High Definition Ultrasound Imaging of the Intermuscular Bridges at the Interscalene Groove: A Prospective Observational Volunteer Study

The Interscalene brachial plexus block (ISBPB), with recent techniques like phrenic nerve sparing interscalene approach, has better safety profile than before and because of this, it is often the technique of choice for anaesthesia and/or analgesia during shoulder and proximal arm surgery. Anatomical variations at the interscalene groove are not uncommon and few have been described in the literature. Understanding the anatomy of the brachial plexus and its sheath at the interscalene groove is vital for the success of the block and to reduce the risk of complications during ultrasound (US) guided ISBPB. Recently, with the use of high definition ultrasound, using high frequency linear transducer, the principal investigator have identified intermuscular bridges appearing between the ventral rami of the brachial plexus at the interscalene groove. These intermuscular bridges may affect the spread of local anesthetic dispersion within the brachial plexus sheath thereby affecting the block dynamics of ISBPB. Therefore, this prospective observational study aim to define the intermuscular bridges at the interscalene groove using high definition ultrasound imaging in a group of healthy volunteers.