Figure 3.

The C7 transverse process usually has only one posterior tubercle. In certain cases, a rudimentary anterior tubercle (white arrowhead) can be visualized (A). The costal tubercle (black arrowhead) on the first rib may be mistaken as the posterior tubercle of the transverse process (B). Swapping the transducer posteriorly to validate the first costotransverse joint (white arrow) helps differentiating the first rib from the C7 transverse process (C). AS: anterior scalene muscle; LOC: longus colli muscle; MS: middle scalene muscle; PT: posterior tubercle; TP: transverse process; VA: vertebral artery. The yellow dashed area encircles the brachial plexus and the blue rectangle represents the transducer position.