Supraclavicular block with corner pocket access + upper trunk versus upper trunk block: anatomical descriptive study of its distribution over the lower trunk of the brachial plexus

The upper trunk block is used for proximal upper limb surgery. Little is known about its effect on the lower trunk of the brachial plexus, which is necessary for distal hand surgery. The objective of our study in its clinical phase is to evaluate whether there is motor and sensory alteration of the LT after performing a UTB. In the anatomical phase, we aimed to visualize whether staining occurs in cadaveric models using two groups of blocks: Group 1 supraclavicular block with corner pocket approach + UTB, and Group 2 UTB alone. Methods: In the clinical phase, 11 patients undergoing shoulder arthroscopies received UTB, and subsequent motor and sensory changes were evaluated. Anatomical phase, two types of ultrasound-guided brachial plexus blocks were performed on 12 cadaveric upper limbs; both groups received a volume of 15 ml. In Group 1, two approaches were performed: SCB at the corner pocket with 7.5 ml of methylene blue followed by UTB with 7.5 ml; in Group 2, only UTB was performed with 15 ml of dye injected. Results: Clinically, patients who received UTB showed a 46.7% reduction in strength in upper limb muscle groups and had involvement of C8 in 55% and T1 in 18%. Anatomical phase, the group with SCB corner pocket approach + UTB showed 100% staining of the lower trunk versus 50% involvement of C8 and 17% of T1 in those who received UTB. Conclusions: UTB is a selective block with partial involvement of the lower trunk, demonstrated both anatomically and clinically.