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AN15.1-5 | Front & Medial side of thigh — Part 2

Femoral Nerve and Femoral Artery

Femoral nerve (L2, L3, L4):
- Largest branch of the lumbar plexus
- Formed in the psoas muscle; emerges lateral to psoas at the pelvic brim
- Enters the thigh through the muscular lacuna (lateral compartment, under the inguinal ligament — lateral to the femoral sheath)
- NOT within the femoral sheath
- In the femoral triangle, it immediately divides into anterior and posterior divisions
- Anterior division: supplies sartorius; sensory — medial and anterior thigh (anterior cutaneous femoral nerves)
- Posterior division: motor — quadriceps femoris; gives the saphenous nerve (longest cutaneous nerve; accompanies femoral artery through adductor canal; emerges at the knee; supplies medial leg and foot)
- Clinical: femoral nerve block (inguinal approach) → anaesthesia for quadriceps and medial thigh; femoral nerve injury → quadriceps paralysis (cannot extend knee), loss of knee jerk

Femoral artery (continuation of external iliac artery below inguinal ligament):
- Enters the femoral triangle at the midinguinal point (midpoint of inguinal ligament — NOT the same as the mid-inguinal point for the deep ring, which is the midpoint of the ASIS-to-pubic tubercle line)
- Lies in the middle compartment of the femoral sheath
- Major branches in the femoral triangle:
- Profunda femoris (deep femoral artery) — largest branch, arises ~3–4 cm below inguinal ligament; supplies most of the thigh via perforating arteries; gives medial and lateral circumflex femoral arteries
- Superficial epigastric, superficial iliac circumflex, and superficial external pudendal arteries (small)
- Continues into the adductor canal
- Clinical: femoral artery pulsation is the landmark for femoral vein access in central line insertion; femoral pulse is palpable at the midinguinal point

The Adductor Canal (Hunter's Canal)

The adductor canal (subsartorial canal / Hunter's canal) is an aponeurotic tunnel in the middle third of the thigh.

Boundaries:
- Anterior wall / roof: vastoadductor membrane (dense fibrous sheet between vastus medialis and adductor muscles) — overlaid by sartorius
- Lateral wall: vastus medialis
- Posteromedial wall: adductor longus (upper) and adductor magnus (lower)

Extent: from the apex of the femoral triangle (where sartorius crosses adductor longus) → to the adductor hiatus in adductor magnus

Contents:
1. Femoral artery → becomes the popliteal artery after passing through the adductor hiatus
2. Femoral vein → runs posterior to the artery in the canal
3. Saphenous nerve (branch of femoral nerve) → exits through the vastoadductor membrane in the lower canal → travels with the great saphenous vein on the medial side of the leg
4. Nerve to vastus medialis
5. Occasionally: descending genicular artery

Clinical significance:
- Femoral artery aneurysm or thrombosis can occur within the adductor canal
- Hunter's canal was used historically for thigh amputation access (hence the eponym)
- Saphenous nerve can be injured during great saphenous vein (GSV) harvesting for coronary artery bypass grafting (CABG), causing medial leg numbness