I currently wear a very soft but conventional silicone shoulder harness.
Due to some anatomical reason that I cannot change, the harness now started to cause problems by pressing onto my brachial plexus. It has come to the point where two out of three nerves of my ('sound') left hand are (slightly but measurably) damaged and to start with, the harness design needs to address that. The damage will likely be reversible, but pressure has to be relieved permanently away from the anterior axillary fold.
We are now attempting to redesign the harness. While this is work in progress and while I will surely share the final result of our current practical developments, I would like to know what other/existing shoulder harness systems are there that avoid or minimize pressurizing brachial plexus branches and axillar vessels?
Wolf - sorry I seemed to have missed this. I have a solution posted here that I like very much. The friction of the webbing and shirt against the skin is enough to hold, and it doesn't apply axillary pressure at all. A more recent modification that I have made is to use lightweight ripstop nylon, which almost feels like it is not there and works just as well. I'll post some more pics after my next iteration.
Hi Wolf or anyone interested really.
I realise this is a little late for a response but I have only recently discovered Open Prosthetics.
I seem to have exactly the same problem as you had and would love to know how you are getting on. I have, as near as, stopped wearing my prosthetic arm until my good arm recovers. I am an above elbow amputee.
I have some thoughts though on how I might overcome my problem when/if the good arm recovers. Please excuse the possible naivety of some of these suggestions but it seems we are in the Dark Ages here in the UK. Here we have only “conventional webbing” that crumples up into the formation of cheese wire and it hurts. Sorry I digress. Here goes:
Any reduction in weight is an advantage I find. Use child’s terminal device, shorten forearm as much as possible. (This also leads to more control). Drill holes in prosthetic. (Minimal but hey every little helps.)
Change load bearing nature of harness as has been suggested. This sounds really promising. I very much hope to hear how you get on. I did try a chest harness once but well …. anyway.
Lastly increase padding and area bearing weight. I would love to see “conventional silicone shoulder harness.” Genuine request if anyone can point me in the right direction of a picture/diagram I’d much appreciate it. I rigged up something made out of an old silicone liner, which helped but there was room for improvement.
We tried conventional silicone, we tried also anatomically shaped silicone. From 5kg + load / cable pull they ALL crumpled up though.
Currently I am not wearing my prosthetic as I am getting a totally new socket and liner, all manually custom fitted with some new stuff. As that is a very experimental build, the generations of tests / test sockets are numerous and total build time is long. In other words, I had a first custom liner and socket and despite the socket breaking after 4 days it was enough to generate a problem list of say 6 items or so to improve. So currently an improved socket is in the works but won't be ready until in about 2 weeks time due to many technical issues : ) will photograph and document once ready though.
Inasmuch as cable / harness is concerned, we developed a new shoulder mount with a range of materials. Once I get all my stuff back for keeps I'll sit down and write up the documentation. As always there are advantages and problems and depending on how you go about it it is heaven, hell or something in between. If anything that shoulder mount item is comfortable and allows for virtually unlimited cable pull weights. With that, other parts start to top the list of the "most fragile item on the arm" ; ) \
Sorry for my delay in replying. I have no email at home, only in work and I’ve been away on Easter break. I assume that your good arm is recovering, as you are considering getting a new limb soon. I am very pleased to hear this, well done! This gives me hope with my nerve damaged arm. The nerve damage I have is in the upper arm/shoulder as well as the hand.
I understand, what seems like the never ending treadmill of test sockets, sockets and fittings. I need to mention here Swansea artificial limb and appliance centre in South Wales U.K. Who after 35 visits were still unable to supply a standard limb that fitted and worked as it should. They were truly outstanding in their incompetence and inexperience. Mostly I’ve had the hell with artificial limbs. On the plus side though I now have huge experience of how NOT to build a successful limb.
I am looking forward to learn of any progress you can make. I think we’re at crossed purposes though with the use of silicone. I’m talking about simply using it as a pad to spread the load on harness pressure points, which I’ve found very successful. It seems you are experimenting on using it as a socket. Sounds very interesting. The crumpling I had was with the harness strapping, particularly under the armpit, becoming like a cheese wire. I have never seen what you refer to as “normal silicone padding” but that too sounds very interesting.
You say that due to “anatomical reasons” the harness caused problems with your nerves. Don’t know if I’m opening a can of worms here but in my case I believe that a major factor for my nerve damage has been harness pressure points. One health service professional hinted at “badly fitting limbs.” What I can say for sure is that since hugely reducing the time spent wearing a limb my good arm is slowly showing signs of recovery. I have also heard anecdotally of several upper limb users who have “problems” with their remaining real limb. Anyone got any thoughts?
Thanks for your time and input.
Thing is that after examining my axillary anatomy in my left shoulder there are exactly two reasons for compression - one is a bone shape of the acromial bone that extends like a spur with the effect that long drawn out and extensive stretching, extension, of my left arm at the shoulder will compress the brachial plexus. I find that to be the case when I swim or ride a bike, and doing that, I stretch that arm. Then after 15 to 30 mins my left hand starts to go numb. Second problem is the conventional harness. The problem was slightly but not perfectly improved by just soaking the strap in silicone hence getting it padded that way. But now with the new build the problem is almost gone.
Still the test socket / liner parts are work in progress. The last model was so narrow it still hurt after putting it on, and it hurt for over 2 hours without getting much better. That means they will now make the third attempt at liner / socket.
Will report once there is a sustainable solution : )
Sorry to hear about your shoulder problems. It seems pretty certain that your problems are not due to "badly fitting harnesses" as I suspect mine are.
I wish you well with your next liner/socket fitting.
Very interesting what you say about "soaking the strap in silicone"
Could you tell me where or in what context I might find/buy liquid silicone?
This could be a great help to me.
Thank you very much John.
Lots of food for thought there. More webbing width means less pressure. My point exactly. Your point of less slip too is interesting. My mind is jumping towards "spider bungees". A product that is readily available but would take your idea of the "individual threads" part of the way fairly easily.
I shall be taking these ideas along to my prosthetist when my good arm recovers.