Obturator Nerve Block: An Anatomical Perspective.

Background A comprehensive understanding of the anatomy of the obturator nerve after its emergence from the obturator foramen is essential when undertaking an obturator nerve block effectively. This study was conducted to provide precise anatomical guidance of the obturator nerve block with surface landmarks in the inguinal region. Materials and methods A cross-sectional observational study was carried out on 34 dissected embalmed cadaveric lower limbs to investigate anatomic variability of obturator nerve localization concerning bony/ligamentous landmarks viz. the pubic tubercle, anterior superior iliac spine, inguinal ligament, and femoral artery as well as the adductor longus. Results The pubic tubercle and inguinal ligament were found to be the "least variable indicator" and palpable landmark for localization of the main trunk of the obturator nerve exhibiting lesser standard deviation of the mean distance from the obturator nerve exit. Among the soft tissue (vessel/muscle) parameters, the shortest distance of the adductor longus muscle from the obturator nerve exit was found to have the lowest standard deviation, thus making it the most reliable parameter for obturator nerve localization. Conclusion High anatomic variability in the obturator nerve's localization does exist, and this explains the difficulty frequently encountered in the application of regional anesthetic techniques. The pubic tubercle and inguinal ligament points were found to be the least variable and most reliable landmarks for localization of the main trunk of the obturator nerve.