Variable osteology of the sixth cervical vertebra in relation to stellate ganglion block

Background and Objectives: Stellate ganglion block is often carried out using palpation of surface landmarks to guide needle placement. However, anatomic variation of the surface landmarks used is common and block failure has been reported in as many as 30% of patients, even when the surface landmarks that guide needle placement can be easily identified. Methods: Computed tomography (CT) images of the cervical spine of 70 adult patients were examined to measure the distances in the coronal and sagittal planes between various points on the cricoid cartilage, anterior tubercle, posterior tubercle, and nadir of the vertebral gutter. The width of the tubercle in the caudal and cephalad plane was determined through multiplanar reformatted CT images in 6 randomly chosen patients. Results: The mean distance from the lateral margin of the cricoid cartilage laterally to the anterior tubercle was 13 +/- 5 mm (range 3-22 mm) in men and 12 +/- 3 mm (range 6-22 mm) in women. The mean depth of the anterior tubercle as measured posteriorly from the midpoint of the trachea was 20 +/- 4 (range 10-33 mm) in men and 19 +/- 4 mm (range 9-33 mm) in women. The maximal and minimal cephalad-caudad dimensions of the transverse process of C6 were 9.3 +/- 0.3 mm, and 6.7 +/- 0.3 mm, respectively. Conclusions: Large variability was observed in the size and location of the landmarks used for needle placement during stellate ganglion block. Placement of the needle medially where the transverse process joins the lateral margin of the vertebral body provides a larger bony target that may potentially provide a safer, more reliable block.