CHAPTER 11: Sonoanatomy Relevant for Ultrasound-Guided Thoracic Paravertebral Block

INTRODUCTION

Thoracic paravertebral block (TPVB) is the technique of injecting local anesthetic alongside the thoracic vertebral body close to where the spinal nerves emerge from the intervertebral foramen. This produces unilateral (ipsilateral), segmental, somatic, and sympathetic nerve blockade in multiple contiguous thoracic dermatomes, ^1,2 which is effective for managing acute and chronic pain of unilateral origin from the thorax and abdomen. ² TPVB can also be used for surgical anesthesia in patients undergoing inguinal herniorrhaphy ³ and breast surgery ^4–6 with improved postoperative outcomes. ^2,5 TPVB is traditionally performed using surface anatomical landmarks. ² Recently there has been an increase in interest in the use of ultrasound for peripheral nerve blocks, ^7–9 including TPVB. ^10–18 However, published data on ultrasound-guided (USG) TPVB are limited. ^10–20 This chapter describes the sonoanatomy relevant for USG TPVB.

GROSS ANATOMY

The thoracic paravertebral space (TPVS) is a wedge-shaped space ^2,21 that lies on either side of the vertebral column (Fig. 11–1). It is wider on the left than on the right. ²² The parietal pleura forms the anterolateral boundary. The base is formed by the vertebral body, intervertebral disc, and the intervertebral foramen with its contents (Fig. 11–1). ^21,23 The superior costotransverse ligament (SCTL), which extends from the lower border of the transverse process above to the upper border of the transverse process below (Figs. 11–2 and 11–4), forms the posterior wall of the TPVS. Also interposed between two transverse processes is the intertransverse ligament (Figs. 11–2 and 11–4). The SCTL is continuous laterally with the internal intercostal membrane, which is the medial extension of the internal intercostal muscle, medial to the angle of the rib (Fig. 11–4). The apex of the TPVS is continuous with the posterior intercostal space lateral to the tips of the transverse processes (Fig. 11–4). ^21,23

Interposed between the parietal pleura anteriorly and the superior costotransverse ligament posteriorly is a fibroelastic structure, ²⁴ the “endothoracic fascia” ^25–30 (Figs. 11–1 and 11–2), which is the deep fascia of the thorax ^2,25–27 and lines the internal aspect of the thoracic cage (Figs. ...