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A 27-year-old male is an unrestrained passenger in a motor vehicle accident. He was medically stabilized in the emergency room. His initial injury CT scans are seen in Figures A and B. He is neurologically intact and placed in a halo fixator prior to surgical treatment. What is the most common neurologic complication with halo traction?
Weakness in biting and chewing strength
Deficit in medial and downward eye movement
Deficit in lateral eye movement
Inability to close eyes against resistance
Tongue deviation toward the affected side
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Figures A and B depict a patient with an Type II odontoid fracture. Cranial nerve VI palsy is the most common nerve palsy associated with halo cervical traction. A cranial nerve VI palsy would result in paralysis of the lateral rectus, causing a deficit in lateral eye movement. The cranial nerves and functions are in Illustration A.
Halo fixation is indicated for a number of conditions in the cervical spine including definitive treatment for fractures and preoperative reduction. In adults, four pins are placed at 6-8in/lbs. The safe zone is defined 1cm superior to the outer 2/3 of the orbit. Absolute contraindications include active infection, cranial fractures and severe soft-tissue injury at pin sites. Pin loosening is the most common complication in adults, followed by pin site infection.
Wilkens et al investigated cranial nerve complications with halo immobilization and traction in 70 patients. They found the sixth cranial nerve was most commonly affected by distraction and resulted in weakness in lateral gaze. They emphasize that frequent monitoring of the patients in skeletal traction is necessary, and prompt recognition of the clinical signs of these complications must be stressed.
Bono et al report halo immobilization can be used for the definitive treatment of cervical spine trauma, preoperative reduction in the patient with spinal deformity, and adjunctive postoperative stabilization following cervical spine surgery. They state skull fracture, infection, and severe soft-tissue injury at the pin sites as absolute contraindications. Relative contraindications include severe chest trauma, obesity, advanced age, and a barrel-shaped chest.
Figure A shows a sagittal CT showing a Type II odontoid fracture with anterior displacement. Figure B is an axial CT at the level of the odontoid again showing anterior diplacement of the dens. Illustration A lists the cranial nerve. Illustration B & C illustrate how to place a halo fixator. Illustration D shows the safe zone for placement of your anterior halo pin.
Wilkins C, MacEwen GD.
Clin Orthop Relat Res. 1977 Jul-Aug;(126):106-10. PMID: 598096 (Link to Abstract)
J Am Acad Orthop Surg. 2007 Dec;15(12):728-37. PMID: 18063713 (Link to Abstract)
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With halo immobilization the anterior pin should be placed in which of the following regions in Figure A to avoid injury to the supraorbital nerve and optimize stability?
The safe zone for anterior pin insertion with halo immobilization is an approximately 1-cm region just above the lateral one third of the orbit (eyebrow) at or below the equator of the skull. More lateral pin insertion risks penetration of the thin temporal bone. More medial positioning risks injury to the supraorbital and supratrochlear nerves (see Illustration A). An injury to the supraorbital nerve may lead to pain and numbness over the medial one third of the eyebrow. The supratrochlear nerve supplies sensation medial and inferior to the supraorbital sensory distribution. Regions A, B, and C are all above the equator of the skull and would not be ideal from a biomechanical perspective. The review article by Bono explains the history, indications, proper placement, and complications of halo immobilization.
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The halo vest is most effective at controlling which of the following spinal motions?
Rotation at the atlantoaxial joint
Flexion and extension in the subaxial cervical spine
Rotation in the subaxial cervical spine
Lateral bend in the subaxial cervical spine
Flexion and extension at the cervicothoracic junction
The Halo vest immobilizes the skull relative to the torso. Therefore is is ideal for controlling motion at upper cervical spine (occipitocervical junction and atlantoaxial junction. Halo immobilization allows for intercalated paradoxical motion in the subaxial cervical spine, and is therefore less ideal for lower cervical spine injuries.
Ivancic et al performed an invitro study measuring motion of cervical spine specimens with the variables of a normally applied halo, a loose vest, a loose superstructure, and an absent posterior uprights. They found that lateral bending was increased at the C6-7 level when there was a loose superstructure.
Johnson et al evaluated the ability of different cervical orthoses to control cervical range of motion at each cervical intervertebral joint. At the atlanto-axial joint, the halo vest restricted flexion-extension by 75%, which compared to only 45% by conventional cervical braces. The halo vest was less effective at controlling motion in the subaxial cervical spine below C3.
Bono et al reviews the literature and discusses the indications, contraindications, and complications for halo immobilization. They recommend the halo can be used for definitive treatment of C1 burst (Jefferson) fracture and type II and III odontoid fractures. Absolute contraindications include cranial fracture, infection, and severe soft-tissue injury at the proposed pin sites. They discuss the high mortality rate associated with using halo immobilization in the elderly population.
Illustration A shows the table from the Johnson articles that compares the effectiveness of different orthosis at controlling different types of motion (combined measurement from occiput to T1)
Answers 2,3,4,5: The halo vest is less effective at controlling motion in the subaxial cervical spine and cervicothoracic junction than at the atlanto-axial joint.
Ivancic PC, Beauchman NN, Tweardy L
Spine. 2009 Jan;34(2):167-75. PMID: 19139667 (Link to Abstract)
Johnson RM, Hart DL, Simmons EF, Ramsby GR, Southwick WO.
J Bone Joint Surg Am. 1977 Apr;59(3):332-9. PMID: 849944 (Link to Abstract)
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A 20-year-old man presents with a type III odontoid fracture and undergoes halo application. What nerve structure is in danger if the anterior pins are placed too medially?
The supraorbital nerve is at risk if the anterior pin is placed too medially.
When placing pins during halo immobilization a relative safe zone for anterior pin placement is located 1 cm above the orbital rim and superior to the lateral two thirds of the orbit. This prevents injury to both the supraorbital and supratrochlear nerve which are both located medially (supratrochlear nerve more medial than supraorbital nerve). Posterior pin-site locations are less critical and can be positioned on the posterolateral aspect of the skull, diagonal to the contralateral anterior pins. Pins should enter the skull perpendicular to the cortex, with the ring or crown sitting below the widest portion of the skull and passing about 1 cm above the helix of the ear.
Garfin et al. review complications associated with halo immobilization. They found pin-loosening in 36% of the patients, pin-site infection in 20%, pressure sores under either a plastic vest or a plaster cast in 11%, nerve injury in 2%, dural penetration in 1%, dysphagia in 2%, cosmetically disfiguring scars in 9%, and severe pin discomfort in 18%.
Botte at al. report superficially infected pins are managed with local pin care and oral antibiotics. Persistent or severe infections require pin replacement to a nearby site, parenteral antibiotic therapy, and incision and drainage as needed.
Illustration A shows the region of the safe zone in relation to the supraorbital nerve and supratrochlear nerve. Illustration B shows a surgical image of the supraorbital nerve. Illustration C shows the branches of the Trigeminal nerve (CN V) which include the supraorbital nerve and supratrochlear nerve.
Answer 2: The facial nerve (CN VII) controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity. It is not at risk with anterior pin placement.
Answer 3: The abducens nerve (CNVI) is an intracranial nerve that is not at risk from direct damage with pin placement. Abducens nerve palsy, leading to absence of lateral gaze, is one complication of halo placement but is thought to be related to a traction injury on the nerve.
Answer 4 and 5: The zygomaticotemporal nerve and zygomaticofacial nerve are both branches of the Trigeminal nerve, but are not in the region of the medial-superior orbit.
Botte MJ, Byrne TP, Abrams RA, Garfin SR.
J Am Acad Orthop Surg. 1996 Jan;4(1):44-53. PMID: 10795038 (Link to Abstract)
Garfin SR, Botte MJ, Waters RL, Nickel VL.
J Bone Joint Surg Am. 1986 Mar;68(3):320-5. PMID: 3949826 (Link to Abstract)
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