Responses to Thermoplastic AK

Responses to Thermoplastic AK

Randy Duncan

9/14/2007

Thanks to all who responded. I have convinced the pt that a carbon outer
frame is the better way to go. I will use a grace plate for my distal
attachment, drill through the threads and use cap screws down into the knee
frame. His primary concern was for the weight of the prosthesis. His
current prosthesis was fabricated very heavy, seems to be a standard nyglass
layup and a carbon layup too. I assured him a carbon frame could be
constructed that would be as light as a polypro frame. Again, thanks to all
who responded.
 
Randy Duncan, CPO
----------------------------------------------------------------------------
----------------------------------------------------------------------------
----------------------------------------------------------------------------
----------------------------------------------------------------------------
-
2. grace plate. no, you won't be able to adjust it in the final product,
but you'll be able to attach all kinds of slide adaptors to 4hole in the
test socket, to get it perfect in the final product, and it's the lowest
clearance possible. as far as i know, lowered knee center does not matter in
test socket for alignment purposes. actually, we did a lot pf thermoplastic
sockets at dillard's o and p in nashville. trick was to install a pelite
distal end pad, then grind it flat to create a platform for grace plate. i
think bulldog has stainles steel graceplates.
chuck dillard really liked all kinds of plastic sockets, obvious why. more
i think about it, more i'm positive i just plastered grace plates on the
distal end, but chuck's way was to create pelite pad and shave it distally
to make a platform for graceplate.
endolite has mercury knee, which is mauch, and pyramid rotates/slides/ plus
you have angular change in it. might be an option.
 
1. you can either pull a thick polypro, i'd drape it for safety reasons, or
shoot for one of the unbreakable plastics from daw or ottobock.
i have only limited experience with them, remember they were finecky to
handle.
----------------------------------------------------------------------------
----------------------------------------------------------------------------
----------------------------------------------------------------------------
----------------------------------------------------------------------------
You should have no problems with the thermoplastic porvideded you use a
thick enough piece. I would start with at least a 1/2 inch. The attachment
piece is of your choice with in wieght limits. Take it slow and think it
through. It will work.
----------------------------------------------------------------------------
----------------------------------------------------------------------------
--------------------------------------------------
Build a light,(much stronger than polypro) carbon frame. Laminate in or
simply build in a void for your attachment choice.

At 280lbs fatigue could be an issue-danger for polypro. My opinion my
experience.

----------------------------------------------------------------------------
----------------------------------------------------------------------------
----------------------------------------------------------------------------
--------------------------------------------------------------------------

Yes it can be done but have him sign a waiver of knowing it may break.

You need to look at his old one, and place struts in the isheal containment
area one between posterior and lateral.

----------------------------------------------------------------------------
----------------------------------------------------------------------------
----------------------------------------------------------------------------
-------------------------------------------------------------------------

I've made lots of thermoplastic TF sockets out of Poly Hi Solidur white
pigment modified Polypropylene. It's very strong, stiff and tough, but for
someone this size I'd expect you'd need a 15mm sheet, which when blister
formed would result in a finished wall thickness of 5-7mm (prox to distal).

The end, or coupler area can be reinforced with an additional layer of same
material heat welded on at time of molding.

As far as the coupler question, make sure your AP and ML position are good
and then you can adjust any tilt by grinding the thick flat distal end of
the socket frame. I've mounted 4 hole couplers direct with bolts, washers
and a 4 hole spacer plate, but not for someone of this size. Try Bulldog
components for parts.

----------------------------------------------------------------------------
----------------------------------------------------------------------------
----------------------------------------------------------------------------
----------------------------------------------------------------------------
--

I personally would not do a plastic frame on a patient of that weight. If
you do, make sure and have him sign some type of liability release. you
might want to call some plastic companies and ask there advice. You are the
proffesional and have some responsibilty no matter what he signs. You would
be better to lose the leg than lose your credentials. Try explaining the
benefits of the strength (extra beefy) and weight of a carbon fiber socket.

----------------------------------------------------------------------------
----------------------------------------------------------------------------
---------------------------------------------------