Appearance Test [how to test if your prosthetic hand is life like]


Test reason and goal: appearances are everything.

It is of ultimate importance to understand that hand amputation as a disfigurement as much as a manual handicap.

Is cosmesis so important?

Disfigurement as such, per se, and in an isolated world of the person that is concerned would not be such a big issue at all. One is disfigured, one gets used to it at least to some degree, and that is that.

If one follows rational thought at all, then:

  • We know already - without any visualization - that current attempts to simulate a "life like" appearance all fail totally. Only a few bone hard illusion fans believe just how totally "life like" a, say, iLimb with cosmetic glove is; for these: see below tests and videos.
  • Spending money towards a top technology still fails, but that type of goal may set you back by around 35'000 CHF (customized cosmetic but otherwise just passive arm) or a whole lot more (for a "bionic" arm) - and still just fail to really hide the amputee status.
  • But not only do serious attempts to simulate human life like appearances fail, worse, they are thought and known to cause a particularly bad effect described by the Uncanny Valley. That model [link1] [link2] tells us that the correlation between life likeness and acceptance is not linear, but complicated.
  • We furthermore know from experience and from trial and error that non life-like prosthetic arms can take a lot of stress away, in fact they tend to exceed the top expensive solutions in achieving a better appearance or solution to some aspects of body image issues.
  • Body image is body image - and whatever we do there, is up to us. So if I do or do not wear a prosthetic arm is only a part of what all of me is, and what other people see and think is beyond control anyway.
  • If prosthetic arms generally have a bad acceptance, then one interpretation certainly is that the industry fails us. And that is certainly a correct interpretation for many reason all of which (at least in theory) can be changed. So as industrial representative, the best angle of attack is to understand what all is wrong with prosthetic arms in order to make better ones first and sell more then. This website is full of tips, clues and rather hard indicators along that direction.
  • If prosthetic arms generally have a bad acceptance, another interpretation however is that so and so many amputees cannot be wrong. Given the current prosthetic arm options, not wearing a prosthetic arm also can have great advantages [link1 SHAP rip] [link2 comparison]. These are not unknown or obscure: even though one gets recognized as amputee, prosthetic arms never change that; even though one has diminished function, prosthetic arms may yield somewhat but not drastically improved function or actually provide a greater handicap. The total cost of prosthetic arms includes spent time, finances and discomfort, damaged clothes and damaged objects as well as possibly injured other people (scratches, bangs, etc).

And so all that follows is probably not too rational

But it would be cool to be able to have the perfect apperance. Forget function for a moment. The missing arm part and hand is a communication barrier (unless one waltzes over it). People attach hopes to this aspect. They nowadays believe that if they own a piece of overpriced gadget junk their life improves. So within that realm of perception, let us think aloud.

And advertising can come across as rather progressive (Otto Bock: "The Michelangelo Hand and the Axon-Bus system are milestones on the path to perfection",  Touch Bionics: "With the i-limb ultra, your prosthesis looks and moves more like a natural hand than any other powered prosthetic hand"; RSL Steeper: "bebionic3 utilises leading-edge technology and unique, ergonomic features that make it unlike any other hand available. These innovations combine to give the hand unrivaled versatility, functionality and performance").

Conversely, did you ever think of wearing one of these hands, sitting in a meeting, and pouring a glass of water - and despite all cosmetic glove and "bionic" lookalikes, the loud noise would be the dead giveaway of the hand being a prosthetic?

Any feature that gives the prosthetic nature of a hand away would not be considered so "life-like" and thus any such feature should lead to immediate removal of the product from the line-up of prosthetic hands that can be considered "life-like".

Functional grip engineering and everyday usage from functional view point brought us the Becker hand and various hooks. Really difficult things may best be achieved without disabling prostheses [link]. So optimizing grip function gets us nowhere in terms of "life like" prosthetic hand and arm design. So we should abandon grip aspects altogether when starting out from anew.

If you think that is not a very friendly assessment, do consider the prices of these hands. Do consider that the discovery of an amputee as amputee is the actual tragedy when in fact the amputation was what the amputee wanted to hide, completely, by way of your "life like" product. So if you build hands that do not result in totally life like appearances and you still advertise that, you at least owe us a sincere apology. You will realize that, and on top of that, your absence in acknowledging of these facts do not alter reality the slightest bit either. Then reflecting on all the money that went into the prosthetic arm that could have bought 1/2 a house maybe, a few big or many small cars, or anything else? So now, time's up.

Claims and hand constructions point to a suggested "life-like" appearance as the actual selling point, and prices of the "bionic" hands mean that their "manu"facturers mean business. And these "bionic" and cosmetic prostheses do aspire to cover a real need: to allow an arm amputee to hide their amputation. They just do not get there.

The good old times where people just believe that a bit of painted silicone on squeaking motors constitute "adequate" prosthetics are long over. Insurances by and large do not pay prosthetic hands that are "bionic". Clearly that is because these are neither bionic, nor life like, nor anywhere near useful as sorry as we may be to admit it that is the case. And so we have been reading the saga of the myoelectric arm for too long now, time now to put ink into the ink pen, time to put the money where your mouth is.

And in all decades of covering up stumps, no one ever found it necessary to test just that? So then, it is now that that should be tested: life-like-ness. Hic Rhodus, Hic Salta. And you read that here first.

Test description

An amputee with one full remaining hand wears a prosthetic arm and hand. No hands or forearms may be covered with gloves in the full test. Short sleeves or no sleeves should be worn to expose the arms, after all you advertise for biomimicry, for "life like"

The procedure consists in the amputee acting as if he was buying a movie ticket, and, the audience trying to see which of his two hands is the prosthetic or which one is the side with the handicap.

For all activities that the amputee manages to complete along the procedure of buying a movie ticket, points are awarded until his "bluff" is "called": because the audience has one shot at yelling which of the amputee's hands (right or left as seen from the amputee) (not as seen from the audience). It is mandatory that both hands (left and right, named A and B here as it is up to the amputee which to prefer) are used. It is obvious that at one point, the amputee will be easy to spot as that.

  • Part 1. Walks towards audience with arms swinging hanging down, wallet in rear pocket of standard jeans trousers or similar.
  • Part 2. Produces a wallet with one hand (A).
  • Part 3. Opens wallet with other hand (B).
  • Part 4. Produce bank note (A or B) while holding wallet (B or A).
  • Part 5. Take exchange money consisting of a few bank notes and a few coins and put it into the wallet (A or B).
  • Part 6. Close wallet and put it into pocket (A, B).
  • Part 7. Walk off.

Comments to the test

It is the ultimate challenge to the industry to build a prosthetic hand model that passes this test, and, that passes similar tests.

A next test could be "eating a 300 gram steak using knife and fork"; points there will be awarded by the seconds into the process that users spend without being spotted as wearing a prosthetic.

Obviously, who hears a squeak or worse a loud motor, also will know which hand is the prosthetic.

And if an amputee waltzes in wearing a hook on the right arm, and if then the audience does not know any better to scream out "RIGHT SIDE!" - then we realize what jocks they are.

Thank you for being so observant y'all. Thanks for keeping an open eye for what side that hook was again. We could have forgotten but you reminded us.

Watering down the test for pansy boy engineers

Pansy boys that cannot build real products may still wish to "test" their product for "life like" appearances, so consider the following test modifications for the pansy boy variation:

  • long sleeves
  • thin gloves on both hands

However, the full test contains short or no sleeves and no gloves.

If you take offense in me calling you a pansy boy engineer then consider that the likes of you equates hook wearing with "arcane" technology or with "Captain Hook". As long as industry and research representatives spit on useful modern materials being used for proven robust technology in prosthetic arms, and moreover, as long as they have nothing substantially better and cheaper to sell and offer, they will have to put up with me belittling them in the exact very same way.

There is trade ethics that also works for arrogance against the handicapped. By "it works" I mean that it is quite effective. Whenever I returned the favor of such treatment, they never came back for seconds.

To-do list, check list for getting there

  • Socket design in terms of shape and cover must blend into the body shape of the amputee. Bulky parts, protruding buttons, cables or batteries bulking out are all a no go. If you want to wear a custom liner, you will need a pin lock so shallow that you can equip people with relatively long stumps as well. Using lanyard suspensions always is cool, and so are protruding pin lock buttons - but here we are not talking practical and pragmatical (I have that with a body powered arm and a hook already). Here, we are talking life-like.
  • The total length of the prosthetic arm and hand must match the length of the other arm. Why? Because over days of wearing different arm lengths, the shoulders, neck and back will hurt first, then hurt a lot later.
  • Wrist motion must be natural. With long stumps and the suspension issue, a number of innovations can be expected. Maybe.
  • Hand and finger motions does not have to be fully controlled. A partly intrinsically animated hand will also do, if that is necessary to be life like. But the overall setup may be tested such as here.

Inspiration on the path towards the full life like hand

  • Silicone skin like appearance research [1] [2] [3] [4] [5]
  • Myoelectric control   [6]
  • Body powered control  [7] [8] [9] [10]
  • Life like wrist, hand and finger dynamics and motion [11], but interestingly, dynamical life likeness has so far never been specifically and systematically attempted in industry or research for prosthetic arms and hands, so I guess it is no wonder that all of these prostheses - ALL! - are so awkwardly stiff looking.


Illustrating just how totally far off the mark of life like prostheses current options are

I will demonstrate you the effects of wearing currently available prosthetic arms, with currently sensible glove or cover options.

You will see just how so very far off the mark these products are in terms of being life-like.

Say "beep" the very moment that you recognize which arm is the one with the handicap.


No prosthetic

While no prosthetic arm is a method that has its learning curve, and while it is the exact opposite of hiding the amputation, you can see quite easily that that is how cinema tickets are purchased without prosthetic arm. It is totally not a problem technically to do stuff. A prosthetic arm is absolutely not required to watch a movie in a cinema.

Of course, "bionic" arm sales people will tell us that "it is the little things that count". But then, not sweating due top prosthetic socket inflicted excessive heat counts and it is not a little thing to sweat less, it is big and important. Not suffering considerable stump skin damage simply by wearing it counts too (because if you suggest I wear a "bionic" arm with you knowing about the consequences, you might fail the Voight Kampff test, and thus classify as non-human). Besides, eating pop c0rn with myoelectric control can be a real bitch [link].

Acceptance wise, not wearing a prosthetic is widely accepted, it is also authentic and very direct.

iLimb Ultra Revolution

The iLimb finger movements are nicely adaptive. But if you suggest I wear a "bionic" arm with you knowing about the consequences, you might fail the Voight Kampff test, and thus classify as non-human. It is paramount that you understand that.


  • The glove has wrinkles, and it looks artificial. The glove is not life like, particularly when examined by eye. If you reduce image resolution such as in this video, then the surface details of real skin compared to the prosthetic hand glove may resemble each other to a degree. In a real situation, the prosthetic skin simulating glove is eerie and strange.
  • The posture of the iLimb Ultra Revolution when walking in already is stiff, and awkward. It will be awkward no matter what as that is what myoelectric or current "bionic" prostheses are. It has been suggested that the iLimb is not awkwardly stiff [link] but it quite simply is. The wrist, the hand shape and the hand itself are not so good in terms of life likeness.
  • If one wants to avoid the iLimb to be a dead giveaway for arm amputee status, then learning to be a perfect puppeteer is the next logical step. The one must master the art of animating the dead object just like a puppet.
  • The socket is totally ill shaped were one to examine any "life like" aspect about this prosthetic arm.
  • Aspects of prosthetic rather than life like quality are told in parts, so people must keep watching to detect these as staring in such situations is partly built in. The almost life like aspect makes it a stare magnet. Other people report this as very stressful. Conversely, the hook is very relaxing for other people, so is a red Becker hand - why? Because ever so rapidly everyone knows they are dealing with an arm amputation and a prosthetic arm.
  • Other people consistently rate the natural color glove covered iLimb as weird, eerie and not acceptable.
  • It is ever so totally ruinously and vastly expensive. For that price, it is not anywhere near enough life like. And it is far too loud, by any standard.

And so despite all efforts and expenses, split seconds into this, the appearance test is failed.

Passive arm

It is unnaturally stiff. But then, what isn't.

But otherwise it just does not look as bad. This is a stock glove, not a custom glove. It has a relatively light weight. It has a high reliability in that you can count on its mechanic properties. It is not so expensive.

Passive arms and its options to be extended to something that is almost passive are underrated by current research. Many people tend to like them.


Cannot be more obvious than a hook.

But people tend to like it for that quality. Also, the overall dynamics and motion pattern is a lot more fluid and natural than when wearing a myoelectric arm, where weight distribution and control paradigm are unnatural and difficult. Grip wise, the hook wins over all other devices and by far. Ripping pop corn bags, carrying drinks, and so on, is no problem.

Becker hand

The Becker hand is not a sophisticated "bionic" hand that still fails to satisfy requirements of being "life like".

The Becker hand is a hand shaped terminal device, it can be covered with very hip looking gloves, it has a very precise and reliably "precision grip" (unlike the iLimb Ultra Revolution [link]), it is very robust, temperature and fluid insensitive, and it is affordable. If the hook is a problem shape wise, the Becker hand may be the best option. It may be stiff as well, but it is not just as awkward as the iLimb.

Monestier hand

Do check out the Monestier hand.

You will hopefully now realize why...:

  • Not at all wearing a prosthetic arm but placing the stump end into the jeans pocket for walking in public is by far the most realistic in terms of "hiding the handicap".
  • Any manipulation that requires both arms is an instant dead giveaway for the arm amputation status. The appearance test as described above is totally failed always by any currently available method.
  • One can consider wearing long sleeves. One can even consider wearing a glove or even two gloves. These attempts lie along an axis that ends with "not leaving home".
  • In terms of covering up the handicap, long sleeves and the passive arm go a very long way. The passive arm is very light, has no problematic contours and costs not too much in case it gets damaged. Also its cosmetic glove is rather thick and durable.
[1] G. L. Polyzois, P. A. Tarantili, M. J. Frangou, and A. G. Andreopoulos, "Physical properties of a silicone prosthetic elastomer stored in simulated skin secretions," The Journal of prosthetic dentistry, vol. 83, iss. 5, pp. 572-577, 2000.
  title={Physical properties of a silicone prosthetic elastomer stored in simulated skin secretions},
  author={Polyzois, Gregory L and Tarantili, Petroula A and Frangou, Mary J and Andreopoulos, Andreas G},
  journal={The Journal of prosthetic dentistry},
[2] K. Xiao, F. Zardawi, R. van Noort, and J. M. Yates, "Developing a 3D colour image reproduction system for additive manufacturing of facial prostheses," The International Journal of Advanced Manufacturing Technology, vol. 70, iss. 9-12, pp. 2043-2049, 2014.
  title={Developing a 3D colour image reproduction system for additive manufacturing of facial prostheses},
  author={Xiao, Kaida and Zardawi, Faraedon and van Noort, Richard and Yates, Julian M},
  journal={The International Journal of Advanced Manufacturing Technology},
[3] K. Xiao, F. Zardawi, R. van Noort, and J. M. Yates, "Color reproduction for advanced manufacture of soft tissue prostheses," Journal of dentistry, vol. 41, p. e15--e23, 2013.
  title={Color reproduction for advanced manufacture of soft tissue prostheses},
  author={Xiao, Kaida and Zardawi, Faraedon and van Noort, Richard and Yates, Julian M},
  journal={Journal of dentistry},
[4] J. T. Simpson, I. N. Ivanov, and J. Shibata, Method of making self-cleaning skin-like prosthetic polymer surfacesGoogle Patents, 2013.
  title={Method of making self-cleaning skin-like prosthetic polymer surfaces},
  author={Simpson, John T and Ivanov, Ilia N and Shibata, Jason},
  month=aug # "~26",
  publisher={Google Patents},
  note={US Patent App. 13/975,434}
[5] P. J. Biermann, "The Cosmesis: A Social and Functional Interface," JOHNS HOPKINS APL TECHNICAL DIGEST, vol. 30, iss. 3, p. 250, 2011.
  title={The Cosmesis: A Social and Functional Interface},
  author={Biermann, Paul J},
[6] H. Fuketa, K. Yoshioka, Y. Shinozuka, K. Ishida, T. Yokota, N. Matsuhisa, Y. Inoue, M. Sekino, T. Sekitani, M. Takamiya, and others, "1$\mu$m-thickness 64-channel surface electromyogram measurement sheet with 2V organic transistors for prosthetic hand control," in Solid-State Circuits Conference Digest of Technical Papers (ISSCC), 2013 IEEE International, 2013, pp. 104-105.
  title={1$\mu$m-thickness 64-channel surface electromyogram measurement sheet with 2V organic transistors for prosthetic hand control},
  author={Fuketa, Hiroshi and Yoshioka, Kazuaki and Shinozuka, Yasuhiro and Ishida, Koichi and Yokota, Tomoyuki and Matsuhisa, Naoji and Inoue, Yusuke and Sekino, Masaki and Sekitani, Tsuyoshi and Takamiya, Makoto and others},
  booktitle={Solid-State Circuits Conference Digest of Technical Papers (ISSCC), 2013 IEEE International},
[7] R. M. Bongers, P. J. Kyberd, H. Bouwsema, L. P. Kenney, D. H. Plettenburg, and C. K. Van der Sluis, "Bernstein’s levels of construction of movements applied to upper limb prosthetics," JPO: Journal of Prosthetics and Orthotics, vol. 24, iss. 2, pp. 67-76, 2012.
  title={Bernstein’s levels of construction of movements applied to upper limb prosthetics},
  author={Bongers, Raoul M and Kyberd, Peter J and Bouwsema, Hanneke and Kenney, Laurence PJ and Plettenburg, Dick H and Van der Sluis, Corry K},
  journal={JPO: Journal of Prosthetics and Orthotics},
[8] M. Hichert, "Feedback in voluntary closing arm prostheses: Investigation of optimal force feedback in shoulder controlled arm prosthesis operation," PhD Thesis, 2010.
  title={Feedback in voluntary closing arm prostheses: Investigation of optimal force feedback in shoulder controlled arm prosthesis operation},
  author={Hichert, M},
  school={TU Delft, Delft University of Technology}
[9] K. Berning, S. Cohick, R. Johnson, L. A. Miller, and J. W. Sensinger, "Comparison of body-powered voluntary opening and voluntary closing prehensor for activities of daily life," Journal of Rehabilitation Research & Development, vol. 51, iss. 2, 2014.
  title={Comparison of body-powered voluntary opening and voluntary closing prehensor for activities of daily life},
  author={Berning, Kelsey and Cohick, Sarah and Johnson, Reva and Miller, Laura Ann and Sensinger, Jonathon W},
  journal={Journal of Rehabilitation Research \& Development},
[10] J. S. Hebert and J. Lewicke, "Case report of modified Box and Blocks test with motion capture to measure prosthetic function," J Rehabil Res Dev, vol. 49, iss. 8, pp. 1163-74, 2012.
  title={Case report of modified Box and Blocks test with motion capture to measure prosthetic function},
  author={Hebert, Jacqueline S and Lewicke, Justin},
  journal={J Rehabil Res Dev},
[11] J. Cabibihan, R. Pradipta, and G. S. Shuzhi, "Prosthetic finger phalanges with lifelike skin compliance for low-force social touching interactions," Journal of neuroengineering and rehabilitation, vol. 8, iss. 1, p. 16, 2011.
  title={Prosthetic finger phalanges with lifelike skin compliance for low-force social touching interactions},
  author={Cabibihan, John-John and Pradipta, Raditya and Shuzhi, S Ge},
  journal={Journal of neuroengineering and rehabilitation},
  publisher={BioMed Central Ltd}

Cite this article:
Wolf Schweitzer: - Appearance Test [how to test if your prosthetic hand is life like]; published 18/06/2014, 12:55; URL:

BibTeX: @MISC{schweitzer_wolf_1685683183, author = {Wolf Schweitzer}, title = {{ - Appearance Test [how to test if your prosthetic hand is life like]}}, month = {June}, year = {2014}, url = {} }