Ultrasound-guided proximal suprascapular nerve block: a cadaveric study

Difficulty in identifying the susprascapular nerve (SSN) limits the success of US-guided regional anesthetic injections. A proximal SSN block could be an effective and reliable approach. The primary objective was to validate the feasibility of the US-guided proximal SSN block. The secondary objective was to quantify the spread of the colored local anesthetic to the phrenic nerve (PN). Fourteen brachial plexuses from seven cadavers were included. Characterization of the proximal SSN was performed using US to determine the diameter and depth of the origin of the SSN (orSSN). Ten mL of methylene blue-infused ropivacaine 0.2% were then injected to the proximal portion of the SSN. After dissection, the distances between the tip of the needle and the orSSN and the PN were anatomically determined. The PN was also judged to be colored or not by the methylene blue. The mean diameter and depth of the orSSN were 0.2 cm (range, 0.1-0.3 cm) and 1.5 cm (range, 0.6-2 cm) respectively. The orSSN was successfully targeted in 14 of 14 specimens with US; the tip of the needle was a mean of 1.6 cm (range, 0.2-2.5 cm) and 5.1 cm (range, 4-6.5 cm) from the orSSN and PN respectively. The orSSN and PN were marked in 14 and 3 cases respectively. US-guided proximal SSN block is effective and reliable. The origin of the SSN is an easily identifiable landmark. This regional anesthesia could also reduce the risk of phrenic nerve palsy following interscalene brachial plexus block.