[Ultrasound-guided axillary block: anatomical variations of terminal branches of the brachial plexus in relation to the brachial artery]

Abstract

Objectives: To describe the distribution of the terminal branches of the brachial plexus at the axillary level and define distribution patterns after ultrasound evaluation.

Material and method: Fifty volunteers underwent ultrasound bilateral axillary brachial plexus scanning exploration. Nerve distribution around the humeral artery was described and the distance between each nerve and the center of the artery was measured. The distance and relationship between the ulnar nerve and the humeral vein were also recorded.

Results: The median nerve was located in the anterolateral quadrant (-29±40°) and at a mean distance of 2.1±0.9mm from the artery (85%). The ulnar nerve was found at 53±26° and at 4.2±2.1mm from the artery in the anteromedial quadrant (90%), anterolateral to the vein in 46% of cases, and deep to it in 54%. The radial nerve was at 122±38° and at 3.3±1.7mm from the artery in the posteromedial quadrant (86%). The musculocutaneous nerve was found at -103±22° and 9.3±5.6mm from the artery in the posterolateral quadrant (90%) and in the anterolateral quadrant (-55±16°) at 4.8±2.7mm (10%). There were no differences regarding laterality, gender or overweight patients.

Conclusions: Our results allow defining four different anatomical patterns, two based in the position of the musculocutaneous nerve and two based on the disposition of the ulnar nerve with respect to the humeral vein. These patterns were not related to laterality, gender or body weight.

Keywords: Anatomical variations; Bloqueo axilar ecoguiado; Median nerve; Musculocutaneous nerve; Nervio cubital; Nervio mediano; Nervio musculocutáneo; Nervio radial; Radial nerve; Ulnar nerve; Ultrasonidos; Ultrasound; Ultrasound-guided axillary block; Variaciones anatómicas.