Here’s a modified version of the Alpha (mine is a 9mm with pin and I am a
RBK 7″) I have been using for several months and have come to prefer it
for all nonathletic activities. First some background.
When I first got into ICEROSS 3 years ago, my prosty whacked one of my
liners off about 4″ above the pin without even asking me about it. After
all that careful fitting, the loss of the thickness of the liner about
the condyles really screwed up the fit. The new ICEROSS still sits in my
drawer unused. I prefer the feeling of the long liner anyway, as knee
support and suspension are improved for some of the more rigorous
activities I engage in.
I have been using a 9mm Alpha for several years (I love `em) in that same
socket designed for ICEROSS and 3-ply sock. There is compression, yes,
and I sometimes pump up the gastroc worse than I would otherwise at the
beginning of walking, running, etc. I pump up no matter what, but it was
worse having all that extra material in there. Overall comfort and fit
was greatly improved by the Alpha, even though the socket was not
designed for it…a good design in the liner for sure.
Anyway, I had an Alpha around that had worn through just above the knee.
I was a bad boy and did not wear a sheath over the liner and it
eventually wore through. I shelved it. Thinking I could relieve
pressure on the gastroc and get more use out of the liner, I cut it way
down in the back to 3″ above the pin, then cut straight up the sides and
up just below the anterio-medo-lateral trim lines of the socket (I use
mid-patellar, and non-suspending supra condular trim lines). The liner
if cut that way, with the proximal edges being a full 7″ below the lowest
part of the cut, will open up like a flower due to the tension of the
fabric. This is not a problem when wearing it, especially if the liner
is donned with a nylon sheath.
At first, it felt weird having no knee brace effect that a long liner
gives, but after habituating that, I came to like that shorty liner a
lot, and wear it all the time now when I am not engaged in athletics. I
even ran in it for a while. Running was OK until I sweated a lot and
lost suspension. The Alpha is relatively thin in the back, but
lusciously thick where it counts. By not cutting below the tibial
condyles, I did not severely affect socket fit, as whacking the liner off
square down low does. I tried that and made one of my old liners totally
useless.
My wife and I ride road motorcycles quite a bit (his and hers). The
low-cut liner has been a huge benefit for that application, as I can bend
my knee back to 120 degrees of flexion with no spring back effect and the
discomfort of bunching. Note also that the posterior trim line on my
socket is not “text book” but follows the anatomy very closely during
flexion. The medial hamstring cutout is radically low, and the socket
actually rises between the tendons. There is no shelf at all. The
appearance is so odd I once had a Japanese prosthetist feeling on my leg
at that point and oohing at a show. They don’t apparently have a problem
touching people without their permission behind their backs! Funny how
cultures differ…. Anyway.
I offer this successful experiment to file away in your solution pools.
If your Alphas are failing in the fabric above the socket or right at the
proximal brim, this is a way to get much more life from them and/or
broaden application. The Alpha tends to blow out if the fabric wears
through. On mine, the blowouts – when they happen – occur just at the
anterio-medial trim line where reaction forces are high and much bending
occurs. My short liner has shown no further sign of wear in months. I
definitely still wear the full-length liner still for running and
racquetball, fro example. Better suspension, it protects the knee, and
offer a bit of psychological sense of security.
I’m veryhappy to have stumbled upon thus. Hope it helps someone out
there too.
Chris (CJ) Johnson
Director of Engineering,
College Park Industries, Inc. http://www.college-park.com
(810) 294-7950 (at CPI), (616) 664-4173 (home office)
