Silicone and stiffness

Karl Montan

Regard. partial foot amputation

Karl:

I am a partial foot amputee (Lisfranc) in Sweden with a long

experience as service consumer and have had this dialogue with

Michael in Germany. If you are involved in these problems and want to

join the discussion, you are welcome to me or

Michael Maier <"maier.ortho"@t-online.de >

http://home.t-online.de/home/maier.ortho/

Michael:

I am born in 1964, my profession is orthopedic shoe-technician, which

is an indepentent working area here in Germany (indepentend from the

orthopedic technicians)

I have, together with my father, a workshop here in Karlsruhe, 140 km

south of Frankfurt. Our working areas are all kind of foot ortheses,

orthopaedic shoes, insoles.

Karl:

For the moment I will only mention one question.

I have – as one of the very few in the Scandinavian countries – tried

to use a siliconprostheses for my Lisfrancstump. It was just a

siliconfoot put on my stump without any other applications. It was

not bad but as I since some years have a thight and stiff prostheses

with a supporting splint on the front of the leg, which

is acceptable and never gives soars, I prefer this old one. The

prostheses I thus am used to, takes up a lot of pressure through the

splint.

It has surprised me that in literature and contacts with friends

outside the Nordic countries, it seems as the siliconprosthesis are

very common and also appreciated. How is it in Germany ? Do you have

any experience ?

Michael:

In my opinion silicon feet are too soft. It has the full forces on the

front part of the foot stump. We use normaly a modified type of the

ortheses you wear.

That means, we use also an supporting splint on the leg, but in

different lengths and different stiffness. It depends from the

amputee, if he is very active and, of course, of his weight. The

splint itself is build up in a sandwich technologie, with glas fibre

or thermoplastic material. So we can transfer the load up to the leg

and release the footstump in the front part, without giving an

uncomfortable feeling of pressure to the leg. The forefoot is

made out of soft material, which gives more comfort and makes a

dynamic walking

possible.

We could not reach all this mechanical effects with an simple silikon

foot.

There might be people who find them sufficent, but I prefer the other

kind of ortheses.

Karl:

. Are you speaking about a silicon foot with supporting splint ?

Michael:

No, we are using two types of foot prosthesis. One is made of a

polyethylen foam, with little weight and flexible for very active

persons. Another is made of cork and one layer of flexible rubber,

which gives a feeling of more stability than the foam

foot for the fore foot amputee. Silicon has more weight and is much

more expensive.

Karl:

In Sweden we have tried to find a compromise between a quite stiff

splint, which don´t allow any movement of the ankle joint, and an

insert

without supporting splint and full movement of the joint. Experiments

are going on with some disappointments.

When you mention the stiffness of the supporting splint, I have the

impression that you are able to vary the stiffness, which may give

more or less of ankle movment. If so, don´t you have difficulties

with breaks in the material which is bending for every step ?

Michael:

Yes, that was a big problem. The normal materials like polypropylen or

polyethylen will break very fast. We have tested a special durable

elastic thermoplast, which does not break under load. With this

material we get only a half stiffened ankel joint. It is a

thermoplast which is very flexible and with a melting point around 90

degree celsius, which is much lower than the normal used thermoplasts.

We use it for longer fore foot stumps, up to the Lisfranc

line. For shorter stumps it depends, if the stump can bear the higher

load compared to a normal stiffened ortheses. We use this material

since about 3 years, and up to now we have very good experiences.

These orthesis are much more comfortable than the totaly stiffened.

 

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