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2010's "bionic" prostheses and why they fail

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - 2010's "bionic" prostheses and why they fail; published February 8, 2010, 11:19; URL: https://www.swisswuff.ch/tech/?p=282.

BibTeX: @MISC{schweitzer_wolf_1574153535, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - 2010's "bionic" prostheses and why they fail}}, month = {February},year = {2010}, url = {https://www.swisswuff.ch/tech/?p=282}}


[Find all articles about the Otto Bock Michelangelo hand]

We wonder why these very cool looking and beautifully designed "bionic" prostheses [BeBionic, iLimb, Michelangelo] remain cumbersome and why, as products, they just tank.

The mechanism why we must love them is neurological. Our brain is programmed to positively respond to certain triggers. We like shiney objects. We love 3D. And we sure love things that promise both. So it is clear why "boinic" hands are loved by engineers, tinkerers, media and the (non disabled or otherwise disabled) public alike: by virtue of the Mesmerized Bunny Effect.

They do not stand up to promise. And if previous clear indications keep getting ignored, I'll repeat them here. After all, upper extremity prostheses are rejected by 33% to 38% of those users that do participate in surveys - and that is a lot. Not counting these that areĀ disillusionedĀ and stop participating. That failure rate is so high, in fact, that we see it is an industry failing its clients through small time tinkering and greed, not an industry facing a daunting job.

If these prostheses actually were 'bionic', they would not just look like a movie prop. Instead, by being truly bionic, they would:

  1. Feel 'bionic' - that is, painless, seamlessly integrated, worrilessly angulated, stress free in grip control,
  2. Move 'bionic' - prosthetic parts move in a fluid and effortless motion together with existing joints rather than just doing simple grasp/ungrasp motion,
  3. Degrade and fail 'bionically' - that is, fail gracefully and gradually.

But in reality, 'bionic' used for such constructions is probably a straight plain lie. It is most likely founded in hyped up overadvertising and not at all in reality as particularly these myoelectric prosthetic arms:

  1. do not feel seamlessly integrated, worrilessly angulated and stress free in their grip control but quite the contrary: grip control is typically unreliable, elbow motion is heavily and painfully restricted, there is no wrist motion at all at my level of amputation, so the term 'bionic' has no bearing here;
  2. do not move in a fluid and effortless motion together with existing joints and residual extremities but in reality, they produce isolated uncoordinated motion that turn my elbow and shoulder muscles to painful hardwood;
  3. do not at all fail gracefully and gradually, but are alive one moment, dead next moment, grip hard one moment and let go the next; I never dropped as much stuff as when wearing the myo arm. These are embarassingly unreliable. I much rather go out without prosthesis.

If we look at the materials, make, design, care of build and other details of many commercially available parts, it is mind-bogglingly easy to understand: prosthetic arms are built rather affordably and then sold for huge amounts of money, and getting that money back as a client, or revising any technical decision - as a client - is next to impossible. Once insurance buys that prosthesis, money is gone.

It takes a simple user as me just about a year to figure that out - but so-called specialists have been playing pogo-pogo with the subject for decades. Absent wrist and restricted elbow motion due to a painful and hard to use socket - and then act 'surprised' that shoulders and back are overused and painful and hard when just touched gently? Obviously that type of outcome is common and in each and every instance it is very bad. Then what? More 'bionic' gadgets? Why insurances don't investigate this is beyond me. Can't they afford specialists?

Of course, amputees don't melt or go away. Were you thinking that? Long lasting disappointment is one outcome, another one is to not even showing up for studies no more. Yet another outcome is shoulder overuse due to poor fitting of the prosthetic parts into one's overall activity, and poor shoulder function is conversely associated with particularly poor prosthetic usage. A recent outcome is that amputees start to network and create their own activity to remedy the lack of cogent care by finding better representatives of support.

No, really we are dealing with an industry that is shooting itself into its own foot. In a major way. And it is necessary to address that in very clear terms.

When I tried my first myoelectric arm, I had a special socket made for testing purposes. It was very painful, I could not lift stuff, the hand was not reliable, the elbow could not be leaned upon. And all it all it was a particularly cumbersome experience so I read up in current medical literature. Also, I was surprised and asked other users.

  • A user of > 20 years of experience: "And everything you describe is how it was for me. The elbow was pushed inward to fit tight over my elbow, to help hold the thing on...yeah right! The tiniest bit of sweat and it would slide down and pinch my elbow bones to the point of pain. And so, besides the cost of the thing, that's why I don't wear anything anymore."
  • A user of > 50 years of experience: "I have not yet seen any myo that can out perform a body powered unit unless there is no residual limb left to work with. Particularly if it's bang for my own buck....there is no comparison. Just ask for a reference of a satisfied myo user with similar condition to yours. I'll bet you don't get one or if you do it will be disappointing. Also demand a gratis build if you find it too uncomfortable to use. I predict that there will be a lot of shuffling and maybees. 50 + years of experience here and nothing has changed but the costs."
  • Another user: "I have a myo electric arm and the not in control, I am finding out..(..) Just the slightest muscle movement its like the arm goes into a "fit"."

So, here is why these "bionic" hands tank.

They do not deliver intelligent control at all. Two electrodes are outdated technology. They simply are. You cannot get a hand to do complex grip or movement patterns if you stick to two electrodes. Yet, complex motion rather than stiff open/close robot type action is what a modern hand could and can achieve. For that, lots of information needs to be processed in an intelligent way. While that is available in computing as such, prosthetic manufacturers will withhold that from the users until they have made enough money with these "bionic" gadgets. However, the future is here and we want it all and we want it now.

Interference was and is a major issue. In the middle of action, a myo hand can just stop. Bzzt. Stop. Out of order. If you are always stared at, if you always feel pressure to perform, then this is not cool.

Prostheses are not consumer electronics, they are body parts and should be built with that thought in mind. Amputees don't just carry an item with them when wearing a prosthesis - we adopt these parts as our own. Matching that, disappointment for product failure can be truly heart breaking. While cold hearted customer representatives of big German manufacturers tend to forget that and give stand-offish replies throughout and consistently, we invariably learn just how much (or how little) professionalism these people really have.

Prosthetic hands are still extremely flimsy. And weak. When I walk into a supermarket for shopping and one to two out of three milk bags risk to be dropped and burst open, the prosthesis has somewhat missed its purpose. They do have a mind of their own, politely speaking. And thy may not grip the simplest of items really.

Dude, where's my arm - but: dude, where's my money? If ripping open a popcorn bag is a struggle such as here, the prosthesis is more a nightmare than support. May I recommend the scissors...., Try to take out the garbage with that. Try to not make it look too idiotic when you do that.

Myoelectric sockets are really painful. They have been painful and they still are. If - as mine - your stump is so long that you cannot be fitted with a pin lock system the reality is that of pain and absent comfort. That is not a deal that works. Unless new socket technology is developed, I see a dark future for myoelectric impediments advertised and sold as "bionic". See comparison of myoelectric against other systems: they are not as functional as the sellers may want to make believe. Let me put it to you bluntly: if these prostheses were actually halfways 'bionic', the interface would be painless :) Now go, sleuths, research.

Hand grips are uselessly diverse unless I can reduce shoulder strain. In my personal view this is best achieved with a Dorrance hook, V2P Prehensor or Becker hand. Hanging up laundry using a hook device without even doing open/close operations is a comfortable and relaxing, well balanced act without restricted elbow or shoulder motion. Try a Carroll test approximation. I may have to say it maybe in another way: was such a prosthesis approximating "bionics" as in "biomimicry" - why would my shoulder hurt wearing it? Now, go, bionics researchers, research!

Companies still sell proprietary parts that are incompatible across systems. It should be me and my technician that choose what liner, what lock, what socket and what wrist goes with which terminal device. Actually, it will be me and my technician making that choice.

Products are humongously overpriced. I can buy a drill hammer for 300$, a top of the line workstation for 2000$, a huge computing workstation for 10'000$ and production of an expensively sold BMW costs around 15'000$ in maximum. But that is free enterprise. The closed and heavily skewed market of upper extremity prosthetics sells iLimbs for a total of 78'000$ here - and they offer no complex grip patterns, no multi electrode readings, no comfortable socket developments and no interference control that goes beyond the little we see today. In short - that stuff is not at all worth all that money.

Try to look backward from the future. If you have an extremely expensive hand, but it only opens and closes with squeaking motors while you literally die of shoulder and elbow pain, you be happy? No? Why not? Explain with diagrams ;) Tell us who hangs up the laundry then. Tell us that on your diagram. What if the diagram is one red dark red sheet of paper? If red signifies pain? How do you then politely adress the Mrs Customer Service of the German Company that Means So Well (TM)? Married to Quality, Quality for Wife, but now The Honeymoon Is Over? Hm?

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