Variations in the distance between the cricoid cartilage and targets of stellate ganglion block in neutral and extended supine positions: an ultrasonographic evaluation.

Purpose: Anatomic variations complicate surface landmark-guided needle placement, thereby increasing nerve blockade failure rate. However, little is understood about how anatomic distances change under different clinical conditions. As the cricoid cartilage is an easy and accurate landmark, we investigated changes in distance between the sixth or seventh cervical transverse processes (C6TP or C7TP) and the cricoid cartilage in neutral and extended supine positions.

Methods: Forty-two patients (16 men, 26 women) were included in this study. Distances between the cricoid cartilage and C6TP/C7TP were measured using ultrasonography with the patient in neutral and extended supine positions.

Results: C6TP and C7TP were caudally located at 6.0 ± 8.1 and 15.1 ± 7.2 mm, respectively, from the cricoid cartilage in the neutral supine position, and at 15.2 ± 8.0 and 25.3 ± 8.0 mm, respectively, in the extended supine position. In the extended supine position, the cricoid cartilage was more cephalad than C6TP and C7TP in all patients. The distance from the cricoid cartilage to C6TP was 12.1 ± 7.6 mm in men and 17.2 ± 7.7 mm in women.

Conclusion: C6TP and C7TP are located approximately 15 and 25 mm, respectively, caudal to the cricoid cartilage in the extended supine position. Our results highlight the fact that there can be significant anatomic variation between the extended and neutral supine positions used in stellate ganglion block, which should be kept in mind when devising easily identifiable and palpable surface landmarks.