Anatomy of Carpal Tunnel

-  Discussion:
     - transverse carpal ligament, is a heavy band of fibers which runs between hamate & pisiform medially to scaphoid and trapezium laterally, and forms
            fibrous sheath which contains carpal tunnel anteriorly within fibro-osseous tunnel;
            - posteriorly, tunnel is bordered by carpal bones, and transports median nerve & finger flexor tendons from forearm to hand;
     - lies deep to palmaris longus & is defined by 4 bony prominences;
            - proximally, by pisiform & tubercle of scaphoid;
            - distally by hook of hamate & tubercle of trapezium;
     - from hamate & pisiform medially to scaphoid & trapezium laterally;
     - transverse carpal ligament, portion of volar carpal ligament, runs between these 4 prominences & forms fibrous sheath which contains
            carpal tunnel anteriorly w/in fibro-osseous tunnel;
     - posteriorly tunnel is bordered by carpal bones;

- Superficial Anatomy:
     - palmaris longus passes in front of flexor retinaculum to become continuous with the palmar fascia (see transverse carpal ligament);
     - palmar cutaneous branch of median nerve, which innervates skin over base of thenar eminence, arises short distance prox to flexor
            retinaculum, pierces deep fascia, & course superficial to the flexor retinaculum to reach the skin;
            - palmar cutaneous nerve of ulnar nerve course superficial to transverse carpal ligament & is not involved in CTS;
     - distal volar flexion crease crosses proximal end of scaphoid and pisiform & marks proximal edge of TCL;
     - references:
            - Safety of carpal tunnel release with a short incision. A cadaver study
            - Anatomy of neurovascular structures around the carpal tunnel during dynamic wrist motion for endoscopic carpal tunnel release

- Contents of Tunnel:

     - tunnel transports median nerve & finger flexor tendons (FDS, FDP , & FPL);
     - motor branch of median nerve in hand arises under or just distal to flexor retinaculum, & winds around distal border of retinaculum
            to reach hypothenar muscles and the lateral 2 lumbricals;
            - numerous variations in the branching have been described;
     - sensory branches innervate lateral three and 1/2 digits & palm of the hand;
     - references:
            - Anatomic variations of the median nerve in carpal tunnel release
            - Anatomical relationships among the median nerve thenar branch, superficial palmar arch, and transverse carpal ligament

- Guyon's Canal
      - ulnar nerve & artery do not pass thru tunnel but lie superficial to it in guyon's canal
      - pisiform is palpable & serves to mark entry, on its lateral aspect, of ulnar nerve and artery into the hand;

- Landmarks:
    - distal volar flexion crease crosses proximal end of the scaphoid & pisiform & identifies proximal edge of the transverse carpal ligament;
    - pisiform is palpable and just laterally will identify entry of ulnar nerve and artery into hand;
    - all thenar & hypothenar muscles, except the abductor minimi, originate partly from the transverse carpal ligament.
    - The Palmar Fat Pad Is a Reliable Intraoperative Landmark During Carpal Tunnel Release

    - Kaplan's Line:
           - Kaplan oblique line (line drawn from apex of interdigital fold between thumb and index finger, toward ulnar side
                   of hand, parallel w/ proximal palmar crease, & passing 4-5 mm distal to pisiform bone

The transverse carpal ligament. An important component of the digital flexor pulley system.

Transverse carpal ligament reconstruction in surgery for carpal tunnel syndrome: a new technique.

Anatomy of the flexor retinaculum.

Prevalence of anatomic variations encountered in elective carpal tunnel release

The Carpal Insertions of the Transverse Carpal Ligament

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, April 1, 2013 9:47 am