Anatomy of carpal tunnel

Anatomy of the carpal tunnel
- 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;




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;

- 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.


- 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;