Accessory Obturator Nerve, Anterior View

Description

Arising from the anterior rami of the upper lumbar roots, the accessory obturator nerve is traced from the lumbar plexus along the medial border of psoas major, then carried anteroinferiorly across the pelvic brim toward the superior pubic ramus. Medial to the iliacus and lateral to the vertebral bodies and intervertebral discs, it runs in close company with the obturator nerve but remains a distinct, variably present branch. Distal to the pubic body, the nerve courses toward the proximal thigh, where it typically passes anterior to the obturator canal and approaches the region of pectineus near the femoral triangle. Orientation is straightforward. Anterior anatomy, clean relationships. Clinical interest centers on variation: when present, the accessory obturator nerve often supplies pectineus and can contribute articular fibers to the hip joint, creating a pathway for persistent anterior hip pain after selective obturator neurectomy or an incomplete obturator nerve block. Surgeons working around the superior pubic ramus, acetabular rim, or anterior pelvic ring (including ilioinguinal and modified Stoppa approaches, and mesh placement for inguinal or femoral hernia repair) will recognize how this slender nerve may be at risk near the pectineal line and lacunar region. It also helps explain mixed sensory and motor findings that do not fit a classic obturator neuropathy, since adductor weakness can spare pectineus when this accessory branch is robust. Ideal for gross anatomy teaching on the lumbar and pelvic plexuses, for atlas plates addressing lumbosacral nerve variants, and for clinical education on regional anesthesia of the hip and medial thigh. Useful in operative anatomy references for pelvic ring fixation and anterior approach hip surgery where variant neural structures affect exposure and postoperative symptoms. Anatomical accuracy verified by SciePro's Medical Advisory Board.