Anatomy notes

Brachial Plexus and Common Injuries

Gross Motor Function by Nerve Roots

C5, C6

• Functions :
  • Shoulder abduction
  • Elbow flexion

C7

• Functions :
  • Triceps function
  • Wrist extension (which may be affected if C7 is involved)

C8, T1

• Functions :
  • Hand function

Common Brachial Plexus Injuries

Upper Brachial Plexus Injury (C5-C6 roots)

• Deformity :
  • Arm: Abducted and internally rotated
  • Forearm: Extension and supination (+/- wrist in flexion)
• Condition : Waiter’s tip deformity
• Causes :
  • Lateral traction to upper limb
  • Common birth injury with shoulder dystocia
  • Accidental injury to neck (e.g., motorbike accidents)
• Affected Actions :
  • Shoulder abduction
  • Elbow flexion
  • Triceps and wrist extension if C7 is involved

Lower Brachial Plexus Injury (C8-T1 roots)

• Causes :
  • Upward force (pulling) to the upper limb
  • Vaginal birth injury
  • Accidental injury to neck (e.g., motorbike accidents)
• Muscles Affected :
  • Muscles of the hand: Intrinsic, Thenar, Hypothenar
  • Forearm pronators
  • Wrist flexors (may be involved)
• Associated Conditions : May be linked to Horner’s syndrome (meiosis + ptosis)
• Deformity :
  • Claw hand
  • Forearm supinated
  • Wrist extended

Summary of Key Injuries and Deformities

• Winging of Scapula : Caused by injury to the Long thoracic nerve (C5, C6, C7) leading to weakness of serratus anterior muscle.
• Erb’s Palsy : Upper brachial plexus injury characterized by Waiter’s tip deformity.