Innervation Motor radial nerve proper triceps anconeus ECRL ECRB supinator brachioradialis PIN ED EDM ECU APL EPL EPB EIP Sensory posterior cutaneous nerve arm posterior cutaneous nerve - forearm superficial branch radial nerve dorsal digital branch Origin Radial nerve originates from the posterior cord of the brachial plexus (C5-T1) behind axillary artery Course Posterior wall axilla courses on the posterior wall of the axilla (on subscapularis, latissimus dorsi, teres major) 3 Branches in axilla posterior cutaneous nerve of the arm branch to long head of triceps branch to medial head of triceps Triangular interval it then runs through the triangular interval with profunda brachii artery in posterior compartment between long head of triceps and humerus Spiral groove next it courses through the spiral groove between lateral and medial heads of triceps bottom line = Safe zone posteriorly of 10 cm distal to the lateral acromion and 10 cm proximal to lateral epicondyle branches in spiral groove inferior lateral cutaneous nerve of the arm posterior cutaneous nerve of the forearm branch to lateral head of triceps branch to medial head of triceps and anconeus Lateral intermuscular septa next it passes through the lateral intermuscular septa never less than 7.5 cm above the distal articular surface. runs between brachialis and brachioradialis (anterior to lateral epicondyle) gives branches to supply: lateral brachialis, brachioradialis, ECRL, ECRB Terminal branches level of radiohumeral joint line, divides into terminal branches superficial sensory branch Deep branch/PIN ECRB branch Injury & Clinical Conditions PIN compression Syndrome Radial Tunnel Syndrome Radial claw hand injury to the radial nerve with characteristic "claw" hand involving the loss of wrist extension and finger extension