Sophia Leung,Dan A. Zlotolow,Scott H. Kozin,Joshua M. Abzug

Background: Brachial plexus exploration is performed in infants when addressing birth palsies and in children and adults following trauma. The upper trunk is most often injured. Traditional drawings of the brachial plexus depict the suprascapular nerve as a branch of the midportion of the upper trunk, with the more lateral branch of the upper trunk as the anterior division. We have not found this orientation to be accurate in clinical practice. The purpose of this study was to determine the branching patterns of the upper trunk and to delineate nerve orientations at the level of the divisions.

Methods: Bilateral brachial plexus dissections were performed on eight adult cadavers. The length of the upper trunk and distance of the takeoff of the suprascapular nerve from the anterior and posterior divisions was measured. The native positions of the divisions and of the suprascapular nerve from lateral to medial were recorded across all trunks.

Results: In six (38%) of the sixteen specimens, a trifurcation was found at the level of the upper trunk. The suprascapular nerve was the most lateral structure at the clavicular level in all specimens, followed by the posterior division and then the anterior division. The mean distance of the takeoff of the suprascapular nerve was 4 mm proximal to the branch point of the divisions; however, in two specimens, the nerve was found to take off from the posterior division proper.

Conclusions: These findings differ from the standard illustrations and descriptions of the brachial plexus. A thorough understanding of the course of the upper trunk and its branches, such as the suprascapular nerve, is vital to performing nerve transfer surgery or neuroma excision and grafting.