The radial nerve is the largest branch of the brachial plexus, originating from the posterior cord and providing motor function to the forearm and arm's extensor muscles. Its course includes passing behind the axillary artery and lying in the spiral groove of the humerus, where it becomes vulnerable to injury, resulting in conditions like wrist drop if damaged. Additionally, injuries at different levels, such as the axilla or spiral groove, yield distinct clinical manifestations, affecting elbow extension and sensory functions.

1. RADIAL NERVE - ANATOMY
 DR.Murali.M.S;M.B.A
Prof. of Surgery
D Y Patil Medical College
Mauritius.

2. Objectives
 Origin
 Course & Relations
 Branches
 Distribution
 Applied Anatomy

3. Radial Nerve
 Originates as the
terminal branch of the
posterior cord of the
brachial plexus
 Roots from C5, 6, 7, 8, &
T1.
 Largest branch of
brachial plexus
 It is primarily a motor
nerve

6. Course – RN – Ant.view
 It commences its
decent into the arm by
passing anterior to the
latissimus insertion
and dives into the
triceps to lie on the
posterior surface of the
humerus

7. Post view Ant view

8. Course of Radial Nerve
 Largest terminal branch
of posterior cord
 Enters posterior aspect
of humerus through
lower triangular interval
 Teres major (superior)
 Long head triceps (medial)
 Humerus (lateral)
 Gives posterior
cutaneous nerve of arm
in axilla

9. Course of Radial Nerve
 It lies on the surface of
the medial head of the
triceps, rather than the
bony surface – of the
humerus and does not
do so until it crosses to
the lateral aspect of
the humerus along the
spiral groove

10. Course of R N
 Comes to lie in distal part
of spiral groove with
profundi brachii artery
 Beneath lateral head of
triceps and proximal to
origin of medial head
 Gives branches to
triceps, anconeus and
inferior lateral cutaneous
nerve of arm

11. Course of Radial Nerve
 The lower portion of
the radial nerve crosses
the midline at an
average of 15 cm from
the distal articular
surface and pierces the
lateral intermuscular
septum at
approximately 8-12cm
from the lateral
epicondyle

13. Course of Radial Nerve
 Enters the forearm
anterior to lateral
epicondyle
 More specifically over
articulation between
capitulum and radial
head
 At some point 1-3cm
above & distal - LE &
deep to BR divides
into:
 Superficial radial
 PIN

14. Course of Radial Nerve
 In anterior
compartment of arm
lies between brachialis
and brachioradialis
 At its division – closely
related to radial
recurrent artery

16. Course of Superficial
R.Nerve
 Runs down the forearm
along the lat.border of
BR with radial artery on
its ulnar side in the
middle 1/3 of forearm
 Passes posteriorly
through tendon of BR
proximal to radial
styloid.

17. Course of Superficial
R.Nerve
 Passes over tendons of
snuffbox
 Terminates as
cutaneous branches to
dorsum of hand and
lateral 3 1/2 digits
short of nailbeds

19. Course – P I N
 The PIN continues
down the forearm
diving between the
heads of supinator and
then emerging to split
into several branches
that supply the
extensors of the wrist
and hand

21. Posterior Interosseous Nerve
 After exiting the
supinator divides into
deep and superficial
muscular branches
 Superficial
 EDC, ECU, EDM
 Deep
 APL, EPL, EPB, EI

26. APPLIED ANATOMY

27. Lesions
 Level I – Axilla
 Level II – Spiral groove
 Level III – Elbow
 Level IV – Forearm

28. Axilla
 Lesions in the axilla
Involves the
posteriorcord / high
axillary lesions.
* Etiology:
Crutches / shoulder
dislocation

29. Position
• Hand hangs in flexion(wrist
drop)
• Wasting of dorsal arm
(triceps)& muscle mass on
the posterior surface of the
forearm
• Paraesthesias & sensory
loss on the entire extensor
surface of the arm &
forearm & on the back of
the hand & dorsum of the
first 4 fingers.

30. Spiral Groove
 Etiologies
Humeral factures/Compressive
lesions / Saturday night palsy
Entrapment by tendinous arch
of lateral head of triceps
muscle/damaged after arm
excercise .
Soldiers developing palsies at
the lateral border of humerus
after military shooting training
 Sensibility on the
extensor aspect of arm
is spared .
 Sensibility on the
extensor aspect of
forearm may or may
not be spared.
 Wrist drop + / No loss
of elbow extension

32. Elbow – Radial Tunnel Syn.
• Involvement of the
PIN.
• Etiologies
A constricting band at
the radiohumeral joint
capsule.

33.  Lacerations ,gunshot
wounds,closed
injuries(fracture of
proximal radius),chronic
repeated trauma related
to stressful supination &
pronation in swimmers,
frisbee players,tennis
players,violinist .

34. Position
 Atrophy & paresis of
the ECU,ED,Extensor
digiti minimi
APL,EPL,EPB &
extensor indices.
 Extensor carpi radialis
is intact.
• Drop finger deformity
Difficulty in extending
the MCP of all five
fingers
 Partial wrist drop
 No sensory loss
 The wrist deviates
radially,when the
patient makes a fist.

35. Cheiralgia Paresthetica
• The superficial cutaneous branch of the radial
nerve → pure sensory syndrome that
affects the radial part of the dorsum of the
hand & dorsal aspect of the first 3 ½ fingers.
• Etiology:
Crushing/twisting injuries of the wrist/forearm
( “Hand-cuff / Wrist watch neuropathy” )
Repetitive pronation & supination.

37. Summary
 Radial nerve arises from posterior cord of the brachial
plexus
 It passes posterior to the axillary artery between long
and medial 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 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

38.  Radial nerve supply all the extensor muscles 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 causes inability to extend

39. Clinical case presentation