Anatomy and Location of the Fossa Ovalis
The fossa ovalis is located on the anteromedial aspect of the thigh, 1–2 cm inferior to the medial third of the inguinal ligament (lig. inguinale). It is an oval opening in the superficial lamina of the fascia lata.
Borders and structures of the fossa:
- Falxiform margin (margo falciformis) — a thickened lateral margin bounding the opening laterally.
- Superior horn (cornu superius) — the superior part of the falxiform margin.
- Inferior horn (cornu inferius) — the inferior part of the falxiform margin. It is easily identifiable anatomically as the great saphenous vein arches over it.
- Cribriform fascia (fascia cribrosa) — a perforated, sieve-like medial part of the superficial lamina of the fascia lata that closes the opening of the fossa ovalis.
Structures Passing Through the Saphenous Opening
Through the apertures in the cribriform fascia filling the hiatus saphenus, the subcutaneous tissue communicates with deeper layers. The following vessels and lymphatics pass through this area:
- Great saphenous vein (v. saphena magna) — dives deep through the saphenous opening, arching over the inferior horn to drain into the femoral vein (v. femoralis).
- Superficial epigastric artery (a. epigastrica superficialis) — a superficial branch of the femoral artery.
- Superficial circumflex iliac artery (a. circumflexa ilium superficialis) — a branch of the femoral artery.
- External pudendal arteries (aa. pudendae externae superficialis et profunda) — branches of the femoral artery.
- Lymphatic vessels — lymph flows toward deep nodes. The inferior superficial inguinal lymph nodes (nodi inguinales inferiores) are located near the saphenous opening.
Clinical Significance: Femoral Hernias
Under normal conditions, the femoral canal (canalis femoralis) does not exist as a patent tube; this potential space forms only when intra-abdominal contents herniate beneath the inguinal ligament.
The fossa ovalis (hiatus saphenus) serves as the external (subcutaneous) opening of this canal. After passing through the femoral ring (anulus femoralis) and the vascular lacuna, the hernial sac emerges precisely at the fossa ovalis beneath the fascia lata. Femoral hernias are more common in women.
During surgical repair of femoral hernias (e.g., Bassini repair), the saphenous opening is reinforced: the lateral falxiform margin (margo falciformis) is sutured to the fascia of the pectineus muscle.