Objective: To obtain the adequate surgical anesthesia from thoracic paravertebral block (TPVB), identifying the correct thoracic spine level is mandatory. Ultrasound has become a recent standard to perform regional anesthesia including TPVB. This study aimed to investigate two techniques of using ultrasound to identify C7 spinous process compared with the palpation method.
Material and Method: Twenty volunteers were invited to participate in the investigation. Each volunteer was evaluated using palpation method with flexion and extension maneuver, ultrasound transverse scan (US-TS) and parasagittal scan (US-PS) to identify C7 spinous process. All volunteers were scanned on both sides randomly, and finally checked with fluoroscope. The examinations were independently performed by different investigators. The invisible marker pen was used to locate C7 spinous process from each technique. The accuracy and frequency of identified level, both correction and errors, were recorded and compared.
Results: The accuracy of palpation method with flexion and extension maneuver for C7 spinous process identification was 72.5%. While identifications of C7 by using US-TS and US-PS were correct 52.5% and 30% respectively. Interestingly, most errors were one level higher than actual C7 spinous process.
Conclusion: Identifying C7 spinous process using ultrasound assisted, both US-TS and US-PS techniques had a lower accuracy compared with palpation method with flexion and extension maneuver. Thus, the technique of ultrasound assisted C7 spinous process identification need to be modified.

Keywords: C7 spinous process identification, Ultrasound assisted, Thoracic paravertebral block, Palpation method with flexion and extension maneuver