Radial Nerves, Posterior View

Description

Posterior upper limb anatomy is rendered with the scapula superiorly and the humerus descending to the distal arm, while the radial nerve (musculospiral nerve) courses obliquely from medial to lateral across the posterior surface of the shaft in the sulcus nervi radialis (spiral groove). Proximally it lies deep to the long head of triceps brachii near the triangular interval with the profunda brachii artery, then tracks inferolaterally between the lateral and medial heads of triceps. Distal to the groove, the nerve approaches the lateral intermuscular septum and moves toward the lateral epicondylar region, where its terminal division into superficial and deep branches is typically introduced. Understanding this posterior trajectory matters because it is the segment most exposed in midshaft humeral fractures and during posterior approaches to the humerus, where the nerve is tethered in the spiral groove and at the lateral intermuscular septum. A short lesion here produces the classic combination of triceps weakness (variable, depending on the level), wrist and finger drop from extensor denervation, and sensory change over the dorsolateral hand, while sparing patterns help you localize whether injury is proximal to the branch to brachioradialis and extensor carpi radialis longus. The close pairing of the radial nerve with the profunda brachii artery also frames bleeding risk and hematoma-related neuropraxia after trauma. Use this artwork in gross anatomy and neuroanatomy teaching when introducing posterior arm compartments, in orthopedic and trauma texts discussing humeral shaft fracture patterns and iatrogenic palsy, or in surgical education for posterior humeral exposure and radial nerve exploration in an adult male patient. It also supports patient-facing diagrams for counseling on expected deficits and recovery after radial nerve palsy. Anatomical accuracy verified by SciePro's Medical Advisory Board.