Subinguinal Space

spatium subinguinale

The subinguinal space is the gap beneath the inguinal ligament between the anterior superior iliac spine and the pubic tubercle, through which the iliopsoas, pectineus, femoral nerve, femoral artery, femoral vein, and femoral canal pass from the abdomen into the thigh. The muscular lacuna (lateral) and vascular lacuna (medial) are its two subdivisions.

Anatomical Data

Boundaries & Contents

Location	Gap between the inguinal ligament and the hip bone, from the anterior superior iliac spine to the pubic tubercle
Boundaries	Inguinal ligament (front) Upper edge of the hip bone (back) Iliopectineal arch (divides it into a lateral and a medial part)
Contents	Muscular lacuna: iliopsoas, femoral nerve and lateral femoral cutaneous nerve Vascular lacuna: femoral artery, femoral vein and femoral canal Femoral branch of the genitofemoral nerve

Biomechanics

Function & Actions

The main doorway between the abdomen and the front of the thigh. The iliopectineal arch keeps the muscle and nerve compartment separate from the vessel compartment.

Clinical Relevance

Clinical Notes

The subinguinal space is the site of femoral nerve block, which is the primary regional technique for femoral shaft and knee surgery. The femoral nerve lies lateral to the femoral artery in the muscular lacuna and is blocked with in-plane ultrasound guidance. Femoral nerve compression at this level by haematoma, lipoma, or lymphadenopathy produces femoral neuropathy with anterior thigh numbness and quadriceps weakness.

Pathology

Common Injuries & Conditions

Femoral Neuropathy

Compression of the femoral nerve in the subinguinal space from haematoma, psoas abscess, or lymphadenopathy producing quadriceps weakness, loss of the patellar reflex, and anterior thigh and medial leg numbness.

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