The radial nerve arises from the posterior cord of the brachial plexus and passes posterior to the axillary artery between the triceps muscle heads. It lies in the spiral groove on the humerus and pierces the lateral intermuscular septum to run between the brachialis and brachioradialis muscles. At the lateral epicondyle, the radial nerve divides into the posterior interosseous nerve and superficial radial nerve. The radial nerve supplies all the extensor muscles of the forearm and arm, and the brachioradialis muscle. Damage to the radial nerve in the spiral groove causes wrist drop but spares elbow extension.

1. Radial nerve
• Surgical anatomy
• Motor and sensory innervation
• Clinical symptoms and sign
• Clinical case illustration

2. • Branches from each nerve root from C5/T1. 2

3. • Alone the humerus in the spiral groove
3

4. Surgical Anatomy
• Deep to the lateral head of the triceps, piercing the intermuscular
septum; lie between the brachialis and brachioradialis.
• Motor branches to the brachioradialis, extensor carpi radialis longus,
and to the lateral part of the brachialis muscle.

5. At the level of the lateral epicondyle the radial nerve divides
into superficial and deep branches.
Motor branch to supinator.

8. 8

11. Anatomy

12. Summary
• PIN arises from radial nerve. Radial nerve pulak
arises from posterior cord of the brachial plexus
• It passes posterior to the axillary artery between
long and media heads of triceps muscle, to lie in
the spiral groove between medial & lateral heads
of triceps muscle.
• Here it is accompanied by the profunda brachii
artery before it pierces it lateral intermuscular
septum of the lower third humerus to run between
brachialis & brachioradialis
• At the lateral of epicondyle humerus, it gives rises
to PIN & superficial radial nerve

13. • Radial nerve supply all the extensor muscle of forearm &
arm. However it also supply brachioradialis, which is
flexor of elbow when forearm pronated
• Damage to the nerve in the spiral groove causes
wrist drop but no loss of elbow extension, as fibres of
triceps remain intact proximal to this site
• Only damage in the axilla will causes loss of elbow
extension & wrist drop
• Damage to posterior interosseus nerve (PIN) does not
cause wrist drop because extensor carpi radialis
longus receives its innervation from the main radial
nerve
• Pin only cause unable to extend metacarpophalangeal
joint  finger drop.

14. Clinical case presentation
M/34 左手遭玻璃切割傷

15. Radial Nerve Median Nerve
Brachial artery