Anatomical investigation of a new vertical obturator nerve block technique

Abstract

We evaluated a vertical obturator nerve block (VOB) using a single morphological landmark and no additional distance measurement or obligatory changes of the needle's direction. A total of 88 cadavers (176 lower limbs), prepared using Thiel's embalming method, were examined. The index finger was placed lateral to the palpable pubic tubercle and the needle inserted laterally to the distal part of the fingernail at the tubercle's level and advanced strictly perpendicular to the table's surface. If bone contact was made, the needle was slightly turned to pass the bone distally. Colored latex (5 ml) was then injected. The injection depth was documented, then followed by dissection and nerve exposition. The real skin-nerve distance and the degree of difficulty in orientation and of palpation were measured. Additionally, the dissemination around the nerve or its branches and the intrapelvic spread were documented. The nerve was colored completely in 93.75%, partially in 1.71%, and not colored in 4.54% of cases. The mean injection depth was 3.9 cm (±0.7 SD) and real nerve depth was 3.8 cm (±0.69 SD). Bone contact necessitating the needle's redirection was found in 20 (11.4%) cases. Easy orientation and palpation of the tubercle was always found. In 40 cases, the latex spread via the obturator canal into the lesser pelvis. In this anatomical study, the VOB technique exhibits easy orientation without stimulation or ultrasound guidance. The nerve was located at a constant depth. The injection offered a high percentage of colored nerves.