Inguinal Region Beyond the Canal
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Direct answer
Below the arching inguinal ligament of Poupart, running from the anterior superior iliac spine to the pubic tubercle, the groin's anatomy is a story of named ligaments and one dangerous canal. The lacunar ligament of Gimbernat extends medially to the pecten of the pubis with a sharp crescentic edge, the pectineal ligament of Cooper anchors repairs to the same bony ridge, and between the inguinal ligament above, the lacunar ligament medially, the femoral vein laterally and Cooper's ligament below lies the femoral ring — the mouth of the femoral canal, through which a femoral hernia descends below and lateral to the pubic tubercle, strangulating more readily than any other groin hernia.
What you must remember
- Inguinal ligament (Poupart): the rolled lower free edge of external oblique aponeurosis from the anterior superior iliac spine to the pubic tubercle, giving origin to fibres of internal oblique and transversus.
- Lacunar ligament (Gimbernat): the triangular medial extension of the inguinal ligament to the pecten pubis; its sharp, unyielding lateral edge is what strangulates a femoral hernia.
- Pectineal ligament (Cooper): a strong aponeurotic band along the pecten pubis — the anchor of the McVay repair and of open femoral hernia repair.
- Iliopubic tract: the fibrous band from the iliac crest to Cooper's ligament forming the true posterior-inferior boundary of the deep ring as seen at laparoscopy.
- Femoral canal: a 1 to 2 cm medially placed compartment of the femoral sheath containing fat and the lymph node of Cloquet (Rosenmuller's); its ring is the femoral hernia's gateway.
- Femoral versus inguinal hernia: femoral — below and lateral to the pubic tubercle, through the femoral canal, commoner in women, high strangulation risk; inguinal — above and medial, through the canal, may reach the scrotum.
- Richter hernia: only part of the bowel circumference enters, so obstruction is absent yet gangrene and spontaneous reduction of dying bowel can occur — a recognised femoral hernia trap.
- Structures under the ligament: from lateral to medial — femoral nerve outside the sheath, then artery, vein and the canal (the mnemonic NAVL).
Examinining a groin lump through the ligaments
A 70-year-old woman has a tender, irreducible lump below the right inguinal ligament, with vomiting and distension. The lump lies below and lateral to the pubic tubercle — a strangulated femoral hernia caught on the sharp edge of the lacunar ligament. At operation the inguinal ligament is retracted, the lacunar edge is nicked to release the bowel, and viability is assessed before repair — classically by suturing the inguinal ligament down to Cooper's pectineal ligament (the McVay principle) or by a mesh plug filling the canal. Her counterpart with an inguinal hernia — a lump above and medial to the tubercle, cough impulse at the superficial ring — is repaired with a Lichtenstein tension-free mesh reinforcing the whole posterior wall.
For the laparoscopic surgeon the same region wears different labels: in the preperitoneal plane, the iliopubic tract replaces the inguinal ligament as the visible boundary, and two triangles are named to keep the stapler out of harm — the triangle of doom, between the vas deferens and the gonadal vessels overlying the external iliac vessels, and the triangle of pain, lateral to the gonadal vessels, carrying the lateral femoral cutaneous and femoral branch of the genitofemoral nerves.
Where students slip
The femoral canal is called "a gap in the fascia" — it is the medial compartment of the femoral sheath, bounded anteriorly by the inguinal ligament, posteriorly by Cooper's ligament over pectineus, medially by the sharp lacunar ligament and laterally by the femoral vein through its septum. Cloquet's node inside the canal is forgotten, yet it is a sentinel on the lymphatic route from leg and genitalia to the pelvis. And a reducible femoral hernia in an obese patient is passed off as fat; the examiner's rule stands — every irreducible lump below and lateral to the pubic tubercle is a strangulated femoral hernia until proven otherwise.
Frequently asked questions
What are the derivatives of the inguinal ligament?
The reflected part, the lacunar (Gimbernat's) ligament to the pecten pubis, and indirectly the pectineal (Cooper's) ligament along the pecten — the anchors of groin repair.
What are the boundaries of the femoral ring?
Anteriorly the inguinal ligament, posteriorly the pectineal ligament over pectineus, medially the lacunar ligament, and laterally the femoral vein.
Why do femoral hernias strangulate so often?
The ring is small, rigid and edged by the unyielding sharp border of the lacunar ligament, so bowel entering it is compressed and its blood supply cut off.
What is the McVay repair?
Suture of the conjoint tendon or transversus arch down to Cooper's pectineal ligament, closing the femoral canal and reinforcing the direct inguinal floor.
What are the triangles of doom and pain in laparoscopic hernia repair?
The triangle of doom — between vas deferens and gonadal vessels over the external iliac vessels; the triangle of pain — lateral to the gonadal vessels containing the lateral femoral cutaneous and genitofemoral nerves; both are no-staple zones.