Bimanual activities that require a prosthetic arm (one with industrial qualities) often times evade the prosthetist, the societal arm chair citizen, the academic researchers, the media makers that "use" amputees as stereotypes, in many aspects - one risks to overlook the simple glory, the sunshine that goes with doing it, the hardness of it, the pride. And the fact that it requires putting one's mind to something that is not just as self understood as it may appear.
What seems to be never considered is the fact that I really need a prosthetic arm for actual bimanual activities. It is for these situations where there is a need to work two-handedly, where a prosthetic arm attains a deeper relevance and importance. And it is not just me, that as a need there, actually. That is the type of stuff one generally needs a prosthetic arm for. Those activities are the ones where insurances usually tend to agree to pay for a prosthetic arm - a prosthetic arm that works through these tasks, mind you: hard work, repetitive work, two hands required, very hot, very cold, dangerous. Leaving the amputee totally intact, by the way.
Operating a hedge cutter is just not possible, safe, or easy with just one hand. In other words, we talk about real work. And no, you cannot "just put your mind to it". Sure with a small tiny clipper you can approximate the sound and feel - but with 2-3 kg and overhead work with a long powerful cutter, one-handed is a big risk, and operating the switch together with directing the blade is very hard.
That, as opposed to drinking coffee, reading news paper, just going for lunch with a food tray, cutting pizza or meat, shopping with bags or baskets, tying shoe laces, talk past a Bialetti when making remarks about "making coffee", opening a fridge, wearing correctly sized trousers, walking a dog, drinking alcohol, or such - all of these work with a Becker hand, with a passive arm, with a hook or without prosthesis quite well, too.
Not, like, hedge cutting. This requires, like, a real prosthetic arm. It cannot be done without prosthetic arm, with a passive arm, with the "bionic" stuff (their control paradigm is just not safe for that type of work), certainly not with "3d printed" gadgetry that risks to scratch up your stump in no time. I talk about reliability, comfort, overuse, asymmetry, grip function, the stuff that hopefully, my real sustainable living future is made of.
To show what is required, or done, with a prosthetic arm in 2015, I cut the outer and inner perimeter of my hedges in the early afternoon of what turned out to be the hottest day in July in Switzerland since a long time, at over 37 deg C, using a Bosch AHS 55-16 (2,7kg) 450W electric cutter and a super tweaked body powered prosthetic arm with a Hosmer model 6 (back lock containing) work hook. The work contains overhead as well as low down feet height cutting.
There is really not a lot of servicing required to work through the afternoon. I dried the arm half ways through the work. That was it. Wearing a tubular gauze underneath the liner avoids friction rashes. I was wearing long trousers and shoes for protection, and a protective hat. Really, at these temperatures one sweats in streams no matter what.
Backlocking grip of Hosmer mod. 6 work hook
The Hosmer 6 work hook has a backlocking feature so it cannot open once pressure is applied to the claw. That means, the cutter is very safely held with it. Due to its handle design, the cutter may slide out sideways, but that can be controlled and prevented a lot easier as this is easier to stop or deal with than an unplanned opening of the hook.
Stump after this task looks FAR better than after wearing a "bionic" arm for a bit of office work
People assume that body powered arms with hooks are "painful to wear", that stumps cannot bear these as they are "outdated", and whatnot. Really, that does not stand the test of reality here. Actually, the truth is totally reverse. Worse, I knew that since a long time : )
While my stump was out of order after a bit of "office work" with a "bionic" arm (which logically makes anyone less human that demands that I wear it and use it, really) (yes that'd be the Voight-Kampff test that you would fail) my stump is in a mostly pristine condition (although a bit soggy) after this task was completed; certainly (photos below), there is no rash, there is no pimple, no infection and no blister; in fact there is no actual relevant discoloration.
You know, people never listen when I talk about the importance of sockets, body powered arms and grip mechanics.
Alright, here are the achievements in a nutshell:
- I was totally soaked. It was the hottest day in July that I picked. 37 deg C at least if not more. And yet, I had full control over my prosthetic arm no matter how sweaty I was. All the time. I had full and very fast control. When operating machines that cut, you want full control, and you want fast control. Maybe.
- The grip was reliable. Reliable!
- The suspension was reliable. Reliable!
- My stump survived the garden works in a pristine condition.
- The prosthetic arm suffered not the mildest damage.
Consumables: 2L water, 1L ice cold Calanda Radler 0,0 (alcohol free), work glove Wonder Grip Thermo Plus Latex WG 338. Prosthesis with design by both me and Balgrist Tec, built by me and Balgrist Tec; containing Puppchen wrist, patented cable sheath setup, specialized shoulder anchor, Hosmer work hook model 6, Ossur Icelock pinlock, Ohio Willowwood Alpha gel liner, Molynlycke tubular gauze (size indicator with a green stripe) worn under liner to avoid friction rash.