Ultrasound-guided axillary approach for axillary nerve block: a cadaveric study

Interscalene brachial plexus block is widely used for pain management in shoulder surgery. However, because of the risk of phrenic nerve palsy, combined suprascapular and axillary nerve blocks (ANBs) are increasingly being used. Although the posterior approach is often used for ANB, several studies have reported on the axillary approach. The purpose of this study was to perform ANB using the axillary approach under ultrasound (US) guidance to investigate the injection point and spread of the solution.

18 fresh-frozen cadaveric specimens (8 male and 10 female specimens) were used in this study, with a mean age of 67.2 years (range, 37-92 years). The cadavers were placed in the lateral position with the upper limb in abduction. The transducer was placed on the axillary fold, and the axillary nerve (AN) was identified in the superficial layer of the humeral head underneath the teres major muscle. Using the in-plane technique, a block needle was inserted posterior to the anterior. 0.1 mL of blue latex solution was injected into 12 specimens (12 shoulders) to confirm the needle tip position, and 10 mL of saline solution colored with methylene blue (MB) was injected into six specimens (six shoulders) to evaluate the spread of the solution.

In all cases, the AN was identified by US, and block manipulation was possible. The bifurcation of the anterior and posterior branches of the AN within the quadrilateral space was stained with blue latex solution. The anterior branch of the AN, posterior branch to the deltoid muscle, and posterior branch to the teres minor muscle were stained with MB in all cases.

The anterior and posterior branches of the AN were accurately blocked using an US-guided axillary approach. The axillary approach is an effective alternative to the posterior approach.