What does Otto Bock mean by "significant benefits" with their Michelangelo hand?

[Find all articles about the Otto Bock Michelangelo hand]

In their ISPO World Congress 2010 Leipzig contribution, Otto Bock stated their Michelangelo hand would show significant benefits for arm amputees.

After an initially very appealing presentation of the Otto Bock Michelangelo hand, absence of further functional improvements at the Leipzig 2010 exhibition appeared to miss out on some functions that we would expect by now, given that 2008 research already reported some of these. Also, the Otto Bock Michelangelo hand is *not* thought-controlled as some may believe.

So when I see my prosthetic technicians spending their time traveling to Otto Bock Michelangelo demos, instead of conducting seminars about how to build better body powered arms, and instead I find myself in my own work shop every now and so often, revising their work, fixing their work, coming up with the technical designs they would be paoAs rotatory cuff problems are one of the bigger and more neglected aspects, improvement of shoulder strain certainly would count as significant. For that, grip geometry and weight are key issues.

The following video shows a Otto Bock Michelangelo hand demonstration.

We see the following interesting features regarding posture and shoulder:

(1) During a first ADL (activity of daily living), the demonstrator opens a plastic bottle. Between 0:31 and 0:38 he presents a tense elevated right shoulder while turning the cap / bottle. The shoulder and neck muscles will be hard and painful after a while and he will surely want a massage later that day. That is alright, Otto Bock can pay him - but if I have my choice I want a prosthetic arm where I only need a massage once a week or better once a month.

(2) While closing the bottle again (0:40 to 0:47) we see his shoulder being pulled up again. No way this can be sold as symmetric shoulder position.

What is going on, anyway? Instead the bottle should be held with the prosthetic hand, and the cap should be turned with the other hand. But that bottle task could be done with any prosthetic device that allows to hold that bottle - hook or hand, cable controlled or cosmetic, even without prosthetic arm would I be able to fix the bottle against my tummy and open it. And in any way, it can be done without shoulder strain. No Michelangelo needed at all.

(3) Manipulating some other objects, we see a severely elevated shoulder yet again (0:50 to 0:53) and a bit later again (0:55 to 0:58).

(4) He holds some type of mobile phone without problems (1:04 to 1:18). Great :)

(5) Flipping through a newspaper, his total body line is not vertical but oblique. Check his posture against the line of the wall in the background (1:22 to 1:40, getting worse after 1:33). We should take a closer look at magazine reading I guess. But I am convinced that Michelangelo hand must be pretty heavy too.

(6) Nice handshake at 1:58. But from what I found out, others do not like to shake my prosthetic hand because the other one is just so much more authentic. So I am not sure I would make many new friends with the artificial handshake.


Same in still images:

There is no shoulder level difference that is structurally persistent anywhere here:


And yet, upon activation of the prosthesis, up goes that shoulder:






In the following sequence, an Otto Bock employed actor / demonstrator still exhibits grip failure with his Michelangelo arm. The tooth brush drops down. Bums fallera.

Still images, showing how unsafe the tooth brush grip really is:






And yet even though this might have happened in a public toilet somewhere on a main train station, we brush our teeth with a smile?


This is relevant as Otto Bock did present research claiming advantages in that area due to better grip patterns. Had they advertised it as "another crappy attempt" I would have laughed and agreed. But in the light of direct visible proof of significant shoulder and posture issues and a rather negotiable grip function, it may be valid to ask these questions:

(1) On what exact rationale was the Michelangelo hand constructed? What rationale in terms of biomechanical motion analysis preceding the construction, that is. Were people analyzed in grip situations, were these deconstructed and solutions sought? Why did it not work out if that was the research that went into the hand geometry? And if not, why wasn't that done?

(2) What would be required to improve posture and balance, shoulder issues and elbow issues? Wouldn't a well balanced body powered arm with 35% to 50% of the weight just be better? I feel an uncomfortable answer lurking around the corner...?

(3) What about hand construction? Why are the fingers stiff? How good is that grip really? What do comparisons to other terminal devices in terms of grip, posture and overall usage show?


With an unknown (and probably significant) weight, with only two electrodes, with non-programmable non-complex grip patterns, with no known improvements for sockets for long stumps, with no known improvements for integrated hand/wrist motion, I would see it best to clearly dig very deep into these open problems / questions before spending too much money on such an arm.

A similar performance is delivered by a good hook or by the Becker hand. With these on a body powered arm, you run probably less than half if not just a third of the weight, you spend a whole dimension less money, you don't depend on batteries or unreliable electronics, you will still look like wearing a prosthetic arm but at least you can get comfortable sockets. At the End of the Day, you may just find that pure mechanical high tech is best.

Currently, I avoid shoulder problems by using a new prosthetic wrist, by swapping terminal devices often to match task and task geometry and by wearing an extremely light weight body powered arm. I avoid performance drop-outs (due to sub freezing temperatures, interference, time away from battery rechargers et cetera) by wearing a body powered arm. I avoid surface problems by using adequate terminal devices (i.e., steel hook for work that requires thorough cleaning or disinfection afterwards). So the comparison against a Michelangelo hand is a range of options adapted to situations, not just one.

The software and hardware to actually build a user friendly "bionic" system are undoubtedly there. It is up to the amputees as clients, up to insurances as stake holders to insist on strict product and performance control. When I go and buy such a "bionic" hand, I want the full modern day electronics, I want to access all the program features myself, I want a data glove on my left hand to teach the prosthetic hand new grip patterns, I want a range of software learning options, the whole shebang.

Now, as to the list of ADL allegedly performed by Otto Bock Michelangelo hand and rated measures posture, speed and handling (see also article below):

  • Holding a credit card [SA]: I can hold a credit card with a myoelectric prosthesis such as Otto Bock suggests so their proposed result seems correct. But it is absolutely not necessary to do that. I can hold a credit card perfectly well between stump and wallet, between stump and belly, using a passive arm squeezing it between the silicone fingers, pressing it against wallet or belly, using a body powered arm with a prosthetic hand or a hook. So really, holding a credit card is not a test at all for establishing anything.
  • Picking up a pen from a table [SA]: Picking up a pen is best done with a hook with pointed ends. Sure one can use blunt finger ends but any prosthetic hand's grip is not dependent on the hand itself but on the glove that is worn. If that is the type of seedy looking, sticky soft and almost melting cheap silicone that Centri manufactures and that I wear on my Becker hand, then there is no problem and any hand can lift a pen.
  • Holding a plate [SA]: I can hold a plate with my stump (against belly, on a tray, balance it), or with the passive arm (press against belly, balance), or better with Becker hand or a hook using the body powered arm. Absolutely no requirement to use a Michelangelo hand for that.
  • Sweeping a broom [RA]: sure, housework requires a good grip. Now, then I sweat, I require full elbow range of motion and a myoelectric arm sure does not give me a full elbow range of motion. Instead I would wear the body powered arm that has a silicone liner / pin lock suspension, sits snug on the stump, and that allows for relaxed usage of heavy duty terminal devices such as the V2P or Hosmer hooks. These are what are best for house work.
  • Preparing a sandwich; preparing a pancake [SA]: since when does anyone need a prosthetic arm to cook complex meals? Heat protection gloves, tools, sharp knives and good food - that is what's needed for that. A heat, acid, detergent and mechanics resistent terminal device is important if anything. A hook is best, the stump (as it is sensitive) alternatively equipped with a heat protective stump sock, are highest on the list of preferred ways. The last thing ever that I'd wear for kitchen works was a Michelangelo hand.
  • Do not mix up requirements for Single Action [SA] and Repetitive Action [RA] tasks. [SA] tasks can also be done using a heavy cumbersome myoelectric arm such as the Michelangelo hand promises to be. There, posture is no issue, also it can be easily compensated for a moment. But repetitive [RA] tasks require sturdy function combined with light weight. These [RA] tasks are what increase my neck strain - first and foremost by typing, secondly, by carrying loads and weights. That is the exclusive domain of high tech body powered arms. For Otto Bock, that train has departed. They now have to define the action range they want to cover.

13th ISPO World Congress Congress Lecture [3046] Abstract [244] | Topic: Prosthetics

Author - Kalmar, Janos (Vienna AT) Otto Bock Healthcare Products GmbH - R&D

Title - Usability Analysis of the Multi Degree of Freedom Prosthetic Hand System “Michelangelo” - A First Case Study

Coauthors - van Vliet JW

Summary - A case study shows that the Michelangelo hand system clearly brings advantages. In comparison to a hand system with a current state of technology, the user can successfully master a significant amount of additional tasks of daily living.

Introduction - Most of the currently available prosthetic hand systems are limited to one degree of freedom. This merely enables the user to open and close the hand with a simple pliers-movement. Separate components are available which allow a pro- and supination as well as a wrist flexion and extension. Michelangelo offers both, an integrated passive pro- and supination plus a passive, lockable wrist flexion and extension. An integrated powered thumb offers the user additional hand/fingerpositions: the pinch grip, the lateral grip, the open-hand flat and the open-hand natural position. The integration of four degrees of freedom into a prosthetic hand results in an improved quality of life on an every day basis when gripping, holding and fixing objects.

Methods - Two male probands (29 and 34 years old) were tested and supplied with an Otto Bock sensor hand speed and a new Michelangelo hand. Both probands – who are amputated transradial in the upper third – were asked to do common activities of daily living. A team consisting of 48 international specialists observed and evaluated the test. After finishing the test the probands filled out a survey.

The team was divided into four groups (G1-G4). Each group made two independent tests with both probands as follows:

Test 1 (simple actions):

• Holding a credit card

• Picking up a pen from a table

• Holding a plate

• Sweeping a broom

Test 2 (complex actions)

• Preparing a sandwich

• Preparing a pancake

The first cycle was carried out by the probands with the sensor hand speed. The second cycle was done with the Michelangelo hand.

The team evaluated:

• posture (spine, shoulders, compensating motions, balance)

• hand movement (accuracy, way of movement)

• required time

• handling

The tests showed significant benefits when using the Michelangelo hand. The probands especially judged the far more natural gripping patterns as positive, in comparison to the current prosthesis.

Conclusion - The test showed that Michelangelo clearly offers advantages to the user. The functional advancements in connection with the normal acting gripping patters undoubtfully demonstrate a big gain for the broad user field. The customer requirements of users of all kinds of cultures clearly point out that it is important not to stand out with the prosthesis in every day life. The mentioned advantages of Michelangelo become very transparent if all degrees of freedom are operated myo-electrical. Then there is no need for the user to reposition joints of the prosthesis with the sound hand. The end goal is to enable intuitive and simultaneous control of all joints.

Cite this article:
Wolf Schweitzer: swisswuff.ch - What does Otto Bock mean by "significant benefits" with their Michelangelo hand?; published 03/11/2010, 05:31; URL: https://www.swisswuff.ch/tech/?p=363.

BibTeX: @MISC{schweitzer_wolf_1638543554, author = {Wolf Schweitzer}, title = {{swisswuff.ch - What does Otto Bock mean by "significant benefits" with their Michelangelo hand?}}, month = {November}, year = {2010}, url = {https://www.swisswuff.ch/tech/?p=363} }