Mobilization of the Scalene Fat Pad

One of the keys to simplifying the supraclavicular exposure is proper mobilization and lateral reflection of the scalene fat pad. This begins with detachment of the fat pad along the lateral edge of the internal jugular vein and the superior edge of the clavicle, followed by gentle fingertip dissection in the underlying tissue plane directly over the anterior scalene muscle. The thoracic duct is usually observed near the junction of the internal jugular and subclavian veins (most consistently present on the left side), where it is ligated and divided. The fat pad is progressively elevated in a medial to lateral direction, exposing the surface of the anterior scalene muscle along with the phrenic nerve, which passes in a lateral to medial direction along the muscle surface. The remaining inferior and superior attachments of the fat pad are divided, and small blood vessels and lymphatics are secured between ligatures.

The fat pad may then be rotated laterally until there is ample exposure of the anterior scalene muscle and phrenic nerve, the brachial plexus nerve roots (posterior and lateral to the anterior scalene muscle), and the middle scalene muscle (behind the brachial plexus). The lateral aspect of the first rib is palpated and visualized, and the long thoracic nerve is observed as it perforates the middle scalene muscle to course across and past the first rib. Direct visualization of the above-mentioned structures represents the first of six critical views to be obtained during supraclavicular decompression (Box 1). The scalene fat pad is then held in position with several retraction sutures and kept moist during the remainder of the procedure. The exposure is maintained with a Henley self-retaining retractor (Figure 1A and B).

Anterior Scalenectomy

Attention is next turned to the insertion of the anterior scalene muscle upon the first rib, which is isolated by blunt dissection under direct visualization in order to avoid injury to the phrenic nerve, the subclavian artery, and the brachial plexus nerve roots (see Figure 1C). The anterior scalene muscle is then sharply divided from the bone under direct vision with curved scissors. The inferior edge of the anterior scalene muscle is lifted superiorly and detached from the underlying subclavian artery, brachial plexus nerve roots, and extrapleural fascia. Any scalene minimus muscle fibers present are also divided. The anterior scalene muscle is passed underneath and medial to the phrenic nerve, and dissection of the muscle is carried superiorly to its origin on the C6 transverse process, which is easily palpated in the upper aspect of the operative field (see Figure 1D and E). The anterior scalene muscle is then divided under direct vision and removed. Anomalous fibrofascial bands may be observed after the anterior scalene muscle is resected. They typically pass in front of the lower brachial plexus nerve roots. These structures are also resected as they are encountered to ensure thorough decompression and full nerve root mobility.