Prescription writing for foot orthoses

As this topic is falling down the recent threads list, does anybody else want to vote, before I ask the single voter (to date) who believes that they can rationalize the angle of the rearfoot post to explain their rationale...

Vote now.

 

Kevin,

Wasn't the original Root device fabricated with a hard post (acrylic) and designed to be used in a shoe with a hard foot bed (like the men's wing-tip oxford that my grandfather wore). As such, it rocked over the bi-planar grind.

Today most orthoses are worn in athletic shoes with a cushioned foot bed, and the posts are made with semi-compressible materials (firm EVA). Considering these factors, doesn't the notion of grinding motion seem pointless ??? I just don't see much "motion" going on in the shoe. Of course, I could be wrong- as this has happened in the past.

Nick

 

No guesses to votes if this poll was held ~ 20 yrs ago

 

Nick:

Yes, the dental acrylic rearfoot posted Rohadur foot orthoses made by Mert Root, John Weed, Tom Sgarlato and their contemporaries were designed to function in leather soled or hard rubber soled shoes. As such, I would imagine that a patient might be able to readily feel or detect when the motion in the rearfoot post was changed by as little as 2 degrees due to the harder soled shoes of yesterday.

However, in the shoes of today's world, many of which are of much too low durometer for the weight and foot type of the individual, then a 2 degree change in rearfoot post motion would probably be insignificant and not readily detectable. However, a 4 degree change in rearfoot post motion is probably very significant for many patients in today's softer soled shoes. I still add a 4 degree post with 4 degrees of motion to most of my patient's orthoses. Seems to work but possibly a flat rearfoot post with no motion would work just as well. Until someone does the study, we just won't know.

 

Thanks to everyone who voted in this poll. It doesn't look like it will hit the 95% "unconfidence level", but it's "close enough for jazz"

I think it would be very helpful to the 94.74% of voters and to the profession as a whole if the one voter who believes that they can scientifically rationalize the angulation of extrinsic rearfoot posts, please provide their rationale now.

Once again, many thanks.

 

Simon,

Take a vote on how ibuprofen is dosed. Some will give 400mg q6hrs, some 600mg, others 800mg. Furthermore, a within analysis will show that most clinicians do not adjust for patient size (ie 120# female given same dose as 230# male). This is a common practice- and as long as you stay under the recommended max of 3200mg per day (and were did that come from??) and avoid the contraindicated patient- most do fine.

Almost all of what we do is ballpark estimation based on years of experience and scant research. You can extend this observation to the angle of osteotomy cuts, duration of stretching, number of weightlifting reps, length of treatment time for a bone stimulator, the amount of tissue removed for a skin plasty, how much anti-fungal cream to rub onto the foot, and the number of degrees of posting (just to name a few).

I await the day research tells me how much to post- perhaps I should be posting 3.64 degrees - or not posting at all - for now 4 is working for the vast majority of my patients.

Nick

 

I agree with you. The point of the poll was to highlight just this. Once upon a time we pretended that a formulaic approach could be taken in which we measured a number of angles on the foot and lower leg and arrived at a number of degrees for a rearfoot post. The paradigm shifted and now it seems few (if any) podiatrists here can rationalize their choice of angle- we still await the explanation from the one voter who believes that they can rationalize this. BUT I'm sure there are lots of podiatrists out their still measuring their angles and pumping them into the formula so that they can fill out the box on the prescription form. What we appear to be saying is "you are wasting your time".

So what is better: the quasi-science of Root, or the guess work of the "meat-pie"- blindly give out 4 degrees because that seems to work "for the vast majority of my patients"? Did we throw the baby out with the bath water as Daryl Phillips warned?

I don't have the answers, but it begs the question, why bother including this as a prescription variable at all, why not just give everyone a 4/ 4 post? The answer I'll probably get to this question is: because a 4/4 post doesn't work for everyone- right? So then I ask you to rationalize who gets a 4/4 and who gets a 6/4 etc. and the bottom line is that you/ we don't appear to be able to at this time. :deadhorse::sinking:

I'd kind of guessed how the poll would turn out. I hoped it would allow people to stand-up and say "I don't know- I use an educated guess"; to cut through the pretence, and to highlight that nobody here really knows what they are doing- despite how clever we all think we/ they are. I'm sure this is cathartic for some and frustrating (like it is to me) for others. But maybe this will spur on those with the enthusiasm to take up the challenge and do the science. :boxing:

What is being taught in the Schools of Podiatry?

 

Simon:

Now that you have tackled the problem of rearfoot post motion angle with your poll question: "I believe that I can scientifically rationalize the angulation of extrinsic rearfoot posts," the next obvious question that I would like to see answered by you or anyone else that wants to join in:

"Are there any aspects of foot orthosis therapy that you can scientifically rationalize?"

I would imagine that the majority of respondents to your poll would answer "no" to this question also. In other words, are there any parts of custom foot orthoses that you, or any other podiatrist, can scientifically rationalize? If so, which parts?

 

Some years ago we did some predictive model building of fat pad expansion beneath the heel in transition from non-weightbearing to weightbearing. So I guess we could scientifically rationalize the addition we put around the heel on the positive cast. Or at least we could if the study had been published. Unfortunately, I do not have the dissertation that was written-up for this, so I can't provide you with the list of predictors or the equation!

If you really wanted it, I could put you in touch with the person who wrote it up. She is now a lecturer at University of Plymouth. I'm sure she will still have a copy of this information. But to be honest, we can just take a weightbearing measurement using a vernier calliper and add the correct amount of addition to the cast. Either way, I think this is a scientific rationalization of an aspect of foot orthoses therapy.

I think if we look through the published research regarding foot orthosis therapy there will be a number of aspects that can be scientifically rationalized. You seem to be suggesting that you do not think this is the case. Do you believe that there are no aspects of foot orthoses therapy that you can scientifically rationalize?

 

No. I believe that I can scientifically rationalize all the parts of the foot orthoses that I use as long as mechanical modelling and clinical observation are allowed to be included to consider the process "scientific rationalization". However, how many podiatrists can scientifically rationalize the use of foot orthoses as a whole, without picking out one small design variable of the orthosis to see if they can scientifically rationalize its use? My guess is that very few (less than 5%) of podiatrists could make a good scientific argument for the use of foot orthoses as a whole, with many of them here following along on Podiatry Arena.

Therefore, if only a small percentage of podiatrists can scientifically rationalize the foot orthoses that they use for their patients on a daily basis, then where does that leave us with asking them whether they can scientifically rationalize any of the specific components of a foot orthosis, whether that be the rearfoot post grinding angle, shape/flexiblity of the medial longitudinal arch, rearfoot post material, length of the orthosis, heel cup height, etc, etc??

My point, Simon, if you asked in a poll on Podiatry Arena about any of the specific structural components of a foot orthosis and about whether the clinician could "scientifically rationalize" their shape or design, then you would probably get very similar percentages in your poll as to what you got about rearfoot post angles. In other words, they would vote that they also can't scientifically rationalize, for example, the height of the heel cup, the rearfoot post material, the length of the orthosis and/or the shape/flexibility of the medial longitudinal arch of the orthosis.

I guess it all depends on what your definition of "scientifically rationalize" is and how loosely or tightly you define as to what consitutes a "scientific process".:drinks

 

I think we are singing from the same sheet here Kevin. I think that I have always had a tendency to break structures into their component parts to try to fathom them out. This started with a lawn-mower engine when I was aged about 5 years. Perhaps we need to look at the whole?

Don't you think the profession would be in a stronger position if we could rationalize our actions and stand up to the scrutiny of the scientific community? I hope that one day we will have the research base to say exactly why I use an x degree rearfoot post or a y mm heel cup. "I have a dream...":drinks

 

Isn't that what we have already been doing over the past 22 years? In the relatively short time I have been involved, we have finally moved away from foot orthoses "locking the midtarsal joint", "balancing the forefoot to rearfoot relationship", and "holding the subtalar joint in neutral position" to now saying they are "increasing the external subtalar joint supination moments" and "decreasing the external forefoot dorsiflexion moments".

Wouldn't you say, Simon, that we have made progress and are better off now in being able to stand up to the scrutiny of the scientific community than we were a quarter century ago? I personally believe the progress we have made has been phenomenal, especially considering what I was taught by the world renowned experts in podiatric biomechanics at the California College of Podiatric Medicine 25 years ago about how foot orthoses work.

 

I think we have moved a long way, but I think there is much further to travel than the distance we have already come. Now that we know we are altering moments we need to learn how to control them better. I think by analyzing the effects of each of the component parts we may better understand the workings of the whole.

Sorry to keep :deadhorse: Kevin, but I think this is an important educational point. Could you scientifically rationalize the selection of rearfoot posting angle using the above processes please?

 

Scott

Thought I'de give you a reply as to your question.

Your PIP paste sounds similar to engineers blue. When trying to finish a piece to a high tolerence one applies the blue to the reference work plate, then apply the face of interest of the work piece to the work plate and any high areas are highlighted and can be filed or machined off. This works fine when one has a reference plate with a known surface geometry. In your case as a dentist your reference plate is the patients gums or palate, which I would imaging remains fairly rigid and constant. The foot on the other hand is flexible and the ground has varying topography, which means that there is not a good reference medium.
Another point is that knowig which part touches the foot does not give any idea about where the highest point of plantar pressure is. IE one part of the foot may contact early but be highly compliant to applied force - this causes no trauma or pain. On the other hand an area which contact the orthosis later may not be compliant to applied force and so may cause trauma and pain. The areas of contact indicated by PIP would depend on the force applied to the foot as it interfaced with the orthosis. This may be body weight but with refernce to the above will not tell you about pressure distribution.
One way that we can tell something about pressure distribution over the orthosis foot interface is to use in shoe pressure indicating insoles EG Tekscan.

Tolerate - Again for the above reasons and the limits of technology we cannot make a device that is a perfect fit at all times during all activities. Also to change the pathological forces acting on a tissue of interest that is causing pain it may be necessary to chage the forces acting on the foot. Sometimes this takes time to get used to. The the offset of induced discomfort against the benifit of relieved pain must be weighed up by the clinician and patient. If the induced discomfort is minor and short lived and can cause no other distal pathology and the relief of historical pain and pathology is great, then it may be worth tolerating the induced discomfort. Vice Versa and it may not / would not be worth tolerating.
Having said that most of my own orthoses are milled from various densities of EVA and are not rigid and therefore are usually comfortable from dispensing and are efficatious most times. Sometimes I use a direct milled Polypropelene device which I usually specify to be semiflexible and rarely have problems with discomfort and further modifications are rare, while at the same time efficacy is high.

Thanks for your interaction

Cheers Dave

 

Simon

This is always tricky to answer but this is my conclusion.

If one were to statistcally analyse STJ range of motion over flat floors, normal pavement (sidewalk) and rough country side terrain then on might find the following.

Flat floor - Stress RoM ratio = 3dg/second sd+/-1dg

Pavement -Stress RoM ratio = 1dg/sec sd+/-2dgs

Rough terrain-Stress Rom ratio = -1dgs/sec. sd+/-5dgs

Assume 0dgs is optimum for minimum stess and pathology of soft tissue.
Where eversion is positive and the ratio is calculated from sum of stance phase RoM samples (at frequency of 1 per sec)/time (in seconds)

From this you could see that when walking on a flat floor the tendency was for the STJ to maintain a 3dg eversion with only a small sd. The consequency of this tendency would mean that a passive tissue that tends to invert the STJ would under go more stress per second than whe walking on rough ground even though when walking on rough terrain the peak stress may be greater.
Walking on rough terrain may even cause inversion pathology, which in my experience it does, taking into account that generally there is more RoM available for inversion and so inversion pathology is less likely for the equivalent minus values.

Adding a 3dg varus rearfoot post may change all these ratios by 3dgs repectively.

This is just an of the top of my head theory but do you see what I getting at.

Cheers Dave

 

Dave,
Interesting. But I'm not following you. I have a number of questions, I'll start with four:

1. How do we know the value of "stress"?
2. Where do you get your numbers from? The standard deviations etc.
3. What validation do you have for your theory?
4. From your stress (Nm2)/ Rom (degrees) ratio how do you get to degrees/sec? Math never was my strong point.
Perhaps you need to expand upon your explanation.

 

Isn't the 4 degree 'posting' our reference point which was just Uni lectured / branded into the grey matter when fresh.

From there, we use +/- degrees to give 'a little more or little less support' and help justify the 'Applied Science' part of our time spent at Uni when not at the pub. In other words, an extrapolated way of saying '"mild, moderate or severe".

I haven't thought of the 'posting angle' as in degrees for years, but we all have our reference points

 

No problem, Simon. First of all, let's analyze the function of the biplanar grind of a rearfoot post that has a good ability to resist compression forces, such as a polypropylene rearfoot post on a polypropylene orthosis. For more compressible rearfoot posts, such as EVA or rubber, the following argument may not apply.

The biplanar grind of the rearfoot post was originally intended to "allow pronation of the rearfoot during the contact phase of gait" by the Biomechanics Professors at CCPM who invented it back in the late 1960's to early 1970's. I don't agree with their analysis, but instead offer the following mechanical analysis that stands as my scientific rationalization for using biplanar grinds on rearfoot posts.

If a flat rearfoot (i.e. no motion) is used on an orthosis, then during the contact phase of gait, when the posterior-lateral heel is contacting the ground, the posterior-lateral aspect of the rearfoot post directly transmits fairly large compression forces to the lateral-plantar heel which will tend to rapidly increase external subtalar joint (STJ) pronation moments and tend to cause increased angular velocity of STJ pronation motion during the contact phase. This increased initial STJ pronation angular velocity may likewise cause increased angular velocity of internal shank rotation and internal thigh rotation due to the moments transmitted through the rearfoot/ankle complex to the lower extremity during contact phase. This has the very likely potential to cause pronation-related pathologies in the very same patients in which the design of the prescription foot orthosis is intended to relieve or cure pronation-related pathologies.

If we instead now use a biplanar grind in the rearfoot post, what does this orthosis modification mechanically accomplish? During contact phase, the biplanar grind of a rearfoot post will lessen the magnitude and increase the time required to cause an increase in the compression forces acting on the lateral-plantar heel. This "softening of the impact force" on the lateral-plantar heel during contact phase will tend to lessen the magnitude of external STJ pronation moments from the orthosis which, in the patient that has pronation-related pathologies, may significantly increase the therapeutic effectiveness of the prescription foot orthosis by relatively increasing the medial-plantar heel compression force relative to the lateral-plantar heel compression force.

This change in force application from the orthosis on the plantar heel of the patient's foot may also cause the patient to volitionally choose to change their angle of rearfoot inversion at heel contact due to their unconscious sensory perception that landing in a more inverted calcaneal position will not cause more STJ pronation moment. They may immediately sense that landing more inverted may cause less STJ pronation moment, due to the biplanar rearfoot post grind, and therefore land more inverted. Many researchers have shown that human subjects will alter their pre-contact phase kinematics within one or two steps when moving from one type of surface to another type of surface. This phenomenon also likely applies to the pre-contact phase kinematics of walking or running on orthoses with different designs and constructions.

Now, does this biplanar rearfoot post grind need to always be exactly 4 degrees in order to work optimally for the patient. Of course not. In fact, Dr. Root and Weed would often vary the rearfoot post grind angle to match the STJ axis inclination angle. The optimum rearfoot post grind may be any number of degrees depending on the patient's foot type, their symptoms, and their shoes, to name only a few factors. However, like all other orthosis construction parameters that experienced clinicians use when designing their patients' prescription foot orthoses, without ever knowing exactly if the orthosis design they are contemplating is indeed the best orthosis construction for their patient, the rearfoot post biplanar grinding angle of 4 degrees allows the lateral heel cup of the orthosis about 2-3 mm of plantar deflection during heel contact that, in turn, allows the impact forces of heel contact on the lateral-plantar heel to not be instantly transmitted into large magnitudes of STJ pronation moments that may defeat the intended therapeutic purpose of the prescription foot orthosis. The optimum angle may be 1 degree, 2.5 degrees, or 6 degrees or some other angle. However, in my trial and error experimentation with rearfoot post grinding angles, 4 degrees seems to be a very good compromise between giving the orthosis some contact phase flexibility without so much contact phase flexibility that supination instability occurs during contact phase.

As has been the case other times during my career, it appears again as if I am standing alone in making a case for the scientific rationalization of the mechanical function of either a part or the sum of the parts of prescription foot orthoses (I am the 1 of 24 that voted affirmative in the poll.):drinks

 

Agreed. Also, as previously discussed, the compliance of the sole and heel of the shoe may also negate the need for "motion" to be ground into the post.

What has become evident to me over the course of this discussion is that there may be a difference in our terminology. To illustrate this I will use the example of a "classic" 4/4 degree post. That is: a 4 degree varus post with a 4 degree motion grind. To me the posting angle is the first 4 of the 4/4, yet throughout, you appear to have focused on the second 4, i.e. 4/4, the motion or medial grind-off. Obviously these are both angles ground into the post and together form the posting angles. However, it was the "primary" posting angle that I was interested in; the one Root had us measuring the angles from the back of the leg and foot to arrive at. Nevermind. To avoid further confusion and for the purposes of this discussion, I'll refer to the first angle, i.e. the 4/4 as the primary post and the second angle, i.e. the 4/4 as the motion post.

You seem to be talking about a 0/0 degree post here Kevin? If we had a 4/0 degree post, that is a 4 degree varus primary post without any motion grind off such that the whole inferior surface of the post is a 4 degree varus wedge, wouldn't this tend to decelerate pronation due to the increased compression of the medial plantar heel; the shift in the CoP more medially and the fact that the heel "is rolling up-hill"? You described this varus wedge effect in one of your newsletters. Are you now saying that a varus wedge will tend to accelerate pronation? If both the primary post and the motion were flat, i.e. 0/0, how would this accelerate pronation any more than the flat surface of the heel of the shoe? How does the addition of a flat 0/0 degree post within the shoe accelerate this further?

I don't follow you. If we are talking about the foot

then during this time it is the surface of the primary post that is in contact and transmitting load, so at this point in the gait cycle, I'm not sure that the motion post has any effect:

If we assume a stiff rearfoot post and an equally stiff insole/ sole to the shoe that did not allow the "apex" between the primary and motion posts to embed, then during contact it would seem reasonable to assume that the surface of either the primary or the motion posts can be in contact at any one time, not both. So if we have a 4/4 degree post, initially the primary post is in contact. This will tend to decelerate pronation due to the varus wedge effects described above and in your newsletter, as the stance phase continues the orthosis will have to rock across from the primary post to the motion post. This can only occur when the pronation moment acting on the orthosis from the body is greater than the supination moment from the orthosis. At this time there will be a net pronation moment, so surely we should see a pronatory acceleration at this point?

Thanks for this. So what you are saying is that everyone gets a 4 degree motion post, regardless of pathology or biometric variation; that you know that this isn't the optimal angle for some patients but it is a reasonable guess.

How do you "scientifically rationalize" your "primary" posting angle?

 

The proper terminology for the angles involved in rearfoot posts involves two components: posting angle and post motion. Posting angle is defined as the frontal plane angle that the anterior orthosis edge makes with the supporting surface when the lateral-posterior aspect of the rearfoot post is in contact with the supporting surface. Post motion is defined as the amount of frontal plane angular difference between the lateral and medial planes of the rearfoot post.

What Dr. Mert Root did teach about the rearfoot post and the mechanical effects of these angulations during my podiatric training was that he recommended using 4 degrees of rearfoot posting angle with 4 degrees of motion on the vast majority of foot orthoses, assuming a normal inclination angle of the subtalar joint (STJ) axis. He recommended always making the plane of the medial rearfoot post and the anterior orthosis edge being parallel to each other to avoid foot orthosis breakage (this was in the days when Rohadur was king). Dr. Root and Dr. John Weed also advocated increasing the rearfoot posting angle to approximately 6 degrees when the inclination angle of the STJ axis was low and decreasing the rearfoot posting angle to approximately 2 degrees when the inclination angle of the STJ axis was high. Really, for 25 years ago, I would consider this very good scientific rationalization as to why when one would have wanted to increase or decrease the rearfoot posting angle.

A flat rearfoot post is a 0/0 degree post.

I have never used a 4/0 rearfoot post on any of the over 10,000 orthoses I have prescribed, and probably won't use it any time in the near future. I don't understand many of your questions, Simon. However, a flat rearfoot (0/0) post would tend to accelerate STJ pronation over a standard 4/4 post due to the increased ground reaction force on the lateral heel during contact that would be caused by the increased thickness of rearfoot posting material plantar to the lateral calcaneus with a 0/0 post when compared to a 4/4 post.

Pronation motion of the STJ will occur in most feet in most foot orthosis designs during contact phase. Pronation acceleration will occur regardless of the rearfoot posting angle. However, how the body internally responds to the rearfoot posting angle may change with different rearfoot posting angles, even though the rearfoot kinematics during contact phase may be measured to be identical with each posting angle used. This analysis is based on theories proposed by Benno Nigg's and colleagues in their Preferred Motion Pathway Model (Nigg BM, Nurse MA. Stefanyshyn DJ. Shoe inserts and orthotics for sports and physical activities. Med Sci Sports Exerc 31:S421-S428, 1999).

No, that is not what I am saying. What I am saying is that my first choice of rearfoot post design is a 4/4 post (4 degree varus rearfoot post with 4 degrees of post motion). If the patient is experiencing supination related symptoms during contact phase with the orthosis, then I may decrease that rearfoot post angle to 1 to 2 degrees. If the patient is experiencing increased rearfoot pronation during contact phase I may grind off a little bit of lateral rearfoot post motion to make it, for example, 6 degrees of rearfoot post angle.

I also commonly use flat rearfoot posts (0 degrees of varus rearfoot post with 0 degrees of post motion). I will commonly use these posts in patients with laterally deviated STJ axes that are experiencing symptoms due to increased external STJ supination moments. I will also commonly use these posts when treating tarsal coalitions, peroneal spastic flatfoot, and when making foot orthoses for ice skating, roller blading and alpine skiiing orthoses. All of these rearfoot posting angulation alterations that I have used over the past 20+ years of practice can be scientifically rationalized using my STJ axis location and rotational equilibrium theory of foot function (Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. JAPMA, 91:465-488, 2001).

This has already been answered in this posting and my last posting.:drinks

 

Please define the angle of STJ axis inclination that equals "low" in degrees. Similarly, could you define "high" in degrees? How is this measured clinically and what degree of error is likely to exist in this? Why increase or decrease by 2 degrees, why not 3 or any other number? Can you rationalize the numbers?

I have never applied a medial grind to the rearfoot post on any of the several thousand pairs of orthosis I have prescribed, manufactured and dispensed, and probably won't use it any time in the near future.

OK, before you said that

hence I wasn't certain whether you were talking about a 0/0 or any post angle without motion. Do you think a flat 0/0 post would accelerate the pronation any more than the shoe alone?

Agreed. Do you think the pronation would be accelerated more in a 4/4 post or 4/0 post? The problem is we do not know the relationship between the internal response and the posting angle. This is my point, which I have asked repeatedly over the past few years: why 4/4 degrees? What internal response does this give that a 5/4 degree rearfoot post doesn't? Is there a significant difference in this response? Saying use a 4/4 post because Root and Weed said so doesn't really cut the mustard. What published evidence is there to say a 4/4 post is more effective than a 5/5 post or any other angle?

So what you are saying is that everyone gets a 4/4 post regardless of the pathology or biometric variation. If this doesn't work then you either increase it by 2 degrees or decrease it by 2 degrees. So we could equally "rationalize" to give everyone a 5/5 and adjust it by 1.75 degrees in either direction as required. This just seems like guess work to me, not a scientifically rationalized approach.

I use flat 0/0 extrinsic rearfoot posts with heel skives.

Perhaps you'd be kind enough to answer this then: What % change would we see in the supination moment acting about a 42:16 subtalar joint axis when we change the extrinsic rearfoot post of an orthosis from 4/4 to a 6/4 degree? This is my idea of scientific rationalization.

I suspect we will have to agree to disagree on this one Kevin, "trial and error" and giving everyone a 4/4 post as "a first choice" is not my idea of "scientific rationalization". However, I am reminded of Gary Morgan ;-)

 

Simon:

I know the direction you are going with this and want to point out some facts that are obvious to me. You, like me, want more well-designed scientific experimental studies that support the 4/4 degree posting angle, which is one of the basic design elements of many shank independent foot orthoses used throughout the world. Of course I understand your concern and I share a similar philosophy as you do, as you already know.

However, Simon, why just look at rearfoot posting angle and ask a question by way of a poll on Podiatry Arena: "I believe that I can scientifically rationalize the angulation of extrinsic rearfoot posts" ?? Why not now go to any specific component that forms an important part of current foot orthoses and ask the same question about that specific foot orthosis component to the members of Podiatry Arena? In other words, here are some more questions that you may want to consider in your next poll:

I believe that I can scientifically rationalize the height of the heel cup of foot orthoses.

I believe that I can scientifically rationalize the durometer of EVA used in foot orthoses.

I believe that I can scientifically rationalize the amount of medial heel skive of foot orthoses.

I believe that I can scientifically rationalize the amount of lateral heel skive of foot orthoses.

I believe that I can scientifically rationalize the thickness of polypropylene of foot orthoses.

I believe that I can scientifically rationalize the width of foot orthoses.

I believe that I can scientifically rationalize the length of foot orthoses.

I believe that I can scientifically rationalize the medial arch contour of foot orthoses.

I believe that I can scientifically rationalize the lateral arch contour of foot orthoses.

I believe that I can scientifically rationalize the frontal plane balancing angle of foot orthoses.

I believe that I can scientifically rationalize the use of plantar fascial accommodations in foot orthoses.

I believe that I can scientifically rationalize the type of material used in rearfoot posts on foot orthoses.

I believe that I can scientifically rationalize the heel contact point thickness of foot orthoses.

Now, after all these polls are conducted on Podiatry Arena, what do you think the results will be? In all likelihood, over 90% of podiatrists will not be able to "scientifically rationalize", according to your definition of the term, "scientifically rationalize", any of the specific components they use on their patients' foot orthoses, including the "angulation of rearfoot posts". They use these specific components, which together make up their patients' foot orthoses, for the following reasons: 1) because they have been taught to do so by their instructors or other clinicians they respect, 2) they have found that orthoses with these specific modifications tend to work well for their patients, and 3) they have found that these specific orthosis modifications make sense to them using their current theoretical understanding of how foot orthoses work.

That is not to say that some podiatrists, including myself, can't use theoretically analyses of the mechanics of foot orthoses along with their clinical experience of observing hundreds or thousands of patients in order to be able to propose scientifically plausible mechanisms by which each specific foot orthosis modification may precisely function on all human feet. To me, this method is, simply, the best method currently availabe to those of us who want to provide quality foot orthoses to our patients suffering from painful mechanically-based pathologies until research arrives which can adequately inform us of what is the "best" orthosis component construction technique for each and every patient that we provide this important therapeutic modality to.

The bottom line is, Simon, that none of the other "scientific rationalization of orthosis component questions" that I have listed above currently have enough scientific research behind their continued use to determine the best orthosis design for all patients. If you don't agree with me on this, then possibly you can point out a single specific orthosis component that you feel has been researched enough to allow for you to say with confidence that you can "scientifically rationalize" its continued and widespread use in foot orthoses?

 

Hi Kevin and Simon,

Fun questions. I can see both sides of your discussion. You may be talking past each other on the definition of "scientifically rationalize." There is a study showing that a varus wedge orhtosis changes STJ moments. After modeling that posterior tibial tendon dysfunction is related to high pronation moment from ground reaction force, could you then scientifically rationalize the use of a varus wedge orthosis for the treatment of posterior tibial tendonitis. Or, would you have to do a RCT with normal orhtoses and varus wedge orthoses to scientifically rationalize the use of a varus wedge orthosis?

With that standard, I'm still having a hard time rationalizing a 4/4 post under an orthosis. I know, under my foot, I can feel the difference between medial only post and a flat post. I can rationalize this theortically using center of pressure. I still wonder whether a 4/4 post is going to make that much difference. Especially when the shoe surface molds to the bottom of the post. I see the shoe molding even in shoes that I would consider hard at the point of post contact.

Regards,

Eric Fuller

 

Hi Kevin,

A scientific rational for angulation of the RF post in general - yes indeed.

But if the question continued

...individually for each patient whom walks throught the door,

would your poll response be the same?

Your quote

And I definitely agree that many prescriptions completed tomorrow by clinicians all around the world will have the rational you've outlined squarely in mind.

Sound scientific rational gets the ball rolling... but where does it stop

Cheers,

Paul

 

Agreed.

You're right, I could have chosen any of the aspects that you listed. I selected rearfoot posts because I'm interested in the effects of rearfoot posts:

Joanne S. Paton and Simon K. Spooner
Effect of Extrinsic Rearfoot Post Design on the Lateral-to-Medial Position and Velocity of the Center of Pressure
J Am Podiatr Med Assoc 2006 96: 383-392.

Catherine Smith, Simon K. Spooner, and John Alan Fletton
The Effect of 5-Degree Valgus and Varus Rearfoot Wedging on Peak Hallux Dorsiflexion During Gait
J Am Podiatr Med Assoc 2004 94: 558-564.

The reason I was interested in the poll, was to see what everyone else reading this thread thought. Also as Mark pointed out, if we had asked the same question at the height of Root based podiatric biomechanics we may have seen a very different response, so I think that this was something I wanted to gauge also. Most of all the reason I asked Craig to include the poll is because the technology of this site allows it. In other words, I wanted to highlight that this kind of thing can be done here and to use the technology.


I've modified your list of "polls" to what we really want to see, a list of publications Perhaps these could form the foundation of a multi-centre research strategy?:

The kinetic and kinematic effects of the height of the heel cup of foot orthoses.

How does the durometer of EVA used in foot orthoses effect kinetics and kinematics?

The influence of the amount of medial heel skive of foot orthoses on kinetics and kinematics.

The kinetic and kinematic effects of the amount of lateral heel skive of foot orthoses.

The effect of the thickness of polypropylene of foot orthoses on kinetics and kinematics.

Effects of the width of foot orthoses on lower limb kinetics and kinematics.

The kinetic and kinematic effects of the length of foot orthoses.

The kinetic and kinematic effects of the medial arch contour of foot orthoses.

The kinetic and kinematic effects of the lateral arch contour of foot orthoses.

The kinetic and kinematic effects of the frontal plane balancing angle of foot orthoses.

The kinetic and kinematic effects of the use of plantar fascial accommodations in foot orthoses.

The kinetic and kinematic effects of the type of material used in rearfoot posts on foot orthoses.

The kinetic and kinematic effects of the heel contact point thickness of foot orthoses.

What if we designed methodologies for each of these studies and published them here on this forum, so that those wanting to get involved could download the protocol and follow a "recipe" of how to collect the data, how to analyse it etc.? If each of these studies were performed just as single case designs over the next few years by undergrads, podiatrists and researchers around the world, this would be a monumental step forward. Don't you think Kevin, Craig et al.? Personally, I would love to be involved in the completion of these projects and would gladly offer my time and knowledge freely to any budding researcher attempting to complete one of these studies. It's Friday- I'm optimistic.

Then Kevin, after all these studies have been conducted by readers of Podiatry Arena, you and I will sit back, open a bottle of champagne and drink to the health of our profession, knowing that the impetus for the creation of this body of knowledge was you and I and the others contributing and debating the merits of extrinsic rearfoot posts on Podiatry Arena in January 2008. Like I said: "I have a dream..."

Have a good weekend Kevin its been fun and as enlightening as ever :drinks

 

This had been an excellent discussion. I even gave you your first "thanks". Have a nice weekend.:drinks

 

And one more thing....could more people vote against me in this poll so I can feel even more special.....24 to 1?.......I like the odds.........

 

Agree with that. From my perspective it seems the last 25 years has been progressing painfully slowly in podiatric biomechanics. I recall an exuberant lecturer in Edinburgh holding aloft Root, Orien & Weed and claiming this was all we would need to know about the foot and lower limb and how we could now treat and prevent the majority of common foot disorders as well as knee, hip and back pathologies with polyprop shells and extrinsic posts! Orthosis design and manufacture certainly has come some way but the knowledge and understanding of how they interact with the foot and lower limb mechanics appears still very much in its infancy.

Playing devil's advocate, one has to ask whether the investment - in terms of time and money - is worth the effort? Why spend vast hours learning and keeping up-to-date with current biomechanic research when, at the end of the day, the vast majority of foot and lower limb conditions improve with basic preformed orthosis? To quote from Rx Labs.....

However, what we didn't have 25 years ago was a resource like Podiatry Arena and individuals like Simon, Dave, Eric, Jeff, Kevin et al., who are willing and able to share and build the profession's knowledge base, so hopefully, by the time I finally get round to closing the surgery door for the last time, we might be more able to make claims like my lecturer did all those years ago!

Thanks for the discussion.

 

Mark

In reply to the above quote,

I went to a seminar yesterday, the morning speaker was Prof Rami Abboud. Dundee University. His speciality research is the normal and pathological interaction of the foot and shoe in terms of biomechanics and pathology. His presentation was entitled, 'Footwear, The enemy of the foot.' NB he is an engineer not a clincian.
In one research project (not yet published) he found that plantar fasciitis (in its broadest sense ie as defined by symptoms) is often caused by the pressures due breakdown of the midsole i many high street shoes and trainers. This is not uncomfortable but causes unusually high pressure areas in the heel.

If this is so then might it not be so that adding any firm, well structured OTC or bespoke/custom orthosis / insole would have the effect of reducing peak plantar pressure 'hot spots' and thereby resolving 'plantar fasciitis'.

This may account for findings that OTC orthoses perform as well as custom orthoses especially where the researchers were not to selective in distinguishing between different foot pathologies.

Interesting I thought and I had not seen any research like this before. What do you think

Cheers Dave

 

You'll always have a special place in my heart and head Kevin. As you know, your writings got me here. No BS igs:

Here's to the genius, mentor and friend. Thanks for your patience and trust. AND I ain't just blowin' gas up your ass (lovely expression I picked up recently from "me home boys"):drinks

 

In addition to kinematic and kinetic effects I think you should add patient preference. Even though I've been interested in the "scientific" aspects of these modifications we still have to pay attention to the patient outcome aspect of these modifications.

For example heel cup height, I would bet has very little effect on kinematics and kinetics, but could have significant impact on whether or not the patient likes it. It could go either way. A skived device with a low heel cup could cause heel irritation as the person slides off of the cup, or the patient could dislike a high heel cup becuase it is difficult to fit into their shoes. I could go on and on.

Regards,

Eric

 

Dave

Interesting view but the researcher would have to ensure all participants in the study wore the same shoes with the same amount of wear over similar terrain to draw any reasonable conclusion - I'm increasingly sceptical of research these days which can more often be manipulated to suit what the authors want - see Prof Rothbart et al.

By no means a robust study, but this year I gave 38 pairs of Rx Skive preformed orthoses to patients who were prescribed custom devices with various design parameters. Patients were asked to wear the custom devices for the first month then try the preformed orthosis for two weeks then come back for review. 37 out of 38 patients reported an improvement in their symptoms but no discernable difference in the performance of the devices - with the remaining patient favouring the preformed device over the custom externally posted device.

It would be good if we could get some scientific data which could back the assertion that custom devices perform better and relieve symptoms more effectively than preformed orthoses, but the difficulty will always be in quantifying the many variables.

Mark

 

Mark:

Interesting to see you are dispensing so many of those Rx Skive orthoses especially considering your comments regarding these devices from last year.......

 

Simon:

Thanks for that. At this point in the latter half of my career, having such intelligent and creative friends as you, Eric and Craig, gives me great hope for the future of podiatric biomechanics when I am no longer around to contribute. (Guess I'm feeling my age these days, one grandson, a second on the way and my 51st Birthday is in 4 days.)

Cheers.:drinks

 

Simon

I've been away on some courses so sorry for the delay in getting back.

Simon wrote

4) Methinks you are probably very good at maths since you currently study finite element modeling, which requires a good knowledge of diferentials and integral calculus and you are also a bof at statistics.
Degrees RoM imply a change in length of some structure IE strain, which requires stress to achieve. Seconds imply a time element so that we have an integral or impulse of force. IE area under the curve. I didn't want to bother with the steps in between as this was purely hypothetical.

3) Pressure integrals are considered more indicative of pathology than mere peak pressure and so why not the same with stress which, in tension is the inverse of pressure.

2) Just hypothetical example based on reasonable assumption (IMO)

1) Do you nean in terms of a numerical value, a philisophical value or something else?

To Misquote--

The value of stress is not strained it ,

It droppeth as the gentle rain from heaven
Upon the place beneath: it is twice blest;
It blesseth him that gives and him that takes:
'Tis mightiest in the mightiest: it becomes
The throned monarch better than his crown;
His sceptre shows the force of temporal power,
The attribute to awe and majesty,
Wherein doth sit the dread and fear of kings;
But mercy is above this sceptred sway;
It is enthroned in the hearts of kings,
It is an attribute to God himself;
And earthly power doth then show likest God's
When mercy seasons justice. Therefore, Jew,
Though justice be thy plea, consider this,
That, in the course of justice, none of us
Should see salvation: we do pray for mercy;
And that same prayer doth teach us all to render
The deeds of mercy. I have spoke thus much
To mitigate the justice of thy plea;
Which if thou follow, this strict court of Venice
Must needs give sentence 'gainst the merchant there.


All the best Dave:dizzy: