The arteries

In the forearm (Fig. 7.15) the interosseus membrane unites the radius and ulna and separates anterior and posterior compartments. Anteriorly lie the flexors of the wrist and fingers, flexor digitorum superficialis and profundus. Posteriorly are the extensors of the wrist and fingers and the abductor of the thumb - extensor carpi ulnaris, digitorum and pollicis longus, and abductor pollicis longus. The muscles abducting the wrist - flexor carpi radialis and extensor carpi radialis longus and brevis - lie superficially on the radial side and those that adduct the wrist - flexor carpi ulnaris and extensor carpi ulnaris - lie on the ulnar side.

The interosseous nerves and arteries lie close to the interosseous membrane. The radial nerve and vessels and the ulnar nerve and vessels lie anteriorly on each side, and the median nerve lies in the midline between the superficial and deep flexor muscles.

The individual muscles may be difficult to distinguish on axial CT because of the lack of fat in the forearm. MRI is the superior method in this respect and has the added advantage of allowing direct imaging in many planes.

THE ARTERIAL SUPPLY OF THE UPPER LIMB

(Fig. 7.16; see Figs 1.42 and 1.43) The upper limb receives its supply from the subclavian artery. This has four branches, namely: • The vertebral artery; • The thyrocervical trunk, which supplies the inferior thyroid, suprascapular and transverse cervical arteries; Fig. 7.16 Arteries of the upper limb.