The femoral triangle is a wedge-shaped area formed by a depression between the muscles of the thigh. It is located on the medial aspect of the proximal thigh.
This article will outline the boundaries and contents of the femoral triangle, as well as the fascial compartments and relevant clinical anatomy.
Lateral border: sartorius muscle
Medial border: adductor longus muscle
Base or superior border: inguinal ligament
|Contents (NAVEL)||Femoral nerve, femoral artery, femoral vein, femoral canal (empty space), lymphatics|
|Clinical Importance||Femoral pulse, vascular access and catheterization, femoral hernias|
|Lateral Border||Sartorius (S)|
|Medial Border||Adductor Longus (A)|
|Base or Superior Border||Inguinal Ligament (IL)|
The boundaries of the femoral triangle can be remembered using the word SAIL, as demonstrated in the table above. As well as these boundaries, the femoral triangle also has a floor and a roof. The floor is composed of the pectineus and adductor brevis muscles medially, and the iliopsoas muscle laterally. The roof is formed by the fascia lata, superficial fascia, and the skin. The apex of the triangle is pointed downwards towards the adductor canal.
The word NAVEL is used to orientate the contents of the femoral triangle from lateral to medial as follows:
|E||Femoral Canal (Empty Space)|
The femoral nerve is the most lateral of the contents in the femoral triangle. It supplies the sartorius, rectus femoris, vastus lateralis, vastus intermedius and vastus medialis muscles in the anterior compartment of the thigh, and the pectineus muscle in the medial compartment. It originates from the union of the L2, L3, L4 spinal cord segments in the lumbar plexus on the posterior abdominal wall. It enters the thigh by passing deep to the inguinal ligament.
The nerve divides into anterior and posterior branches immediately after it enters the thigh, giving both motor branches to muscles and sensory branches to the skin and the knee joint. All of the branches of the femoral nerve terminate in the thigh, apart from one cutaneous branch, the saphenous nerve, which accompanies the femoral artery through the adductor canal. It pierces through the deep and superficial fascia of the thigh to accompany the great saphenous vein along the medial aspect of the leg.
The femoral artery is the continuation of the external iliac artery in the thigh becoming the femoral artery as it passes under the inguinal ligament. The femoral artery is located between the femoral nerve and the femoral vein. It is the main blood vessel supplying the entire lower limb. It gives off a large branch in the proximal thigh, the profunda femoris artery, which passes into the posterior compartment of the thigh. The femoral artery passes distally towards the apex of the femoral triangle and through the adductor canal, where it passes through an opening in the adductor magnus muscle, the adductor hiatus. Through here it enters the popliteal fossa posterior to the knee joint, becoming the popliteal artery.
The femoral vein in the proximal continuation of the popliteal vein. It enters the thigh from the popliteal fossa through the adductor canal, passing superiorly in the thigh towards the femoral triangle. In the femoral triangle, the femoral vein is located medial to the femoral artery. A large superficial vein of the lower limb, the great saphenous vein, pierces the fascia lata through the saphenous ring to drain into the femoral vein in the femoral triangle. The femoral vein continues superiorly to become the external iliac vein in the pelvis, having passed deep to the inguinal ligament.
In the femoral triangle, the contents (excluding the femoral nerve) are enclosed in a wrapping of fascia called the femoral sheath. The sheath is funnel-shaped, and best described as a sleeve of fascia extending towards the apex of the femoral triangle, where it fuses with the adventitia of the vessels. It is continuous superiorly with the transversalis fascia and iliac fascia of the abdomen.
Each of the structures located in the femoral sheath is individually enclosed in its own compartment. The most medial compartment is the femoral canal, which contains the lymphatic vessels. The proximal opening of the femoral canal is the femoral ring. The femoral ring is bound by the inguinal ligament anteriorly, the pectineal part of the lacunar ligament posteriorly, the base of the lacunar ligament medially, and a fibrous septum on the medial side of the femoral vein laterally.
The femoral pulse can be palpated through the skin in the femoral triangle. The pulse can be located on the medial aspect of the proximal thigh at the mid-inguinal point. The artery can be used for drawing arterial blood when the pressure in the radial and ulnar arteries in the upper limb is too low to locate the arteries.
As the femoral triangle contains the relatively large femoral artery and vein, it is a popular site for vascular access. The femoral artery is palpable midway between the anterior superior iliac spine laterally and the pubic tubercle medially, just inferior to the mid-inguinal point. It can also be easily located using ultrasonography. The femoral triangle is used as a site for vascular catheterization for a number of interventional and corrective procedures. Catheterization of the femoral vessels provides access to the ipsilateral and contralateral lower limb, the vessels of the abdomen and thorax, as well as the cerebral vessels.
In cardiology, catheterization of the femoral artery provides access to the arch of the aorta through the descending and abdominal aorta. This approach is used to obtain access to the ascending aorta for aortic valve replacements, as well as to the coronary arteries for angiography and angioplasty procedures. The left side of the heart is also easily accessible by this approach.
The femoral vein is frequently used to obtain access to the right side of the heart through the inferior vena cava. This approach is commonly used when repairing a patent foramen ovale, a congenital heart defect involving the persistence of an embryological opening between the right and left atria.
The proximal opening of the femoral canal, the femoral ring, is a weak point in the lower abdominal wall. This is the site where femoral hernias occur. Femoral hernias are the protrusion of some of the abdominal viscera, usually part of the small intestine, into the femoral triangle. They are less common than inguinal hernias, accounting for 2-4% of hernias. They are more common in females than in males. Femoral hernias characteristically appear as a round, often tender bulge in the groin in the medial region of the femoral triangle just inferior to the pubic tubercle. Strangulation of femoral hernias can occur because of the rigid boundaries of the femoral ring. Treatment is usually via elective, minimally invasive, laparoscopic surgery.