Posterior Region of the Arm

Description

Centered on the posterior brachium, the highlighted field corresponds to the extensor compartment overlying the humeral shaft. Superficially, the triceps brachii dominates the region, with the long head lying medially and proximally near the posterior axillary fold, the lateral head occupying the posterolateral arm, and the medial head contributing deeper fibers that become more apparent approaching the olecranon. Inferiorly, the muscle mass converges into the triceps tendon inserting on the posterior ulna, while the contour of the posterior deltoid frames the proximal boundary near the shoulder. Clear surface anatomy. Clinically, this is the corridor where humeral shaft fractures and posterior approaches to the humerus intersect with neurovascular risk, because the radial nerve and profunda brachii artery traverse the radial (spiral) groove on the posterior humerus, then pass anterior to the lateral epicondyle as they enter the forearm. That relationship explains classic findings of midshaft humeral fractures, with weakness of wrist and finger extension plus sensory change over the dorsolateral hand, while elbow extension may be partly preserved depending on the level of injury. It also anchors teaching of the triceps reflex (C7) and of safe dissection planes between the long and lateral heads when exposing the posterior humerus. In an upper-limb anatomy lab, this posterior arm view supports instruction on compartment organization, surface landmarks for palpation, and the pathway of the radial nerve relative to the humerus. It also fits orthopedic and sports medicine publications discussing humeral fixation, radial nerve palsy, and triceps tendon injury, as well as patient-facing diagrams for postoperative counseling about expected deficits and recovery. Anatomical accuracy verified by SciePro's Medical Advisory Board.