Flexible sockets

Flexible sockets

Molly Pitcher

8/9/1998

Dear O&P List
Here is my original message with the replies. Thank you for your help.

What are preferences regarding flexible inner sockets for a
trans-femoral prosthesis? I am considering using PE but am concerned
about shrinkage. My patient has been using a suralyn 1/4 draped molded

check socket now for several months. The finished product will be
bubbled molded with a carbon frame(no cutouts). Am looking for a
flexible proximal edge. Thank you for your suggestions. Molly Pitcher
CPO
Molly - I routinely use suryln, 1/4 x 20 x 20 bubble molded. I put

that in quotes because the technique is a little different. Heat the
surlyn
on the teflon, pick up the corners (two man pull) flip smooth side down
and
lower the center of the sheet onto the distal end of the mold. Pull the

sides and corners down (not out!) until the mold is covered. Your
distal
end will be nearly 1/4 the sidewalls about 1/8 and the brim about
3/16'.
It rarely cracks, is dimensionally stable and puts the flexibility where
you
want it. Call me if you have questions.

517-784-1142

 Have a great solution for you. There are newer plastics that are
better than PE, or surlyn. DAW and USMC have an elasomer type of
plastic. The cons, is very flexible, and post fab adjustable to a
degree. I have reduced, and enlarged the proximal brim areas with
heat and compressing or stretching the material to get the desired
effect. I have not notice hardly any shrinkage. You can also get fab
recommendations from the manufacturer. Suction is great also. Valve, try

the centri valve. Clean finish and can connect the frame to inner
socket.
        Jeff

How about Bio-elastic or Pro-flex? Both are very flexible and you can
thin
them on the trautman to make them especially flexible at the proximal
brim.
 Bio-elastic edges are easily rolled with a little heating as well.
I have used lInear PE several times and no longer will. With linear,
shrinkage was not an issue, but we eventually had rolled, and
eventually,
cracked edges. They just don't seem to last. In a thickness provide
enough flexibilty, it just doesn't seem to have enough ability to return

to it's formed shape.

Our CPO suggests Otto Bock Thermalyn Soft.....hope this is
helpul.....would
also appreciate your checking us out at www.espllc.com......we
manufacture
AEGIS & AEGIS Z, the softest silicone interface for BK's. Thanks in
advance! Janet, ESP Sales

There are several options that I would consider superior to standard PE.

American Plastics has a product that I believe is called Semi-flex.
USMC has
a product that I believe is called Bio-Elastic and Fillaurer has a
plastic
that has a silicone additive, I don't know the name.

Hope this helps,
Jack Uellendahl, CPO
Northvane from Northsea plastics
Distributed by Endolite in Ohio
USMC has a similar product but more expensive.
Lots of others out there but Northvane has a reputation for not
stretching out
if you cut out windows in your socket.
-Mark Benveniste

It's been my experience, although short, that we use bioelastic, a
silicone
base, flexible plastic.

Flexible sockets are vastly superior at reducing shear stresses for
gradients especially around socket brims (ask David Jendrzejczyk, he
once
said he would rather fight than switch back!!!) As for fabrication I
would
stay away from polyethylene. Try something like DuraFlex Plus from Guard

Industries (314) 534-6952, or American Flexilene from American Plastics,

watch shrinkage though by letting the socket sit on the cast after
molding
for a couple of days. We are investigating changes in material
properties
and ways of preventing them by annealing, etc. to prevent or minimize
things like shrinkage and stress/strain hardening from vacuum forming
and
subsequent thermal diffusivity gradients, etc. Hopefully we will have
some
recommendations in several months (baring research funding interruptions
by
the VA RR&DS prosthetics peer review board which doesn't seem to think
this
type of research is important or has any clinical relevance).

Vern Houston

I have tried lots of different materials, and so far the one that has
work the best is BioSkin from USMC. I've used it with or without
cutouts,
it holds its molded shape, is easy to work with. I have not had any
tears
or rips and sockets seem to last forever.

Steve Childs

Try Thermo-flex from SPS or any type similar to that. All Companies
carry it
or something close to it. Hope this helps.

We have had excellent results using American Plastics' SemiFlex (aka
bioElastic plastic). We gave up using PE long ago due to shrinkage
and it
really isn't all that flexible.

My patient has been using a suralyn 1/4 draped molded
check socket now for several months.
Surlyn cold flows and if a scratch occurs it will eventually fail along
the
scratch.

The finished product will be bubbled molded with a carbon frame (no
cutouts).
Am looking for a flexible proximal edge. >>

You did not specify what style socket--Quad-ish or ischial
containment-ish???

Why have a flexible socket if you don't let it flex? (A flexible socket

surrounded by a frame is still hard...) All of our flexFrame sockets
are cut
out in the posterior and windowed in the anterior. This is extremely
comfortable--cooler that standard design; allows the muscles to expand
as you
walk; allows the socket to collapse when sitting making that activity
more
comfortable as well. Just make sure the plastic is at least 3/16 thick
over
the medial ischial support (if ischial containment-ish) and has a frame
strut up over it for support.

I wear one of these myself and wouldn't go back to a hard socket.

JTA

I've recently been using Bioflex from USMC. I think it is a mix of
silicone
and ethylene (according to a prosthetist from OSSUR). Have had good
results.

Tom Padilla, C.P.O.