Posterior acoustic enhancement and transducer compression during axillary block

Posterior acoustic enhancement (circled) observed during axillary block at the level of the conjoint tendon (arrowheads) of the latissimus dorsi and teres major muscles. Images recorded (A) with and (B) without transducer compression. With light touch, the ulnar nerve (arrow) is identified just deep to an axillary vein (between the axillary vein and axillary artery).