Oyvind Stavdahl–
Actually, it looks to me like Steve and I were possibly discussing different
things. Steve, correct me if I’m wrong, but weren’t you talking about hooks?
Indeed, the function of a hook type terminal device can be improved by wrist
alignment that is slightly flexed and sometimes ulnar deviated–although I
prefer Otto Bock’s Ball & Socket wrist which allows virtually any position
the patient desires!
HANDS on the other hand are a different story as I described in my original
response. Until hand manufacturers begin building hands with the correct
angle of approach, we will keep EXTENDING the wrist.
There was a presentation some years back at an AAOP National where a group
from a Scandinavian country presented this hand shape/angle of approach
problem and modified Otto Bock hands appropriately to achieve this optimum
alignment. There is a hand, I believe made by Centri–the Ultralight I
think, that extends the back of the hand when it opens so there is direct
access to the palm without a lot of body english.
One might also note the relative success of Liberty Tech’s so called
“FlexiWrist”
in the children’s area.
JTA (Tom Andrew)
In a message dated 11/12/97 4:27:31 AM, [email protected] wrote:
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between different prosthetists and fitting centres with respect to
wrist alignment.
Tomm Kristensen, CPO, who fits more than half of all upper-limb
prostheses in Norway, tells me he uses slight ulnar deviation and
flexion of reasons similar to those reported by Childs. He adds
that occationally he has fitted prostheses with the wrist slightly
extended. Male amputees have reported that people around them
perceive such prostheses as feminine-looking, and thus ask the
prosthetist to redo it with a straight or flexed wrist. So apparently
there are cosmetic reasons for flexing as opposed to extending.
I welcome further comments on this issue, but conclude that
no particular static wrist posture is “The Appropriate One” for
upper-limb prostheses.
Sincerely,
Oyvind Stavdahl (Siv.ing., Dr.ing. student)
Department of Engineering Cybernetics
NTNU, The Norwegian University of
Science and Technology Direct line: +47 73 59 43 77
O. Bragstads plass 8 Switchboard: +47 73 59 43 76
N-7034 TRONDHEIM Fax: +47 73 59 43 99
NORWAY Email: [email protected]
http://www.itk.ntnu.no/ansatte/Stavdahl_Oyvind
————- Original Query ————-
Dear all,
I am currently looking at wrist alignment in upper-limb
prostheses. A rather old reference (Manual of Upper-Ext.
Prosthetics, UCLA, 1958) suggests certain angles for
ulnar deviation and flexion, but I have been unable to find
more recent publications.
It would be interesting to know your personal opinion on
this issue – at what angle should the wrist be set, and
why (functional and/or cosmetic reasons)? To the extent
that it matters, I am mostly concerned with transradial
amputations and cosmetic/electric hands.
Furthermore I’d be very thankful for references to more
recent literature on this subject, in particular any
publication that builds on actual studies rather than
“just” expert opinions.
The responses will be compiled and posted as always.
————- Responses ————-
From: [email protected]
Oyvind–
Over 70% of my practice is upper limb prosthetics with a specialty in
externally powered systemms. I worked for the Utah Arm guys for many many
years and helped design and teach the fitting methods used with it.
With respect to hands:
Nearly all prosthetic hands, electric or otherwise, are built nearly the same
way–the back of the hand is in a straight line with the back of the forearm.
This already creates an un-ergonomic alignment requiring the amputee to use
enormous amounts of shoulder movement to achieve grip. Conventional wisdom
(and UCLA’s instuctions) recommend some significant amount of wrist flexion
in addition. While this may be somewhat useful in some cases where a hook
type terminal device is used, it only serves to make the functionality of a
hand worse.
In almost every case we fit here in Salt Lake City, the wrist is EXTENDED 10
or more degrees to allow the plam of the open prosthetic hand DIRECT access
to the object being grasped. Observe how you reach out for a glass of water
or a cup. The back of the hand easily creates a 45o angle with the back of
the forearm!!!
Feel free to contact me directly to discuss this issue further.
J. Thomas Andrew, CP
—————————————
From: [email protected] (Steven Childs)
Dear Oyvind,
The wrist angle deviations suggested by the old UCLA manual are still
very applicable today. As I learned it, the ulnar deviation put the
terminal device closer to the working surface or table top, and wrist
flexion made it easier to reach the mouth. I am not sure of the actual
angles in degrees, but they are minor. This how I acheive these setings.
After setting the wrist in the proper position accorrding to the
measurements and tracings, slightly tilt the wrist in the ulnar and
flexion deviation. I have never had any trouble with this technique.
Steve Childs>>
