Posterior Scalene, Lateral View

Description

Running deep to the sternocleidomastoid and anterior to the prevertebral musculature, the posterior scalene is isolated in lateral profile as it descends from the posterior tubercles of the transverse processes of the mid to lower cervical vertebrae (classically C4 to C6). Its fibers course inferiorly and laterally to insert on the external surface of the second rib, placing it posterior to the middle scalene and superior to the first rib and pleural cupola. Adjacent bony landmarks include the occipital region and mastoid process superiorly, the cervical vertebrae C1 to C7 with intervertebral discs, and the clavicle and superior scapular margin at the root of the neck. Clean relationships. No guesswork. This lateral view matters when teaching the scalene triangle and the crowded neurovascular corridor at the thoracic inlet. The posterior scalene helps define the posterior boundary of the interscalene space, a region implicated in thoracic outlet syndrome and targeted during interscalene regional anesthesia, where needle trajectory and spread can threaten nearby structures such as the brachial plexus, subclavian artery, and pleura. Rib elevation during forced inspiration also becomes easier to explain when the muscle’s line of pull to the second rib is visible. Use it in head and neck anatomy blocks, musculoskeletal respiration lectures, or as a figure in surgical and anesthesia texts discussing the lateral cervical approach and scalene-related pain generators after whiplash. It also supports radiology teaching when correlating lateral neck imaging with muscular boundaries at the thoracic inlet. Anatomical accuracy verified by SciePro's Medical Advisory Board.