Lecture Notes: Nerve Injuries at the Elbow and Forearm Region

Anatomy Review

Bones:
- Radial bone
- Humerus bone
Nerves:
- Radial nerve
  - Splits into:
    - Superficial branch (sensation)
    - Posterior interosseous nerve (PIN) (motor)
- Median nerve
- Ulnar nerve

Overview:
- PIN stands for posterior interosseous nerve
- Purely motor nerve; penetrates through the supinator muscle
Symptoms:
- Weakness in motor functions innervated by PIN
  - Supinator, wrist extensors, finger extensors
- Possible wrist extension on radial side (extensor carpi radialis longus and brevis are innervated by radial nerve)
- Unable to extend fingers or ulnar side of the wrist
Specific Conditions:
- Radial tunnel syndrome: Sensory fibers are affected, not motor fibers

Overview:
- Compression or injury of the median nerve as it passes through the pronator teres muscle
Symptoms:
- Pain in the forearm and wrist
- Sensory disturbances in median nerve distribution
- Differentiation from carpal tunnel syndrome (CTS): No symptoms in forearm for CTS
Evaluation Tests:
- Resisted forearm pronation and elbow extension
- Resisted elbow flexion
- Resisted PIP flexion of the middle finger
- Most commonly used: Resisted forearm pronation and elbow extension

Overview:
- Median nerve compression affecting:
  - Flexor pollicis longus
  - Flexor digitorum profundus
  - Pronator quadratus
Symptoms:
- Difficulty forming an “O” with the thumb and index finger (hyperextension instead)

**Second most common nerve injury at the elbow (after carpal tunnel syndrome)*
Symptoms:
- Nerve compression posteriorly near the humerus
Causes:
- Overuse of the elbow/muscles (e.g., bodybuilders)
Evaluation Tests:
- Tinel’s sign: Tapping the ulnar nerve region
- Elbow flexion test: Full elbow flexion, forearm supination, wrist extension for 60 seconds to 3 minutes

Differentiate the conditions by their symptoms and the specific muscles/nerves involved
Use specific provocative tests to diagnose nerve injuries