Axillary nerve

Structure

• The anterior branch winds around the surgical neck of the humerus, beneath the deltoid muscle, with the posterior humeral circumflex vessels. It continues as far as the anterior border of the deltoid to provide motor innervation. The anterior branch also gives off a few small cutaneous branches, which pierce the muscle and supply in the overlaying skin.
• The posterior branch supplies the teres minor and the posterior part of the deltoid. The posterior branch pierces the deep fascia and continues as the superior lateral cutaneous nerve of arm, which sweeps around the posterior border of the deltoid and supplies the skin over the lower two-thirds of the posterior part of this muscle, as well as that covering the long head of the triceps brachii.
• The motor branch of the long head of the triceps brachii arises, on average, a distance of 6 mm from the terminal division of the posterior cord termination.
• The trunk of the axillary nerve gives off an articular filament which enters the shoulder joint below the subscapularis.

  Variation

Function

Clinical significance

• Paralysis of the teres minor muscle and deltoid muscle, resulting in loss of abduction of arm, weak flexion, extension, and rotation of shoulder. Paralysis of deltoid and teres minor muscles results in flat shoulder deformity.
• Loss of sensation in the skin over a small part of the lateral upper arm.

  Additional images