The Novel Costotransverse Foramen Block Technique: Distribution Characteristics of Injectate Compared with Erector Spinae Plane Block

Background: The costotransverse foramen (CTF) is a space continuous with the paravertebralspace. We hypothesized that injections passing through the CTF will result in a successfulinjectate spread to the paravertebral space.Objectives: We investigated patterns of dye spread to assess characteristics of neural blockadefollowing ultrasound-guided CTF and erector spinae plane (ESP) injection in an anatomic andclinical study.Study Design: Prospective cadaveric study, and case studies.Setting: University hospital.Methods: Six soft cadavers were studied. The boundaries of the CTF and the needle pathwayof CTF injection were identified in the first cadaver. The CTF and ESP injections were performedon either the left or right sides of the T4 vertebral level in cadavers 2 to 6. Fifteen millilitersof 0.2% methylene blue was injected in each block, and the spread of dye was assessed byanatomic dissection. We also report 2 case studies of CTF and ESP blocks.Results: Cadaver studies of CTF injection demonstrate that with injection to the inferior aspectof the base of the transverse process, the dye mainly passes anteriorly through the CTF intothe paravertebral space, with minimal track-back to the deep back muscles. Consistent sensoryblockade was achieved in 2 case studies. With the ESP injection, the spread of dye was observedcephalocaudad to the fascia of the erector spinae muscle, with no dye spreading within theparavertebral space in all cadavers.Limitations: Prospective case series.Conclusions: CTF block was consistently associated with a mainly anterior spread of injectateinto the paravertebral space that involved the thoracic spinal nerves, and minimal posteriorspread of injectate to the deep back muscles.Key words: Thoracic vertebrae, rib cage, paraspinal muscle, nerve block, joints