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.
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.
