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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.