Femoral Nerve Block
The femoral nerve (L2–L4) is the largest branch of the lumbar plexus. Other important branches of the lumbar plexus include the lateral femoral cutaneous and obturator nerves as well as the iliohypogastric and ilioinguinal nerves.
It descends through the psoas major muscle, exiting the muscle at its lower lateral border, before coursing between the psoas major and iliacus muscles, deep to the iliacus fascia (iliopectineal fascia), towards the inguinal ligament.
The femoral nerve (L2–L4) is the largest branch of the lumbar plexus. Other important branches of the lumbar plexus include the lateral femoral cutaneous and obturator nerves as well as the iliohypogastric and ilioinguinal nerves.
It descends through the psoas major muscle, exiting the muscle at its lower lateral border, before coursing between the psoas major and iliacus muscles, deep to the iliacus fascia (iliopectineal fascia), towards the inguinal ligament.
At the inguinal ligament and just distal to it, the nerve lies slightly deeper (0.5–1 cm) and lateral (approximately 1.5 cm) to the femoral artery; the vein is medial to the artery.
In the proximal thigh, the femoral artery gives rise to the profunda femoris (deep femoral) artery from its lateral aspect. This is a useful landmark because if ultrasound scanning fails to locate the nerve immediately lateral to the femoral artery at the block location, the profunda femoris artery can be traced proximally to locate the femoral nerve before
it divides.
In the proximal thigh, the femoral artery gives rise to the profunda femoris (deep femoral) artery from its lateral aspect. This is a useful landmark because if ultrasound scanning fails to locate the nerve immediately lateral to the femoral artery at the block location, the profunda femoris artery can be traced proximally to locate the femoral nerve before
it divides.
At the femoral (inguinal) crease, a few centimeters caudad to the inguinal ligament, the nerve lies underneath the fascia iliaca (iliopectineal fascia) which is itself deep to the fascia lata. At this point the nerve is separated from the femoral artery and vein by the iliopectineal ligament and often a portion of the psoas major muscle (local anesthetic spread is therefore unlikely here).
