Re: Posterior knee in 3-S B.K.s

Re: Posterior knee in 3-S B.K.s

Chris L Johnson

10/4/1997

On Thu, 2 Oct 1997 11:04:19 -0700 ecat < <Email Address Redacted> > writes:
>Many of my 3-S BK's have the perennial problem of discomfort and
>occasional
>skin breakdown at the posterior brim of the socket and/or liner
>(Fillauer
>or ALPS). I believe that the hamstring channels are modified to
>provide
>enough relief, because this problem does not occur with cuff
>suspension
>types from this clinic. It seems isolated to triple-S pattern
>sockets.
>Does anyone have any answers or suggestions to this problem?
>Richard Ziegeler
>E.C.A.T
> <Email Address Redacted>
>

Some direct experience tips on 3S liners and other thotz:

When I use vasoline before donning (a thin film on my limb) I can almost
completely eliminate this problem. Another precautionary measure that
works well is to reflect back the posterior rim of the liner if one is
going to be sitting a lot during the day - and therefore putting pressure
on - the proximal/posterior edge. Another trick is I take my leg off
when I drive (I have full-length zippers in every pair of long pants),
and if I have sweated a lot, I reflect back the liner to below the knee
to dry out the interface. Yet another is washing the liner every few
days. For silicone liners, I use the dishwasher. Yup, throw `em in with
the dishes! For the Alpha, which I now wear and won't part with because
the feel of the thing is vastly superior to silicone, I shower it when I
shower myself.

My socket has truly anotomical shape in the posterior brim. My medial
ham string is really low on the tibia. The socket shape is so different
looking I get a lot of questions at the shows. I find it so odd that so
many sockets are made with what I call text-book trim lines. The
socket is anotomically matched. Why not the posterior brim?

This does not seem to have an effect on break down. I have therefore
concluded traction is not the primary cause. I think is skin exhudates
(metabolites), combining with oxygen or something else, at or near the
proximal brim. Vasoline creates a barrier that slows this process
drastically.

I was using mineral oil for a while on advice of OWW because they said
Vasoline is not good for the material Alpha is made of. When I used a
small amount of mineral oil the effect was so so. When I used a lot, I
discovered why people sometimes complain about the distal end of the
liner pulling hard on the end of the residuum. If you use a low
viscocity lubricant in higher quantities, the liner will slide on the
residuum and place a great amount of negative pressure on the end of the
residuum! I have wondered if rejections of 3S-type liners may be due in
some cases to this effect.

The conclusion I have come to is that Vasoline is a superior agent on the
Alpha as well, because of the higher tack a thin film lends (better
suspension and no slide). I have found whatever damage Vasoline may do
to the material is not evident over the normal life of a liner when
normal is considered 6 months. So far the Vasoline has not done anything
to my longest lived liner (8 months).

I have not tried anything else and am open to suggestions.

For context my current specs are:

Very high activity level 8 RBK with symmetric gait.

A see-through thin carbon-glass-acrylic laminate (for 2 years...Stakosa
made).

Non-suspending supra-condular medial and lateral flares for stability.

Mid-patellar trim line for more force bearing surface and no pressure
sores (ever!).

Anatomical posterior trim line.

9mm Uniform Alpha liner left full length.

Prefer some other shuttle lock than I have. I'd like to try Century 22
smooth pin.

Endoskeletal 30mm format with Ortho Europe components.

No cosmesis other than techie look of components.

College Park foot (since Jan. `95).



Chris Johnson
Director of Engineering,
College Park Industries, Inc.
(810) 294-7950 (at CPI), (616) 664-4173 (home office)
<Email Address Redacted>