Depth by ultrasound from skin surface to the C6 transverse process while applying pressure

A stellate ganglion block is commonly performed on the anterior tubercle of sixth cervical spine's transverse process. When the procedure is performed, identifying the anatomical landmarks and confirming the depth of the needle insertion to the transverse process are essential for ensuring safety. The purpose of this study was to determine the depth of the needle insertion from the skin to the transverse process for a safe stellate ganglion block.

One hundred patients were enrolled for this study. The patients' heights, weights, and neck circumferences were measured. In the supine position, the anterior tubercle of the transverse process were palpated and pressed with the examiner's fingers. While spreading the fingers, an ultrasound probe was placed with the same strength as the fingers and the depth from the skin to the transverse process was measured.

The mean depth from the skin to the transverse process in men was 9.5 ± 2.7 mm on the left side and 9.7 ± 2.5 mm on the right side, whereas in women, it was 8.0 ± 2.2 mm on the left side and 8.2 ± 2.0 mm on the right side. There was no significant difference between the right and left sides among or between the genders but men showed greater depths than women. Although both genders showed a correlation between body mass index and depth, only men showed a correlation between the neck circumference and depth.

In this study, the mean depth from the skin to the transverse process did not exceed 10 mm in both genders and the maximum depth was 16.6 mm.