The long thoracic nerve: Cadaveric study of a potential site of dynamic compression?

Neuropathies of the long thoracic nerve (LTN) are rare pathologies whose etiology is still subject to discussion. Anatomical study of the nerve from its origin to its distal innervation could provide information about this condition.

We dissected 12 nerves from their origin in the brachial plexus to their terminal innervation branches. We identified all potential compression sites along the nerve pathway. Each nerve has been classified anatomically into its supraclavicular and infraclavicular parts. We have collected various biometric data.

We identified three potential anatomical elements of nerve compression, all located in the infraclavicular part. First, nerve compression related to crossing zones between the thoracodorsal artery branches with a preferred location between the 4th and 6th ribs. Second, aponeurotic bands derived from the axillary fascia causing a bridging effect located at the level of the 3rd and 4th ribs. Third, compression by the inferior angle of the scapula with its surrounding muscle masses at the level of the 4th and 5th ribs. We observed a predominant anatomical arrangement with crossing of the thoracodorsal artery above the LTN (types I, III, and V). The length of the LTN was measured as 193 ± 20.2 mm, the diameter of LTN main trunk was 2.8 ± 0.5 mm, distance inferior border of scapula to LTN was 35.8 ± 8.2 mm, number of lateral nerve branches was 6.3 ± 1 mm.

The long thoracic nerve is a long, thin nerve that is potentially fragile. The significant mobility of the scapulothoracic joint increases the risk of potential compression. Knowing the preferential locations of anatomical compression sites (artery, fascia, scapula) is complementary to the clinical analysis of winging scapula and the electromyographic topographic analysis of LTN compression. This data can guide the surgeon when neurolysis of the infraclavicular part of the LTN is being considered.