The inguinal region and Hesselbach’s triangle

1. The inguinal ligament

The inguinal ligament is the rolled-under lower edge of the external oblique aponeurosis. It runs from the anterior superior iliac spine to the pubic tubercle and its free edge curls backwards into a gutter, the floor of the inguinal canal. At its medial end it fans back along the pecten pubis as the lacunar ligament.

Surgeon’s corner: The pubic tubercle is the landmark that separates the two groin hernias: an inguinal hernia comes out above and medial to it, a femoral hernia below and lateral to it.

2. The walls of the inguinal canal

The canal is a 4 cm oblique tunnel just above the medial half of the ligament. Front wall: the external oblique aponeurosis. Roof: the arching lower fibres of the internal oblique and transversus abdominis (medially fused as the conjoint tendon). Floor: the inguinal ligament. Back wall: the transversalis fascia.

Surgeon’s corner: In a Lichtenstein repair the mesh is laid on the back wall, under the external oblique, from the pubic tubercle to beyond the deep ring; in a Shouldice the back wall itself is reconstructed in layers.

3. The inferior epigastric vessels

Just above the inguinal ligament the external iliac artery gives the inferior epigastric artery. It runs up and medially on the back of the abdominal wall, behind the transversalis fascia, enters the rectus sheath at the arcuate line and climbs behind the rectus muscle to meet the superior epigastric artery, the end of the internal thoracic artery: an anastomosis between the subclavian and the iliac systems. The deep inguinal ring, where the spermatic cord (or round ligament) enters the canal, lies just lateral to its origin.

Surgeon’s corner: These vessels are the landmark that names the hernia: a sac lateral to them came through the deep ring (indirect), a sac medial to them pushed straight through the back wall (direct). At open surgery you find them by looking just medial to the neck of the sac.

4. Hesselbach’s triangle

The orange triangle on the back wall of the canal: laterally the inferior epigastric vessels, medially the lateral border of the rectus abdominis, below the inguinal ligament. Its floor is only transversalis fascia, reinforced medially by the conjoint tendon: it is the weak spot of the groin.

Surgeon’s corner: Direct hernias bulge through this triangle: they are acquired (weak fascia, raised abdominal pressure), seldom strangulate because their neck is wide, and are typical of older men. Indirect hernias go lateral to the triangle through the deep ring and can be congenital (patent processus vaginalis).

5. Direct, indirect and femoral

Three openings, three hernias. Indirect: through the deep ring, lateral to the inferior epigastric vessels, along the spermatic cord, possibly into the scrotum. Direct: through Hesselbach’s triangle, medial to the vessels. Femoral: below the inguinal ligament, through the femoral ring medial to the femoral vein.

Surgeon’s corner: Clinically you rarely know direct from indirect before surgery, and it does not change the indication. A femoral hernia does: it is more common in women, has a narrow rigid neck, strangulates often and should be repaired soon.

6. The arteries at risk

Four arteries matter in a groin repair. The external iliac artery runs under the inguinal ligament to become the femoral artery. Its inferior epigastric branch borders the direct space. The obturator artery runs along the side wall of the pelvis to the obturator canal; in about a quarter of people an extra branch joins it to the inferior epigastric artery over the back of the pubic bone. In front, the superficial epigastric artery runs in the fat of a groin incision.

Surgeon’s corner: The vessel joining the obturator and inferior epigastric arteries across the lacunar ligament is the “corona mortis”: cut while enlarging a femoral hernia ring medially, or during Cooper’s ligament fixation, it retracts into the pelvis and bleeds badly. Enlarge a tight femoral ring medially only after you have looked for it.

7. From the inside: the laparoscopic view

In TAPP or TEP you look at the groin from behind, under the peritoneum. The same landmarks reappear: the inferior epigastric vessels in the middle, the direct space (Hesselbach) medial to them, the deep ring lateral. Below, the ductus deferens runs medially and the gonadal vessels laterally; between them lie the external iliac artery and vein.

Surgeon’s corner: The “triangle of doom” (between the ductus deferens and the gonadal vessels) holds the external iliac vessels: never tack or staple there. The “triangle of pain” lateral to the gonadal vessels, below the iliopubic tract, holds the genitofemoral and lateral femoral cutaneous nerves: no tacks there either, or the patient keeps a chronic groin pain.