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 (Cranial Nerve VI) 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