How do you identify the long thoracic nerve and thoracodorsal bundle during axillary dissection?

From the Guidelines

To identify the long thoracic nerve and thoracodorsal bundle during axillary dissection, it is crucial to locate the long thoracic nerve along the mid-axillary line on the serratus anterior muscle and the thoracodorsal bundle by following the latissimus dorsi muscle to its insertion point, preserving these structures to prevent complications such as scapular winging and impairment of shoulder function. When performing an axillary dissection, the goal is to accurately stage the disease while preserving important nerves and minimizing the risk of complications such as lymphedema. The long thoracic nerve can be identified as a thin, white structure running vertically down the chest wall, posterior to the brachial plexus, and gentle retraction of the surrounding tissue will help expose it 1. For the thoracodorsal bundle, it can be identified by following the latissimus dorsi muscle to its insertion point, where the neurovascular bundle runs along the posterior axillary fold, entering the latissimus dorsi muscle approximately 1-2 cm from its insertion, consisting of the thoracodorsal nerve, artery, and vein 1. Some key points to consider during the dissection include:

• Maintaining a bloodless field for better visualization
• Using careful blunt dissection techniques
• Preserving the intercostal brachial nerve when possible to prevent numbness of the posterior upper arm
• Avoiding circumferential stripping of the axillary vein to reduce the risk of lymphedema Preserving the long thoracic nerve and the thoracodorsal bundle is essential for maintaining shoulder function and preventing complications such as scapular winging, and the latissimus dorsi muscle can also serve as a flap for breast reconstruction 1.

From the Research

Identifying the Long Thoracic Nerve and Thoracodorsal Bundle

To identify the long thoracic nerve and thoracodorsal bundle during axillary dissection, several anatomical landmarks and techniques can be utilized.

• The long thoracic nerve arises from the C5, C6, and C7 roots and innervates the serratus anterior muscle 2.
• The thoracodorsal nerve can be identified by tracing the lateral thoracic vein bi-directionally, as it is consistently present posterolateral to the lateral thoracic vein 3.
• The mean distance to the lateral thoracic vein from the lateral border of pectoralis minor was 28.7 ± 12.6 mm, and the mean horizontal distance, depth, and displacement from a point along the lateral thoracic vein to the thoracodorsal nerve were 14.5 ± 8.9 mm, 19.7 ± 7.3 mm, and 25 ± 5 mm, respectively 3.
• The thoracodorsal nerve was found in a posterolateral direction, at a 54° ± 12° angle to the horizontal plane, 95% of the time 3.
• The lateral thoracic vein is an accurate guide to the thoracodorsal nerve, and exploring for the thoracodorsal nerve from a point 2 cm from the confluence of the lateral thoracic vein and the axillary vein is recommended 3.

Anatomical Considerations

• The long thoracic nerve has a trajectory parallel to the brachial plexus in the supraclavicular region, contrary to the schematic representation in most textbooks 4.
• The upper division of the long thoracic nerve can be assessed by the shoulder protraction test 4.
• Injury to the long thoracic nerve can result in serratus anterior muscle palsy, which is a frequent but reversible event after axillary node dissection 5.
• Understanding the anatomy structures and good surgical technique in the axillary clearance procedure can identify and prevent such an injury to the thoracodorsal nerve 6.