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Category: Specifications and comparisons

BLUE LIGHT SPECIAL - defect iLimb glove poses tricky Catch-22 for Cybathlon 2020 [review]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL - defect iLimb glove poses tricky Catch-22 for Cybathlon 2020 [review]; published April 21, 2019, 14:42; URL: https://www.swisswuff.ch/tech/?p=9987.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL - defect iLimb glove poses tricky Catch-22 for Cybathlon 2020 [review]}}, month = {April},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9987}}


The Cybathlon 2020 race rules confront us with two interesting Catch-22 aspects:

-hammering (if not other dangerous) activity that is not endorsed by "bionic" hand manufacturers [link]

-use of damaged / perforated covers, not endorsed by Ossur (see here)

The iLimb user / clinician manual clearly states "do not use without an approved cover", "do not use with a damaged cover", and, "damaged covers must be replaced by a qualified Touch Bionics technician or technical partner" 1.

However, the Cybathlon Karlsruhe 2019 footage clearly exhibits a torn and perforated glove (defect over the knuckle of finger II/index finger) being used during the competition during the task that has the competitor push a card into a slot.

From view of a user that had serious issues with these "glove covers" that Touch Bionics (then) / Ossur (now) sold for a premium, and who knows a lot about replacing these with better parts despite manual regulations, this is VERY interesting: because a damaged cover unnegotiably operates far outside the acceptable use condition that appears to be insurable. And insurance seems to be a thing there.

To remind you: Touch Bionics glove covers die by themselves when left alone [link] or when used for something as minor, uninteresting and light as a 10 minute car wash [link]. I was left to myself to identify a work glove [link] and a durable cosmetic glove [link].

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BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]; published April 20, 2019, 10:28; URL: https://www.swisswuff.ch/tech/?p=9594.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]}}, month = {April},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9594}}


The Cybathlon 2020 race rules confront us with two interesting Catch-22 aspects:

-hammering (if not other dangerous) activity that is not endorsed by "bionic" hand manufacturers

-use of damaged / perforated covers, not endorsed by Ossur [link]

A hammer, particularly a cheap or small one, even more so than a heavy dangerous "real" hammer, is an unlikely tool to use with an ~80 000 USD myoelectric "bionic" device that is specifically built to sustain only the lightest of work. And the subject of hammering, technically, as arm amputee with a prosthetic arm, has become relevant since the Cybathlon 2020 directors [link] have taken it upon themselves to make it a "discipline".

STOP - HAMMER TIME?

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Prosthetic split-hooks are by far the MORE MODERN concept than prosthetic hands and they did not take long to get vilified [what you all got wrong about history]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Prosthetic split-hooks are by far the MORE MODERN concept than prosthetic hands and they did not take long to get vilified [what you all got wrong about history]; published March 3, 2019, 23:01; URL: https://www.swisswuff.ch/tech/?p=9423.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Prosthetic split-hooks are by far the MORE MODERN concept than prosthetic hands and they did not take long to get vilified [what you all got wrong about history]}}, month = {March},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9423}}


We are told by prosthetic R&D aficionados, by film makers, fiction authors, popular culture and whatnot, that a prosthetic hook (i.e., split-hook) is "old", and a prosthetic hand is "new". Also, we get told that myoelectric arms are very modern in terms of control technology, whereas some recent media and prosthetic manufacturers even called myoelectric control "brain control".

None of that is true, quite obviously, while we realize that reality is rather different. Rather strikingly different, in fact.

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Was ist mit Cybathlon@SCHOOL moeglicherweise problematisch?

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Was ist mit Cybathlon@SCHOOL moeglicherweise problematisch?; published March 2, 2019, 11:39; URL: https://www.swisswuff.ch/tech/?p=9404.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Was ist mit Cybathlon@SCHOOL moeglicherweise problematisch?}}, month = {March},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9404}}


Cybathlon@SCHOOL ist ein Programm, das Behinderte, Armamputierte auch, als "Material" bezeichnet und anpreist.

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Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]; published February 11, 2019, 04:55; URL: https://www.swisswuff.ch/tech/?p=9322.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]}}, month = {February},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9322}}


I had evaluated, subjectively, the grip performance of various prosthetic options that I have. These have been already analysed in the context of grip taxonomy, where so far, research has largely focused on grip geometry as such, using some idiosyncratic logic that I found not too relevant.

Using a more relevant logic, I approached the question of grip mechanic from a different angle, both verbally and proverbially speaking: from a user angle, both actually geometrically and subjectively speaking.

I realized that most of my frequently used grips and grip situations fall into a far more narrow range of angle distributions than I had ever assumed.

While others keep rambling about compensatory motion [1] where they assume the "cause" to reside inside some extra joint or so, I know, from exposure and from intelligent looking (all that is needed, boys1) that the orientation of the grip angle and shape in relation to the fixed gripper geometry - including wrist rotation - has to work in conjunction with the average orientation of objects in everyday life, work, tasks and jobs. Not everyone understands adaptive or adaptable grip really well2  when really, modern "bionic" prosthetic hands have an electrically controlled adaptive grip that, by definition of "adaptive" (and not: "adaptable" [1]), closes fingers around any irregularly shaped object - just like, since maybe 1938, the Becker Mechanical hand does. So there is nothing new at all with regard to that. With regard to device-angle constraints, adaptive grip options do not change that really. The typical "tests" (ULPOM, SHAP, etc.[1]) do not produce output that forces the examiner onto the answer of "there, angles, you... you" so one is thrown unto oneself yet again, so to speak, in order to shed light into this aspect.

So I sat down to add "typical object angles" to my already present grip success statistics over a list of my most frequently or typically used grips. Then I did that in theory and then I figured, why not go and video some.

Thereby, a prosthetic hook as gripper device appears to be a lot more advanced, design wise, geometrically, in reducing device materials, bulk and design to approximate a really good overall use performance - also with regard to angular constraints - than the iLimb (which I have here also for as much testing as I like) and with that, many current commercial (or other) multi articulated hands.

In fact, prosthetic hands appear to be by far the older (and thus possibly less reflected) geometric design idea of a prosthetic arm's terminal device than the definitely more modern split hook. I may also go history hunting, but the claim that a split hook is old or outdated, and that therefore by inference a prosthetic hand is automatically new or more modern, as an idea, is wrong, particularly technically speaking. But also historically, to replace a hand with a hand is a straightforward design idea, that does not take any particular imagination, thus it is reportedly old, very old indeed, not new, like some uninformed people try to promote. Conversely, split hooks are so transformative and groundbreakingly new that not even the self-proclaimed transhumanists have understood, or adopted this concept. In a way, a split-hook efficiently unmasks a number of wrong beliefs - just look at their faces, listen to a few sentences of these mouths, and you know more about them than they ever wanted to admit.

The far more elegant reduction, also of angles and controls, to fit into the limited action and option constraints of an arm amputee, is certainly that of a body-powered split hook. It boils down the prosthetic needs to a successful sleek elegant reduction of a functional minimum, making it the ideal choice for anyone that wants a maximum of performance from a minimum of failure, cost, decay, bulk, futile grip attempts and total overhead. The subtle distinction is that a "body-powered split hook" is an entirely different beast than a passive hook, obviously, which probably no one ever noticed, particularly not the people that assumed that a body-powered split hook is best portrayed by installing a "Captain Hook" metaphor.

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[1] P. J. Kyberd, "Assessment of functionality of multifunction prosthetic hands," JPO: Journal of Prosthetics and Orthotics, vol. 29, iss. 3, pp. 103-111, 2017.
[Bibtex]
@article{kyberd2017assessment,
  title={Assessment of functionality of multifunction prosthetic hands},
  author={Kyberd, Peter J},
  journal={JPO: Journal of Prosthetics and Orthotics},
  volume={29},
  number={3},
  pages={103--111},
  year={2017},
  publisher={LWW}
}

Myoelectric prosthetic arms do not "really" function - so whom to sell them to? [cynical economic considerations]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Myoelectric prosthetic arms do not "really" function - so whom to sell them to? [cynical economic considerations]; published February 2, 2019, 15:11; URL: https://www.swisswuff.ch/tech/?p=9304.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Myoelectric prosthetic arms do not "really" function - so whom to sell them to? [cynical economic considerations]}}, month = {February},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9304}}


Myoelectric prosthetic arms do not "really" work, we all know that, and it has been clear for decades.These factual aspects are difficult to make that problem go away like, poof. With that the more interesting question is: whom do we sell these to?

While selling to people that are gullible [link] seems to have a lot going for it, it is risky. A more sustained approach may base on taking actual risk factors for myoelectric failure into account:

  • Sweat
  • Weight
  • General error rate

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Academically published myoelectric arm control error rates since ~1980 remain extremely high, far above any real life use requirement, and not even a slight trend to more reliable control in sight: what does this mean?

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Academically published myoelectric arm control error rates since ~1980 remain extremely high, far above any real life use requirement, and not even a slight trend to more reliable control in sight: what does this mean?; published January 29, 2019, 19:00; URL: https://www.swisswuff.ch/tech/?p=9244.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Academically published myoelectric arm control error rates since ~1980 remain extremely high, far above any real life use requirement, and not even a slight trend to more reliable control in sight: what does this mean?}}, month = {January},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9244}}


I took the liberty to review published error rates for myoelectric arm controls since ~1980. In other words: how reliable is the myoelectric arm control? How has the reliability changed over years?

This is hard data that is somewhat impossible to negotiate, and it has always been there for anyone to take. So forgive me when I anticipated some clear conclusions from such information over the last years - after all, I figured, a post such as this would not run away ; ) Even though, you must keep in mind that you read this here first as well. As far as I know, despite its ubiquitous availability, and despite a very obvious background or social reason for this (which is yet another subject), this collection of data has not been formally performed before. In fact, word of mouth had it that even decades ago, no self respecting engineer would deliberately enter the field of myoelectric or robotic prosthetic hands, simply because of all options one could do, that certainly was never a prosperous looking one.

The reason for this subject choice is, that I was interested in possibly identifying a trend, or a useful figure, for the reliability of myoelectric arm controls to consider in context of daily use. I used standard key word searches on Google Scholar and edited the resulting publications for relevance. I thus performed more systematically what I had done anecdotally a few years ago when it became obvious that one should not put too much hope into such prostheses, as their ongoing and intractable issues were somewhat obvious all along - at least from view point of a right below elbow amputee performing real work.

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How does a Helping Hand / LN 4 hand work [test report]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - How does a Helping Hand / LN 4 hand work [test report]; published December 17, 2018, 05:44; URL: https://www.swisswuff.ch/tech/?p=9027.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - How does a Helping Hand / LN 4 hand work [test report]}}, month = {December},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=9027}}


I organized myself the opportunity to test a "Helping Hand" (also known as LN 4 hand) myself.

You know, the one that are being built as a feel-good exercise by business people and others, and that are given away to people that seem in need. It has its own website [link]. The Ellen Meadows Foundation specifically empowers not amputees, but non-disabled people. Verbally, they claim in their mission statement: "Inspire change in the world by empowering individuals to use their hands to support putting hands on people in need. We will not stop until anyone who needs a prosthetic hand has access to one". About the hand, they write: "Originally Ernie intended to design a functional prosthetic hand for children and adolescent land mine victims. Over time he developed a design for a low-cost, light, durable, functional prosthetic hand. He knew that this would help all who need a prosthetic hand and who could not afford the available alternatives".

That means:

  • They empower non-disabled people that have hands to use their hands. That is noble, I guess.
  • They will not stop until anyone that needs a prosthetic hand has access to one. The definition of a prosthetic hand is wide open, I guess,  but they precisely state their hand is functional and durable. That? We will see about that.

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Disability and the public - prosthetic arms and more: do we appear "competent"? (review)

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Disability and the public - prosthetic arms and more: do we appear "competent"? (review); published December 7, 2018, 15:50; URL: https://www.swisswuff.ch/tech/?p=8812.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Disability and the public - prosthetic arms and more: do we appear "competent"? (review)}}, month = {December},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8812}}


The current view of us, what the general public thinks of us, seems to be a major aspect. Of "us", yes.

The research question for this armchair analyst thus will be: are we - arm amputees in specific, and, as people with a visible physical handicap more generally, more broadly as disabled people generally, seen as competent people?

Generally, the answer seems to be a clear "NO" right from the outset.

This should not come as a shock. There are good reasons to believe that, great reasons to make that plausible, perfect reasons to justify that statement. With that, there may be exceptions to that -  people that see through society's fairytales of disability, horror and fears, but they are usually the exception.

As I had figured out quite early into my enquiries into that issue, that this aspect is of absolutely no further practical concern not because it is not disconcerting - but because I cannot change it. And that is a rapid, lean and cynical logical consequence, that I stopped caring about what other people think of me based on, say, visual impression of my prosthetic arm. I may thus safely focus on function and comfort, sustainability and cost, without worrying too much about whether other people treat me as more or less competent based on my looks. Not because it would not be cool to take influence but because it is of no matter as to the target dimension: the tendendy to disregard any mental capacity of people with physical handicap appears to be implemented in many people's thinking outside of any actual experiences. And regardless of what type of prosthesis I wear.

If anything, I might optimize my appearance by simply trying to look reasonably neat.

But to bend over backwards for what really we have to concede are actually strange people? If anything, can we hack their brains?

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Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]; published December 6, 2018, 08:37; URL: https://www.swisswuff.ch/tech/?p=8850.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]}}, month = {December},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8850}}


When I mention real work as opposed to work one does in the role of a pansy boy, I certainly mean this both seriously and tongue in cheek.

Only if you spend your days with real work will you ever understand. You will be dripping wet from sweating. Your clothes will be so entirely smelly from external causes. Your materials will be in dire need for cleaning ever so comprehensively. You have worked for many hours. And you will go back to do it all over again. A prosthetic arm that is built to last 3 years dies within 5 seconds, 15 minutes, or 2 months - using stock commercial parts, it burns and dies like paper consumed by a slow fire, component by component.

Welcome to the world of real work.

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List of possible prosthetic arm failure points [prosthetic reliability]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - List of possible prosthetic arm failure points [prosthetic reliability]; published October 31, 2018, 19:55; URL: https://www.swisswuff.ch/tech/?p=8792.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - List of possible prosthetic arm failure points [prosthetic reliability]}}, month = {October},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8792}}


Here is a list of my experience in prosthetic part degradation and failure intervals.

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BLUE LIGHT SPECIAL: Pitch black cynicism in the Cybathlon 2020: "the role of a disabled person" [not funny]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL: Pitch black cynicism in the Cybathlon 2020: "the role of a disabled person" [not funny]; published October 25, 2018, 23:02; URL: https://www.swisswuff.ch/tech/?p=8680.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL: Pitch black cynicism in the Cybathlon 2020: "the role of a disabled person" [not funny]}}, month = {October},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8680}}


"With that, visitors of the Cybathlon Experience (TM) can test the role of a disabled person" (können in die Rolle einer behinderten Person schlüpfen) (Oral presentation: "CYBATHLON – bewegt Mensch und Technik", 5.15pm–6.00pm, Dr. Roland Sigrist, Cybathlon, ETH Zurich, Raum E 1.2) -- I was there, one among the 8 people that made the audience of this "sold out" Cybathlon talk; amputees are there for "entertainment" (clearly one of the requirements written on a slide in the presentation) (ist es das, was wir als behinderte Personen spielen? eine Rolle, ja?).

After defining a remarkably strange prosthetic arm race, the makers of the Cybathlon 2020 now start to openly bathe us in their pitch-black cynicism.

Why? Pressing question.

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Understanding and informing design issues of a prosthetic arm for below elbow amputation by way of "taxonomy" [literature review, reality check]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Understanding and informing design issues of a prosthetic arm for below elbow amputation by way of "taxonomy" [literature review, reality check]; published July 26, 2018, 21:18; URL: https://www.swisswuff.ch/tech/?p=7651.

BibTeX: @MISC{schweitzer_wolf_1573561593, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Understanding and informing design issues of a prosthetic arm for below elbow amputation by way of "taxonomy" [literature review, reality check]}}, month = {July},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=7651}}


The academic and industrial attempts to approach prosthetic arms so far have been met with less success than the providers must have hoped for. Far less, in fact so little that we wonder what is going on.

Possibly, design issues are the key to this as however vaguely put, some analytic approach needs to inform better design - but how to really inform better design from issues based on analysis? What is a suitable analysis? If we cannot see any better designs anywhere in practice, real life, then what is the analysis worth? Can we analyze analyses to get a better understanding of what might be going on there?

We might best start with what we know to be true.

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