Axillary Nerve (C5–C6) Injury
The axillary nerve is a terminal branch of the posterior cord of the brachial plexus. It is highly vulnerable due to its close anatomical proximity to the surgical neck of the humerus.
| Innervation Affected | Clinical Impact |
|---|---|
| Deltoid Muscle | Loss of arm abduction (beyond first 15°) and shoulder weakness. |
| Teres Minor Muscle | Weakened lateral (external) rotation of the shoulder. |
| Superolateral Skin | Sensory loss over the “regimental badge” area of the shoulder. |
Common Causes:
- Fracture of the surgical neck of the humerus.
- Anterior shoulder dislocation.
- Iatrogenic injury during shoulder surgery (e.g., thermal injury, retractors).