Upper Limb

1. RADIAL NERVE
Dr M Idris Siddiqui

2. Learning objectives
–The applied anatomy of the radial
nerve
–Its anatomical course,
–Motor functions and
–Cutaneous innervation.
–The clinical correlations of damage to
the radial nerve.

3. The radial nerve
• The radial nerve is a continuation of
posterior cord of brachial plexus in the axilla.
• It is the largest nerve of the brachial plexus.
• It supplies the posterior (extensor)
compartment of upper limb.
• It carries fibres from all the roots (C5, C6, C7,
C8, and Tl) of brachial plexus
– (but T1 fibres are not constant).

7. COURSE IN THE AXILLA
• The radial nerve lies posterior to the third
part of the axillary artery and anterior to the
muscles forming the posterior wall of the
axilla.
• Here it gives off the following three
branches:
1. Posterior cutaneous nerve of arm
2. Nerve to the long head of triceps.
3. Nerve to the medial head of triceps.

8. The radial nerve

11. COURSE IN THE ARM
• Radial nerve enters the arm at the
lower border of the teres major.
• It passes between the long and
medial heads of triceps to enter the
lower triangular space, through
which it reaches the spiral groove
along with profunda brachii artery.

12. COURSE IN
SPIRAL GROOVE
• The radial nerve in the spiral groove lies in direct
contact with the humerus.
• At the lower 3rd of the humerus, it pierces the
lateral intermuscular septum to enter anterior
part of the arm again where it lies deeply in the
interval between the brachialis & the
brachioradialis.
• Then between brachialis and extensor carpi
radialis longus before entering the cubital fossa.

15. BOUNDARIES OF THE SPIRAL GROOVE
Anteriorly Middle one-third of the shaft of the
humerus
Above Origin of the lateral head of triceps
Below Origin of the medial head of triceps
Posteriorly Fibres of lateral and long head triceps

16. BRANCHES OF THE RADIAL NERVE
IN SPIRAL GROOVE
• Lower lateral cutaneous nerve of the arm:
– provides sensory innervation to the skin on the lateral
surface of the arm up to the elbow.
• Posterior cutaneous nerve of the forearm:
– Provides sensory innervation to the skin down the middle of
the back of the forearm up to the wrist.
• Nerve to lateral head of triceps.
• Nerve to medial head of triceps.
• Nerve to anconeus (it runs through the substance of
medial head of triceps to reach the anconeus).
• At the lower end of the spiral groove, the radial nerve pierces the
lateral muscular septum of the arm and enters the anterior
compartment of the arm.

17. BRANCHES OF THE RADIAL NERVE
IN THE ANTERIOR COMPARTMENT OF ARM
• The deep branch (also called posterior interosseous
nerve), in the cubital fossa supplies two muscles:
– Extensor carpi radialis brevis.
– Supinator.
• After supplying these two muscles, it passes
through the substance of supinator and enters the
posterior compartment of the forearm and supplies
all the extensor muscles of the forearm.
– It also gives articular branches to the distal radio-ulnar,
wrist, and carpal joints.

20. The radial nerve
• To enter the forearm, the radial nerve moves
anteriorly over the lateral epicondyle of the
humerus.
• Through the cubital fossa.
• It terminates by dividing into two branches:
– Deep branch (motor) called posterior interosseous
nerve:
• Innervates most of the muscles in the posterior compartment
of the forearm.
– Superficial branch (sensory)also called superficial radial
nerve
• Contributes to the cutaneous innervation of the hand and
fingers.

23. posterior interosseous nerve

24. The radial nerve
• The superficial branch (also called superficial radial
nerve) is sensory. It runs downwards over the
supinator, pronator teres, and flexor digitorum
superficialis deep to brachioradialis.
– About one-third of the way down the forearm (at about
7 cm above wrist), it passes posteriorly,
• It emerges from under the tendon of
brachioradialis, proximal to the styloid process
of radius and then passes over the tendons of
anatomical snuff-box, where it terminates as
cutaneous branches.

26. The radial nerve

27. Superficial branch of radial nerve
in hand
• It supplies the skin of the lateral (radial) half
of dorsal aspect of the hand and thumb,
• It divides into several dorsal digital nerves
which provide sensory innervation to skin over the
lateral part of the dorsum of hand and dorsal
surfaces of lateral 3 ⅟₂ digits proxi al to the ail
beds.

28. What is the radial tunnel?
The radial nervenerve passes down the back of the upper
arm. It then spirals outward and crosses the outside
(the lateral part) of the elbow before it winds its way down
the forearm and hand.
On the lateral part of the elbow, the radial nerve enters a
tunnel formed by muscles and bone. This is called the
radial tunnel.
Passing through the radial tunnel, the radial nerve runs below
the supinator muscle.
– The supinator muscle lets you twist your right hand clockwise.
This is the motion of using a screwdriver to tighten a screw.

30. Radial tunnel syndrome
• It is an entrapment neuropathy of the deep branch of
radial nerve at elbow. The compression of radial nerve
at elbow may be caused by the following four
structures:
1. Fibrous bands, which can tether the radial nerve to
the radio-humeral joint.
2. Sharp tendinous margin of extensor carpi radialis
brevis.
3. Leash of vessels from the radial recurrent artery.
4. Arcade of Frohse, a fibro-aponeurotic proximal edge
of the superficial part of the supinator muscle.
• Characteristic in such cases will be as follows:
– Loss of extension of the wrist and fingers but no wrist drop.
– Pain over the extensor aspect of the forearm.

31. The radial nerve
• Motor Functions
• The radial nerve innervates the muscles located in the
posterior upper arm and posterior forearm.
• In the upper arm, it innervates
– The three heads of the triceps brachii – which acts to extend
the arm at the elbow.
– The brachioradialis and
– Extensor carpi radialis longus (muscles of the posterior
forearm).
• A terminal branch of the radial nerve, the deep
branch, innervates
– The remaining muscles of the posterior forearm
• Note: When the deep branch of the radial nerve penetrates the supinator muscle of the
forearm, it is termed the posterior interosseous nerve for the remainder of its course.

32. The radial nerve
• Sensory Functions
• There are four branches of the radial nerve that provide
cutaneous innervation to the skin of the upper limb.
• Three of these branches arise in the upper arm:
– Lower lateral cutaneous nerve of arm – Innervates the
lateral aspect of the upper arm, below the deltoid muscle.
– Posterior cutaneous nerve of arm – Innervates the posterior
surface of the upper arm.
– Posterior cutaneous nerve of forearm – Innervates a strip of
skin down the middle of the posterior forearm.
• The fourth branch – the superficial branch – is a
terminal division of the radial nerve. It innervates the
dorsal surface of the lateral three and half digits, and
their associated palm area.

36. The radial nerve
• CLINICAL RELEVANCE
• Injuries of the radial nerve: The radial nerve
may be injured at 4 sites:
– (a) in the axilla,
– (b) in the spiral groove,
– (c) in the forearm,
– (d) at the elbow.

37. Lesions of the radial nerve
Lesions Motor deficits Sensory loss
Lesion at the axilla
injured by the pressure
of the upper end of
crutch (crutch palsy),
by a dislocation at the
shoulder joint,
By a fracture of
the proximal humerus.
Triceps weakness
Brachioradialis weakness
Extensor weakness of the
wrist - "wrist drop”
Lateral dorsum of the hand and
wrist
Dorsum of the thumb
Proximal dorsum of fingers
2 and 3
Lesion at the spiral
groove of humerus:
Midshaft fracture of
humerus.
Wrongly placed
intramuscular injection.
Saturday night paralysis.
Triceps is spared!
Brachioradialis weakness
Extensor weakness of the
wrist - "wrist drop”
Lateral dorsum of the hand and
wrist
Dorsum of the thumb
Proximal dorsum of fingers
2 and 3
Lesion at the radial
tunnel
(humeroradial joint)
Extensor weakness of the
wrist - "wrist drop" - may be
mild
Lateral dorsum of the hand and
wrist
Dorsum of the thumb
Proximal dorsum of fingers 2 & 3.

38. The radial nerve