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I really have no problem with orthoses that are higher in the medial longitudinal arch, since I have been making orthoses, or having the orthosis lab I use make orthoses, this way for over the past two decades in patients that need that type of control. Rearfoot posts are very important in some patients, and are unneccessary in others. I believe you would have a hard time convincing very many orthosis experts that rearfoot posts are never necessary to achieve optimal foot orthosis control.
Kevin,
You say that you use and have experimented with higher arches but the juxtaposition of the two sentences above makes me seriously doubt it. Early on, we of course, experimented with combining the Sole Support, full contact, MASS position calibrated model with earlier technologies, like rearfoot posting…….. with universally poor results and in some cases I believe, they were harmful and precipitated injury and imbalance. I was not even considering publication at that time, so I was just applying biomechanical principles that I was taught in school with more aggressive arches. Several cases, consistently failed to produce positive results so the idea was abandoned. It also just made sense that combining MASS position with posting would yield a far too aggressive attempt to control pronation and may even over supinate the foot.
Anyway, bottom line……if you say you experimented with MASS position and found that combining it with posting is possible, and even helpful……then you have never even gotten close to MASS position in any of your experiments. MASS position is NOT "neutral" position with minimum arch fill. Where did you describe this particular position and the technique to reliably and repeatably achieve it, in your publications? I can’t find it,
You take this weird point of view…you state:
1. MASS position is the wrong position to put the foot in. It is over-supinated and hurts people.
2. You have used similar positions for years when appropriate but never published it or talked about it or even know about it.
3. Oh and if the MASS position does turn out to be correct…You invented it but don’t even offer it at the lab where you are medical director.
4. If you combine this MASS position with posts and patients have benefited more than MASS position alone….then I know that you have never used the MASS position because the combination is absurd.
Now let me explain my position on posts and skives clearly: They are the best you and many docs had, and in many cases still have to offer because there was no MASS position discovered yet. Posted and Skived orthoses are every bit as effective as prefabs and maybe a little better at blocking the last tiny bit of pronation that causes “tissue stresses”. Posts are CONTRA-INDICATED in Sole Supports or any orthoses that places the foot in the MASS position because the orthotic is already as aggressive as a foot orthoses can be without causing problems associated with over correction. As research will continue to come out showing positive biomechanical changes with Sole Supports technology, I predict that the MASS position will supplant “neutral” as the correct position to put the foot in for optimal foot function. I have had lots of personal experience with posted and skived orthoses before I invented our product. I would say your experience with my technology is rather limited and statistically insignificant.
Quote:
Originally Posted by Kevin Kirby
I make about 90 pairs of custom foot orthoses per month and have been in practice now for 21 years. This makes lots of orthoses (over 10,000 pair) with the vast majority of them having rearfoot posts. I am interested, Don, how many patients have you treated with custom foot orthoses? If rearfoot posts are so unneccessary, then why have my orthoses, and the orthoses of most other podiatrists who are considered experts in foot orthosis therapy, have rearfoot posts added to them to allow their patients to function with less pain and disability.
The worst reason to do anything is because everyone else is doing it. See the quote that begins this article:
There is an article in this month’s Podiatry Management although I cannot seem to link to it easily online by Dr. Paul Sherer entitled, “Root Biomechanics: Does It Still Hold Water?” I think he describes neutral position as a great “guess”; the understanding of which was arrived at by “trial and error”. That’s also how I came up with MASS position. A theoretical hypothesis, followed by invention and experimentation, then evaluation and modification.
BTW, congrats on being named one of the 175 most influential Podiatrists in America in the same issue of Podiatry Managment: Well Done.
Quote:
Originally Posted by Kevin Kirby
I would be interested in any research evidence that you have to show that rearfoot posts are not necessary to have improved gait function and improved symptom improvement in many patients.
We are not saying that they are not necessary….just that their minimal effectiveness has been supplanted by a more obviously correct approach of full contact in the MASS position with calibrated orthoses and that rear-foot posting, the pillar of traditional biomechanics, is not compatible with the more effective new approach and therefore needs to remain in the armamentarium of those that do not yet have our technology in their market or have not bothered to be certified in it…..which is silly…. The DVD is FREE just by emailing mshelby@solesupports.com and is approved by the CPME for 2 CME credits in the USA.
since theory is defined as "any hypothesis or opinion not based on actual knowledge" and proof is defined as a fact or piece of information which shows that "something exists or is true" in such a case both Ed and Don have already many times satisfied this request.
With you until the point where you say "Ed and Don have already many times satisfied this request". Could you point to where they have "many times" satisfied the request for theoretical proof ? In other words can you show where they have proven their hypothesis. Semantics is fun Dieter.
Seem to recall an article titled something like: "no-one stays neutral on negative casting" published (I think) in Biomechanics magazine some years ago- couldn't find it in their archives as they only go back a couple of years. I think Eric Fuller and maybe Kevin Kirby contributed to this article. Perhaps someone would be good enough to give a synopsis of the content as it may be relevant to this discussion.
Kevin,
I thought that this thread was a discussion of DC wedges but you could not resist attacking Sole Supports. I thought we were past this.
Ed
I do not think it was Kevin that brought up the issue of sole supports.
However back to the DC inverted idea. I am not sure why podiatrists seem to think that orthotics work in a vaccuum. Removing the lateral flare on an orthotic does not remove lateral pressure on the foot. All it does is shift responsibility for that pressure from the orthoses to the shoe. In fact the shoe heel counter may do a much better job of it by exerting pressure above the subtalar joint axis. I think that the reduced cupping of the heel may cause extra slipping and shearing stress inside the shoe. Not sure if the whole idea reduces the 'customised' part of the orthoses.
However back to the DC inverted idea. I am not sure why podiatrists seem to think that orthotics work in a vaccuum. Removing the lateral flare on an orthotic does not remove lateral pressure on the foot. All it does is shift responsibility for that pressure from the orthoses to the shoe. In fact the shoe heel counter may do a much better job of it by exerting pressure above the subtalar joint axis. I think that the reduced cupping of the heel may cause extra slipping and shearing stress inside the shoe. Not sure if the whole idea reduces the 'customised' part of the orthoses.
Good point, Steve. Even though the DC inverted orthosis does not have the lateral heel cup that would give a more inferiorly-positioned, medially directed force on the lateral aspect of the plantar calcaneus, it can still rely on the lateral heel counter of the shoe to exert this force over a broader area. In the medial heel skive (MHS) or Blake Inverted Orthosis (BIO), the traditional high lateral heel cup of the MHS and BIO (16-20+mm) is necesssary to prevent lateral heel cup irritation caused by the plantar heel "falling laterally down the slope" of the inverted heel of the MHS and BIO. However, if the calcaneus is effectively prevented from shifting laterally on the orthosis plate by the lateral heel cup of the MHS or BIO device, then this same medially directed orthosis reaction force (ORF) acting inferior to the STJ axis, which prevents lateral calcaneal shifting, will also cause a subtalar joint (STJ) supination moment.
In fact, mechanical modelling of this interaction reveals that the more inferiorly located (i.e. more plantarly located) that this medially-directed lateral heel cup ORF is on the foot, then the longer will be the STJ supination moment arm for this force. However, this "lateral heel cup supination effect" can not be said to occur with the DC inverted orthosis since it doesn't have a lateral heel cup. Instead, the DC invertd orthosis will have a be more superiorly located (i.e. more dorsally located) heel counter reaction force acting on the lateral calcaneus, thus decreasing the STJ supination moment arm length, and potentially reducing the STJ supination moment from the device, when compared to the MHS and BIO that do have a lateral heel cup.
This DC inverted wedge vs MHS and BIO orthosis design difference involves some very interesting mechanical concepts that I have been contemplating for the past two decades. I personally think the DC inverted orthosis is a very cleverly designed device and I think it has great potential to be a very effective orthosis device for many patients with mechanically-based pathologies caused by increased magnitudes of STJ pronation moments.
When I finish the writing project I am currently working on, I will try to devote a little more thought to these concepts to see if I can come up with any more ideas regarding potential positives/negatives for each of these effective anti-pronation, varus heel cup orthosis designs.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
if stj axis is triplanar .... if you control? / influence? one of those planes haven't you controlled? / influenced? all three?
What if the amount of work required varies from plane to plane? That is, what if changing to STJ functional RoM by 1 degree in the sagittal plane is easier to achieve than altering the functional RoM by 1 degree in the frontal plane? What if sagittal plane "wedges" are more efficient than frontal plane "wedges"?
Good point, Steve. Even though the DC inverted orthosis does not have the lateral heel cup that would give a more inferiorly-positioned, medially directed force on the lateral aspect of the plantar calcaneus, it can still rely on the lateral heel counter of the shoe to exert this force over a broader area. In the medial heel skive (MHS) or Blake Inverted Orthosis (BIO), the traditional high lateral heel cup of the MHS and BIO (16-20+mm) is necesssary to prevent lateral heel cup irritation caused by the plantar heel "falling laterally down the slope" of the inverted heel of the MHS and BIO. However, if the calcaneus is effectively prevented from shifting laterally on the orthosis plate by the lateral heel cup of the MHS or BIO device, then this same medially directed orthosis reaction force (ORF) acting inferior to the STJ axis, which prevents lateral calcaneal shifting, will also cause a subtalar joint (STJ) supination moment.
In fact, mechanical modelling of this interaction reveals that the more inferiorly located (i.e. more plantarly located) that this medially-directed lateral heel cup ORF is on the foot, then the longer will be the STJ supination moment arm for this force. However, this "lateral heel cup supination effect" can not be said to occur with the DC inverted orthosis since it doesn't have a lateral heel cup. Instead, the DC invertd orthosis will have a be more superiorly located (i.e. more dorsally located) heel counter reaction force acting on the lateral calcaneus, thus decreasing the STJ supination moment arm length, and potentially reducing the STJ supination moment from the device, when compared to the MHS and BIO that do have a lateral heel cup.
Agreed. Also of significance here is the co-efficient of friction between the orthosis top-cover and hosiery, and, the hosiery and foot. Me, I don't like slippy-slidey top-covers like the one in the picture earlier in this thread as it means I have to increase the posting angle to get the same mechanical effect.
Agreed. Also of significance here is the co-efficient of friction between the orthosis top-cover and hosiery, and, the hosiery and foot. Me, I don't like slippy-slidey top-covers like the one in the picture earlier in this thread as it means I have to increase the posting angle to get the same mechanical effect.
Another thing that is often ignored is the sliding across the orthotic that occurs in gait. Regardless of whatever the shoe looks like, if the heel is sliding lateraly across the orthotic it will be causing eversion of the STj within the shoe. This may increase if there is a slippery top cover, if there is no heel cup, or if there is no lateral flange. The DC orthoses I have seen have been deficit in all of these features. They simply look like a flat varus wedge at the rearfoot.
Moreover, unless the orthotic is only being used to stand on, a static exam outside the shoes are unlikly to capture what is happening during gait.
if stj axis is triplanar .... if you control? / influence? one of those planes haven't you controlled? / influenced? all three?
Being that the STJ is probably the joint of the foot that is the most highly constrained (i.e. forces applied at any direction and to any point on the calcaneus will still tend to make it rotate very close to its axis), then, yes, a decrease of motion in one plane will influence the motion in the other planes that it normally rotates in.
Compare the STJ to the midtarsal joint (MTJ), where the MTJ is one of the least constrained joints of the midfoot. This means that the MTJ rotational axis will be dependent on the magnitude, direction and point of application of the external force applied to the forefoot and, as a result, the MTJ axis spatial location will be highly variable, depending on the mechanical situation.
I will be including this concept of joint constraint in my lecture on MTJ mechanics at the PFOLA meeting in Chicago in December.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
What if the amount of work required varies from plane to plane? That is, what if changing to STJ functional RoM by 1 degree in the sagittal plane is easier to achieve than altering the functional RoM by 1 degree in the frontal plane? What if sagittal plane "wedges" are more efficient than frontal plane "wedges"?
simon, for example, a stj axis that does align instantaneously 16 degrees from the sagittal plane, 42 deg from the transverse plane, and 44 deg (2sig.fig.) from the frontal plane .. wouldn't it take a greater "wedge" reaction force from the sagittal plane "wedge" than the transverse and frontal plane "wedges" .. triplane force / 16 >> triplane force / 42 (or 44)
gents, 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 (assuming no plantarwards force amidfoot from the shoe upper that a custom orthoses of sufficient rigidity would counter?), cheers, mark
simon, for example, a stj axis that does align instantaneously 16 degrees from the sagittal plane, 42 deg from the transverse plane, and 44 deg (2sig.fig.) from the frontal plane .. wouldn't it take a greater "wedge" reaction force from the sagittal plane "wedge" than the transverse and frontal plane "wedges" .. triplane force / 16 >> triplane force / 42 (or 44)
That's kinda what I was trying to say. I don't think we have the answer to this though as it is dependent on so many factors.
gents, 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 (assuming no plantarwards force amidfoot from the shoe upper that a custom orthoses of sufficient rigidity would counter?), cheers, mark
Clarification of our position on rearfoot posts and wedges
Linear Mode
