The carpal
tunnel, located in the wrist joint, is a narrow passageway in which the nine flexor tendons
and median nerve pass through in order to supply
function, feeling and movement to the thumb, index,
middle and one-half of the ring finger.
The
finger and wrist flexor muscles and their tendons originate in the
forearm at the medial epicondyle of the elbow joint and attach to the bones (Metaphalangeal (MP) , Proximal Interphalangeal (PIP),
and Distal Interphalangeal bones) of the fingers
and thumb.
As these muscles contract to bend the
fingers into flexion towards the palm of the hand, the flexor tendons slide through the carpal
tunnel. The median nerve travels through the carpal
tunnel alongside the flexor tendons and then divides into a motor branch that
controls the thumb flexor and adductor muscles and
sensory branches that provide over half the hand
with the sensory of touch.
Eight
rigid carpal bones on the posterior (back) of the wrist
form the carpal tunnel / canal,
and the transverse carpal ligament is positioned on the
anterior, or front side of the wrist. The size of the carpal
tunnel is about the size of the index finger in diameter,
and the flexor tendons and median nerve
glide past each other with ease within the carpal tunnel
when it is of sufficient size. But in such a small, confined
space, especially if it is not stable or is collapsing due to a lack of extensor/abductor muscle supporting the carpal bones where there is little
room for error, the median nerve can become severely damaged. If the tendon size increases from inflammation
or hypertrophy (growth), or if the carpal tunnel size decreases,
the structures within the carpal tunnel become impinged
and carpal tunnel syndrome results.
Muscle Imbalance and the
Narrowing of the Carpal Tunnel
Although
increased size / *hypertrophy of the tendons
can occur, the most prevalent cause
of carpal tunnel syndrome is the **narrowing
of the carpal tunnel due to a musculoskeletal
imbalance between over and underused muscles
in the hand and forearm. Once the carpal tunnel
begins to collapse in on itself, any form of
repetitive or static flexion such as typing,
writing, grasping, etc., will cause friction
of the flexor tendons against the carpal bones,
median nerve and blood vessels, causing irritation,
inflammation and increased swelling of the
structures within the carpal tunnel.
*Muscle
& Tendon Hypertrophy
The
size of the flexor tendons can increase in
size due to increased activity of the flexor
muscles / tendons during activities such as
gripping, typing, etc. These activities directly
exercise and strengthen the flexor muscles
/ tendons, causing them to become shorter and
thicker, than normal, resulting in decreased
space within the carpal tunnel and the compression
of the median nerve and blood vessels. The
solution to reducing the size of the flexor
tendons is to stretch and lengthen the muscles
/ tendons, resulting in increased space within
the carpal tunnel and the elimination of
the impingement of the median nerve and associated
vessels.
Equality of Muscle Strength and Muscle Length
The
most common reason for compression of the median
nerve is a result of the carpal tunnel collapsing
inward. This is thought to be caused by a
muscle imbalance that results from long,
weak extensor muscles not begin able to hold
the carpal bones in position or the extensor
muscles ability to withstand the tremendous
pull from the flexor muscles. The key to eliminating
this muscle imbalance is to stretch and lengthen
the flexor muscles and strengthen and shorten
the extensor muscles to create equality of
length and strength of the muscles within and
around the carpal tunnel, which in turn stabilizes
the carpal bones in their proper position,
keeping them from collapsing into the carpal
tunnel.
It is important to understand that performing
any unidirectional movement pattern on a constant
bases, whether static or repetitious in nature,
can cause muscle imbalances throughout the
entire upper extremity, affecting the fingers,
hands, wrists, forearms, elbows, upper arms
and shoulders, but these imbalances can be
corrected with the appropriate training program.
In
order to provide immediate and long-term
relief, it is suggested that implementing
the medically proven FLEXTEND® training systems into any upper extremity
prevention or rehabilitation program will
correct these musculoskeletal disorders. (Consult your physician before beginning
any type of exercise program.)
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