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Introduction
  • Fixes skull relative to torso 
    • provides most rigid form of cervical spine external immobilization
    • ideal for upper C-spine injury
  • Allows intercalated paradoxical motion in the subaxial cervical spine
    • therefore not ideal for lower cervical spine injuries (lateral bending least controlled) 
      • "snaking phenomenon"
        • recumbent lateral radiograph shows focal kyphosis in midcervical spine 
        • yet, upright lateral radiograph shows maintained lordosis in midcervical spine
Indications
  • Adult
    • definitive treatment of cervical spine trauma including
      • occipital condyle fx
      • occipitocervical dislocation
      • stable Type II atlas fx (stable Jefferson fx)
      • type II odontoid fractures in young patients 
      • type II and IIA hangman’s fractures
    • adjunctive postoperative stabilization following cervical spine surgery
  • Pediatric
    • definitive treatment for
      • atlanto-occipital dissociation
      • Jefferson fractures (burst fracture of C1)
      • atlas fractures
      • unstable odontoid fractures
      • persistent atlanto-axial rotatory subluxation 
      • C1-C2 dissociations
      • subaxial cervical spine trauma
    • preoperative reduction in the patients with spinal deformity
Contraindications
  • Absolute
    • cranial fractures
    • infection
    • severe soft-tissue injury
      • especially near proposed pin sites
  • Relative
    • polytrauma
    • severe chest trauma
    • barrel-shaped chest
    • obesity
    • advanced age
      • recent evidence demonstrates an unacceptably high mortality rate in patients aged 79 years and older (21%)
Imaging
  • CT scan prior to halo application
    • indications
      • clinical suspicion for cranial fracture
      • children younger than 10 to determine thickness of bone
Adult Technique
  • Adults
    • torque
      • tighten to 8 inch-pounds of torque
    • location
      • total of 4 pins
      • 2 anterior pins 
        • safe zone is a 1 cm region just above the lateral one third of the orbit (eyebrow) at or below the equator of the skull  
          • this is anterior and medial to temporalis fossa/temporalis muscle
          • this is lateral to supraorbital nerve 
      • 2 posterior pins
        • placed on opposite side of ring from anterior pins
    • followup care
      • can have patient return on day 2 to tighten again
      • proper pin and halo care can be done to minimize chance of infection
Pediatric Technique
  • Pediatrics 
    • torque
      • best construct involves more pins with less torque 
        • total of 6-8 pins
        • lower torque (2-4 in-lbs or "finger-tight")  
    • pin locations
      • place anterior pins lateral enough to avoid injury to the frontal sinus, supratrochlear and supraorbital nerves 
      • place pins anterior enough to avoid the temporalis muscle
      • place pins posteriorly opposite from anterior pins
    • brace/vest
      • custom fitted vest for children > 2 years
      • children <2 yrs should use Minerva cast
    • CT scans may help in pin placement
      • can help facilitate avoiding cranial sutures
      • can  help facilitate avoiding thin regions of skull
      • help limit risk of complications 
Complications
  • Higher complications in children (70%) than adults (35%)
  • Loosening (36%)
    • can be treated with retightening
    • if continues to loosen, should be treated with pin exchange
  • Infection (20%)
    • can especially occur with posterior pin in temporalis fossa because
      • pins hidden in hairline
      • bone is thin
      • temporalis muscle moves with chewing
    • can be treated with oral antibiotics if pin not loose 
      • if pin infection and loose then pin should be removed
  • Discomfort (18%)
    • treated by loosening skin around pin
  • Dural puncture (1%)
  • Abducens nerve palsy  
    • epidemiology
      • is most commonly injured cranial nerve with halo
    • pathophysiology
      • thought to be a traction injury to cranial nerve 6, which affects abducens nerve (innervate lateral rectus muscles) 
    • symptoms
      • diplopia
    • physical exam
      • loss of lateral gaze on affected side 
    • treatment
      • observation as most resolve spontaneously
  • Supraorbital nerve palsy  
    • injured by medially placed anterior pins
  • Supratrochlear nerve palsy  
    • injured by medially placed anterior pins
  • Medical complications
    • pneumonia
    • ARDS
    • arrhythmia
 

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