The accessory obturator nerve: an anatomical study with literature analysis

Objectives: The accessory obturator nerve (AON) is often underrepresented in the literature and unknown to many surgeons. As this variant nerve has been mistaken for other regional nerves e.g., obturator nerve, nerve injury has occurred. Therefore, the current study was undertaken to better understand the surgical anatomy of the AON. Methods: In the supine position, 20 adult fresh frozen cadavers (40 sides) underwent an anterior approach to the retroperitoneal space. When present, the length and diameter of the AON were measured with microcalipers. The position, course and origin of each AON were documented. Results: The AON was identified on 12 sides (30%). The origin was found to be L2–L3 on four sides; L3 on two sides, L3–L4 from three sides, from the obturator nerve on two sides, and from the femoral nerve on three sides. The average length from the origin to the superior pubic ramus was 14.5 cm. The average diameter was found to be 1.2 mm. All AON were found to lie medial to the psoas major muscle. Additionally, on all sides, the AON was medial to the femoral nerve and lateral to the obturator nerve. Two left sides anastomosed with the anterior division of obturator nerve at its exit from the obturator foramen. Eight sides terminated deep (two) or superficial (six) to the origin of pectineus; two of these had demonstrable branches to the hip joint. Conclusion: The AON is a normal anatomical variant and there are many variations in its origin and terminal branches can be “strong” or “weak.” Knowing the normal anatomy and variations of the AON is important for surgeons including neurosurgeons, orthopaedic surgeons, and urologists who deal with the pathologies of this area.