Radial Nerve Injury

Question 1

AETIOLOGY

Common causes

Answer 1

• Fracturing humerus
• Sleeping with upper arm in awkward position
• Pressure from leaning arm over back of chair
• Falling on or receiving blow to arm
• Long term constriction of wrist

Question 2

CLINICAL FEATURES

What does presentation depend on

Answer 2

• Depends on where injury occurs
  
  • Axilla
  • Radial groove
  • Forearm

Question 3

CLINICAL FEATURES

Presentation when injury in axilla

Answer 3

• Motor
  
  • Weakness of triceps brachii and muscles in posterior compartment
  • Unable to extend forarm, wrist and fingers, unopposed flexion occurs called wrist drop
• Sensory
  
  • Loss of sensation over lateral and posterior arm, posterior forearm, dorsal surface of lateral 3.5 digits

Question 4

AETIOLOGY

Most common cause for different locations of injury

Answer 4

• Axilla - dislocation of shoulder joint or fracture of proximal humerus
• Radial grove - fracture of humeral shaft
• Forearm - stabbing or laceration of forearm, or fracture of radial head of posterior dislocation of radius

Question 5

CLINICAL FEATURES

Presentation when location radial groove

Answer 5

• Motor
  
  • Tricep brachii may be weakened, but not paralysed
  • Muscles posterior forearm affected, unable to extend at wrist and fingers, wrist drop occurs
• Sensory
  
  • Superficial branch of radial nerve damaged, sensory loss to dorsal surface of lateral 3.5 digits and associated area of dorsum of hand

Question 6

CLINICAL FEATURES

Presentation when location forearm

Answer 6

• If superficial branch
  
  • No motor problems
  • Sensory loss of lateral 3.5 digits and associated dorsum of hand
• If deep branch
  
  • Posterior forearm affected, wrist drop does not occur though as extensor carpi radialis longus is unaffected, some extension maintained at wrist
  • No sensory problems