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Hi all,

I have a pt who has PTTD. She has been prescribed orthotics in the past made of a 3mm polyprop. material which she has flattened out over a 12 month period. This has happened three times. They just don't withstand the pt's weight+pronation........i have read Kevin kirbys article re: Conservative Rx of PTTD.......and have followed all treatment steps....however, would like to know if a carbon fibre device would be more appropriate than a 5mm polyprop device??????? Would the carbon fibre device make things worse?

Thanks in advance to all,

FD

If the force causing the pronation is high, then the orthotics has to resist that force with an equal or greater amount - the choice of material has to resist that pronatory force; sounds as though it going to have to be 5mm polypro or a thicker carbon fibre - dosen't matter which one.

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Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia
http://www.latrobe.edu.au/podiatry
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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
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Thanks for the advice and reply, Craig

Just to clarify...............you mean that the carbon fibre device would have to be thicker than 5mm?

Im thinking i'll go ahead with 5mm polyprop...........because the thickest carbon fibre that the lab here has is 3mm.

Thanks again,

FD

Or just make it shank dependabt!

EVA is good, or just void fill the poly. You'd be amazed how much extra resistance you get just by void filling with something as simple as poron.

Don't get too focussed on shells. There is a world of other options out there!

Regards
Robert

Same advice as Robert, go for EVA orthoses medium to high density. I use it for almost all PTD cases and I can't remember any that have not resolved in terms of pain reduction. How heavy is your patient BTW, I've never had a device flattened before whether shell or shank dependant (eva) type and some of my patients have been getting on for 25 stone / 160kg / 350lb. When you say "flattened over a period of 12 months" Do you mean permanent plastic deformation of the shell?? Even if a shell is flattened while load bearing (elastic deformation) it does not mean to say that it is not significantly reducing the post tib load. Is it just a problem of flattened shells or is there also no resolution of symptoms.

Tell us more about the prescription design of your orthoses for this patient.

Carbon fibre is just a stiffer material than polyprop i.e. it has less deformation per unit force for the same cross sectional area or second moment of area where bending moments are applied. Using carbon fibre would mean that you can use the same thickness of material eg 3mm but have a stiffer shell that is less likely to bend flat. Second moment of area means that if you add a corrugation for instance, the same material is stiffer even tho it has the same cross sectional area of material. So adding a plantar fascia groove to a shell and / or increasing the flange height might make it less likely to bend flat.


Cheers Dave Smith

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Hi David and Robert,

Thank you both for your suggestions............great advice.

To let you know more about the pt.........Well, i suspect that this pt has had PTTD for some time. She reports that she has had these symptoms for over 7-10 years and her feet have progressively been getting "flatter". Following my Hx and Ax it was clear that she was suffering PTTD.
However, over the past 7-10 years her treatment revolved around orthotics alone (as i understood it from the pt). Three pairs of 3mm polyprop devices were precribed over the span of 7-10 years by another Podiatrist. And all three pairs flattened out within a 12 month period (permanent plastic deformation of the shell). The pt presented to me about 2 weeks ago.

So my Rx plan for this Pt (and i would estimate her weight to be about 100kg) is as follows;

• Icing
• Topical anti-inflam medication
• Gastroc+soleal stretching
• Hiking boot (supportive, leather upper, lace up etc)
• Orthotics
• Physio 3 weeks after issue of the devices (Strengthening program)

The orthotics have been designed as follows;

-Standard/Mod root device
-5 degrees inversion balance position
-5mm medial heel skive
-18-20mm heel cup height
-heel post
- Shell material and thickness undecided at this point

The Rx is outlined in Kevin Kirby's Conservative Rx of PTTD.

Hope this helps and thanks again for all the advice. Look forward to further suggestions.
Cheers,

FD

As Dave noted carbon fibre is stiffer than poly-prop, so a 5mm carbon fibre device will be stiffer than a 5mm polyprop device which will be stiffer than a 5mm polyethylene device etc. when formed to the same shape. So theoretical you can use a thinner carbon fibre shell and get the same stiffness. The problem I have found with carbon fibre is that it tends to crack and that crack propagates. This will be just distal to the rearfoot post.

In addition to those points already discussed by "me colleagues", you can stiffen up any orthoses by reducing the span distance, that is the distance between the posterior and anterior contact areas of the device. So you can use a relatively thinner polyprop shell but by using a longer rearfoot post you effectively shorten the span distance and therefore stiffen the shell; you can completely fill it if you want- hence "me colleagues" referring to an EVA device that is "shank dependent" (still hate that term, Kevin) and Robert talking about void filling. However, in my opinion the trick is to differentially stiffen the device in the area you want. Personally, I wouldn't completely fill the arch segment, in the kind of case you describe I use an internal oblique rearfoot post design as this shifts the CoP more medially than a standard "square-cut" rearfoot post (see paper attached). Also, I tend not to use Kevin's depth measurement of medial heel skive, but rather use skives in degrees, so you may need to use a skive > 15 degrees (I don't like to go too much over 20, but I have had patients complete marathons in 20 degree medial heel skives + motion control trainers (it feels great Dr Spooner = nutters!); if you use depth as a guide and cut too deep you narrow the heel seat. If that doesn't work- go for a supra-malleolar device.

BTW, are you sure the PT tendon is intact?

What about spring ligament, is this intact- too many toes sign -a high lateral flange may help with this.

Attached Files

Spooner RF Posting CoP.pdf (164.1 KB, 43 views)

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After-thought, as its summer some patients can't get on with walking boot's- if so, go for a motion control trainer- Saucony stabil is one of my favourites. Also (something rarely discussed here) footwear modifications such Thomas heel; medial flare.

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My location

Thanks for the help, Simon....and for the pdf, cheers.

I requested x-rays and u/sounds of both feet (as both feet are affected) to investigate the likelihood of PT tendon tear/rupture and it turned out that both L and R are intact. However, there is signigficant tendinopathy involving both.....Right worse than the Left. Too many toes sign was also present.

It's interesting that you should mention the spring lig............and it didn't even occur to me until you mentioned it now (and hence did not request it be part of the u/sound investigation), but the u/sound results of the R foot revealed a "loose body" of some sort just beneath the medial malleolus................ i was unsure of what this might be, so am planning on referring the pt to her GP for further investigation via MRI. Is it possible that this could be a ruptured spring lig?

Look forward to further input....and thanks again for your help,

FD

In addition to Simon's excellent suggestion, there are some other quality shoes to consider. These all have similar build characteristics, but are made on varying last shapes: Brooks Addiction 8/Beast/Ariel, Asics Gel Evolution/Foundation, New Balance 1123, Aetrex Lenex (now called the Boss and Reina ... why???), Montrail Hardrock, and the Etonic Stabil Pro. There are others, but these are the most consistently made and credibly designed.

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Jeremy Long C Ped
Smoky Mountain Foot Clinic

The question of orthosis material has been covered well by David, Robert and Simon. If the orthosis has actually "flattened" in 12 months, then you have not chosen your orthosis materials appropriately. I would use a polypropylene versus a laminate (e.g. carbon fiber) shell since polypropylene can be easily modified with a grinder.

When treating posterior tibial dysfunction (PTD), I will tend to always use at least a 5 mm thick polypropylene shell which can also be reinforced in the plantar medial arch with a filler material, as others have mentioned. I prefer using a relatively stiff orthosis shell with a rearfoot post that will not flatten significantly when the patient is standing and walking on it. I described the Orthosis Deformation Test over 11 years ago as a means to clinically approximate the amount of orthosis deformation that occurs during walking (Kirby KA: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 157-158).

Regarding shoes, in more severe cases of PTD, low cut shoes simply do not offer enough support superior to the subtalar joint (STJ) to give the patient good mechanical control of their pathological pronation, even with the best orthosis. I will tell these patients to wear their orthosis in a high top shoe/boot as much as possible, in order to increase their mobility and decrease their symptoms. Also, since I wrote my newsletters and paper on PT dysfunction treatment from nine years ago (Kirby KA: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 99-106; Kirby KA: Conservative treatment of posterior tibial dysfunction. Podiatry Management, 19:73-82, 2000.), I now also recommend to many patient to try using an ankle sleeve with their foot orthoses which also seems to reduce ankle edema and ankle/foot pain.

The thinner ankle sleeves do not seem to be a problem in the arch with the orthoses and many patients with PTD seem to do very well with them. The ankle sleeves probably function by reducing the tensile stress within the plantar ligaments in the midfoot that are under greater tensile stress than normal due to plastic deformation of the PT tendon and spring ligament complex that typically occur with PTD.

Icing therapy is also extremely important as well as emphasizing to the patient that they not walk barefoot, should not walk in non-supportive sandals/flats, should always wear some form of orthosis any time the feet are on the ground, should be doing PT strengthening exercises daily and should try to walk in shoes/boots with higher heel height differential than flat shoes, if possible.

Effective conservative treatment of PTD requires more than just a foot orthosis with a medial heel skive; it requires a multi-pronged approach if the clinician wants to optimize the treatment results for their patients.

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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
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Voice: (916) 925-8111 Fax: (916) 925-8136
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Thanks for the advice Kevin,

Just to clear things up a bit. The pt was prescribed the orthotics by someone else..........infact, the whole time (past 7-10 years) she was being treated by someone else, whom i assume was trying to treat her problem with orthotics alone.
I have only come in contact with this pt in the past 2 weeks..........and am trying to treat the PTTD using everything you have suggested in your paper (Conservative Rx of PTTD.....), which i have found extremely helpful.

Thank you once again,

FD

without sounding terribly stupid, what do you mean by a 5 degrees inversion balance position?

Is this just a intrinsic balance done to the +ve cast?

thanks

Matt