Originates
- terminal branch posterior cord / C5 - T1
- runs anterior to subscapularis / teres major / lat dorsi
- passes into triangular space (between humerus / long head of triceps / teres major)
- enters posterior compartment of arm
Arm
- runs in the radial groove between medial and lateral head of triceps, with profunda brachii
- gives a branch to the long and medial head of triceps (this branch runs with the ulna nerve) before the groove
- also gives the posterior cutaneous nerve of the arm
- in the groove branches to the lateral head again to the medial head (this branch also supplies anconeus)
- also the lower lateral cutaneous nerve of the arm and the posterior cutaneous nerve of the forearm, which perforates the lateral head
Elbow
- passes anteriorly through intermuscular septum
- runs between BR / ECRL laterally and brachialis medially
- supplies these muscles and the elbow joint
- at the level of the lateral epicondyle, the radial nerve divides into superficial branch radial and PIN
Superficial branch
- runs under BR until it emerges between it and FCR
- runs superfical to first extensor compartment
- supplies dorsum of hand
Supinator
- has superficial and deep layers
- originates from the supinator crest of the ulna
- inserts onto the lateral surface of the radius between the anterior and posterior oblique lines
PIN
- passes through the radial tunnel which is between the radiohumeral joint and the distal extent of supinator
- passes under a fibrous band of ECRB
- under the radial recurrent leash of vessels
- into supinator (arcade of Frohse)
- then out from under another fibrous band of supinator
- runs over APL
- dips to run on the interosseous membrane
- ending as a small nodule which supplies the wrist joint
PIN then divides
- a superficial branch (supplies EDC, EDM, ECU)
- the deep branch supplies APL, EPB, EI and EPL