The safety zone of percutaneous cervical approach: A dynamic computed tomographic study

STUDY DESIGN. A prospective study using computed tomography (CT) scans. OBJECTIVE. To identify the structures at risk and the safety zone of a percutaneous cervical approach. SUMMARY OF BACKGROUND DATA. A percutaneous cervical approach may injure the important structures of the anterior neck. However, the dynamic locations of vital structures and the structures at risk by routine trajectory have not been analyzed. METHODS. Thirty patients were enrolled for this study. We obtained the CT scans of the cervical spine at each level of the intervertebral disc from C3-C4 to C6-C7, after manually pushing the airway in the same position and manner of discography. The patients ingested contrast materials for imaging of their digestive tracts and were injected intravenous contrast materials for imaging of vascular structures, just before obtaining images. We estimated the distances from the operator's fingertip to the digestive tract on the left side and to the carotid artery on the right side, at each level. The safety zone was determined by the sum of 2 distance calculations. We identified the anatomic structure at risk by simulated needle insertion toward the center of the disc through the safety zone. RESULTS. At C3-C4, the safety zone was measured 18.9 ± 6.6 mm. The superior thyroidal artery (STA) was located in the safety zone of C3-C4 in 86.7%. At C4-C5, the safety zone was measured 23.5 ± 6.5 mm. The STA and the right lobe of the thyroid gland (TG) were located in the safety zone in 26.7% and 30%, respectively. At C5-C6, the safety zone was measured 33.7 ± 6 mm. The TG was located in the safety zone of C5-C6 in 76.7%. At C6-C7, the safety zone was 29.2 ± 4.5 mm. The TG was located on the approach plane in 90%. CONCLUSION. The safety zone was wider at the distal level (C5-C6, C6-C7) than at the proximal level (C3-C4, C4-C5). The safest needle entry point should be between the pushing point of the airway and the pulsating point of the carotid artery. In addition, the needle should be approached toward the center of the disc. A percutaneous cervical approach allows a low risk of pharyngoesophageal structure injury and is considered a safe diagnostic technique in dynamic imaging studies.