The following is an exerpt from Dr. Jameson's
book Repetitive Strain Injuries: The Complete Guide to Alternative
Treatments and Prevention. (Keats Publishing, 1998). ©
1998, Dr. Timothy Jameson.
Figure 21 - The Median Nerve shows the
location of the carpal tunnel, and figure 22 (above) shows
a cross section of the carpal tunnel. Notice on figure 22
how the median nerve, flexor tendons, along with an artery
and vein traverse through the small tunnel within the wrist.
The carpal bones form a U-shaped tunnel. The bones on either
end of this "U" are connected by a tough unyielding
ligament known as the flexor retinaculum, or transverse
carpal ligament. The symptoms of true CTS are because of
compression of the median nerve as it passes through this
tunnel. (The reason I state "true CTS" is because
of the many conditions that mimic CTS.) Compression of the
median nerve is due to a number of factors. The first factor,
and probably the most prevalent is inflammation of the flexor
The hand flexor tendons become inflamed
due to overuse. Any occupation or hobby where the hand is
contracted in a constant flexed position, or involves constant
movement of the hand from extension to flexion (such as
in grocery checkers) makes the tendon susceptible to injury.
The flexor tendons are surrounded by a synovial sheath,
or wrapping, where they pass under the flexor retinaculum.
Inside this sheath is a substance called synovium, a lubricant
aiding movement of the tendons within the sheath. Inflammation
of the tendon leads to enlargement of the tendon/sheath
complex due to overproduction of synovium, as well as a
degradation of the synovium itself. The synovium transforms
into a sticky, viscous compound. This leads to increased
friction of the tendon/sheath complex, which instigates
more inflammation. This irritation of the tendon and sheath
is also known as tenosynovitis. If left untreated, a condition
called "trigger finger" or stenosing tenosynovitis
can result. (See under separate chapter headings). The enlargement
of the tendon-sheath complex exerts pressure upon the median
nerve in the uncompromising tunnel causing the symptoms
of carpal tunnel syndrome.
A second factor involved in carpal tunnel
syndrome is misalignment of the carpal bones. As shown in
figure 22, if the carpal bones become misaligned, the transverse
carpal ligament becomes taught, narrowing the carpal tunnel.
Compression of contents of the carpal tunnel ensues, including
the median nerve. Misalignment of the radius and ulna, the
two forearm bones, can lead to carpal bones misalignments.
In cases of CTS it is common to find the distal end (the
end closest to the wrist) of the radius and ulna slightly
spread apart from each other, causing stress to the interosseous
membrane, the tough ligament that holds joins the two forearm
bones together. Combined with this spreading is weakness,
irritation, and myofascial trigger points in the pronator
quadratus muscle. This muscle is responsible, along with
the pronator teres muscle, for turning the palm of the hand
downwards (pronation). This spreading is slight, but has
a major affect on the carpal tunnel. The radius and ulna
are connected to the carpal bones by ligaments, the radial
collateral and Ulnar collateral ligaments, respectively.
Spreading of the radius and ulna leads to tugging on the
carpal bones, and the misalignments mentioned above.
The radius and ulna become misaligned and
spread apart from compressive forces translating through
the wrist up into the arm. Examples of this are weightlifting
with barbells whereby the weight is forced into the wrist
and arms. This is common in those who perform "benching"
exercises, and "inclines." Pushing activities
involving extension of the wrist and pushing with the palm
lead to this condition. Any sufferer of carpal tunnel syndrome
will tell you how difficult it is to push a grocery cart.
This phenomenon is the cause. Chiropractors suffer from
CTS because of the compressive forces up the arm from performing
spinal adjustments. (I know of a number of chiropractors
who had to change their techniques and adjusting style because
of carpal tunnel syndrome.) Mail handlers who push large
mail carts are susceptible to this forearm problem also.
Anyone involved with pushing heavy objects with the hands
can be affected by this condition.
A third factor in carpal tunnel syndrome
is a combined myofascial syndrome with carpal bone misalignments.
If the forearm and hand muscles which attach into the carpal
bones are suffering from myofascial syndromes (see chapter
under separate heading for more information), they will
tighten and shorten, thus pulling on their attachments into
the carpals. To be specific, the muscles susceptible to
this are the flexor carpi ulnaris and abductor digiti minimi,
which both attach into the pisiform bone, and the muscles
involved in thumb movement which attach into the carpal
bones. Myofascial syndromes in these muscles cause misalignments
of the carpals leading to the series of events stated above.
A fourth factor is any occupation that
involves direct compression upon the carpal tunnel itself.
The major player here is use of a computer mouse. Most people
will rest their wrists on mouse pad, and extend the hand
and fingers to click the button. This posture puts direct
pressure on the area of the carpal tunnel. A prolonged posture
such as this will lead to nerve compression. Of course,
the same goes for anyone who wrests their wrists on the
wrist pad or table top.
A fifth factor is any occupation involving
vibration. Laborers using jackhammers, chain-saws, buffers
or grinders subject their wrists to excessive vibration.
Studies indicate that vibration inhibits blood flow to the
nervous tissue and other tissues in the hand. Researchers
label this repetitive strain injury into its own classification.
I have included a separate chapter on "Hand Arm Vibration
Syndrome" which is the result of excessive vibration.
This syndrome can lead to a disease called Raynaud's Disease.
The sixth factor is the environmental temperature.
People who work in cold environments are much more susceptible
to CTS. The cold temperature causes constriction of blood
vessels, thus decreases the blood flow to the tissues. The
same concept prevails for people who put ice packs on their
arms and hands while working at a computer or other repetitive
task. The decreased blood flow to the tissues because of
the ice pack will predispose the person to increased injury
if they attempt to perform repetitive movements with it
on. Use ice only during rest, not during activity.
A seventh factor is underlying changes
in the carpal bone structure. This may be due to previous
wrist fractures which have caused changes to the size and
shape of one or more carpal bones, hypertophic (enlargement)
changes of the carpal bones due to imposed stresses over
a long period of time, and callus formations in and around
the bones from healing fractures. Changes to the bones because
of pathological processes, such as tumors, must also be
Last but not least, the eighth factor is
spinal subluxations. Misalignments or subluxations of the
lower cervical spine cause swelling in and around the nerves
traveling to the hand. The pinched nerves cause irritation
of the muscles and tissues they supply throughout the arm,
making the subluxation a primary causative factor in the
development of carpal tunnel syndrome. The irritated tissues
cause abnormal tensions in the forearm, predisposing the
person to developing carpal tunnel syndrome complaints.