Boundaries and contents
The femoral triangle is bounded above by the inguinal ligament, laterally by the medial border of sartorius and medially by the medial border of adductor longus. Some texts use the lateral border of adductor longus instead, which gives the same space. The apex, where sartorius crosses adductor longus, leads into the adductor canal.
The roof is the fascia lata, perforated by the saphenous opening, which is covered by the thin cribriform fascia. The floor is gutter-shaped: iliopsoas (psoas major and iliacus) laterally, pectineus and adductor longus medially.
From lateral to medial the contents are the femoral nerve, the femoral artery, the femoral vein and the femoral canal. The nerve lies outside the femoral sheath, a funnel-shaped downward extension of the abdominal fascia (transversalis fascia in front, iliac fascia behind). The sheath has three compartments: lateral for the artery, intermediate for the vein and medial for the femoral canal.
Femoral canal
The femoral canal is the short medial compartment of the sheath, containing fat, lymphatics and usually a deep inguinal node (Cloquet's node). Its upper opening, the femoral ring, is bounded by the inguinal ligament in front, the pectineal ligament behind, the lacunar ligament medially and the femoral vein laterally. The canal gives the vein room to expand.
Course of the femoral vessels
The femoral artery is the continuation of the external iliac artery, beginning behind the inguinal ligament at the mid-inguinal point, halfway between the anterior superior iliac spine and the pubic symphysis. It runs down the triangle on psoas and pectineus and leaves through the apex into the adductor canal.
| Branch | Distribution |
|---|---|
| Superficial epigastric | Skin of the lower abdominal wall |
| Superficial circumflex iliac | Skin towards the anterior superior iliac spine |
| Superficial and deep external pudendal | Skin of the scrotum or labium majus and the lower abdomen |
| Profunda femoris (deep femoral) | Main supply of the thigh, through the circumflex femoral and perforating arteries |
The profunda femoris arises from the lateral or posterior side of the femoral artery a few centimetres below the inguinal ligament. It usually gives the medial and lateral circumflex femoral arteries. The lateral circumflex femoral artery runs laterally between the branches of the femoral nerve, deep to sartorius and rectus femoris, and divides into ascending, transverse and descending branches; the ascending branch climbs towards the anterior superior iliac spine and the trochanteric anastomosis.
The femoral vein lies medial to the artery at the inguinal ligament. The great saphenous vein passes through the saphenous opening, about 3 to 4 cm below and lateral to the pubic tubercle, to join it. Near its end the great saphenous vein receives the superficial epigastric, superficial circumflex iliac and superficial external pudendal veins.
Nerves of the femoral triangle
The femoral nerve (L2–L4) enters the thigh behind the inguinal ligament, lateral to the femoral sheath, having run in the groove between psoas and iliacus. Within a few centimetres it breaks up into branches.
- Anterior division: the medial and intermediate cutaneous nerves of the thigh, and the nerves to sartorius and pectineus. The intermediate cutaneous nerve usually pierces sartorius to reach the skin of the front of the thigh.
- Posterior division: the nerves to the four heads of quadriceps and the saphenous nerve, which follows the artery into the adductor canal.
The femoral branch of the genitofemoral nerve (L1, L2) enters the thigh within the femoral sheath, lateral to the artery, and pierces the sheath and fascia lata to supply the skin over the upper triangle. The lateral cutaneous nerve of the thigh enters close to the anterior superior iliac spine, outside the triangle.
Clinical relevance
The femoral triangle is the most accessible route to the major vessels of the lower limb.
- Femoral pulse: felt at the mid-inguinal point. It is the usual site for arterial puncture in angiography, because the artery can be compressed against the femoral head afterwards.
- Femoral venous access: the vein lies about a finger's breadth medial to the pulse.
- Femoral hernia: abdominal contents pass through the femoral ring into the canal and present below and lateral to the pubic tubercle. They are more common in women, and the narrow, rigid neck makes strangulation likely.
- Femoral and fascia iliaca nerve blocks: local anaesthetic is placed lateral to the artery, deep to the fascia iliaca, for analgesia after a hip fracture.
- Saphena varix: a dilated end of the great saphenous vein that has a cough impulse and can be mistaken for a femoral hernia.
- Psoas abscess: pus tracking down the psoas sheath can point in the femoral triangle.
On the specimen
The two stations show the femoral triangle opened below the inguinal ligament, with the anterior superior iliac spine and pubic tubercle marking the ends of the ligament. Read the contents from lateral to medial: the femoral nerve breaking into a spray of branches, the thick-walled femoral artery, then the wider, thin-walled femoral vein with the great saphenous vein entering its front.
The small artery running medially from the femoral artery towards the scrotum or labium is the superficial external pudendal. The branch running laterally deep to sartorius, splitting into ascending and descending vessels, is the lateral circumflex femoral artery. A fine nerve lateral to the artery is the femoral branch of the genitofemoral nerve; a larger cutaneous nerve piercing sartorius is the intermediate cutaneous nerve of the thigh. In the floor, psoas major and iliacus lie laterally, pectineus in the middle and adductor longus medially, with sartorius forming the lateral border.