The Carpal Tunnel

The ‘carpal tunnel’ consists of ten structures (9 tendons for three muscles, and the median nerve) that pass over the carpal bones and under the flexor retinaculum. The relationship of the ten structures to each other is important for identification as well as the understanding of Carpal Tunnel Syndrome.

Picture from: http://www.aidmycts.com/_img/carpal-tendon.jpg.

The four tendons of the Flexor digitorum superficialis m. are located anterior to (on top of) the four tendons of Flexor digitorum profundus m., and are ‘stacked’ with the tendons to digits III and IV over lying the tendons to digits II and V (see below, click pic to enlarge).

Picture from: 2006 Elsevier Inc. Atlas of Human Anatomy 4^th Edition, Frank H. Netter MD, NetterAnatomy.com

As you can see from the pictures, the Median n. is located anteriorly within the carpal tunnel. When this nerve is compressed due to various issues (swelling of surrounding tissues, mechanical impingement, etc.), often resulting from repetitive motion, the result may be Carpal Tunnel Syndrome. A common treatment for this condition is the surgical release of the transverse carpal ligament (flexor retinaculum).