Ultrasound-Guided Obturator Nerve Block: A Focused Review on Anatomy and Updated Techniques

Figure 1

(a) Illustration showing the right-sided adductor muscles and the course of the obturator nerve. (b) Illustration of the positional relationship between the adductor muscles, the obturator nerve, and the transducer during each ultrasound-guided obturator nerve block technique. Large green squares with the letter A or B indicate the foot print position of the transducer. A small green square with the letter C indicates the side position of the transducer. In the distal approach, the transducer is placed at position A. In the proximal approaches reported by Anagnostopoulou et al. [17], Taha [23], and Lin et al. [42], the transducer is tilted cranially at position A to allow visualization of the plane between the pectineus and obturator externus muscles. In the approach used by Akkaya et al. [35], the transducer is placed at position B to allow visualization of the same plane in the sagittal view. Using the approach described by Yoshida et al. [31], the transducer is placed at position C in the lithotomy position to see the plane between the pectineus and obturator externus muscles. ON, obturator nerve; AL, adductor longus muscle; AB, adductor brevis muscle; AM, adductor magnus muscle; PE, pectineus muscle; OE, obturator externus muscle; SPR, superior pubic ramus; GR, gracilis muscle.

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