Planal Dominance, applications

[robertisaacs]

This was thrown up on another thread so i'm cracking it off by its self.

If you are not biomechanically minded PLEASE STAY WITH ME!! This is not so hard a concept as it first appears!!

I'd really like this to be something that everyone can get into not just the few biomx junkies (you know who you are). So if you don't get it PLEASE tell us. Lets make this a learning thread!

A brief recap for them as is not familier.

[glow=red,2,300]THE LADYBIRD GUIDE TO ... PLANAL DOMINANCE (for the terrified)[/glow]Ignore if you are already familier

The sub talar joint is for the most part obligate triplanar. That is to say it moves in three planes (frontal / sagital and tranverse). A movement in one plane will always cause a movement in the other 2. For Eg if you invert the foot it MUST adduct and planterflex as well.

All wiggling your feet under the table? Good. .

The amount of movement which takes place in each plane depends on the position of the STJ axis. We won't worry about how just now, just accept it.

In most feet the amount of frontal plane and transverse plane motion is approximatly equal. Put another way the navicular will usually drop by the same distance as it travels medially when the foot pronates.

Now. In some feet the position of the axis is different causing different amounts of movement in the planes during pronation.

For EG. Lets take an STJ with a frontal planal dominance. In this foot the navicular may drop by far more than it travels medially.

An STJ with a transverse planal dominance, however, will adduct (push sideways) far more than it everts (drops).

LADYBIRD GUIDE ENDS

OPINION STARTS

My view on the implications of this for orthotic manufacture is as follows.

Orthotics generally operate primarily in the frontal and saggital planes. This is because in these planes the orthotic can work by pushing against the ground. To operate in the transverse they must prevent the navicular from traveling medially. Whilst this is possible with a device with a high medial wrap (EVA hi Wrap, UCBL, AFO) it is more usually the preserve of the footwear.

Let us consider a foot with a frontal plane dominance (in which the navicular will drop loads but adduct little). In a foot like this one can acheive good results by preventing the navicular from dropping. Simple insoles, Biplanar casts (most rigid shells), even pork pies (hey martin) etc work well. Footwear is less important because the support is from the ground up, not the side in.

Now let us consider a foot with a Transverse plane dominance, (in which the navicular will adduct loads but drop little). Simple insoles, all but useless. The foot can be fully, pathologically pronated and yet still have an arch. Casted biplanar insoles, Better, but not much. You'd better be sure they don't put too much arch fill on the cast or the same applies as for simples. Also i would not be surprised if many of the "too hard" complaints come from this foot type due to the magnitude of force in such a small downward movement. Consider trapping your finger in the handle end of the door vs the hinge. Its a leverage thing. In this foot, footwear is key. Too soft and the foot will travel over the arch of your insole and over the other side. The center of gravity will deviate much more medially.
For this foot i would advice an insole with a high medial wrap (like an EVA) minimal arch fill, good, solid footwear and some hedex. (for you not the patient).

Hope this has been of interest / help to people.

Comments arguments? Please?

Regards

Robert

[robertisaacs]

Ian. You said

To be honest I rarely think in terms of dominance. Lazy of me perhaps but over the years have tended to view that what I find none weight bearing may have no link to what I find weight bearing, however what I treat none weight bearing may and frequently does affect the patient weigh bearing. So the none weight bearing treatment may have no bearing directly on what I might prescribe orthotic wise ( Boy would i be even more a pariah on pod arena with that!!). Equally, as I would be mobilising the joints on this guy dominance may alter as joint freedom increases and indeed muscle pattern action changes.

(Do you think Bel and Twirls are coping with the reference to dominance all the time?)

I would dispute that mobilising the joint will alter the dominance unless you are introducing significant translatory range.

ALTHOUGH If you are increasing the range of pronation you will be changing the functioning range of the joint to be in a more pronated position. That being the case and accepting that the axis becomes more medial the more pronated you go i could accept that a mobilised joint will have a slightly (very slightly) more frontal element than an unmobilised joint.

And for the reasons i have outlined above i contend that planal dominance is vital in appropriate orthotic prescription.

Regards
Robert

[ianl]

Hi Robert

Quite happy for you to dispute it and, as I said, it may be lazy of me to not think in terms of dominance. I suspect my News of the World approach to biomechanical terminology frustrated the bioengineer in DH ;D). Terminology wise I tend to look at a foot and have adopted a simpler approach that matches my way of viewing (literally).

Does it bend (rotate)?
Does it bend too much?
Does it not bend enough?
Is the amount of available bend helpful, unhelpful to that individuals posture, function.

That "bend" issue may well be a frontal or saggital plane issue (and of course transverse, indeed all three). How to introduce, maximally use or limit such bend becomes a prescription concern, equally how to counter certain tendencies for the joint to bend in a certain way, but I suspect that we (in many of our average pts) make it more of a concern than we need to. Orthotic prescription for such people is remarkably simple.

Then, of course, we have the more proximal concerns. I have various times seen (immediate none EBM alert ) people who have unhelpful levels of pronation at the MTJ. They have circumducted their leg, landed with a more exterally rotated foot and come over the said foot only to exhibit more pronation at the MTJ at an inappropriate point in their gait (to my mind).

As to planal dominance of the foot here we can place our bets and may well want to prescribe a certain type of device which we have calculated to bring a certain amount of precise force at a specific time in the gait. ( Excuse my cynicism - I can accept that this may be much more applicable in AFO work).

However, a simple Maitland (sadly the Society insurance does not cover me for this - bring back SMAE insurance) peripheral joint mobilisation of the hip reduces said circumduction which often reduces the level of the externally rotated foot and sometimes alters the level of pronation at the MTJ. Has this altered the planal dominance? Don't know? Has it altered the function of that planal dominance? Don't know?

I'm sure this has not addressed your concern (probably beyond me to argue some of the stuff anyway) but it shifts the issue of dominance away from being foot focused and simply foot joint axis focused, which we do become fixated on. (There again if I have inaequate knowlege to shift focuss gets me of the hook!! ;D). It sometimes intrigues me now in podiatry (percentage time wise) at how little I give to foot function for clues of what I want to do .

Cheers
Ian

[Admin]

ianl said:

Quite happy for you to dispute it and, as I said, it may be lazy of me to not think in terms of dominance. I suspect my News of the World approach to biomechanical terminology frustrated the bioengineer in DH ;D). Terminology wise I tend to look at a foot and have adopted a simpler approach that matches my way of viewing (literally).

Hi Ian and Robert,

Ian - have to pick you up on your simplistic approach to biomech. It's OK as far as it goes, but IMO still a bit too complicated ;D.

Robert - I believe planal dominance to be, to quote dtt, just so much b*&&*$ks - unless you can point me in the direction of a piece of meaningful research which shows that such a thing actually exists.

I just think there is so much natural variation (not to mention diurnal variation ;D) that it is futile to label with any degree of certainty.

However, I agree that some feet which roll in are not helped by a standard orthosis and will simply rub against the inside edge of the device, usually causing pain/inflammation/blistering.

In these cases I also agree that a high medial flange is useful. RF posting is necessary to tilt the foot back into STJ neutral, and a deep heel cup is helpful in holding the foot in that position.

Cheers,

[robertisaacs]

Thanks for playing!

I believe planal dominance to be, to quote dtt, just so much b*&&*$ks - unless you can point me in the direction of a piece of meaningful research which shows that such a thing actually exists.

'K

DR Green and A Carol Planal dominance J Am Podiatr Med Assoc 1984 74: 98-103.

I just think there is so much natural variation (not to mention diurnal variation ) that it is futile to label with any degree of certainty.

Diernal variation you say. I can see how that can affect a change in the range of motion of a joint but not the actual planes in which that movement takes place. You don't get knees suddenly developing the ability to abduct at night time!

However, I agree that some feet which roll in are not helped by a standard orthosis and will simply rub against the inside edge of the device, usually causing pain/inflammation/blistering.

And what, IYO is the reason that some feet do this and some don't?

To be honest althought the article i refed is significant my views on the importance of PD are also heavily influenced by empiricism. I do the navicular drift / drop test routinely as part of my assessment and have found it to be pretty repeatable. I have also found that the prescriptions varients i described quite often work as i described with the varying foot types (although i appreciate that "in my experiance" has no scientific validity.

So, to paraphrase you paraphrasing derek...

I believe diurnal variation affecting planal dominance to be, to quote dtt, just so much b*&&*$ks - unless you can point me in the direction of a piece of meaningful research which shows that such a thing actually exists.

Lets probe the extent of your beleifs.

Do you beleive the STJ to be axial?


And to you...

Regards
Robert

[Admin]

Hi Robert,

You said:
"DR Green and A Carol Planal dominance J Am Podiatr Med Assoc 1984 74: 98-103. " when I asked you to point me in the direction of a piece of meaningful research which shows that planal dominance actually exists. This Paper explains the theory (as if it were absolute fact BTW) of planal dominance - and does it very well too. What is does not do is show that a study was conducted which proved that planal dominance exists. Neither the refs nor the Additional refs do that either.

I'm not aware of any good, robust research which shows that planal dominance exists. Are you, or anyone else reading this?

Diurnal variation was a (rather weak) joke .

Yes, I think the tri-axial STJ ROM model is a workable model. If you are asking if I believe tri-axial ROM is applicable for all feet, I don't think so.
Neither do I believe the Author (either R Anthony or Philps - forget which) who stated that if you fit the wrong orthosis to a certain type of dominant axis you will injure the patient.

I trust your empiricism , but would like to see some hard science too.

Regards,

[robertisaacs]

I trust your empiricism , but would like to see some hard science too.

Really?!?! I don't trust my emiricism and its MY empiricism.

Yes, I think the tri-axial STJ ROM model is a workable model. If you are asking if I believe tri-axial ROM is applicable for all feet, I don't think so.
Neither do I believe the Author (either R Anthony or Philps - forget which) who stated that if you fit the wrong orthosis to a certain type of dominant axis you will injure the patient.

Sorry, point of clarity. Tri axial? Not familier with the term. Are we talking about a bundle of instantanious axis which exist in three planes here? Or is tri axial something else.

I'd like to check that before we go on. Just to make sure we are talking the same language.

For the record i don't think it can be said the the wrong orthoses WILL injure the patient. But i do beleive that some types of orthotics work far better on certain foot types than others.

And i do beleive that the wrong orthotic can damage a patient.

Regards
Robert

[TimVS]

Hmm. If I can drag you gents away from the theory to the practical for a moment. In clinic, I certainly find the transverse plane 'bulging navicular' foot types quite hard to manage. Medial flange and deep heel cup, yes, but often two issues, rubbing of the flange and good old shoe fit. Yes, I know we should make all our patients wear sensible shoes, yadda yadda, but...
I'm quite fond of the Muller TPD for this kind of work, but can be tricky with some shoe types.

I'd be grateful for your practical perspectives on how you deal with this in clinic, then you can get back to your debate

Cheerz.

[Admin]

Hi Robert,
I trust your empiricism because it's real to you. It may/ may not stand up to scrutiny from others, but I absolutely believe it is real to you .

Mine is too ;D.

The STJ axis is really at the heart of the problem I have with planal dominance.

Tri-axial ROM should read tri-planar motion - sorry.

Planal dominance, as described by Green and Carol, depends upon the STJ axis being static, so that, for example, at any given point during movement in the sagittal plane, it is possible to determine, with some degree of accuracy (Green and Carol actually quantify this) how much additional movement there will be in either the frontal or transverse planes, depending upon whether the axis is pitched higher or lower than 42 degrees. Is the axis static, is it helical, is it where we think it is?

Lets look at where those axis spatial positions came from...
Manter - 16 specimens -1941.
Root et al - 22 specimens -1966.
Isman and Inman - 46 specimens - 1969.

Note these are not bodies, but feet, so we're talking 84 feet in total.

Results as follows:
Average position of the STJ axis in the sagittal plane = 41 degrees.
But - Manter found a range of positions going from 29 degrees to 47 degrees. Root et al found a range going from 22 to 55 dgrees, and Inman found a range going from 20 degrees to 68 degrees.
I can't put my hands on these Papers at the moment, but from memory the Root study (which was not particularly rigorous - IMO they found what they wanted to find) showed a SD of over 20%.

Move on to 1985 when Philips, Christeck and Philips wrote Clinical Measurement of the Subtalar Joint (JAPA Vol 75, 3, March 1985).
This Paper, for those who have not read it, combines some fairly intense Euler math (X,Y,Z coordinates) with lines drawn on skin, and a hand-held instrument called the Phillips Biometer, to obtain ROM of the STJ. It then proceeds to Tables which give ratios of ROM for various combinations of axis deviation from normal.

My point is this: We do not have enough data to confidently state that we know, to the degree, the spatial location of the STJ axis. In addition, even if we did, there is so much natural body variation that one cannot accurately predict the effects of a high or low-pitched axis.

I don't doubt that you can work from a hypothetical model (planal dominance) and still get good results. I work from a totally different hypothetical model and obtain good results too, but how much of this is down to operator skill and intuition?

If you know of any Papers which disprove what I say I would welcome the refs.

Cheers,

[Admin]

Hi Tim,

High medial flange with a push-out for the navicular is the way to go.

Mulller TPDs are the best casted device for this type of foot IMO.

[robertisaacs]

Hey tim.

As david says, hi medial wrap is a good plan. For me the key here is what material you use. Materials like EVA let you wrap the medial part of your orthotic around the navicular. Rigid ones don't.

Sometimes i find the good ole kirby skive can work well in this foot as well.

But at the end of the day in the transverse plane y type feet you cannot get around the need for good footwear.

Damn. Baby crying, reply to david going to have to wait...

Regards
Harrassed dad.

[ianl]

Hi Tim

I have used either the dress class 3 or the balance light with a high medial flange, navicular push out a Medial heel skive and a flattened heel post. Sometimes done this instead of the Muller.

Cheers
Ian

[TimVS]

Thanks guys! Love the Muller, but a bit hefty for the gals I'll take your tips on board, cheers.

On with your debate then chaps. I'll take a ringside seat from here on in

d**n. Baby crying, reply to david going to have to wait...

Regards
Harrassed dad.

Don't worry Rob, they do calm down eventually!

Cheerz

[robertisaacs]

Don't worry Rob, they do calm down eventually!

Says You!!! Teething. Why Do they teeth .

Aaaaannyway. Firstly i'd like to say thanks for all the information David. There is some good meat there.

Tri-axial ROM should read tri-planar motion - sorry.

Thank goodness for that! You had me worried that i had missed something major there. Tri axial?!?! three axis!?! Brown trousers moment!

Planal dominance, as described by Green and Carol, depends upon the STJ axis being static, so that, for example, at any given point during movement in the sagittal plane, it is possible to determine, with some degree of accuracy (Green and Carol actually quantify this) how much additional movement there will be in either the frontal or transverse planes, depending upon whether the axis is pitched higher or lower than 42 degrees. Is the axis static, is it helical, is it where we think it is?

Lets look at where those axis spatial positions came from...
Manter - 16 specimens -1941.
Root et al - 22 specimens -1966.
Isman and Inman - 46 specimens - 1969.

Note these are not bodies, but feet, so we're talking 84 feet in total.

Results as follows:
Average position of the STJ axis in the sagittal plane = 41 degrees.
But - Manter found a range of positions going from 29 degrees to 47 degrees. Root et al found a range going from 22 to 55 dgrees, and Inman found a range going from 20 degrees to 68 degrees.
I can't put my hands on these Papers at the moment, but from memory the Root study (which was not particularly rigorous - IMO they found what they wanted to find) showed a SD of over 20%.

I would agree with you there. The concept of a single STJ axis is palpably absurd. The studies you have quoted clearly show that.

You do not say (but do infer), that isolating the STJ axis with any reasonable degree of repeatability is well nigh impossible. Here i would also agree. I DO think that the frontal plane element of the STA IS identifiable with a certain degree of accuracy (as described by KK). However this is not useful information in terms of discovering a planar dominance.

Finally you say

My point is this: We do not have enough data to confidently state that we know, to the degree, the spatial location of the STJ axis. In addition, even if we did, there is so much natural body variation that one cannot accurately predict the effects of a high or low-pitched axis.

I agree (with the reservation i've just mentioned).

However. (how did you know i was going to say that ;D)

I think that trying to find the planar dominance by extrapolating from the position of the axis is a very A**E about face way of doing it. If you want to find how much movement happens in a certain plane... wiggle the foot and see!!!

This is the dissonance between researchers (who work in terms of pure mechanics) and clinicians (who work with real, biological, complex specimins.)

I was interested to note that you replied to tim's post regarding

I certainly find the transverse plane 'bulging navicular' foot types

saying

Mulller TPDs are the best casted device for this type of foot IMO.

So you DO recognise that there is a foot type which bulges medially more and that different insoles work differently with this "type" of foot.

Leaving aside planal dominance, axis, degrees of certainty etc, Try this.

Some foot types the navicular drops loads.
Some foot types the navicular drops about as much as it drifts
Some foot types the navicular drifts loads and drops little

Different insoles work better / worse depending on these foot types.

Agree? Disagree?

Regards
Robert

[TimVS]

Some foot types the navicular drops loads.
Some foot types the navicular drops about as much as it drifts
Some foot types the navicular drifts loads and drops little

Different insoles work better / worse depending on these foot types

Now that's my kind of science! I'll use that one on my next biomech cheers