Upper limb
Axillary nerve
Nervus axillaris
- Origin
- Terminal branch of the posterior cord of the brachial plexus (C5–C6)
- Insertion
- Traverses the quadrangular space with the posterior circumflex humeral vessels to wrap around the surgical neck of the humerus
- Function
- Motor to deltoid (all three bellies) and teres minor; sensory to the 'regimental badge' area of the lateral shoulder via superior lateral cutaneous nerve of arm
- Innervation
- Mixed sensorimotor nerve essential for glenohumeral stability and abduction
- Movement & chain
- Drives shoulder abduction beyond initial 15° up to horizontal, and contributes to glenohumeral external rotation
- Palpation
- Sensory territory tested over the lateral deltoid muscle belly ('regimental badge area')
- Clinical
- Most commonly injured nerve in anterior-inferior glenohumeral dislocation and proximal humerus surgical neck fractures; causes deltoid atrophy and abduction deficit
- Segmental innervation
- C5–C6 spinal segments
- In clinical practice
- Mandatory sensory check over lateral shoulder before and after closed reduction of anterior shoulder dislocations
- Region in the model
- Upper limb