Carpal tunnel syndrome, described by Paget in 1854, is the most common upper extremity compression neuropathy and results from median nerve compression within the carpal tunnel. The carpal tunnel is bound by the carpal bones arching dorsally; the hook of the hamate and the pisiform medially; and the scaphoid tubercle and trapezial ridge laterally. The palmar aspect, or “roof,” of the carpal tunnel is formed by the flexor retinaculum, consisting of the deep forearm fascia proximally, the transverse carpal ligament (TCL) over the wrist, and the aponeurosis between the thenar and hypothenar muscles distally. The most palmar structure in the carpal tunnel is the median nerve. Lying dorsal (deep) to the median nerve in the carpal tunnel are the nine long finger and thumb flexor tendons.
