Femoral Triangle

Introduction

Introduction to the Femoral Triangle

The femoral triangle (Scarpa’s triangle) is a clinically critical subfascial space in the superomedial aspect of the anterior thigh. It is bounded by muscular and ligamentous structures that create a well‑defined depression through which the major neurovascular bundle of the lower limb passes from the pelvis into the thigh. Knowledge of the femoral triangle is essential for vascular access (femoral artery catheterisation), assessment of femoral hernias, management of femoral artery injuries, and understanding the spread of infection or malignancy. The femoral canal, located at the medial corner of the triangle, is the site of femoral hernias and contains a deep inguinal lymph node (Cloquet’s node).

Study

1. Boundaries of the Femoral Triangle

The femoral triangle is defined by three borders: the superior border is the inguinal ligament, extending from the anterior superior iliac spine (ASIS) to the pubic tubercle. The lateral border is the medial margin of the sartorius muscle. The medial border is the medial margin of the adductor longus muscle. The apex of the triangle points distally and is formed by the convergence of the sartorius and adductor longus muscles, where the femoral vessels pass into the adductor canal (Hunter’s canal).

The floor of the triangle is muscular and forms a gutter. From lateral to medial, the floor is formed by the iliacus, psoas major tendon, pectineus, and adductor longus muscles. The roof is formed by the fascia lata, the cribriform fascia over the saphenous opening, the superficial inguinal lymph nodes, and the great saphenous vein.

2. Contents of the Femoral Triangle

The contents are arranged from lateral to medial as: femoral nerve, femoral artery, femoral vein, and the femoral canal (containing lymphatic vessels and Cloquet’s node). The mnemonic NAVEL (Nerve, Artery, Vein, Empty space, Lymphatics) describes the order within the femoral sheath, which encloses the artery, vein, and canal but not the nerve.

The femoral nerve (L2, L3, L4) lies lateral to the femoral artery, outside the femoral sheath. It divides into anterior and posterior divisions that supply the anterior thigh muscles and the skin of the anterior thigh and medial leg (saphenous nerve). The femoral artery is the continuation of the external iliac artery distal to the inguinal ligament. It gives off the superficial epigastric, superficial circumflex iliac, superficial and deep external pudendal arteries, and the profunda femoris artery (deep artery of the thigh), which is its largest branch. The femoral vein lies medial to the artery and receives the great saphenous vein at the saphenous opening.

3. The Femoral Sheath and Femoral Canal

The femoral sheath is a funnel‑shaped fascial tube derived from the transversalis fascia (anteriorly) and the iliac fascia (posteriorly). It extends 3–4 cm below the inguinal ligament and is divided into three compartments by septa: the lateral compartment contains the femoral artery, the middle compartment contains the femoral vein, and the medial compartment is the femoral canal. The femoral canal is about 1.3 cm long and contains loose connective tissue, lymphatic vessels, and often a single deep inguinal lymph node (Cloquet’s node). Its proximal opening is the femoral ring, which is bounded medially by the lacunar ligament, laterally by the femoral vein, anteriorly by the inguinal ligament, and posteriorly by the pectineus muscle and its fascia. The femoral canal is the site of femoral hernias, which are more common in females due to a wider pelvis.

4. Clinical Relevance

The femoral artery is palpable just below the inguinal ligament, midway between the ASIS and the pubic symphysis (mid‑inguinal point). It is used for arterial blood gas sampling, coronary angiography, and as a site for large‑bore venous access. A femoral hernia protrudes through the femoral ring into the femoral canal, presenting as a swelling below and lateral to the pubic tubercle. It is at high risk of strangulation due to the rigid boundaries of the ring. The saphenous opening (fossa ovalis) in the deep fascia transmits the great saphenous vein and is a site of saphena varix (dilatation mimicking a hernia). Femoral artery laceration is a surgical emergency; the artery can be compressed against the femoral head.

Summary

Summary of the Femoral Triangle

The femoral triangle is a subfascial space bounded by the inguinal ligament, sartorius, and adductor longus. It contains the femoral nerve, artery, vein, and the femoral canal. The femoral sheath encloses the vessels and canal. This region is of paramount importance for vascular access, the diagnosis of femoral hernias, and surgical approaches to the hip and thigh.