Blocking around the transversalis fascia: behind the scene

Area of Science:

• Anatomy
• Regional Anesthesia
• Surgical Analgesia

Background:

• Transversalis fascia plane and quadratus lumborum blocks target T12-L1 nerves for surgical analgesia.
• The transversalis fascia's role in local anesthetic spread is not precisely defined.
• Anatomical details of the transversalis fascia are crucial for understanding these blocks.

Purpose of the Study:

• To precisely define the anatomy of the transversalis fascia.
• To elucidate the role of the transversalis fascia in quadratus lumborum blocks.
• To clarify the spread of local anesthetics in relation to fascial planes.

Main Methods:

• Conducted 10 cadaveric dissections.
• Obtained full-thickness specimens for microscopic analysis.
• Macroscopic and microscopic examination of fascial layers.

Main Results:

• Macroscopic examination failed to identify a distinct fascial structure between transversus abdominis and peritoneum.
• Microscopic analysis revealed a thin fascial layer (0.1-0.2 mm) identified as transversalis fascia.
• A small fascial triangle (2-3 mm) formed by transversalis fascia and transversus abdominis epimysium contains T12-L1 nerves.

Conclusions:

• The identified fascial triangle is likely a virtual injection site due to its small size.
• Local anesthetic is probably injected into the retroperitoneal space.
• Anesthetic likely reaches target nerves via posterior spread through the thin transversalis fascia.