Location and Structure
The transversalis fascia is a component of the endoabdominal fascia (fascia endoabdominalis) that directly adheres to the deep surface of the transversus abdominis muscle (m. transversus abdominis).
- In the upper abdomen, it is relatively thin.
- Inferiorly, approaching the inguinal ligament, the fascia thickens into a dense fibrous sheet.
- Deeply, the fascia is fused with the parietal peritoneum.
- The transversus abdominis muscle tenses the transversalis fascia, actively participating in expiration and intra-abdominal pressure generation.
Role in Forming the Inguinal Canal
The fascia forms the posterior wall of the oblique, slit-like inguinal canal. Medially, this wall is reinforced by the conjoint tendon (falx inguinalis) and the interfoveolar ligament (lig. interfoveolare, Hesslich ligament).
- Deep inguinal ring (anulus inguinalis profundus) — an oval opening in the transversalis fascia measuring approximately 2.5–3.0 × 1.0–2.5 cm. It is located lateral to the inferior epigastric vessels (a. et v. epigastricae inferiores), serving as a critically important landmark in surgery.
- In the region of the deep ring, the fascia forms a funnel-shaped extension projecting into the canal.
- From the margins of the ring, the fascia continues onto the spermatic cord in males, forming the internal spermatic fascia (fascia spermatica interna).
Role in the Rectus Sheath
The topography of the transversalis fascia changes depending on the level relative to the arcuate line (linea arcuata), located approximately 4–5 cm below the umbilicus:
- Above the linea arcuata: The posterior wall of the rectus sheath is formed by the posterior lamina of the internal oblique aponeurosis and the transversus abdominis aponeurosis; the transversalis fascia and parietal peritoneum lie posterior to the rectus abdominis muscle.
- Below the linea arcuata: The aponeuroses of all three lateral abdominal muscles pass anterior to the rectus muscle. Posterior to the muscle, only the transversalis fascia and the parietal peritoneum remain. This creates a zone of relative anatomical weakness predisposed to herniation.
Topography and Adjacent Structures
The transversalis fascia is closely related to other anatomical structures of the abdominal wall and pelvis:
- Femoral canal: Normally nonexistent, it forms when abdominal contents protrude through the vascular lacuna beneath the inguinal ligament. The transversalis fascia continues into the vascular lacuna as the femoral septum (septum femorale). The canal is also bounded by the inguinal and pectineal ligaments.
- Retroperitoneal tissue: Proper retroperitoneal fat lies directly posterior to the fascia retrorenalis. During surgical approaches, such as an 8–10 cm incision at McBurney's point, the transversalis fascia is exposed after blunt separation of the internal oblique and transversus abdominis muscles, immediately before entering the peritoneum. Preperitoneal adipose tissue is visible just beneath the fascia.
Clinical Significance in Hernia Repair
The transversalis fascia is a key element in abdominal wall surgery, as the posterior wall of the inguinal canal represents its weakest point.
- Bassini repair: Aims to reinforce the posterior wall. The transversalis fascia is incised with a scalpel a few millimeters above the inguinal ligament, extending from the medial edge of the deep ring to the pubic tubercle. Then, a single musculo-fascial edge (the "triple layer": internal oblique, transversus abdominis, and transversalis fascia) is sutured to the inguinal ligament posterior to the spermatic cord.
- Postempski repair: The deep ring is shifted laterally, and the transversalis fascia along with the internal oblique and transversus abdominis muscles are sutured to the inguinal ligament to completely obliterate the inguinal canal, transposing the spermatic cord into the subcutaneous tissue.