What is Carpal Tunnel Syndrome?
Carpal Tunnel Syndrome (CTS) is the name for a group of problems that includes swelling, pain, tingling, and loss of strength in your wrist and hand. It occurs when the median nerve, which runs through the carpal tunnel, a narrow channel running from the lower forearm into the hand, becomes compressed or squeezed at the wrist. It is similar to Tarsal Tunnel Syndrome, which occurs in your ankle, however Tarsal Tunnel Syndrome is far less common.
The carpal tunnel is a space in the wrist surrounded by wrist bones and by a rigid ligament that links the bones together. The median nerve runs through the carpal tunnel, a canal in the wrist that is formed by a series of small bones called the Metacarpals on three sides, and a fibrous sheath called the flexor retinaculum which acts as a pulley for the forearm flexors on the other. There are nine tendons of the hand that also pass through this canal.
The median nerve can be compressed in one of a few ways:
- by swelling of the contents of the canal
- soft tissue swelling in and around the tunnel
- by direct pressure from part of a broken or dislocated bone
Nearly half of CTS sufferers have symptoms in both hands.
Carpal Tunnel Syndrome Anatomy:
The top of the Carpal tunnel is formed by 8 carpal bones that form 2 rows and 4 articulations or joints. The proximal row of Carpal bones (scaphoid, lunate, triquetrum, pisiform) and the distal row of carpal bones (trapezium, trapezoid, capitate, hamate) create the top of the tunnel. These bones are small and glide against each other so that we can move our wrist in different directions. The other side of the carpal tunnel is formed by the flexor retinaculum which forms a retinacular bridge over the carpal tunnel. Its main function is to protect the contained tendon without a significant mechanical action in supporting the transverse carpal arch that acts as a pulley for the wrist flexor ligaments when tension is applied to them by contraction of the forearm flexor muscles.
Inside the Carpal Tunnel there are nine tendons that, when pulled, flex the fingers of the hand. Flexor digitorum superficialis has 4 tendons that pass through the carpal tunnel and insert on the middle phalanx (middle bone of the finger) of digits 2-5 (all fingers but the thumb). Flexor digitorum profundus has 4 tendons that pass through the carpal tunnel and insert on the middle phalanx (middle bone of the fingers) of digits 2-5 (all fingers but the thumb). Flexor pollicis longus has 1 tendon that passes through the carpal tunnel and inserts in the distal phalanx (bone at the tip of the thumb). When inflammation occurs in the onset of tendenosis with any of these tendons the median nerve can become compressed then numbness, muscle weakness and tingling can occur to thumb, index finger, middle finger and ring finger.
