Anatomy: Ultrasound guided interscalene block is performed at the root/trunk level of the brachial plexus (approx. C6/7 vertebral level, corresponding to the cricoid cartilage level). At this level, the roots/trunks lie wedged between the scalene muscles (Fig.1).ig. 1. Interscalane nerve block: illustration of the roots/trunks at the C6/7 vertebral level lying in between the anterior and middle scalene muscles. At the immediate supraclavicular level, the trunks/divisions are closely grouped superolateral (and posterolateral) to the subclavian artery.
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