Location and Structure
The lacunar ligament (lig. lacunare), also called Gimbernat's ligament, is located in the angle between the inguinal ligament and the pecten of the pubic bone (pecten ossis pubis). Anatomically, this structure represents the medial continuation of the inguinal ligament (lig. inguinale) at the pubic tubercle.
Role in Inguinal Canal Formation
The inguinal canal (canalis inguinalis) is an oblique, slit-like passage about 4–5 cm long situated in the inferior part of the anterolateral abdominal wall. It lies 1.0–1.5 cm superior and parallel to the inguinal ligament. The canal courses obliquely from lateromedial and craniocaudal directions, extending from the superficial to the deep inguinal ring. The lacunar ligament contributes to the formation of its inferior wall (floor).
Walls of the inguinal canal:
- Floor (inferior wall) — formed by the inguinal ligament (lig. inguinale), which medially, near the pubic tubercle, transitions into the lacunar ligament (lig. lacunare).
- Anterior wall — aponeurosis of the external oblique muscle (laterally reinforced by fibers of the internal oblique).
- Posterior wall — transversalis fascia (fascia transversalis), reinforced medially by the conjoint tendon (falx inguinalis) and the interFoveolar ligament (lig. interfoveolare).
- Roof (superior wall) — arched lower borders of the internal oblique and transversus abdominis muscles.
Inside the canal runs the spermatic cord (funiculus spermaticus) in males, and the round ligament of the uterus (lig. teres uteri) along with neurovascular structures in females.
Topography of Vascular and Muscular Lacunae
The space inferior to the inguinal ligament is partitioned into two compartments (lacunae). The vascular lacuna (lacuna vasorum) lies medial to the muscular lacuna.
Boundaries of the vascular lacuna:
- Medially — lacunar ligament (lig. lacunare).
- Anteriorly — inguinal ligament.
- Posteriorly — pecten of the pubic bone.
- Laterally — iliopectineal arch (arcus iliopectineus).
Contents of the vascular lacuna include the femoral vein (positioned medially), femoral artery (positioned laterally), and the femoral branch of the genitofemoral nerve.
By comparison, the muscular lacuna (lacuna musculorum) corresponds to the lateral two-thirds of the inguinal ligament. It is bounded anteriorly by the inguinal ligament, posteriorly by the pubic bone, and medially by the iliopectineal arch. It transmits the iliopsoas muscle (m. iliopsoas) and the femoral nerve (n. femoralis) onto the anterior thigh.
Clinical Significance: Hernias and Surgery
The deep femoral ring (anulus femoralis) serves as the abdominal opening of the femoral canal through which a hernia can protrude from the abdominal cavity. The ring is located in the most medial compartment of the vascular lacuna.
Boundaries of the deep femoral ring (four borders):
- Medially — lacunar ligament (lig. lacunare).
- Anteriorly — inguinal ligament.
- Posteriorly — pectineal ligament (lig. pectineale, Cooper's ligament), located on the pecten of the pubic bone.
- Laterally — femoral vein.
The femoral canal (canalis femoralis) normally contains lymphatic structures (such as Cloquet's node), but in a femoral hernia, it houses the hernia sac, which emerges at the saphenous opening (hiatus saphenus) beneath the fascia lata. The inguinal ligament serves as the superior boundary during standard ilioinguinal/femoral lymphadenectomy and forms the base of the femoral triangle.