Anatomic and radiological correlation of injectate spread from first thoracic costotransverse junction in cervical erector spinae plane

INTRODUCTION: Cervical erector spinae plane block (ESPB) provides postoperative pain relief when administered at the level of first thoracic costotransverse junction (CTJ) for surgeries on the proximal shoulder and cervical spine. We propose to describe the spread of 20 ml radiocontrast - dye solution administered at this level from caudad to cephalad direction in a fresh frozen cadaveric model through imaging and cross-sections. METHODS: An observational study with four thoracic to cervical ESP blocks at the level of first thoracic CTJ level on two fresh cadavers (total 4 specimens) was conducted using 20 ml of radiocontrast- methylene blue combination (10 ml through the needle and 10 ml through the catheter). Both cadavers were subjected to computed tomography (CT) scan. An anatomist and radiologist, respectively, analyzed cross-sections of cadavers and CT contrasted images. RESULTS: The spread was assessed in axial, sagittal, and coronal at the levels of C4, C5, C6, C7and T1. The medial limit was articular processes in both cadavers. The lateral limits were the outer border of the middle scalene muscle in cadaver 1 and posterior to the sternocleidomastoid muscle in cadaver 2. Contrast spread was visualized on the superior and anterior aspect of anterior scalene muscle in cadaver 2. An epidural spread was observed at the level of C5-6 and C6-7 in axial and coronal planes in cadaver 1. CONCLUSIONS: The cervical ESPB administered at the first thoracic CTJ with injections directed cephalad has a consistent action on the dorsal spinal nerves of thoracic and cervical area, and spreads in the paravertebral space dorsal to the ventral cervical roots.