.  

Elevating the great toe imitating midstance to load the windlass as you do will have the same effect as the Cluffy Wedge, forcing reduced function of flexor hallucis longus and the core intrinsics during propulsion while creating a potential for functional hallux elevatus, dystrophic toenail formation and the need for higher toe boxed shoe (less stylish) which many patients prefer.  In that light, I would ask how well your devices do in higher than 1” heels, dressier shoes or narrow sneakers, etc.

I continue to maintain that semi weightbearing, depending on the makeup of the fleshy portion of each patient’s foot will allow for soft tissue heel medial collapse (”pronation” and medial plantar nerve impingement), total heel collapse, medial and lateral side soft tissue swell in addition to amounts of vault collapse (navicular sag) and forefoot lengthening and widening that does not occur when off weighted (though less with your casting techniques), foot type-specific.

Foam casting from a lab website:

Thank you Dr. Shavelson.

Unfortunately I am not nearly as well written as you, and for that I am sorry as I cannot explain myself as eloquently and as concise as yourself.

My casting procedure would produce those undesirable effects, however I did not go into enough detail.  After the windlass as been activated I then will press down the metatarsals heads to make them plantar grade to the 1^st and 5^th.  If I find there may be a risk or a existing condition I will include a 2-4 PMP.  I use 3mm polypro as it will give a predictable amount of flex.  The dress shoes are a challenge for anyone using any casting method.

It would be interesting to see a comparison of our two end products.  You make it sound like there would be a huge difference and that because I use a foam box with a modified casting technique that my patients are subjected problems down the road.  My method works and after 15 years I have not seen any of these complications.  Just like if we were to add a lift on the contralateral side of a longer leg do we create an equines deformity?  We are taught that it can or will happen.  I have never actually seen that happen and I have done a lot of lifts.  It would take years, assuming that the patient never went barefoot as this would stretch out the tendons to the original length again.  But they may only be in the orthotics for 12 hours a day.  I can’t see any deformities actually happening.

I have done a small comparison form different labs.  I sent 5 labs the same foot molded in three different positions.  All the orthotics came back with no measureable difference.  What does that tell me?  That regardless of my casting position I get the same orthotic.  I compared these generic under corrective devices to mine and there is a measurable difference.  My arch is higher and the arch length is shorter.  As I am sure yours would be too.  The question here is if there would be a measurable between mine and yours.  I would tend to doubt it.  The end result is determined not entirely from the casting procedure.  The lab will inadvertently modify your cast as they see fit.  Our end products, likely would look the same.

It would be easy if we all agreed on a single process and this was proven through evidence based research and science.  But regardless of this safety net it means nothing it the patient just doesn’t like the way they feel.  So many people have a preconceived idea on how they should fit and feel.  People will complain that there is too much arch height just as an equal amount of people will complain that there is not enough.  Now generally most of my patients are happy, but there are still those whom you know you can help but they just resist, making this discussion redundant.  We just can’t win them all.

Sorry to bother you.

I think my discussion with Dr. Scotti lends credence as to how difficult it is to evaluate biomechanics and out orthotics, scientifically.

One thing is clear, a STJ Neutral cast is no longer the state of the art that Root gifted us with but there are those in our ranks that are leading the way to change.

It also reinforces my position that biomechanics, like much of medicine and surgery, is at least as much Art as Science and any discussion that is skewed to science (The EBM Level 1-ers) is missing the part of Biomechanics that allows one practitioner to perform better than others in practice.

I have been educated by Dr. Scotti that a skilled foamer with control over his/her lab, will dispense superior orthotics , with better outcomes and loftier goals for care than a plaster casting DPM sending their STJ Neutral casted orthotics to a lab that ignores their Rx by routing their devices to a default assembly line.

I think the questions that beg answering are:
What is podiatry, in practice, doing to improve our Biomechanical skills?
and
What are we doing to demand that our labs create excellent positive casts from our negatives and fill our prescriptions custom so that we are dispensing true custom devices that reflect our skills?

Thank you Dr. Shavelson for writing "Beyond Root, STJ Neutral & Pronation".  It is a beautifully written article that says what I have been trying to say for years but don't have the ability to write as well as you.  I refer to your article often when I am teaching my students biomechanics, casting and orthotic principles.  I acknowledge that it is a bit of a battle when trying to educate those whom are trained with Rootian practices.  I am up for the challenge as I hope others will be too and embrace the idea that there is more than just ROOT and we can still do better.

Again Dr. Shavelson, thank you!