View Full Version : Carpal Tunnel and Ulnar Nerve Syndromes

Herman J. Woltring
06-29-1990, 03:11 AM
Dear Biomch-l readers,

The following items were posted this week on the Risks-Digest; I think that
they might be of interest in a biomechanics context. The first item was
originally posted to a Usenet newsgroup, apparently in reply to previous

Regards -- Herman J. Woltring

P.S.: In yesterday's posting, please read "Sunday 8 July 1990".


Reposted from: RISKS-LIST: RISKS-FORUM Digest
Wednesday 27 June 1990 Volume 10 : Issue 12 &
Thursday 28 June 1990 Volume 10 : Issue 13

ACM Committee on Computers and Public Policy,
Peter G. Neumann, moderator

Date: Wed, 27 Jun 90 09:40:34 CDT
From: meyering@cs.utexas.edu (Jim Meyering)
Subject: Info on carpal tunnel syndrome (CTS)
[Submitted via werner@cs.utexas.edu (Werner Uhrig)]

One point the author does not mention is that the "force-depression curve" of
your keyboard may also play a role. It is better to have a linear relationship
between force and depression. But the keys on some keyboards require greater
force to depress the first few millimeters than the last few. This gives what
is sometimes hyped as "positive-touch" or something similar. The net result is
that you have to press (relatively) hard to get over the "hump," then with the
low resistance beyond it, your fingers bang into the base with more force than
with "linear" keyboards. People have suggested that this sort of dynamic may
aggravate or even induce CTS. Many of our HPs have this "nonlinear" keyboards.
The keys on some Sun3 keyboards have become so sticky that they give the same

Jim Meyering meyering@cs.utexas.edu uunet!cs.utexas.edu!meyering


Date: Thu, 28 Jun 90 09:06:49 -0400
From: Mike Tanner
Subject: Re: info on carpal tunnel syndrome (CTS) (RISKS-10.12)

At the risk of turning this into a medical forum I wanted to add to the
excellent summary on carpal tunnel syndrome that there is a related problem
called ulnar nerve syndrome. As with CTS, those of us who spend lots of time
using keyboards are prone to ulnar nerve syndrome, too. The main difference
in the symptoms is that with CTS the numbness and tingling is in the thumb and
first two fingers, with UNS it is in the other two fingers and along the
outside of the forarm. (When you "hit your funny bone", what you've done is
bash your ulnar nerve. The symptoms are similar to that feeling, but they
don't go away.)

My wife's neurologist (she's been going through a bout of it) said there are
many causes, but a common one is some activity that constantly rubs the elbow.
In her case it is almost certainly typing while resting her elbows on the arms
of a chair. One danger is that carpal tunnel syndrome is so hot, such a fad
right now, that a physician might automatically connect "numbness" with
"programmer" and say "carpal tunnel". My wife's physician did this, and only
changed his mind after we had looked in some medical books and found that CTS
symptoms did not match hers. (Physicians deny that they reason this way.
Experience tells otherwise.)

Treatment is basically like CTS: ice, avoid bending the elbow as much as
possible (not easy to do), don't do things that rub the elbow a lot,
anti-inflammation drugs. There is surgery, but unlike CTS, ulnar nerve
surgery is not a good option. Apparently it has about a 50% chance of making
things worse, according to my wife's neurologist. (That might have been an
estimate that took the nature of her condition into account, i.e., there are
cases where it has a high probability of success, but hers isn't one of them.)

-- mike