Anterior Interosseous Nerve, Anterior View

Description

Anterior forearm anatomy is presented with the anterior interosseous nerve (AIN), a motor branch of the median nerve, descending on the ventral surface of the interosseous membrane between the radius laterally and ulna medially. Proximally, the nerve arises just distal to the pronator teres region and then tracks inferiorly with the anterior interosseous artery along the deep flexor compartment. Distally, its terminal branches course toward flexor pollicis longus, the radial (lateral) half of flexor digitorum profundus, and pronator quadratus near the distal radius. Deep, midline, and tightly tethered to the membrane. This anterior perspective matters because the AIN is classically injured by entrapment or neuritis in the proximal forearm, producing the characteristic inability to form the thumb index finger pinch (Kiloh-Nevin syndrome) without cutaneous sensory loss. Surgeons and clinicians use the interosseous membrane, the deep surface of flexor digitorum superficialis, and the pronator teres fibrous arch as spatial cues when localizing the lesion and when planning anterior approaches for forearm fixation or decompression. It is a small nerve with a loud deficit. Ideal for teaching the deep anterior compartment in gross anatomy, upper limb neuroanatomy, and hand surgery modules where learners must connect nerve course to specific motor findings in flexor pollicis longus, flexor digitorum profundus, and pronator quadratus. It also supports figures for neurology and orthopaedic texts discussing AIN palsy, proximal median neuropathy, and anterior forearm surgical corridors. Anatomical accuracy verified by SciePro's Medical Advisory Board.