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another lesson i missed...........had a male 12y/o pt, with a very "heavy" medial heel contact, mother claims "goes through shoes every 2 weeks" (medial heel wear), their p/t has told mother orthotics (sic) will "fix it".... (although my understanding was that they wouldn't) i told the mother i would consult greater minds........so please my advice to an angsty mum would be..

(additional) after consulting a (kevin kirby) post i comprehend that there would be an increased moment of inertia (due to the slight increased mass with long lever arm) but didn't think it relevant to this case

Heavy medial heel wear is generally caused by children that have adducted gait patterns due to torsional problems of the lower extremity. A foot that is adducted at heel contact will strike the posterior-central to posterior-medial aspect of the posterior shoe sole while a foot that is abducted at heel contact will strike the posterior-lateral heel of the shoe sole. In addition, a patient that is maximally pronated at the subtalar joint (STJ) at heel contact will have a greater tendency of a more medial heel wear but most patients that are maximally pronated at the STJ at heel contact have more lateral shoe wear since they have an abducted gait pattern. This is another podiatric myth that medial heel wear indicates a severely pronated foot. Medial heel wear, instead, indicates a foot that is adducted at heel contact.

Foot orthoses can affect the swing phase of gait, sometimes quite dramatically. Many patients with severely pronated feet will function throughout swing phase of walking gait with their feet maximally pronated for the duration of swing phase. Normally, the foot should be pronated at the STJ in early swing and then supinate at the STJ in late swing to prepare the foot to hit the ground in a STJ supinated fashion. This very important late swing phase supination is caused by the anterior tibial muscle which not only functions to cause an ankle joint dorsiflexion moment but also has the potential function to cause STJ supination moment, as long as the anterior tibial tendon is medial to the STJ axis.

Unfortunately, for many feet at the initiation of swing phase, the foot is so pronated and the STJ axis is so medially deviated that the anterior tibial tendon is positioned lateral to the STJ axis. Therefore, when it is contracting during late swing phase to prepare the foot for deceleration of ankle joint plantarflexion at heel contact, it is producing insufficient magnitudes of STJ supination moment during late swing to counteract the STJ pronation moments from the the other muscles of the anterior compartment, the extensor hallucis longus and extensor digitorum longus muscles.

If the foot orthosis can be designed to make the STJ function in a more supinated position in late midstance and propulsion, then there is a higher chance that the orthosis will also allow more normal swing phase function of the STJ by preventing the STJ axis from being so medially deviated at toe off and, therefore, allowing the anterior tibial tendon to be now positioned medial to the STJ axis so it can more easily supinate the foot during late swing. If a supinated position of the STJ at heel contact can be achieved then this has the potential to also improve medial shoe sole wear.

Mark, if you have access to a video camera, especially one where the camera has a good slow-motion mode, posting a video of the patient walking in shoes and in shoes with an anti-pronation foot orthosis so see the gait changes during swing phase would be extremely educational to all those lurkers on Podiatry Arena. Swing phase biomechanics is not discussed much and is understood even less. However, swing phase biomechanics does have a significant effect on stance phase biomechanics during walking and running gait.

__________________
Sincerely,

Kevin

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Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
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Mark,
I don't have a defnitive answer for your case but a couple of things worthy of note:

Firstly, excessive medial heel wear on a shoe doesn't occur during swing phase.

Secondly, during walking there is no float phase so when one limb is in swing, the other is still in contact with ground and is thus capable of indirectly influencing the swing limb. For example take a device which increases hip extension on the contact side, what effect does this have on swing duration/ step length?

__________________
Science is the antidote to the poison of enthusiasm and superstition

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Prof. Kirby- he be typing at the same time as me

__________________
Science is the antidote to the poison of enthusiasm and superstition

My location

Time for bed, Simon. It's 9:10 AM here, its already 90 degrees F, projected to be 110 degrees F (43.3 C). Will be another new heat record for much of the Central Valley of California. However, I'm staying cool with my air conditioning, for now.

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

Cooking with Kirby! I'm sure there is a joke in there somewhere about how many Californian's it takes to switch on the air conditioning, but I'll leave it for now. That Grandpa thing sure must be tiring you out if it's time for bed at 9:10 am Kevin, or maybe you been up all night partying?

5:30pm here and time for a barbeque. Have a relaxing Sunday mate.

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Science is the antidote to the poison of enthusiasm and superstition

My location

I was thinking it was a little later in the evening there in that little island in the North Atlantic. Guess I better consult my time conversion charts again. Being a grandpa so far is very good even though it feels rather odd to be called one. Simon, best wishes to the family and have an extra brew with that barbecue for me!

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

Thank you, to yours too. So is it gramps, grandpa, papa or what? I know how you are hot on correct terminology; I wouldn't want to be calling you by the wrong name.

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Science is the antidote to the poison of enthusiasm and superstition

My location

So far, I'm leaning toward "Grandpa Kevin", even though I still have quite a while to worry about it since the lad is only 17 days old. It's much easier naming new tests and such for podiatry than it is naming a new name for yourself.

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

Yes.

1. There was a publication many years ago in the sensory literature (that I do not have handy) that presented some data and there explanation for the data was that the position that the foot was in when it left the ground influenced the position in which it hit the ground.

2. At the Perth APodC conference in 2003 we presented our data testing the reliability of a thin fibre optic cable for measuring foot motion in-shoe. For that reliability study we used a single subject with and without an EVA heel wedge --- we were able to show that he inverted his heel more during late stance when wearing the wedge ---- we speculated that when the foot was on the ground it "remembered" this and inverted more late swing in preparation .... maybe

__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia
http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________
God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University
This is where I am, where are you?

thanks gentlemen for the responses..........
simon, firstly, my omission, i assumed readers would realise i meant swing phase in relation to how it effected foot position at heel contact......secondly, wouldn't it depend on if the increased hip extension corrected an inadequate hip extension to optimal? in which case contralateral leg swing would be increased >> increased internal 'leg' rotation >> more adducted foot at heel contact... or if it caused over-extension of "contact" hip resulting in decreased step length of swing leg?
kevin, i follow except the 'foot' pronates mid swing to facilitate ground clearance so even if the tib ant tendon is sufficiently medially placed re stj at heel off isn't it 'negated' at mid swing?
craig, more research opportunities?
thanks again, mark conley

Pronating 4 degrees from a supinated STJ position during early swing phase is very different from being close to maximally pronated and pronating 4 degrees (or going to the maximally pronated STJ position) during early swing phase. These two different STJ rotational positions will significantly alter the anterior tibial tendon to STJ axis relationship.

My take on it is that, like Craig said, the individual somehow remembers the new heel contact position when they are more supinated at toe off or don't want to expend the energy to pronate the STJ a large number of degrees for toe clearance and then resupinate the STJ another large number of degrees to allow optimum functioning of the foot with the orthosis. I think much of this occurs mechanically due to changes in spatial relationship of the anterior tibial tendon to STJ axis due to different STJ rotational positions with and without orthoses at toe off. I saw this phenomenom occur a number of times on slow motion video during my Biomechanics Fellowship in 1984-85 in patients and students.

When are we getting to see the video, Mark??

__________________
Sincerely,

Kevin

**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
My location

Voice: (916) 925-8111 Fax: (916) 925-8136
**************************************************

working on it kevin........ the video camera ...... never had one, i work publicly, and i dont have any friends........................
i follow your argument........but what if we have a 'neurological' case, can the foot orthoses 'outforce' the proximal pronatory forces to position the tib ant tendon in a position able to exert supinatory moments (re to stj) at heel lift? toe-off?...