Mapping out the axillary nerve: A cadaveric study

The axillary nerve is a crucial peripheral branch arising from the posterior cord of the brachial plexus. It provides both motor and sensory innervation to the shoulder girdle, enabling essential movements such as abduction and external rotation-functions that are crucial for daily activities and various athletic movements. Despite its significance, detailed documentation of the axillary nerve's branching patterns remains limited. This study aimed to examine the branching configurations of the axillary nerve in a South African cadaveric sample.

Thirty adult cadavers (15 females and 15 males) were examined. To minimise the risk of damaging the axillary nerve during dissection, key surface anatomy landmarks-including the acromion and coracoid process-were identified and marked, enabling accurate location of the nerve as it traversed the deltoid muscle. Dissection followed established protocols, involving careful incision and reflection of the deltoid and pectoral muscles to expose the axillary nerve and associated neurovascular structures.

The study identified and classified four distinct axillary nerve branching patterns. Type 1, in which the nerve branches before entering the quadrangular space, was observed in 16.67% of cases. Type 2, characterized by branching within the quadrangular space, was noted in 18.33%. Type 3, where branching occurred after exiting the quadrangular space, was observed in 25.00%. Type 4, a combination of the previous three patterns, was the most prevalent, occurring in 40.00% of specimens. No significant differences were observed between the left and right shoulders regarding branching pattern (p = 0.9998). However, a significant difference was found in the overall distribution of branching types across all categories (p = 0.01299).

These findings suggest that the axillary nerve does not exhibit a definitive branching pattern, highlighting the anatomical complexity and variability of this structure. This underscores the need for a more nuanced and comprehensive classification system when analyzing the axillary nerve morphology.