Femoral canal and femoral hernia

Femoral canal anatomy

The femoral canal is localized between the superficial and deep layers of the fascia lata of the thigh. It has the shape of a triangular pyramid 1 to 3 cm in length and includes two openings:

• Deep ring (anulus femoralis): faces directly into the pelvic cavity. On the side of the internal surface of the abdominal wall, it is closed by a thin plate of the transversalis fascia — the femoral septum (septum femorale). The deep ring projects onto the medial third of the inguinal ligament.
• Superficial ring (hiatus saphenus): a subcutaneous cleft representing a defect in the superficial layer of the fascia lata. The opening projects 1–2 cm below the inguinal ligament and is covered by the cribriform fascia (fascia cribrosa).

The canal has three walls:

1. Anterior wall: formed by the superficial layer of the fascia lata (in the area between the inguinal ligament and the superior horn of the saphenous opening).
2. Posterior wall: formed by the deep layer of the fascia lata (fascia iliopectinea).
3. Lateral wall: represented by the medial semi-circumference of the femoral vein (v. femoralis).

Important: the medial wall of the femoral canal is absent because the superficial and deep fascial layers fuse tightly with each other in the region of the adductor longus muscle.

Abdominal hernias: general concepts

An abdominal hernia (hernia abdominalis) is the protrusion of abdominal cavity contents through natural or acquired defects of the abdominal wall while preserving the integrity of the parietal peritoneum.

According to their localization, two main groups are distinguished:

• Internal hernias (herniae internae): organs protrude into peritoneal recesses or openings within the abdominal cavity itself. These include hernias of the duodenojejunal recess, omental bursa, retrocecal, and diaphragmatic hernias. They are rare.
• External hernias: occur much more frequently than internal ones. Organs protrude beyond the boundaries of the abdominal cavity. This group includes inguinal (oblique and direct), umbilical, femoral hernias, and hernias of the linea alba.

A typical external hernia has a layered structure (from inside out). At the center is the hernia contents (most commonly a loop of the small intestine). It is covered by a hernia sac formed by the parietal peritoneum. The narrowed part of the sac is called the neck, and it passes through the hernia ring. Externally, the hernia sac is surrounded by tissues that are not part of it: the parietal fascia, musculo-aponeurotic layer, fascia propria (fascia propria), superficial fascia, and skin.

Mechanism of femoral hernia development

A femoral hernia forms when abdominal viscera protrude outward through the femoral canal. The main triggering factor is an increased intra-abdominal pressure.

Under the influence of pressure, a loop of the small intestine begins to push the parietal peritoneum ahead of it. This protruding conglomerate rushes toward the area of least resistance — the femoral ring (anulus femoralis). This ring serves as the hernia ring because it is a "weak spot": it is completely uncovered by muscles.

Having pushed through the thin plate of the transversalis fascia (septum femorale), the hernia enters the femoral canal. Passing through it, the hernia sac with the intestinal loop protrudes into the subcutaneous adipose tissue through the superficial opening — the saphenous opening (hiatus saphenus).

The topography of this region relies on the following structures: the iliac and psoas major muscles, anterior superior iliac spine, inguinal ligament, iliopectineal arch, femoral vessels, and femoral nerve.

Hernia strangulation and treatment

The most dangerous complication is hernia strangulation — a sudden and permanent compression of the hernia contents at the level of the hernia ring.

The pathogenesis of strangulation develops sequentially:

1. Blood circulation in the prolapsed bowel loop is impaired.
2. Venous stasis and progressive tissue edema develop.
3. Clinical manifestations of acute intestinal obstruction develop.
4. Systemic intoxication of the body increases.
5. Without timely assistance, necrosis of the incarcerated viscera occurs.

Treatment of a femoral hernia is exclusively surgical. The main goals of surgical intervention are complete elimination of the hernia protrusion and reliable plastic reinforcement of the abdominal wall ("weak spot") to prevent recurrence. To strengthen the ring, surgeons can use both the patient's own tissues (autologous tissues, such as muscles and aponeuroses) and modern synthetic materials (meshes).

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Classification of external hernias by etiology (congenital, acquired, postoperative).
• Anatomical differences between oblique and direct inguinal hernias.
• Topography of internal hernias (hernia of the omental bursa, retrocecal hernia).
• Techniques for hernia ring plasty using synthetic materials and autologous tissues.
• Topographic anatomy of the inguinal ligament and iliopectineal arch.

Other topics in the "Lower Limb" section

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