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Radial Nerve Anatomy Episode 1 . 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. Cutaneous Innervation. Posterior cutaneous nerve of arm Inferior lateral cutaneous nerve of arm
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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
Cutaneous Innervation • Posterior cutaneous nerve of arm • Inferior lateral cutaneous nerve of arm • Posterior cutaneous nerve of forearm • Superficial branch of radial nerve
Motor Innervation • Muscular branches of radial nerve above elbow: • Triceps • Anconeus • Brachoradialis • ECRL
Motor Innervation • Muscular Branches below elbow: • ECRB (varied innervation: superficial or PIN) • Supinator • PIN: • Superficial • EDC, ECU,, EDM • Deep • APL, EPL, EPB, EI
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 • 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 • Through lateral intermuscular septum 10-12cm above lateral epicondyle
Course of Radial Nerve • In anterior compartment of arm lies between brachialis and brachioradialis • 1-3 accessory branches to brachialis • Large branch to BR (sometimes this branch given by superficial radial below elbow) • ECRL generally innervated proximal to elbow joint
Course of Radial Nerve • Enters the forearm anterior to lateral epicondyle • More specifically over articulation between capitulum and radial head • ECRB innervated distal to elbow joint either PIN or superficial branch • At some point 3cm above or below divides into: • Superficial radial • PIN
Course of Superficial Radial Nerve • Runs over supinator,PT and FDS • Lies under BR with radial artery on its ulnar side from 1/3 of the way down forearm • Passes posteriorly through tendon of BR proximal to radial styloid • Passes over tendons of snuffbox • Terminates as cutaneous branches to dorsum of hand and lateral 3.5 digits short of nailbeds
Posterior Interosseous Nerve • Gains access to posterior forearm by diving posterior and laterally through ligament of Frohse and the interval between the two heads of supinator • Arcade of Frohse is a fibrous arch originating lateral epicondyle superior part of superficial layer of supinator • German Anatomist, Fritz Frohse (1871-1916)
Posterior Interosseous Nerve • After exiting the supinator divides into deep and superficial muscular branches • Superficial • EDC, ECU, EDM • Deep • APL, EPL, EPB, EI
Radial Nerve Compression Sites • PIN • As it traverses the radial tunnel it encounters 4 sites of compression • “Radial tunnel syndrome” • entrapment neuropathy
Radial Tunnel Syndrome • Fibrous bands • Tight fibrous bands anterior to radial head at entrance of tunnel • Arcade of Frohse • Most common • Leash of Henry • Radial recurrent vx that fan out over radial nn • Medial border of ECRB
Cheiralgia paresthetica • Described by Robert Wartenberg 1932 • Superficial radial nerve neuritis • Wartenberg Syndrome • Causes: • Trauma, iatrogenic, compression (muscle anomalies, fascial bands, thrombosis radial recurrent artery, tumour, haemorrhage) • Symptoms: • Dysaesthesia over distribution
Radial Nerve Palsy • Causes: • Fractures esp humerus, Monteggia • Penetrating injury/trauma • “Saturday Night Palsy” “Crutches” • Iatrogenic • tumour