Branch to the Medial Head of the Triceps and Anconeus, Posterior View

Description

Posteriorly, the scapula and proximal humerus frame the course of the radial nerve as it leaves the posterior cord and enters the posterior compartment of the arm. A discrete motor branch departs the main radial nerve trunk and tracks distally toward the medial head of triceps brachii, with continuation toward anconeus near the posterolateral aspect of the elbow. More laterally, the long and lateral heads of triceps occupy the superficial plane, creating the expected relationship in which the medial head lies deep and closer to the humeral shaft. A companion vessel is shown in blue along the arm, consistent with the profunda brachii artery traveling with the nerve in the spiral groove. This view matters because denervation patterns in the triceps do not always mirror the classic “radial nerve palsy” teaching diagram. The branch to the medial head of triceps and the anconeus often arises proximally and can be spared or selectively injured depending on the level of a humeral shaft fracture, entrapment in the radial groove, or posterior surgical exposure for ORIF. Anconeus strength, though subtle on exam, becomes a useful clue in lesions around the lateral elbow and in iatrogenic injury during posterior approaches, where the interval and dissection plane can drift toward the nerve as it approaches the olecranon region. Small branch. Big consequences. Use this plate for upper-limb anatomy teaching on the posterior compartment, for orthopaedic trauma chapters discussing radial nerve risk in midshaft humeral fractures, and for surgical anatomy figures supporting posterior arm or elbow approaches that aim to preserve triceps function. Anatomical accuracy verified by SciePro's Medical Advisory Board.