Anatomical basis of the variable aspects of injuries of the axillary nerve (excluding the terminal branches in the deltoid muscle)

Abstract

The course of the axillary n. is complex with three points of angulation that may be used to delineate four segments and a fifth segment that corresponds to the intramuscular ending of the nerve in the deltoid m. The purpose of this study was to determine the precise anatomy of the nerve and of its branches, and some morphologic features for each segment. Thirty-two shoulders from embalmed adult cadavers have been studied. The axillary n. was divided in five segments: 1) from its origin to the inferior border of the subscapularis m., 2) from the subscapularis m. to the anterolateral border of the tendon of the long head of the triceps brachii m., 3) from the triceps to the posteromedial part of the surgical neck of the humerus, 4) from the humerus to the entry into the deltoid m., 5) the intramuscular distribution of the nerve in the deltoid m. In each segment from 1 to 4 were noted the origins of the branches to the subscapularis and teres minor mm. and to the scapulohumeral joint, and the origins of the lateral cutaneous branchial n. and of the terminal motor branches to the deltoid m. The length and the diameter of the nerve in the segments and the distance from the segment S1 to the musculotendinous junction of the subscapularis m. were measured. The results showed that the mean diameters were about 4.1 mm in segment 1, 4.1 mm in segment 2 and 3.4 mm in segment 3. The mean distance to the musculotendinous junction was 7.7 mm. Many variations in the levels of origin of the different muscular, articular or cutaneous branches were found without symmetry between the right and left sides. The lateral cutaneous brachial n. was absent in four cases. The results are compared with those in the literature. The division into five segments is proposed to radiologists and surgeons for evaluation or operative procedures on the axillary n., and to provide a hypothesis about the variable aspects of injuries of the nerve.

Anatomy of Axillary Nerve and Its Clinical Importance: A Cadaveric Study

“…In a dissection study of 32 shoulders from embalmed adult cadavers, the axillary nerve had been divided into five segments from its origin to intramuscular distribution in the deltoid muscle in order to define a few morphological features of anatomy which is useful for the physician, the radiologist or the surgeon for the evaluation or operative procedures on the axillary nerve and to provide a hypothesis about the variable aspects of injuries of the nerve [10].…”

Variations in the Innervation of the Long Head of the Triceps Brachii: A Cadaveric Investigation

“…From these branches the axillary nerve will innervate the teres minor, deltoid, and inferior aspect of the glenohumeral joint capsule. The exact course of the axillary nerve after exiting the quadrilateral space has proven to be quite variable [1,3,6,7,15].…”

Innervation patterns of the inferior glenohumeral ligament: Anatomical and biomechanical relevance

“…Findings relative to the innervation of the inferior glenohumeral capsule have been widely variable (Duparc et al, 1997). Since Rü dinger (1857), several descriptions of its neural anatomy have been made.…”