Obturator Nerve Block
A block of the obturator nerve is usually required for complete anesthesia of the knee and is most often performed in combination with femoral and sciatic nerve blocks for this purpose. The obturator nerve contributes sensory branches to the hip and knee joints, a variable degree of sensation to the medial thigh, and innervates the adductors of the hip (Figure 46–45). This nerve exits the pelvis and enters the medial thigh through the obturator fora-men, which lies beneath the superior pubic ramus. After identification of the pubic tubercle, a long (10-cm) block needle is inserted 1.5 cm inferior and 1.5 cm lateral to the tubercle. The needle is advanced posteriorly until bone is contacted ( Figure 46–46). Redirecting laterally and caudally, the needle is advanced an additional 2–4 cm until a motor response (thigh adduction) is elicited and main-tained below 0.5 mA. Following careful aspiration for the nonappearance of blood, 15–20 mL of local anesthetic is injected.