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Chapter 32D. Ultrasound-Guided Obturator Nerve Block

Which of the following structures is most likely to remain with intact sensation following the performance of an obturator nerve block under ultrasound?

A. Medial thigh skin

B. Adductor longus muscle

C. Medial hip joint

D. Medial knee joint

C is correct. During the performance of an ultrasound obturator nerve block, the articular branches are least likely to be blocked as they arise (80% of the time) from the common obturator nerve, which isn’t routinely blocked during the ultrasound guided approach.1-3

A, B, and D are incorrect. These choices are more reliably anesthetized using an ultrasound proximal thigh obturator nerve block.

Between which of the following two muscles is the posterior branch of the obturator nerve most likely to be encountered when performing an ultrasound guided obturator nerve block?

A. Adductor longus and pectineus

B. Adductor brevis and adductor magnus

C. Adductor longus and adductor magnus

D. Adductor brevis and pectineus

B is correct. The posterior branch lies between the fascial planes of the adductor brevis and adductor magnus muscles.4

A, C, and D are incorrect. These choices are unlikely to contain the posterior branch of the obturator nerve.

Between which of the following two muscles is the anterior branch of the obturator nerve most likely to be encountered when performing an ultrasound guided obturator nerve block?

A. Adductor longus and pectineus

B. Adductor brevis and adductor magnus

C. Adductor longus and adductor magnus

D. Adductor brevis and pectineus

D is correct. In the thigh, at the level of the femoral crease, the anterior branch is located between the fascia of the pectineus and adductor brevis muscles.4

A, B, and C are incorrect. These choices are unlikely to contain the anterior branch of the obturator nerve.

Under spinal anesthesia, the addition of an obturator nerve block is indicated to prevent involuntary abduction of the thigh during which of the following surgical procedures?

A. Transurethral resection of a lateral bladder tumor

B. Iliopsoas hematoma evacuation

C....

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