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  #1  
Old 18th August 2005, 11:21 AM
nicholas nicholas is offline
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Default Posting for forefoot varus

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I would like to know the the truth regarding the use of forefoot posting in the treatment of forefoot varus. To my knowledge the late stage pronation that occurs as a result of forefoot varus causes dorsiflexion of the first ray and leads to a jamming of the 1st mtpj and therefore a functional hallus limitus.If by posting for instance the 1st to 3rd metsatarsals in an attempt to prevent excesssive pronation do we not still create a situation in the 1st mtpj whereby the 1st ray is still caused to dorsiflex thus preventing dorsiflexion of the hallus on the met head and the perpetuation of functional hjallux limitus.
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Old 18th August 2005, 02:11 PM
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Welcome to Podiatry Arena.....

I have not used a forefoot varus post in years!!! I can not remember the last time I actually have seen a foefoot varus - its very rare, but very frequently misdiagnosed.

You might want to read this thread:
Is forefoot varus posting an anachronism
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Old 18th August 2005, 03:53 PM
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I should have followed up this comment:
Quote:
If by posting for instance the 1st to 3rd metsatarsals in an attempt to prevent excesssive pronation
How does that stop excessive pronation? All it will do is invert the forefoot on the rearfoot around the midfoot joints --> midfoot collapse --> problems.
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do we not still create a situation in the 1st mtpj whereby the 1st ray is still caused to dorsiflex thus preventing dorsiflexion of the hallus on the met head and the perpetuation of functional hjallux limitus.
Yes.
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Old 19th August 2005, 01:27 AM
nicholas nicholas is offline
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Default forefoot supinatus

Thanks Craig for correcting my obvious mistake regarding forefoot posting. It is quite obvious to me when I think about it that posting the forefoot will not reduce pronation, I am recently qualified and therefore still exploring the numerous functions that occur in the mechanics of the foot so I hope that you will bear with me and continue to correct me when I make such obvious mistakes.

Basically the reason that I asked this question was to try to find a way to appropriately produce insoles for a person that I have been treating. Their foot type is a rear foot varus with a flexible forefoot that is inverted on the rearfoot which I believe is a forefoot supinatus resulting from inversion of the forefoot on the rearfoot due to late stage pronation ( am I correct in this diagnosis).

My original thinking was to provide a 4 degree rearfoot wedge and a 3ml poron 1-3 forefoot post to occupy the space required to enable contact with the inverted forefoot and this is where my thinking arose that this would cause a functional hallux limitus due to the hypermobility of the 1st raythat it would cause.

I am also thinking that apart from not wishing to post the forefoot due to the potential to cause FHL, it is also not advisable to do so as this may also lead to the formation of a ridgid forefoot varus over time.

please advise me as to the correct prescription for this foot type.

In the case or of a ridgid forefoot varus with the obvious implications that it would have on the forefoot would it in this case be appropriate to provide medial forefoot posting.

Thanks for taking the time to read my rambles, Im afraid I will probably need call many more times in the future.
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Old 19th August 2005, 04:20 PM
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My original thinking was to provide a 4 degree rearfoot wedge and a 3ml poron 1-3 forefoot post to occupy the space required to enable contact with the inverted forefoot and this is where my thinking arose that this would cause a functional hallux limitus due to the hypermobility of the 1st raythat it would cause.
I would just invert the rearfoot and generally either leave the forefoot alone --- but maybe do the opposite in the forefoot to get the medial column down to the ground.
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Old 2nd September 2005, 09:55 PM
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I am a little confused. When I supinate a pronated foot in stance, the medial forefoot comes off the ground most of the times when I place the foot in neutral. How can an orthotic that does not support this imbalance put the foot in neutral, or close to it?
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Old 5th September 2005, 03:02 AM
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The logic is this...if what you are seeing is "supinatus" then the medial forefoot is "lifted" off the ground when you supinate the STJ up to neutral...because during the life and development of the individual the dorsal soft tissue structures of the over pronated foot have contracted or grown short....so it can no longer reach the floor when the foot is not pronated.

You don't want to support this kind of planal anomaly....you want to try to reduce it over time.....stop rear foot pronation and maybe even put a lateral forefoot wedge to exert even more force to get the first met shaft back down to the floor.
Regards Phill
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Old 5th September 2005, 03:06 AM
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To differentiate between supinatus and varus (bone anomaly) just put weighted foot in STJ neutral then attempt to bring 1st met down to floor without letting STJ pronate...if you can it's not bony....I have seen one where the tension on EHL was so great it caused hallux D/F before the 1st met reached the floor.
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Old 5th September 2005, 08:13 PM
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Phill,

Thanks for the reply. Now I am more confused.

You said, "To differentiate between supinatus and varus (bone anomaly) just put weighted foot in STJ neutral then attempt to bring 1st met down to floor without letting STJ pronate...if you can it's not bony...."

I may be wrong, but isn't the concept of neutral position at midstance the Subtalar joint in neutral, the midtarsal joint maximally loaded and the metataral weighted (At midstance there is weight on the forefoot, isn't there?) So why would the first met-cuneiform joint be in maximal plantarflexion?

You also said "stop rear foot pronation and maybe even put a lateral forefoot wedge to exert even more force to get the first met shaft back down to the floor".

I am assuming that you are using a rigid orthoses (rohadur). When you use a lateral forefoot post, why doesn't the rearfoot become more pronated (it is rigid, isn't it?) How do you stop pronation in this pronated position?


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Old 6th September 2005, 12:55 AM
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According to how I see it...forefoot varus is a theoretical idea about unresolved torsion of the neck of talus that results in a rigid bony reason why the STJ when brought to neutral carries the distal structures with it...."up off the floor".....this condition is supposedly real....but I don't think I've ever seen one since I've been qualified. Yes there is the articulation between the talus and navicular...but these guys are supposed to be congruent for STJ neutral...so all you should have to do to bring the 1st met shaft down is stretch out any soft tissue that is "a little short".
This should not be bringing your first met shaft to its max p/f'ed position specifically at that articulation...you should be able to see/feel the difference....I think I can....but maybe I'm just kidding myself.

A supinatus is a varus presentation of the forefoot which can be reduced while holding the STJ in neutral...in other words it is not a bony relationship problem but a contracture that can "be stretched out". This one I think I see a fair bit, particularly in those mobile pronators that evert freely in the frontal plane. These feet commonly move into late stance and propulsion with a failure of midtarsal lock, failure of windlass, failure to make transition from adaptable to rigid at or near midstance...generally pretty poor foot stability and prone to intrinsic foot symptoms.

When I set out to limit rear foot eversion the aim is to get the first met shaft plantarflexed...get the windlass engaging and the midtarsal lock working to move to propulsion with at least some kind of lever to push with....this is usually more stable and efficient.
The lateral forefoot extension wedge that I put onto a rigid shell is 300-350 density EVA so that it alters the relationship of the met heads in the frontal plane but allows them to move into dorsiflexion freely at the normal metatarsal break angle for that individual. The plaster work I do to the foot involves a bit of lateral column cuboid type grind to lift the shell a little and this allows the EVA overlay to blend anteriorly and this EVA maybe anything up to 15mm high(only this high for monster forefoot valgus types like in cerebellar degen, I usually only use 6mm or so) at the lateral side under the 5th met head tapering medially to 0mm under the 1st met head and distally to zero just prox to IPJ'S.This kind of rear foot inversion and forefoot eversion has been around for ever...and used to be called "screwing" the foot....works great for loads of people.
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Old 6th September 2005, 06:08 AM
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Quote:
Originally Posted by nicholas
I would like to know the the truth regarding the use of forefoot posting in the treatment of forefoot varus. To my knowledge the late stage pronation that occurs as a result of forefoot varus causes dorsiflexion of the first ray and leads to a jamming of the 1st mtpj and therefore a functional hallus limitus.If by posting for instance the 1st to 3rd metsatarsals in an attempt to prevent excesssive pronation do we not still create a situation in the 1st mtpj whereby the 1st ray is still caused to dorsiflex thus preventing dorsiflexion of the hallus on the met head and the perpetuation of functional hjallux limitus.
This has been an interesting thread to follow. First of all, I don't use forefoot varus extensions on my orthoses very often. However, I do use forefoot varus extensions, and have found them very helpful, in the treatment of running injuries where it is thought that excessive STJ pronation moment is the cause of the injury, such as medial tibial stress syndrome (MTSS) and patellofemoral syndrome, and the patient has what appears to have a varus forefoot alignment while running. They are particularly helpful in MTSS, which I will be lecturing on next month in Melbourne.

The whole idea of forefoot varus vs. forefoot supinatus is one I have seen come and go ever since I started podiatry school back in 1979. In the early years of podiatric biomechanics and in the early Root biomechanics teachings at CCPM, nearly all feet had forefoot varus which caused STJ pronation. As they started to either understand things better or measure differently (I don't know which), then people started to get more forefoot valgus. This was a very interesting story that I heard from a few lecturers that experienced the years at CCPM during the 1960s and early 1970s vs the early 1980's and later.

I believe that forefoot to rearfoot alignment is partly structural but also is changeable due to changes in foot function. Increased ground reaction force (GRF) medially on the forefoot will tend to cause, over time, an increase in forefoot varus or a decrease in forefoot valgus. Whereas, increased GRF laterally on the forefoot will tend to cause, over time, an increase in forefoot valgus or a decrease in forefoot varus. These changes are due to the known viscoelastic characteristics of ligaments and tendons whereby they will either stretch or shorten depending on the magnitude and duration of load they are subjected to over time and are also strain-rate dependent (stress-relaxation response, creep response).

For these reasons, I think the term "forefoot supinatus" is a poor term since nearly all feet probably have some "forefoot supinatus" in that if they started functioning in a more STJ supinated fashion their forefoot to rearfoot alignment would either become, over time, more valgus or less varus.
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Old 6th September 2005, 09:45 PM
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Phill,

You answered my question about the forefoot post not efffecting the rearfoot. It is kind of interesting that the cast when it modified has only a small sliver on the lateral side that is the original non modified cast, and now after modifications, you have even less of the original cast.
How efficient is the rearfoot of the orthotic? Do you draw a line on the back of the heel and see what happens when the patient stahds on it?
Does it pronate, supinate or not change?
This is the essence of this discussion.
If the calcaneus everts, then we are dealing with a forefoot varus. If the calcaneus inverts, then we are dealing with a forefoot supinatus.

I have not had to worry about this. . I make leather orthotics, and I just read where the first metatarsal is. Sometimes it plantarflexes, and then I grind underneath it to let it drop. and sometimes I have to add more underneath. I see changes within a week. I don't expect to get the final answer immediately. I let the body tell me what it needs.
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Old 9th September 2005, 07:33 AM
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Smile Forefoot supinatus position

Phill,
I think that supinatus as a position is easy to understand, in that in STJ neutral non weight bearing with the forefoot maximally pronated, the forefoot is in a supinated (inverted) position relative to the heel bisection - and crucially when we check the movement of the hallux above and below the level of the plane of the lesser metatarsals, we find that the 1st ray is in a dorsiflexed position. If it has equal movement above and below then this distinguishes it from a forefoot varus. I agree that this is rare and patients who demonstate this have excessive rearfoot pronation. However from my own experience the greater the degree of forefoot supinatus and hence rearfoot pronation the greater the ankle equinus or 'stiffness'. In younger patients more corrective control can be attempted by cranking up the rearfoot post to NCSP but with older patients this level of control is harder to tolerate. The forces acting through the MTJ make too heavily posted devices difficult reducing the compensation available within the foot and tend to cause compensatory adjustments higher up the chain with patients complaining of knee or hip problems. When to post and how high to post is difficult to determine and for me has come through 18 years of experience. However with the older patient (35+) who is less likely to make the neccesary life changes i.e. diet, exercise, exersises, footwear etc I find casting the pateint semi weightbearing is best. I sit the patient with their foot in a mould (thermo-plastic) where I can adjust the positon of the foot to allow some pronation of the rearfoor but with all the metetarsal heads in alignment in the same plane (all touching the floor). Doing this also allows me to dispense with medial or lateral expansions (which are at best inaccuate guesses) and also not to post the forefoot. These are extremely comfortable for the patient, easy to manufacture and less intrusive to footwear. I find that adding a 0 degree extrinsic rearfoot post to hold the rearfoot 'near' neutral (slightly pronated) and a soft composition arch fill on a semi flexible shell is the best combination. These are particarly useful for plantarfasciitis, arch pain, achilles tendernitis and especially for the more difficult ankle equinus patients. :)
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Old 9th September 2005, 07:47 AM
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Philip - I would have to disagree with this:
Quote:
I agree that this is rare and patients who demonstate this have excessive rearfoot
..we had a poster at a conference on our research on it last week. It is assumed that a forefoot supinatus must have a calc that should evert past vertical for the soft tissue contracture of the forefoot to develop in a supinated position. We found no relationship between rearfoot pronation/position and forefoot supinatus......we did find that the force needed to supinate the foot was greater in those with a supinatus. (ie as I have been saying a lot lately --- its the forces and not the motion thats the problem)
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Old 9th September 2005, 09:02 AM
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Question Resupination forces

Hi Craig
Are you saying that the rotation of the calcaneus is not responsible for leaving the foot permanently in a supinated POSITION from heel contact through to heel lift in patients with excessive rearfoot pronation and in time that this does not cause contracture of the tissues over time. I would have assumed that the force needed to resupinate the whole foot would have to be higher than a foot that has little rearfoot pronation. I would contend that it is the excessive motion that increases these forces as the foot accepts the full body weight and has a direct impact on those forces of resupination.
I am trying not to be stuck in the dark ages but I remain to be convinced that true forefoot supinatus is not caused by the EXCESSIVE pronation if not why would the first ray be dorsiflexed even off weight bearing?.
Motion first followed by the force?
Respectfully yours
Philip
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Old 9th September 2005, 09:12 AM
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Quote:
Are you saying that the rotation of the calcaneus is not responsible for leaving the foot permanently in a supinated POSITION from heel contact through to heel lift in patients with excessive rearfoot pronation and in time that this does not cause contracture of the tissues over time
Thats exactly what I am saying.

Rearfoot eversion past a vertical calcaneus does produce a compensatory supination of the forefoot on the rearfoot - there is no doubt about that.

HOWEVER, if this was the cause of forefoot supinatus we would expect to see a higher incidence of forefoot supinatus in feet with an everted calcaneus and a conversely a lower incidence of forefoot supinatus in those feet that do not have an everted calcaneus....the data was not even close to showing that.

What we did find was that the force to supinate the rearfoot was higher in the supinatus group and the force to establish the windlass mechanism was higher in those with a forefoot supinatus.
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Old 9th September 2005, 09:46 AM
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Craig

if this was the cause of forefoot supinatus we would expect to see a higher incidence of forefoot supinatus in feet with an everted calcaneus and a conversely a lower incidence of forefoot supinatus in those feet that do not have an everted calcaneus....the data was not even close to showing that. What we did find was that the force to supinate the rearfoot was higher in the supinatus group and the force to establish the windlass mechanism was higher in those with a forefoot supinatus.

This is what I summised in my earlier reply.

If they did not have forefoot supinatus how many had forefoot varus/valgus and how many had mets in same plane with the feet with everted calcaneus?
How many of these had a forefoot varus?
Interesting stuff!

How would you address reducing these forces at the forefoot/ With just rearfoot varus posting? What about the control from heel lift at the forefoot.

PS having to pray for rain to ensure we get the Ashes back to their rightful owners.

Phil the Pommie
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Old 9th September 2005, 10:02 AM
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To our disappointment in all the subjects we could get our hands on none had a forefoot varus (its thats rare) - it would have been good to have compared supinatus to varus on the parameters we measured.

We did not measure the supinatus (just present/absent) due to measuement reliability issues.

Even though we found forces to supinate the rearfoot and establish the windlass were higher, that does not mean they were the cause --- they could just as easy have been a result of the supinatus (though it does make intuitive sense that some sort of windlass dysfunction may be related to forefoot supinatus; ie windlass dysfunction --> possibly get more dorsiflexion of medial column of forefoot relative to lateral --> supinated forefoot.).

Our standard approach to supination resistance forces, is to wedge the rearfoot more if the forces are higher. For the higher forces to establish the windlass, this is easily reduced with rearfoot inverting wedges; or lateral forefoot wedges; or met domes; or first ray cut outs; etc ... probably nothing more than most do for a forefoot supinatus now, but there should just be a shift in the understanding of the underlying pathogenesis.
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PS having to pray for rain to ensure we get the Ashes back to their rightful owners.
I am watching the Patriots play the Raiders even though I am in the UK at the moment (Liverpool) and know the cricket is on ....my loyalities still reside across the other side of the Tasman
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Old 9th September 2005, 10:13 AM
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It seems like a chicken and egg situation. The windlass action is a good contender but is it not made more lax by the repetitive excess pronation? If we only post the rearfoor with a patient with a disfunctional windlass or supinatus foot what happens to the forefoot once the heel begins to lift?
If casts are taken semi weight bearing I think the windlass channel on the orthoses is not necessary.

Rain stop play.
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Old 10th September 2005, 02:22 AM
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I have another question related to the forces acting upon the medial column of the foot, whilst the answer may seem quite obvious to some, please bear with me as I am a newcommer.

|My question related to hypermobility of the first ray. If, for instance the calcaneum sits in a vertical position when in sub talar neutral position but the first ray is hypermobile and therefore dorsiflexes upon weightbearing which would case the forefoot to invert on the rearfoot re3sulting in late stage pronation and functional hallux limitus, how do you prevent tyhe first ray from dorsiflexing. If the stj is vertical in neutral calcaneal stance then (if I am correct in this) posting the rearfoot in an attempt to prevent late stage pronation would not be appropriate.
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Old 10th September 2005, 08:20 AM
Philip Clayton Philip Clayton is offline
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Hi Nicholas
Your question seems similar to mine and I am sure that this was the reasoning behind Rootian forefoot posting. Many contributors now say they don't bother posting the forefoot which means that Root was completely wrong or that something else is taking place that is not being described well enough. Sorry to harp on about it but this is why I often cast semi weightbearing because I feel it controls the 'fluid' movements and distributions of forces across the orthotic and maintains a better relationship between the rearfoot and forefoot (when posted at the rearfoot and not at the forefoot), preventing late stage pronation and FHL after heel lift.
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Old 10th September 2005, 10:49 AM
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In the case of the hypermobile 1st ray would it be appropriate to post the rearfroot (even if the calcaneum was vertical in NCSP) and use an insole that lay beneath mets 2-5 and have a cutout for the 1st ray My thinking here ias that the rearfoot posting will prevent the rearfoot from pronating excessively and remaining so in late midstance, and the 1st ray cutout serving to delay dorsiflexion ground reaction forces on the 1st met.
My main confusion here is regarding the use of medial rearfoot posting in a calcaneum that is vertical in NCSP. My thinking here is if you were to put for example 4 degrees of posting to the rearfootthat was vertical in NCSP then by the time midstance was reached then the rearfoot would be 4 degrees less everted than it would if it were not posted and therefore reduce the forces acting upon the forefoot and provide greater opportunity for the rearfoot to resupinate.
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Old 10th September 2005, 11:55 AM
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In the case of the hypermobile 1st ray would it be appropriate to post the rearfroot (even if the calcaneum was vertical in NCSP) and use an insole that lay beneath mets 2-5 and have a cutout for the 1st ray
Thats exactly what you do. Forget about what NCSP and RCSP and the amount of posting/wedging - they are not related to outcomes - if the rearfoot needs posting/wedging, it needs posting/wedging - the actual amount does not appear to be relevant and is certainly not related to outcomes. The determination of much much/how hard should probably be based on the forces needed to supinate the foot.
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Old 11th September 2005, 03:24 AM
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This 2-5 wedge is what I was talking about, changing the frontal plane relationship but allowing natural metatarsal dorsiflexion, helps maintain 1st ray plantarflexion after heel off, helps stop inversion of forefoot on rearfoot.
How much you do it is based on patient tolerance (and what fits in the shoes ) as one of you suggested via partial w/b casting.
If we hark back to Roots idea of midtarsal lock...this should happen and if it does the 1st met should be much less likely to move into dorsiflexion after heel lift (transition to rigid lever). I think some feet make this transition well past neutral, but never actually get there in their own gait, (more inverted at STJ, )
Some feet do this with major cuboid support, and these tendencies can be enhanced by addition of the forefoot lateral extension.
I try to find a set of factors which combine to create this MTJ locked foot in late stance and I "play " with the foot until I find it....if I can't , I know I'm going to have less effect on what is already happening.
In the end how you arrive at the shape and dimensions of the device matter less than whether or not it works...I don't really think one method is inherently better than another....success determines whether you have done the right thing.
If we ignore historical attempts to explain particular conditions because new work shows the old explanation not to fit....it still does not alter what actually is happening....and what your patient is actually feeling.
Hopefully new explanations will be closer to the real situation, but it won't change me listening to my patient for feedback....and doing pretty much whatever solves their problem.....I also think there is often more than one right answer.....As has been said the body often sorts out a pretty good pattern of compensation...we just need to find a pattern that allows this.

I look forward to more of Craigs stuff lighting up the dark corners of our well worn assumptions.

Regards Phill Carter
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Old 11th September 2005, 05:10 AM
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Hi, do any of you use Ray Anthony's techniques pouring the cast inverted and adding forefoot intrinsic balances, taking into account planal dominance and inclination of STJ axis. Or is this now out dated or unproven?
Also I don't here much now about polysectional trixial posting, is this 'old hat'.

Is there any new approach based on looking at the forces rather than the range of motions, I have to admit I tried the .... Footmaxx system..... aarghhh ..... there I own up! Nothing like the confessional.

Ps I don't use it anymore.

Phil
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Old 11th September 2005, 12:52 PM
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Originally Posted by Philip Clayton
Hi, do any of you use Ray Anthony's techniques pouring the cast inverted and adding forefoot intrinsic balances, taking into account planal dominance and inclination of STJ axis. Or is this now out dated or unproven?
Also I don't here much now about polysectional trixial posting, is this 'old hat'.

Is there any new approach based on looking at the forces rather than the range of motions, I have to admit I tried the .... Footmaxx system..... aarghhh ..... there I own up! Nothing like the confessional.
Eric Fuller and I have developed a theory of mechanical foot therapy which is based on the concept of STJ axis spatial location, STJ rotational equilibrium, MTJ rotational equilibrium, and tissue stress. A thorough description of this theory, including ideas on how to approach treatment, will be published in a chapter we wrote last year titled "Subtalar Joint Equilibrium and Tissue Stress (SJETS) Approach to Biomechanical Therapy of the Foot and Lower Extremity". This should be published in a book by Stephen Albert, DPM, hopefully which will be available by the end of the year.

This is the same approach that Eric and I have been independently developing using the concepts of STJ axis location and rotational equilbrium over the last 20 years. In my two books on foot and lower extremity biomechanics (Kirby KA.: Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997; Kirby KA.: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002) I have detailed, over the last 15 years, the treatment methods that I have used for mechanically based foot and lower extremity pathologies. These treatment methods are partly based on the Root et al techniques that I was taught at CCPM as a student and during my Biomechanics Fellowship at CCPM, but also are largely based on independent development of the concept of STJ axis spatial location and rotational equilibrium. As you may know, I have been contemplating, developing, writing, lecturing and using these theories and techniques for the last 20 years.

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The basic goals of the SJETS Approach is as follows:

1. Reduce the pathological loading forces on the injured structural components of the foot and lower extremity.

2. Optimize overall gait function.

3. Prevent any other pathologies or symptoms from occurring.
The SJETS Approach also relies on a basic knowledge of modelling techniques and free-body diagrams so that the clinician can predict how internal stresses will be changed within the structural components of the foot and lower extremity by different types of therapeutic techniques including foot orthoses, shoe modifications, braces, stengthening and stretching exercises. Even though this may be difficult for some clinicians who don't have good knowledge of biomechanics, I have profusely illustrated the chapter to demonstrate the concepts with more clarity with drawings. The SJETS Approach also relies on the idea of center of pressure and its relative position to the STJ axis and how that changes the moments acting across the STJ axis during weightbearing activities.

I am taking the time to contribute to this discussion since I feel that the concepts embodied in the SJETS Approach are, indeed, a new approach to mechanical foot therapy that all podiatrists should know about. The SJETS Approach is based on the first principles of Newtonian mechanics, well-established engineering and biomechanics principles, and is not necessarily based on "range of motions", "foot deformities" or "STJ neutral". Both Eric Fuller and I feel that this approach to mechanical therapy of the foot and lower extremity greatly clarifies and simplifies the decision making process of clinicians when it is used as a theoretical basis for developing treatment plans for patients with mechanically-based pathologies of the foot and lower extremity.
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Old 11th September 2005, 04:00 PM
Philip Clayton Philip Clayton is offline
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Kevin
From someone with a laterally displaced STJ axis with an increased supination moment acting across the joint axis this is music to my ears. I have often let my students try and complete a biomechanical examination of my own feet and have found a great variation in results ( and with a few well known clinicians!). As well as tight posterior group muscles and a rearfoot varus I have a low angle of inclination of the calcaneus, but curiously a laterally deviated STJ axis which increases the supination moment. I have never found the average 4 degree post comfortable as I am inclined towards a supination moment anyway, although from quick visual inpection I appear to have pes planus type feet.
I feel that our theoretical basis has changed but our treatment modalities are rather stuck in controlling only the frontal plane and rather simplistically with only rearfoot varus posting. We all need to expand our understanding and consider completely different ways of testing, and treating the foot and lower limbs. At least the footmaxx system introduced time into the equation and also forces and the position and direction of those forces. It is a pity that the results were made too simplistic and the devices produced were more off the shelf. However from my own perspective it was nice to view the hidden motions of the foot (pressure, time, spacial orientation etc). Also Ray Anthony's work along with your own and that of Erics and Craigs has offered a more detailed analysis and examination and can only lead to different treaments and more appropriate orthotic control. I wonder how the deviation of the STJ axis is altered by the increase in heel height bearing in mind the increase in frontal plane motion caused by the thinner end of the talus being placed between the tib and fib. Will this alter the STJ axis in situ considering that the average shoe lifts the rear of the foot by approx 1/2" to 1 ". From your response I determine that shoe design is also important for the deviated axis and I just wonder how we approach this from the 'fashion' point of view, including sportswear. :)
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Old 11th September 2005, 08:03 PM
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Kevin
From someone with a laterally displaced STJ axis with an increased supination moment acting across the joint axis this is music to my ears. I have often let my students try and complete a biomechanical examination of my own feet and have found a great variation in results ( and with a few well known clinicians!). As well as tight posterior group muscles and a rearfoot varus I have a low angle of inclination of the calcaneus, but curiously a laterally deviated STJ axis which increases the supination moment. I have never found the average 4 degree post comfortable as I am inclined towards a supination moment anyway, although from quick visual inpection I appear to have pes planus type feet.
I feel that our theoretical basis has changed but our treatment modalities are rather stuck in controlling only the frontal plane and rather simplistically with only rearfoot varus posting. We all need to expand our understanding and consider completely different ways of testing, and treating the foot and lower limbs. At least the footmaxx system introduced time into the equation and also forces and the position and direction of those forces. It is a pity that the results were made too simplistic and the devices produced were more off the shelf. However from my own perspective it was nice to view the hidden motions of the foot (pressure, time, spacial orientation etc). Also Ray Anthony's work along with your own and that of Erics and Craigs has offered a more detailed analysis and examination and can only lead to different treaments and more appropriate orthotic control. I wonder how the deviation of the STJ axis is altered by the increase in heel height bearing in mind the increase in frontal plane motion caused by the thinner end of the talus being placed between the tib and fib. Will this alter the STJ axis in situ considering that the average shoe lifts the rear of the foot by approx 1/2" to 1 ". From your response I determine that shoe design is also important for the deviated axis and I just wonder how we approach this from the 'fashion' point of view, including sportswear.
Philip:

When teaching students and residents, I have the patient stand in relaxed bipedal stance and have the student/resident find the talar head and neck at the anterior ankle. This takes some practice but is fairly easy once the landmarks of the talus are identified. The STJ axis will always pierce through the dorsal neck of the talus so that the bisection of the dorsal neck of the talus is generally the anterior exit point of the STJ axis. Posteriorly, the STJ normally exits somewhere very close to the lateral-superior aspect of the posterior calcaneus, but this does vary somewhat more than the anterior exit point. Then I take a pencil and put one end at the dorsal neck of the talus and "aim" the pencil toward the posterior-lateral-superior calcaneus to approximate the STJ axis location. This generally is a very good approximation of the STJ spatial location in relaxed bipedal stance.

Simon Spooner, PhD and I codeveloped a STJ axis locator that we did a preliminary radiographic study on and my data above comes from its use. Our paper describing the device and our small radiographic study should be published in JAPMA within the next 6 months (Spooner SK, Kirby KA: The subtalar joint axis locator: A preliminary report. J Am Pod Med Assoc, In Press, 2005). I will show a video of this device in my Melbourne lecture in four weeks.

I am also working with Steve Piazza, PhD and Greg Lewis, MS of Penn State Biomechanics lab on a way to find the STJ axis via motion analysis in cadavers and live subjects without drilling bone pins in the talus (Lewis GS, Kirby KA, Piazza SJ: A motion-based method for location of the subtalar joint axis assessed in cadaver specimens. Presented at 10th Anniversary Meeting of Gait and Clinical Movement Analysis Society in Portland, Oregon. April 7, 2005). I will be discussing that research a little at my talks in Melbourne also. My hope is that this research will allow us to track the spatial location of the STJ axis while a subject walks over a force plate or pressure mat with a 3D motion analysis system which will, for the first time, allow researchers to accurately determine the STJ moments at any instant of the stance phase of gait.

Too much work to do in one short lifetime!
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Old 12th September 2005, 01:25 PM
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Kevin,
I have found the best way of putting the patient in 'relaxed bipedal stance' (angle/base of gait) is to place my hands on their shoulders when facing and walk them forward two or three steps. I then walk them backwards still holding their shoulders and then ask them to stop two paces backwards and not to move. It seems to work well each time and prevents them from thinking about where to place their feet.

Your research sounds very interesting.

When at a weekend conference 2 yrs ago that Ian organised in Luton with some people from different disciplines (pods, physios, knee surgeons, etc) the Knee surgeon was giving an excellent presentation of surgery to the cruciate ligaments and described how they work like a towel being rung tight when the lower limb internally rotated. This helped to bind the tibia against the femur and I just wondered if overposting the medial interferes with this process and could allow the tightning to lessen and cause subsequent knee problems.
Any thoughts on this one?
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Old 12th September 2005, 09:55 PM
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When at a weekend conference 2 yrs ago that Ian organised in Luton with some people from different disciplines (pods, physios, knee surgeons, etc) the Knee surgeon was giving an excellent presentation of surgery to the cruciate ligaments and described how they work like a towel being rung tight when the lower limb internally rotated. This helped to bind the tibia against the femur and I just wondered if overposting the medial interferes with this process and could allow the tightning to lessen and cause subsequent knee problems.
Any thoughts on this one?
Philip:

Increased varus posting of a foot orthosis would, in general, cause the following mechanical effects at the knee:

1. Increase the compression force on the medial compartment of the knee
2. Decrease the compression force on the lateral compartment of the knee
3. Increase the tensile force in the lateral collateral ligament of the knee
4. Decrease the tensile force in the medial collateral ligament of the knee

Knee joint mechanics is interesting however I doubt that overposting would somehow "interfere" with function of the anterior and posterior cruciate ligaments of the knee since these ligaments are at the center of the knee joint where they are probably well-shielded from foot orthosis stresses (the cruciate ligaments effectively lie on the "neutral axis" of the knee). The cruciate ligaments will likely be more affected by anterior-posterior shearing forces acting on the knee than by frontal plane forces generated at the knee by foot orthoses.
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California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

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**************************************************
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