Femoral plexus
Nerve root | Major Nerves | Important Motor Supply | Sensory | Course |
L1 | Iliohypogastric | Muscles of the anterior abdominal wall | Posterolateral buttock | iliohypogastric nerve emerges from the lateral border of psoas major, passes anterior to quadratus lumborum and behind the kidney, then pierces the transversus abdominis near the iliac crest. It divides into lateral (gluteal skin) and anterior (suprapubic skin) cutaneous branches between transversus abdominis and internal oblique. |
L1 | Ilioinguinal | Muscles of the anterior abdominal wall | Inguinal and suprapubic | Ilioinguinal nerve travels with the iliohypogastric initially along the lateral psoas border, then descends within iliac fascia posterior to the ureter. It pierces the internal oblique near the superficial inguinal ring, supplying the root of the penis/scrotum/labia majora and medial thigh skin. |
L1-L2 | Genitofemoral | Genital branch to cremaster muscle | Femoral triangle | Genitofemoral nerve pierces psoas major, descends along its anterior surface, and tracks the external iliac artery. It bifurcates above the inguinal ligament into genital (cremaster/skin of genitalia) and femoral (skin of upper anterior thigh) branches |
L2-L3 | Lateral cutaneous nerve of thigh | - | Anterolateral thigh | Arising from psoas lateral border, it courses under iliacus fascia lata, then passes under or through the inguinal ligament medial to ASIS. It pierces fascia lata over sartorius to supply lateral thigh skin, dividing into anterior/posterior branches |
L2-L4 | Femoral nerve | Iliacus and quadriceps | Anterior thigh; saphenous nerve branch supplies medial leg/foot | The femoral nerve descends through psoas major, emerging lateral to its lower border behind the inguinal ligament into the femoral triangle. It divides ~1-4 cm distal to the ligament into anterior (sartorius, cutaneous thigh nerves) and posterior (quadriceps, adductor) divisions. |
L2-L4 | Obturator nerve | Motor to thigh adductors | Medial thigh | Obturator nerve exits psoas medially, descends behind common iliac vessels, and enters the pelvis along the lateral pelvic wall. It passes through the obturator canal, dividing into anterior (adductor longus/brevis/gracilis) and posterior (obturator externus, adductor magnus) branches. |
- Ilioinguinal and Iliohypogastric is located between the internal and external oblique. Just anterior to the quadratus lumborum
Images
This is a dissection within the psoas muscle showing the intrinsic motor nerve (Direct motor nerves to the Psoas)
IOM is to monitor the femoral nerve
Images
MRI T1/prosection of the lumbar spine and plexus -Nysora
- Abbreviations: ESM, erector spinae muscle; ITS, intrathecal space; IVC, inferior vena cava; LPVS, lumbar paravertebral space; NR, nerve root; QLM, quadratus lumborum muscle; VB, vertebral body.
- The “reference-marker” of the prosection is seen as a “green cross-hair,” which represents the same anatomical point in the multiplanar cadaver anatomical sections
- Transverse view at the level of the L4 vertebral body and the transverse process.
- Transverse view from just below the L4 transverse process and through the lower half of the body of the L4 vertebra and the articular process (inferior)
- Note the hypointense L4 nerve root as it exits the intervertebral foramen (IVF) and enters the hyperintense fatfilled lumbar paravertebral space (LPVS).
- Also seen in the posterior aspect of the psoas muscle is the L3 nerve of the lumbar plexus, which is surrounded by a layer or hyperintense fat and situated within an intramuscular compartment (the “psoas compartment”).
- Sagittal view of the lumbar paravertebral region at the L3–L5 vertebral level showing the steep caudal course of the lumbar nerve roots
- Coronal view at the L3–L5 vertebral level showing the steep caudal course of the lumbar spinal nerves after they emerge from the IVF.
Clinical significance
- For ExLIF
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