Understanding fascial anatomy and interfascial communication: implications in regional anesthesia.

With the extensive application of ultrasound in regional anesthesia, there has been rapid development of interfascial plane block techniques recently. Compared with neuraxial anesthesia or nerve plexus blocks, the interfascial plane blocks have many advantages, such as technical simplicity, fewer complications and comparable or better analgesia. The concept of fascial interconnectivity is fundamental in understanding the effects and complications of interfascial plane blocks. Many fascial planes are continuous and communicate with each other without a clear anatomical boundary. The prevertebral fascia of the neck, endothoracic fascia of the chest, transversalis fascia of the abdomen, and the fascia iliaca of the pelvic cavity form a natural fascial continuation. This anatomical feature suggests that the space beneath the cervical prevertebral fascia, the thoracic paravertebral space, the space between transversalis fascia and psoas muscles (psoas major and quadratus lumborum), and the fascia iliaca compartment are a confluent potential cavity. Additionally, the permeability of the fascia at different anatomical locations to local anesthetics is different, which can also influence the block effect and the incidence of complications. This article summarizes the anatomical characteristics and communication relationships of the major fascia which are related to regional anesthesia, and their relationships with block effects and complications.