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Radial Nerve is very important topic for first year MBBS Students and as well as for day today clinical practice. This slide gives you full course & relations with clear diagrams as well as applied anatomy with clinical Co-relation.
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RADIAL NERVE - ANATOMY
DR.Murali.M.S;M.B.A Prof. of Surgery D Y Patil Medical
College Mauritius.
Objectives
Origin Course & Relations Branches Distribution Applied Anatomy
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
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
Post view Ant view
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
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
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
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
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
Course of Radial Nerve
In anterior compartment of arm lies between brachialis and brachioradialis
At its division – closely related to radial recurrent artery
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.
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
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
Posterior Interosseous Nerve After exiting the
supinator divides into deep and superficial muscular branches
Superficial EDC, ECU, EDM
Deep APL, EPL, EPB, EI
APPLIED ANATOMY
Lesions
Level I – Axilla
Level II – Spiral groove
Level III – Elbow
Level IV – Forearm
Axilla
Lesions in the axilla Involves the posteriorcord /
high axillary lesions.
* Etiology: Crutches /
shoulder dislocation
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.
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
Elbow – Radial Tunnel Syn.
• Involvement of the PIN.
• Etiologies A constricting
band at the radiohumeral joint capsule.
Lacerations ,gunshot wounds,closed injuries(fracture of proximal radius),chronic repeated trauma related to stressful supination & pronation in swimmers, frisbee players,tennis players,violinist .
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.
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.
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
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 metacarpophalangeal joint finger drop.
Clinical case presentation