Tendon and nerve displacement at the carpal tunnel during finger movements

Carpal Tunnel Syndrome (CTS) is the most common upper extremity disorder and results from intrinsic (anatomic, physiologic) and extrinsic (forceful grip, awkward wrist positions, repetitive activities) factors. The use of the hand in activities of daily living induces to and fro motion of the tendon and nerve at the wrist and causes biomechanical stresses inside the carpal tunnel. This potentially could lead to the generation of friction between the tendons and nerve which could progress to degenerative demyelination of the median nerve associated with CTS. Office and industrial activities have been implicated as contributory to CTS. Various methods have been used to determine the displacement of tendons and nerves such as the measurement of joint rotation angle of known or assumed moment arms, magnetic resonance imaging and ultrasound. To date, most studies have measured displacements in either the longitudinal and/or radial-ulnar directions, but no study has reported 3D displacements of the tendons and nerve in the longitudinal. radial-ulnar and dorsal-palmar directions at the wrist.

The purpose of this study was to determine the 3D displacements of the median nerve (MN) and extrinsic finger flexor tendons (flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) at the wrist as a function of flexion of metacar-pophalangeal (MCP) joints of the index and middle fingers.