How to really test prosthetic arms [from real life, for those that are amazed and wonder]

After we have read a bunch of articles on how we all do not know how to test or go about evaluating prosthetic hands it may be time to give concise tips.

About the "use" of SHAP [1] for prosthetic hands, we repeat together that "the Southampton Hand Assessment Procedure (SHAP) was devised to assess quantitatively the functional range of injured and healthy adult hands" [2]. The idea was to monitor disease or healing processes in diseased or injured human hands. To use such a test to rate prosthetic devices is as clever as trying to use a street car to race over unpaved degree 3 climbing hills. It can be done but it would be weird to do so.

Mostly, relevant aspects are missing from the usual clinical hand tests when going for prosthetic hands  - prosthetic hands and arms do lack in specific areas that then need to be specifically tested.

As suspension (sockets, liners) play a very relevant role, it is fruitless to test prostheses without testing the suspension as well. If you do not believe me, I will make you spend 30 minutes walking through a supermarket, buying ice cream (2 kg), milk (2 x 1 L = 2 kg), meat (300 g), beer (2 x 0,5 L) and other stuff, totaling 7 kg, with the stuff hanging off your prosthetic hand and arm - and if you so much as blink an eye because you are uncomfortable, you will be disqualified on the spot. Because I am not sure y'all are following me here. Testing prosthetic arms is not brainless fun, nor is wearing them for everyday activities.  So your testing setup might want to convey a minimal appreciation of how serious this is for everyone else that is involved in the subject. And appreciation might start with reading and researching, and being mindful about what you do.

As appearance is a key aspect for prosthetic arms, it necessarily must be tested. And remember: you read that here first. Then, there are a number of activities that warrant real evaluation of prosthetic functionality. It is not that hard to list these.

Please note that my tests contain a reason and goal. It is very important to verbally and clearly define these, in order to make sure we all understand what we are talking about.

So far, I am glad no one has asked me (other other amputees) to help defining a testing procedure ; ) - But seriously. How can you allow 2013 to come and almost pass and not question outdated old boring testing procedures of no relevance?


How to test function and appearance of terminal devices of prosthetic arms

0. Base line

Reason for base line definition: we really do not know why we need one or two hands and thus cannot clearly define who needs one or two hands. Not in a world where no armed people fly airplanes [link] or change brake pads on a car [link]. So in order to create a scientific basis for manual performance testing, the following tests should be offered to all applicants, and, to all applicants as many times as they like, with or without prosthetic equipment as they like.

I would propose that I pass many tests with very close or equal scores without prosthesis and with passive arm [see also SHAP getting ripped]. I then assume that I will get good scores with the hook. How prosthetic hands fare, who knows. I would also be interested to see the results of 20-30 non disabled peers of my age,  performing the tests two-handed. Generally, different people require different prosthetic arms for different tasks. But not everything goes. So that is that and we are not a bit smarter.

Really, who pays for our prostheses is disability insurance. What they pay for is clear: they support work and job integration. They specifically do not pay for sports or entertainment related prostheses ("I need an iLimb to operate my game boy"?) and certainly not for excessive equipment - it has to be simple and useful, by Swiss law.

So really we should test crucial manual elements for different jobs.

In fact, we need the physiotherapy and ergotherapy skills test for all jobs that there are, to see what prosthetic arms can do, what they cannot do, what work steps have to be performed differently or with a different technique and where there is room for improvement.

Once we have all relevant jobs' overview of tasks and manual challenges, we can maybe try to coalesce some into some more general tests, more general grip tasks, more general prosthetic arm requirement.

That would then allow us to proceed in a more economic way when assessing a person's manual ability for jobs, generally, and by and large.

If such a bench test series is done in a realistic way, it can also be used for people with two arms and two hands that recovered from injuries, or for people with illnesses or all kinds of impairments. Not just for people with prosthetic arms. So filling an event hall with dozens of professional organizations' demo and test benchmark tents, for all visitors - handicapped or not - to be visited, well, that'd be fairly useful.

For a first comprehensive overview of jobs and job descriptions, go here: DICTIONARY OF OCCUPATIONAL TITLES.

1. Appearance test

This test is now described extensively on a separate page [link].

2. Removing splinter from finger

Test reason and goal: self sufficiency in these cases of pain and emergency are crucial for the survival and relative well being.  If you miss a hand, removing a splinter from the finger of the remaining hand can be a real challenge.

Test description: The amputee must use his terminal device (or, if he is able to specify it, a better technical setup or procedure) to hold and operate a tiny pincer that works as precisely as ever possible in order to remove his splinter. Stability of grip holding a tiny tweezer, and success in removing the splinter, are scored.

Spoiler: my approach:

  • always have a big vice mounted at home
  • place tweezer or pincer into vice
  • close vice using prosthetic or stump
  • pull splinter

This has the big advantage that the vice does not shake or shiver. Shaking and shivering has never been contemplated by any robotics researcher doing prosthetic arm "development" ever, even though the usage of motion sensors for prosthetic control would be a feasilibity. Always remember, you read that here first.

Materials needed: we need a standardized splinter dummy. Ideally, technical researchers could create this as a student project.

3. Carrying a shopping basket

Test reason: carrying a shopping basket is an important task to perform with the prosthetic arm in order to avoid overuse of the other arm. The goal is to shop til you drop also because shopping can have beneficial effects on the psyche of the shopper.

Test description: Carrying a shopping basked tests stability of the grip, it tests the suction power of the prosthetic suspension, and it is extremely realistic. Weight is 3-7 kg, and time to carry it around is 10-30 minutes.

4. Hanging laundry

Test reason and goal: hanging laundry is an important task to perform with the prosthetic arm in order to avoid overuse.

Test description: classic one, this one. Weigh laundry basket first. Hang the basket's full content on some clothes lines at about eye level or height. No parts are to drop. Functional usage of prosthetic hand grips is counted and scored.

5. Cut hedges using a motorized cutter

Test reason: cutting hedges is an important task to perform with the prosthetic arm in order to avoid overuse.Otherwise it is a useless activity unless orderly appearance of your hedges is a regulatory requirement of where you live or where you are the hedge owner.

Test description: cutting hedges using a motorized cutter requires a steady and reliable grip. This is to weed out unreliable setups. A hedge of 1,9 meters height and 20 meters length is to be cut at its front and top parts. The device has two grips, both of which are to be compressed to activate the cutter. If the test subject and his prosthetic arm fails, points are deducted. Otherwise, time is counted. Otherwise, the users is free to go about usage of the hedge cutter as they please.

6. Mount Westinghouse ceiling fan

Test reason: full use of all hands and prosthetic parts test for realistic and fun activities always should be included in comprehensive tests. After all, not only Westinghouse relies on the "project banana" product model (i.e., "product matures at customer's site"). Also, Ikea, other furniture, automotive parts and much more is sold for customers to assemble themselves.

Test description: using tools of one's own choice, the amputee will "single handedly" assemble and mount a ceiling fan as packed and sold by Westinghouse. Each activity that is performed bi-"manually" is scored.

Spoiler: as introduction to some aspects encountered there, check the Retro details on this blog.

 7. Downhill and uphill mountain bike riding

Reason: health, sports and activity must be promoted as design test of prosthetic hands. Otherwise we will never see commercially available prosthetic hands that are actually built to also reliably race bikes.

Bring your own bike and show and tell. This test is to see how steep uphill and downhill sections can be as they are still mastered by the amputee. Achieved maximal and minimal angles are measured for scoring. Check the Mert Hand infos on this webpage for more details if you are interested.

8. Reliably holding a cell phone and tablet (such as Samsung or Apple tablet)

Reason: holding a gadget nowadays is an important task to perform with the prosthetic arm for very functional reasons.

Test description: current cell phones or tablets require a firm grip of the outer rims of the device. The test documents, how far out on the rim the cell phone or tablet can be held by the terminal device, and how long it stays there before it falls down. Maybe a trampoline is needed to augment the test a bit.

9. Typing on keyboard, quantifying posture error and typing speed as well as weight issues of the prosthetic

Test reason: typing well is an important task to perform with the prosthetic arm in order to avoid overuse and posture inflicted problems.

Test description: typing on a keyboard using the amputee's preferred method, his posture (and its error) are measured and quantified. Then, improvements are attempted until the posture is good. This test has true real life applications as it shows a terminal device's capability to be turned into a comfortable typing tool. Amount of remaining posture error is scored.

10. Scrubbing, vacuum cleaning, ironing

Test reason: household tasks are important to perform with the prosthetic arm in order to avoid overuse.

Test description: household chores are to be performed using extensive amounts of time to show wear and tear of various prostheses. Scrubbing using corrosive detergents usually is done to clean calcified toilets or fat covered ovens or so. Vacuum cleaning would require carrying of the vacuum cleaner across a few stairs (while vacuuming these) to make this interesting. Ironing, obviously, must be shown and demonstrated. Overall, clean result, bi-"manual" technique and time used to process a given area or amount is scored.

11. Opening a bunch of envelopes

Test reason: opening a bunch of envelopes is an important task to perform with a prosthetic arm in order to avoid overuse.

Test description: opening a bunch of envelopes using a prosthetic device always is a challenge. So, here we go. Score these too. A good number of envelopes to open would be 30 or so. In the hard core category, no tools are to be used. The free style category will allow users to bring their own tool to complete the task (I have a battery driven envelope opener; as any good rehabilitation specialist will agree on, the best way to solve a manual task is to avoid the task becoming manual).

12. Operating pliers, scissors, screw drivers, hammers, sewing of fabric or leather

Test reason: using any of these are important to perform with the prosthetic arm in order to get better results.

Test description: toolbox test of various applications. I am sure we can find ways to test usage of these tools to measure precision and overall outcome of the handling tests. But I am not definitive here yet.

13. Shifting a person / dummy of 80 kg weight, with both hands / arms; push-ups

Test reason: this is a really very important task to perform with the prosthetic arm in order to avoid overuse.It is totally obvious that some tests require significant fitness. However, building prostheses for the perpetually lazy then defines the activity restricted prison for people like me? Is that the idea of rehabilitation? So far, prosthetic hands were mainly built for people at rest and at ease, for people without any duties of the manual kind, and these hands still failed to successfully cover up the defects in a massive way. At the end of the comfort times, we now want to see action. 

Test description:

  • Just to see how the prosthesis holds up, an act of medical or social care (shifting a dummy / person of 80 kg such as "from bed to a stryker" or so) has to be performed.
  • Additionally, a number of regular style push-ups may have to be performed using both arms / hands.

Here, scores signify completion or repetition if several shifts are to be done within a certain amount of time.

14. Retrieval and undressing of a body

Test reason: As forensic pathologist, I deal with cases such as these:

  • male, 85 kg, tightly dressed, in reclined car seat; retrieve body from car to outside, place on ground, then undress fully and examine all body parts (this involves manual turning)
  • male, 90 kg, advanced post mortem decay, hanging; examine in hanging position, then retrieve body to ground, undress (clothes fitting very tightly due to gaseous soft tissue dilation) fully and examine all body parts (this involves manual turning)

It is the conviction of academic researchers that they can somehow sail into a safe future where they can dodge uncomfortable questions such as: have you researched your prosthetic arms well? Can arm amputees now go back to work? To make them see the work they want to build prosthetic arms for, we need tests that have a hard requirement for prosthetic arms. Doing this does require a prosthetic arm, it is almost impossible to do these one handedly.

Test description: to simulate this, get a shop window dummy, fill it with sand so it weighs 85 kg, dress with three layers of tight clothing and perform above mentioned steps, alternatively at standard 20 deg C ambient temperature, at -5 deg C ambient temperature with previous 20 minutes of waiting (to get any batteries to cool down as well) and then, at +35 deg C ambient temperatures to simulate realistic summer conditions. There should be score points awarded to clothes being intact and not torn, to body not being scratched, and to time for test completion.

15. General test - do gymnastics with the prosthetic arm on in activated state and see when and how the device remains or does not remain closed

Test reason: co-activation of the prosthesis by unintended other activities can be a problem.

Test description: To see how a particular solution fares, a gymnastics sequence should be done where many other activities are done to see how stable the prosthetic device remains - closed, open, etc.

[1] C. M. Light, P. H. Chappell, and P. J. Kyberd, "Establishing a standardized clinical assessment tool of pathologic and prosthetic hand function: normative data, reliability, and validity," Archive of Physical Medicine and Rehabilitation, vol. 83, pp. 776-783, 2002.
[Bibtex]
@article{light2002establishing,
  title={Establishing a standardized clinical assessment tool of pathologic and prosthetic hand function: normative data, reliability, and validity},
  author={Light, Colin M and Chappell, Paul H and Kyberd, Peter J},
  journal={{Archive of Physical Medicine and Rehabilitation}},
  volume={83},
  pages={776--783},
  year={2002},
  publisher={American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation}
}
[2] P. J. Kyberd, A. Murgia, M. Gasson, T. Tjerks, C. Metcalf, P. H. Chappell, K. Warwick, S. E. M. Lawson, and T. Barnhill, "Case studies to demonstrate the range of applications of the Southampton Hand Assessment Procedure," The British Journal of Occupational Therapy, vol. 72, iss. 5, pp. 212-218, 2009.
[Bibtex]
@article {kyberd2009,
  author = "Kyberd, Peter J and Murgia, Alessio and Gasson, Mark and Tjerks, Tristan and Metcalf, Cheryl and Chappell, Paul H and Warwick, Kevin and Lawson, Sian E M and Barnhill, Tom",
  title = {{Case studies to demonstrate the range of applications of the Southampton Hand Assessment Procedure}},
  journal = {{The British Journal of Occupational Therapy}},
  volume = "72",
  number = "5",
  year = "2009",
  abstract = "The Southampton Hand Assessment Procedure (SHAP) was devised to assess quantitatively the functional range of injured and healthy adult hands. It was designed to be a practical tool for use in a busy clinical setting; thus, it was made simple to use and easy to interpret. This paper describes four examples of its use: before and after a surgical procedure, to observe the impact of an injury, use with prostheses, and during recovery following a fracture. The cases show that the SHAP is capable of monitoring progress and recovery, identifying functional abilities in prosthetic hands and comparing the capabilities of different groups of injuries.",
  pages = "212-218",
  url = "http://www.ingentaconnect.com/content/cot/bjot/2009/00000072/00000005/art00006",
  keyword = "COMPENSATORY MOTION, FUNCTION, FUNCTIONAL ASSESSMENT, HAND, IMPLANT, MOTION ANALYSIS, PROSTHETICS"
}

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - How to really test prosthetic arms [from real life, for those that are amazed and wonder]; published 30/10/2013, 00:09; URL: https://www.swisswuff.ch/tech/?p=2233.

BibTeX: @MISC{schweitzer_wolf_1603475686, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - How to really test prosthetic arms [from real life, for those that are amazed and wonder]}}, month = {October},year = {2013}, url = {https://www.swisswuff.ch/tech/?p=2233}}