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Competitive prosthetic action - compare movement and function II

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Competitive prosthetic action - compare movement and function II; published August 26, 2009, 04:13; URL: https://www.swisswuff.ch/tech/?p=220.

BibTeX: @MISC{schweitzer_wolf_1555648996, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Competitive prosthetic action - compare movement and function II}}, month = {August},year = {2009}, url = {https://www.swisswuff.ch/tech/?p=220}}


In 2018, a prosthetic hook will still be by far the best device for real work (Wolf Schweitzer, 2008).

After iLimb publicity (see here) as well as Michelangelo publicity (here) suggests a superior function of these products I find it helpful to give a more comprehensive side by side view of some "demo actions". Just a simple test of a hook will show you to be very careful when analyzing "performance".

Some comparisons are surprisingly unspectacular. Some are easily performed using almost any prosthesis and then may not count as specific highlight for a particular type of prosthesis.

So if you see a prosthetic hand "perform" - be careful before wasting too much money: try the same "performance" with other options. Be thorough in your evaluation and network with others before spending too much money. You could end up with a different procedure and a different product than initially thought.

I currently favor these parts for best performance:

  • MSM wrist 0.1rev (I find it far more stable than Otto Bock's)
  • Becker Lock Grip hand (allows for more natural grip than Otto Bock hand)
  • Otto Bock MovoHook 2Grip (in absence of a better competitive product)

Handling eggs

Demonstrating egg handling using a mechanical Becker Lock Grip hand. If you can do that you can fry your own eggs. I am not entirely sure but I bet you'll have trouble with these using iLimb, Michelangelo or Otto Bock Sensorhand Speed.

Picking grapes

Precisely this is why I am not sure the DARPA invested their tax payer's money correctly by *solely* supporting myoelectric technology. Otto Bock also seems to currently neglect the development of sophisticated hand or hooks for cable controlled arms. Also iLimb is only available as myoelectric version. This is wrong in my view.

Cable controlled arms go a far way. You just have to walk that path. This arm is light, robust, does not at all require batteries or electricity, it is very affordable and it also looks technical. The Becker Lock Grip hand can be also ordered customized.

Now check this out.

Cutting up tomato

Kitchen work involving cutting up round stuff - taters, maters, onions, .. - is great with the Becker Lock Grip hand. I was not able to do it that easily using any other terminal device - none of Otto Bock's parts was as useful. Also, cable control allows me to deliver a very graded force application, something important for many manual activities.

Grabbing can

Grabbing can using Otto Bock Movo Hook 2Grip. While hook claws are the most robust being solid steel all they manage is a 2-point squeeze of that can- so obviously you will see a slight slip or twist. If you have an open can you may actually spill some. That is not as likely to happen with the Becker Lock Grip hand.

The Otto Bock hand is simple and the way it is built it sometimes forces me to do corrective movements of elbow, shoulder and trunk. Here that is not as pronounced though.

Grabbing can using Becker Lock Grip hand. Smooth, fast, with one sweep, silent, adaptive and very cool.

Grab a bag of snacks

Grabbing a bag of snacks seems to be a real no-issue in terms of grabbing and holding. It is definitely not a discriminating benchmark activity regarding three different terminal devices.

Using Otto Bock's voluntary hand this grab is an absolute no brainer.

But no hand is required. The hook does the job equally well but its wear down is cheaper.

Here is the Becker Lock Grip hand in action.

Grab detergent pack

Using the Becker Lock Grip hand, a more sophisticated way of grabbing the object comes to play - its fingers wrap and that helps stabilize the object better.

Otto Bock voluntary opening hand grabs the pack well:

Becker Lock Grip hand used to pick up detergent pack. Fingers wrap around irregular grip/shapes, check little finger of prosthesis.

Testing grip strength

The Becker Lock Grip hand wraps around objects and delivers a relatively strong grip.The overallcomfort lies in less arm, shoulder and trunk motion necessary to make up for the prosthetic hand's inherent shortcomings.

And I had heard rumors that a more complicated mechanical hand would be necessarily weaker. In this instance these rumors appear to be false.

The Otto Bock hand benefits from a really sticky and well fitting synthetic glove - its grip does not feel as strong as the Becker hand's grip but as you see the ruler can also be yanked around without much of a slip.

The Otto Bock hand is simple and the way it is built it sometimes forces me to do corrective movements of elbow, shoulder and trunk.


This is a response to TouchBionics "get a grip on functionality" demo videos http://www.touchbionics.com/professionals.php?pageid=44&section=5 and to Darin's demos on http://theadventuresoftheilimb.wordpress.com/

To the representatives of the Fondation de la Haute Horlogerie http://www.hautehorlogerie.org that visually allude to amputees with 'fake people' in their ill fated 2009 ad campaign: I am real, authentic and I wear real watches. What you see is real action. Thank you for taking note. https://www.swisswuff.ch/tech/?p=205

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