Erb’s Palsy (C5–C6 Brachial Plexus Injury)
Erb’s palsy, or “waiter’s tip” palsy, results from an injury to the superior trunk of the brachial plexus. This typically occurs due to excessive increase in the angle between the neck and the shoulder, causing traction on the C5 and C6 nerve roots.
| Functional Deficit | Key Muscles Involved |
|---|---|
| Abduction of arm | Deltoid, Supraspinatus |
| External rotation | Infraspinatus, Teres minor |
| Flexion of elbow | Biceps brachii, Brachialis |
High-Yield Clinical Notes:
- Classic Position (“Waiter’s Tip”): The limb hangs by the side, medially rotated (due to unopposed action of the pectoralis major and subscapularis), and the forearm is pronated.
- Common Causes: Lateral traction on the neck during difficult vaginal delivery (shoulder dystocia) or trauma to the shoulder (e.g., motorcycle accident).
- Sensory Loss: Typically observed over the lateral aspect of the arm and forearm.