Detailed anatomy of accessory obturator nerve blockade

Abstract

Background: The accessory obturator nerve (AON) often innervates the hip joint and adductor longus. The AON is present in 10-30% of patients, and thus it is clinically important that it is also considered during obturator nerve (ON) blockade.

Methods: The study was performed on 12 cadavers (24 body-sides) and the AON beginning from the lumbar plexus was observed. The needle was classically penetrated into the ON to gain access to the AON and upon definition of detailed AON anatomy, morphometric measurements were conducted. In addition, novel maneuvers used in the study were described.

Results: Throughout the dissections, the AON was detected on three sides (12.5%) and the mean AON- pubic tubercle distance was measured as 4.0 cm. The needle was withdrawn and positioned medially and almost parallel to the skin. It was then advanced through the superior pubic ramus to reach the AON.

Conclusion: Owing to its anatomical structure, the AON can be easily accessed during classical ON blockade using the maneuvers described here. Further clinical studies are needed to investigate if supplementing ON blockade with AON blockade might improve the clinical efficiency and quality of the blockade.