Radial Nerve Injuries and Examination

Introduction

• Radial nerve injuries are common in medical practice.
• Clinical examination is key to determining the injury level.
• Common symptoms include wrist, thumb, and finger drop.

Clinical Examination of Radial Nerve

• Goals: Assess nerve palsy, recovery, and identify donor muscles for transfer.
• Steps:
  1. History: Note patient details (age, sex, occupation, handedness), injury duration/type (crush, sharp, avulsion, blunt, needle prick), fractures, and initial weakness/treatment.
  2. Inspection: Examine limb posture and presence of wounds/scars.
  3. Palpation: Focus on TINEL sign, passive range of movement, two-point discrimination, and SOMS-Wenstein testing.
  4. Motor Examination: Test muscles supplied by radial nerve (details below).
  5. Sensory Examination: Test sensation in specific regions (posterior cutaneous nerve of arm, lower lateral cutaneous nerve, posterior cutaneous nerve of forearm, superficial branch).
  6. Donor Muscles Examination: In case of tendon transfer.

Motor Examination of Radial Nerve

• Triceps: Test elbow extension against gravity. Support forearm, resist extension, and palpate triceps.
• Brachialis: Test elbow flexion with forearm in pronated position.
• Brachioradialis: Test elbow flexion with forearm in mid-prone position.
• Anconeus: Palpate on radial side of the ulna during elbow extension.
• Supinator: Test forearm supination against resistance. Biceps should be elongated (elbow extended).
• Extensor Carpi Radialis (Brevis and Longus): Test wrist extension.
  • Deviation to radial side: Potential extensor carpi ulnaris issue.
  • Deviation to ulnar side: Brevis/longus issue.
• Extensor Digitorum Communis: Test by extending fingers one by one from a flat hand.
• Extensor Digiti Minimi: Extend only the little finger from a closed fist.
• Extensor Indicis Proprius: Extend only the index finger from a closed fist.
• Extensor Carpi Ulnaris: Extend wrist and palpate tendon.
• Extensor Pollicis Longus: Support proximal phalange, ask for interphalangeal joint extension with resistance.
• Extensor Pollicis Brevis: Extend metacarpophalangeal joint and offer resistance.
• Abductor Pollicis Longus: Abduct thumb at carpometacarpal joint against resistance.

Sensory Examination

• Test sensation in regions innervated by radial nerve.

Examination of Donor Muscles

• Common donor muscles: Pronator teres, flexor carpi ulnaris, flexor carpi radialis, palmaris longus, flexor digitorum superficialis (middle and ring fingers).
• Pronator Teres: Forceful pronation against resistance.
• Flexor Carpi Ulnaris/Radialis: Flex wrist against resistance.
• Palmaris Longus: Oppose thumb and little finger, flex wrist against resistance.
• Flexor Digitorum Superficialis (Middle/Ring Fingers): Flexion of proximal interphalangeal joint while restraining other fingers.

Examples of Radial Nerve Injuries

• Spiral Groove Injury: Total palsy of wrist, thumb, and finger extensors.
• Proximal Posterior Interosseous Nerve Injury: Wrist extension preserved; finger/thumb extension lost.
• Distal Posterior Interosseous Nerve Injury: Selective loss of specific muscles.

Conclusion

• Importance of clinical examination in diagnosing radial nerve injuries.
• Further resources: Links to more information on radial nerve basics and repair techniques.