Which vertebrae (vertebral bodies) are involved when there is a loss of arm mobility due to a spinal injury?

Cervical Vertebral Injuries and Loss of Arm Mobility

Injuries to the C3-C5 vertebrae are most commonly associated with loss of arm mobility while preserving lower extremity function.

Neuroanatomical Basis

The pattern of arm weakness with preserved leg function relates to the somatotopic organization and function of the spinal cord:

• The cervical spinal cord contains motor neurons that control upper extremity function
• C3-C5 vertebral injuries commonly result in disproportionate upper extremity weakness compared to lower extremity function 1
• This pattern occurs because the corticospinal tract in primates is critical for hand function but less essential for locomotion 1

Specific Vertebral Levels and Clinical Presentation

C3-C4 Level Injuries

• Most commonly associated with complete loss of arm mobility while preserving some leg function
• Represent approximately 2.8% of cervical spine injuries in athletic contexts 2
• Unique characteristics include:
  • Infrequency of bony fracture
  • Difficulty maintaining reduction
  • More favorable recovery with early intervention 3

C4-C5 Level Injuries

• Also commonly associated with arm weakness/paralysis
• May present with the classic "central cord syndrome" pattern
• Often results from axial loading mechanisms 2

Diagnostic Approach

Imaging is crucial for accurate diagnosis:

• CT is the gold standard for identifying cervical spine fractures 4
• MRI is essential for assessing:
  • Soft tissue injuries
  • Discoligamentous complex integrity
  • Spinal cord signal changes 4
• CT angiography should be considered to evaluate for vertebral artery injury, which occurs in up to 46% of patients with unstable cervical spine injuries 5

Management Considerations

1. Initial Management:

   • Early immobilization is critical to prevent secondary injury 6
   • Careful airway management with manual in-line stabilization if intubation is required 6

2. Surgical Considerations:

   • Early surgical decompression (within 24-96 hours) may improve neurological outcomes 4
   • C3-C4 injuries often require specialized approaches due to difficulty maintaining reduction 3

3. Complications to Monitor:

   • Respiratory compromise (especially with higher cervical injuries)
   • Hemodynamic instability
   • Pressure sores with prolonged immobilization 6

Prognosis

Prognosis varies based on:

• Timing of intervention (earlier treatment generally yields better outcomes)
• Extent of initial neurological deficit
• Presence of spinal cord signal changes on MRI

For C3-C4 injuries specifically, more favorable recovery has been observed with immediate reduction of facet dislocations 3.

Common Pitfalls

• Failing to recognize isolated ligamentous injuries (which occur in 0.1-0.7% of blunt trauma patients) 4
• Overreliance on plain radiographs (miss up to 15% of injuries) 4
• Delayed diagnosis leading to secondary neurological deterioration 6
• Prolonged immobilization causing complications after 48-72 hours 6

Understanding the specific vertebral level involved is crucial for predicting functional outcomes and guiding appropriate management in patients with cervical spine injuries and arm mobility loss.