Describe the boundaries and contents of the femoral triangle. Add a note on the femoral sheath and the femoral canal.

Definition

Boundaries

• Older descriptions include adductor brevis in the floor

Contents — Lateral to Medial

• Mnemonic — NAVEL
• N — Femoral nerve and its branches (outside the femoral sheath)
• A — Femoral artery and branches
• V — Femoral vein and tributaries
• E — Empty space (the femoral canal)
• L — Lymphatics — deep inguinal nodes including the node of Cloquet
• Also — femoral branch of the genitofemoral nerve, lateral cutaneous nerve of thigh, and the terminal part of the great saphenous vein

Femoral Sheath

• Anterior wall — from the fascia transversalis; posterior wall — from the fascia iliaca
• Divided by two septa into three compartments

• The femoral nerve is outside the sheath, lying on iliopsoas — a point frequently asked

Femoral Canal and Ring

• The femoral canal is the medial compartment, about 1.25 cm long; its upper opening is the femoral ring, closed by the femoral septum
• Function — a dead space allowing the femoral vein to expand during increased venous return, and a route for lymphatics

Femoral Artery

• Continuation of the external iliac artery at the mid-inguinal point — midway between the anterior superior iliac spine and the pubic symphysis
• Becomes the popliteal artery at the adductor hiatus
• Branches — superficial epigastric, superficial circumflex iliac, superficial and deep external pudendal, and the profunda femoris (the largest, from the lateral side about 4 cm below the inguinal ligament)
• Profunda femoris gives the medial and lateral circumflex femoral arteries and four perforating arteries

Saphenous Opening and LYMPH Nodes

• The saphenous opening is a gap in the fascia lata about 4 cm below and lateral to the pubic tubercle, with a sharp falciform margin
• It is closed by the cribriform fascia, pierced by the great saphenous vein and lymphatics — hence the name
• Superficial inguinal nodes lie in the superficial fascia — a horizontal group below the inguinal ligament draining the anterior abdominal wall below the umbilicus, perineum, external genitalia (not testis), lower anal canal and buttock; and a vertical group along the saphenous vein draining the lower limb
• Deep inguinal nodes lie medial to the femoral vein, the highest being the node of Cloquet in the femoral canal
• All drain onward to the external iliac nodes

Applied Aspects

• Femoral hernia — lies below and lateral to the pubic tubercle; commoner in women (wider pelvis); high risk of strangulation because the ring is narrow and rigid
• Inguinal hernia lies above and medial to the pubic tubercle — the single reliable clinical distinction
• The femoral artery is the standard site for arterial puncture — cardiac catheterisation, angiography, and femoral arterial blood gas sampling
• Femoral vein cannulation uses the same landmarks — the vein lies immediately medial to the artery
• Femoral nerve block is given lateral to the artery, remembering the nerve is outside the sheath
• Psoas abscess tracks beneath the inguinal ligament and presents as a swelling in the femoral triangle, mimicking a hernia; it has a cross-fluctuant swelling above the ligament
• Saphena varix at the saphenous opening may also mimic a hernia, but has a fluid thrill on coughing and vanishes on lying down