dorsum

extensor retinaculum

· thickening of deep fascia of forearm

· ribbon-like band 1” wide

· lies obliquely across extensor aspect of wrist

· from proximal radial to distal ulnar

· attached

· to radius at anterolateral border above styloid

· to pisiform and triquetrum (not ulna)

Compartments

· septa pass from deep surface to radius and ulna

· divide extensor tunnel into 6 compartments

1st

· lateral surface of radius

· transmits EPL and APB

· each in separate synovial sheath

2nd

· dorsal radius to Lister’s tubercle

· transmits ECRL and ECRB

· each in separate synovial sheath

3rd

· to ulnar sideof Lister’s tubercle

· transmits EPL

4th

· to ulnar border of radius

· transmits 4 tendons of EDC and EIP (deep)

· common synovial sheath

5th

· over DRUJ

· transmits EDM (double tendon)

6th

· over distal ulna

· transmits tendon of ECU

Snuffbox

· concavity on radial side of dorsum of wrist when thumb extended

· borders are

· EPL on ulnar side

· EPB and APL on radial side

· floor is

· radial styloid

· scaphoid

· trapezium

· base of 1st MC

· relations

· cutaneous branches of radial n cross it

· radial a lies in floor

· cephalic v starts in it

tendons

Wrist extensors

· ECRL inserts into base of MC II

· ECRB inserts into base of MC III

· ECU inserts into base of MC V

Long finger extensors

· fan out over dorsum of hand

· interconnected near MC heads by oblique bands

· EIP passes to index finger

· on ulnar side of EDC

· 2 tendons over MC II are EDC and EIP

· EDM passes to little finger

· split into 2

· 2 tendons over MC V are both EDM

· EDC to V lies over MC IV

vessels

Dorsal carpal arch

· formed by

· dorsal carpal branch of radial a

· dorsal carpal branch of ulnar a

· anterior interosseous a

· lies on back of carpus

· sends dorsal metacarpal aa into interMC spaces

· supply dorsal aspects of adjacent fingers

· communicate with palmar metacarpal aa

Veins

· dorsal venous arch beneath skin

· drain into

· cephalic v on radial side

· basilic v on ulnar side

nerves

· cutaneous innervation by

· superficial radial n (radial 3 1/2 hand and digits)

· dorsal branch of ulnar n (ulnar 1 1/2 hand and digits)

· stop short of nailbeds

· supplied by median and ulnar nn

· posterior interosseous n passes along dorsum of interosseous membrane as far as wrist joint