The Validation of Ultrasound-Guided Target Segment Identification in Thoracic Spine as Confirmed by Fluoroscopy

The role of ultrasound in the thoracic spine has been underappreciated, partly because of the relative efficacy of the landmark-guided technique and the limitation of imaging through the narrow acoustic windows produced by the bony framework of thoracic spine. The aim of this study was to make a comparison between the 12th rib and the spinous process of C7 as a landmark for effective ultrasound-guided target segment identification in the thoracic spine.

Ultrasonography of 44 thoracic spines was performed and the same procedure was carried out 1 week later again. The target segments (T3-4, T7-8, and T10-11) were identified using the 12th rib (group 1) or the spinous process of C7 (group 2) as a starting landmark. Ultrasound scanning was done proximally (group 1) or distally (group 2) toward the target transverse process and further medially and slightly superior to the target thoracic facet. Then, a metal marker was placed on the T3-4, T7-8, and T10-11 and the location of each marker was confirmed by fluoroscopy.

In the total 132 segments, sonographic identification was confirmed to be successful with fluoroscopy in 84.1% in group 1 and 56.8% in group 2. Group 1 had a greater success rate in ultrasound-guided target segment identification than group 2 (p = 0.001), especially in T10-11 (group 1, 93.2%; group 2, 43.2%; p = 0.001) and T7-8 (group 1, 86.4%; group 2, 56.8%; p = 0.002). The intrarater reliability of ultrasound-guided target segment identification was good (group 1, r = 0.76; group 2, r = 0.82), showing no difference between right and left sides. Ultrasound-guided target segment identification was more effective in the non-obese subjects (p = 0.001), especially in group 1.

Ultrasound-guided detection using the 12th rib as a starting landmark for scanning could be a promising technique for successful target segment identification in the thoracic spine.