A needle introduced 1.5 cm inferior and 1.5 cm lateral to the pubic tubercle will be in close proximity to which nerve?

A needle introduced 1.5 cm inferior and 1.5 cm lateral to the pubic tubercle will be in close proximity to which nerve?

• A. Obturator nerve
• B. Femoral nerve
• C. Lateral femoral cutaneous nerve
• D. Sciatic nerve

Answer: (A)

The key idea is where the obturator nerve sits in relation to the pubic bone. The obturator nerve travels from the pelvis and exits through the obturator canal in the region of the superior pubic ramus near the pubic tubercle. From there it courses toward the medial thigh. A needle placed about 1.5 cm inferior and 1.5 cm lateral to the pubic tubercle sits right near this path, where the nerve lies as it leaves the pelvis and enters the medial thigh, making it the most likely nerve encountered. In contrast, the femoral nerve stays more laterally under the inguinal ligament in the femoral triangle, the lateral femoral cutaneous nerve runs toward the outer thigh near the ASIS, and the sciatic nerve lies posteriorly in the gluteal and posterior thigh regions. Those trajectories are farther from this anterior pelvic landmark, so they’re less likely to be in proximity to the needle at that site.

The key idea is where the obturator nerve sits in relation to the pubic bone. The obturator nerve travels from the pelvis and exits through the obturator canal in the region of the superior pubic ramus near the pubic tubercle. From there it courses toward the medial thigh. A needle placed about 1.5 cm inferior and 1.5 cm lateral to the pubic tubercle sits right near this path, where the nerve lies as it leaves the pelvis and enters the medial thigh, making it the most likely nerve encountered.

In contrast, the femoral nerve stays more laterally under the inguinal ligament in the femoral triangle, the lateral femoral cutaneous nerve runs toward the outer thigh near the ASIS, and the sciatic nerve lies posteriorly in the gluteal and posterior thigh regions. Those trajectories are farther from this anterior pelvic landmark, so they’re less likely to be in proximity to the needle at that site.