Requirement specifications

I believe that detailed requirement specifications are important to find out what prosthetic solution to go for. Speed, fluency, weight, appearance, reliability, specific comfort and price.

My own requirements are located around the red dot (following graph, click on it to enlarge).

Prosthesis / Criterium No prosthesis Body powered Cosmetic arm Myoelectric
Dirt, fluid, contamination no problem no problem no problem considerable problem
Electric fields, interference, machines, power lines no problem no problem no problem big problem
Weight up to 12 kg up to 15 kg up to 10 kg painful in excess of 2 kg
Temperature no issue no issue no issue no function if too cold
Comfort good very good good very bad - painful
Grab, hold items no / very limited only yes no yes
Off the shelf / initial coolness uncool uncool uncool uncool
Accessibility to modify items to be cool no easily manageable modification possible but can wear cool t-shirts to make up for it, wear colored socks or bandages to protect stump and look cool, or get a tattoo as extreme attempt at coolness own wrist, own terminal devices are possible, artwork can be applied - so technical coolness and artistic coolness can be approximated own hands and arms can be found, adapted and modified so artistic coolness is easily accomplished limited options only
Need for major technical support no after design issues of parts are solved, once every two months maybe a part breaks or paint comes off - but usually this setup does not require major technical support once every couple of days to once every two weeks
Need for daily support skin care skin care, clean liner, clean arm and parts skin care, clean arm, wash sock skin care, clean liner or socket, clean arm, recharge batteries, do not forget batteries

The performance of a very delicate open/close mechanism that sophisticated myoelectric prostheses offer does currently not constitute a full requirement for me as other disadvantages of these systems make them hard to justify.

Darin Sargent's documentation shows that a bit more than a month of very careful usage mainly to show an iLimb around rather than really getting it dirty seems to suffice and two fingers are broken; conversely I use my mechanical arm full blast - and it takes me half a year to get rather lightly designed parts to start wiggling.

As office worker who is able to parade high tech innovations and who can afford using an iPhone or Apple computers, I would add the iLimb without much hesitation. But I do need brute performance with raw reliability, so I wear a cable controlled prosthesis and run PC based Linux workstations.

If a prosthetic hand will allow sturdy action in combination with sophisticated grip patterns, then things will start to look different. If grip patterns will be programmable, adaptable, complex and powerful at the same time, then the product will cover new application domains and become a candidate for many people.

In terms of looks, people react so differently that no universal answer is probably 'correct'. The looks are extremely important and yet extremely hard to get right. Also, the looks of what happens at the end of the stump are only a small part of a whole.

When I wear the hook, people hardly stare. I feel very comfortable as the hook allows for precise and well controllable action. But it is a look so unlike a hand yet one that so clearly communicates "this is a technical solution, nothing else to see, keep moving". Some people liked the clear and raw tool appearance over any other attempt to what they'd call 'ornament' the stump.

When I see someone wear a sophisticated motorized hand such as the iLimb, I do not get the impression of a particularly well done cosmetics - but I get the feeling of wanting to compliment the wearer.

When my five year old god child looks at me, she thoroughly hates any prosthesis. She wants to be able to interact with the authentic and real me, however much is there or missing. Some people close to me told me they'd prefer the natural look and want to be able to visually check rather than being impeded by prosthetic or other coverage.

When I wear the prosthetic hand, people compliment me about two things - first, it does not scare them as it looks entirely prosthetic and artificial, secondly, it does not overly distract them. And I have to say that I appreciate its heart wearming totchke look - despite some PVC related annoyances such as permanent discoloration. Obviously that product manages to hit that fine line between educating the environment and not being too tense to bear. And when I wear my prosthetic hand even covered with a sophisticated glove, some people do stop and look. So it is not possible to effectively fool people. So we are dealing with a communication issue, not a hide-my-disability issue. What I want to communicate is adequacy of performance.

Cite this article:
Wolf Schweitzer: - Requirement specifications; published 29/10/2008, 23:50; URL:

BibTeX: @MISC{schweitzer_wolf_1656510633, author = {Wolf Schweitzer}, title = {{ - Requirement specifications}}, month = {October}, year = {2008}, url = {} }