Fig. 3. Schematic diagram. Local anesthetic was injected between the erector spinae muscle and transverse process, and spread to the thoracic vertebral and intercostal space via bony gaps, such as the costotransverse foramen. Additionally, local anesthetic will pass through fenestrations in the costotransverse ligament, reaching the nerve root in the paravertebral space.

TP = transverse process, ESM = erector spinae muscle, RMM = rhomboid major muscle, TM = trapezius muscle.