This letter describes the unexpected visualization of the DSA during pre-operative sonographic assessment in a 60-year-old woman who was scheduled for surgery due to a fracture of the distal radius in January 2021. The DSA, a vessel branching from the subclavian artery, was identified beneath the inferior trunk while attempting to optimize imaging of the corner pocket (Fig. 1). Because the DSA was directly in the needle pathway, the corner pocket approach could not be utilized. Therefore, the intertruncal approach was used to inject between the trunks [2]. We first carefully injected a small amount of local anesthetics consisting of a 1 : 1 mixture of 1% lidocaine and 0.75% ropivacaine to open up to open up the adipose tissue layer between the inferior and middle trunk and subsequently by securing a safe route for needle advancement in the intertruncal plane [3].

The DSA often crosses the brachial plexus compartment, mostly between the inferior and middle trunk or between the middle and superior trunk [4]. Although this may increase the risk of vascular-related complications, the DSA has been rarely visualized on optimal sonographic images for the corner pocket approach [5]. If the DSA crosses beneath the first thoracic nerve root, as in the present patient, it lies directly in the path of the needle when performing the corner pocket approach. Moreover, the DSA has been reported to pass beneath the inferior trunk in 6.6% of cadavers [4]. Thus, although this condition is relatively uncommon, it is important to confirm the absence of the DSA during sonographic pre-assessment before utilizing the corner pocket approach. If the DSA is visible, an alternative technique should be used.