The erector spinae plane (ESP) and retrolaminar blocks are ultrasound-guided techniques for thoracoabdominal wall analgesia involving injection into the musculofascial plane between the paraspinal back muscles and underlying thoracic vertebrae. The ESP block targets the tips of the transverse processes, whereas the retrolaminar block targets the laminae. We investigated if there were differences in injectate spread between the 2 techniques that would have implications for their clinical effect.
The blocks were performed in 3 fresh cadavers. The ESP and retrolaminar blocks were performed on opposite sides of each cadaver at the T5 vertebral level. Twenty milliliters of a radiocontrast dye mixture was injected in each block, and injectate spread was assessed by magnetic resonance imaging and anatomical dissection.
Both blocks exhibited spread to the epidural and neural foraminal spaces over 2 to 5 levels. The ESP block produced additional spread to intercostal spaces over 5 to 9 levels and was associated with a greater extent of craniocaudal spread along the paraspinal muscles.
The clinical effect of ESP and retrolaminar blocks can be explained by epidural and neural foraminal spread of local anesthetic. The ESP block produces additional intercostal spread, which may contribute to more extensive analgesia. The implications of these cadaveric observations require confirmation in clinical studies.
From the *Department of Anaesthesiology and Perioperative Medicine, Penn State College of Medicine;
†Department of Radiology, Penn State Hershey Medical Center; and
‡Department of Orthopedic Surgery, Neural & Behavioral Sciences and Radiology, Penn State Hershey College of Medicine, Hershey, PA; and
§Department of Anesthesia, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.
Accepted for publication January 28, 2018.
Address correspondence to: Ki Jinn Chin, FRCPC, Department of Anesthesia, Toronto Western Hospital, McL 2-405, 399 Bathurst St, Toronto, Ontario, Canada M5T 2S8 (e-mail: firstname.lastname@example.org).
The authors have no sources of funding to declare for this article.
The authors declare no conflict of interest.