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Supratrochlear nerve and optic nerve
5%
208/4496
Supraorbital nerve and optic nerve
13%
568/4496
Supratrochlear nerve and cranial nerve VI
214/4496
Supraorbital nerve and cranial nerve VI
16%
704/4496
Supraorbital nerve and supratrochlear nerve
62%
2775/4496
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Placing a pin for a halo vest orthosis over the medial third of the orbit, as labeled in red in Figure A, places the supraorbital nerve and supratrochlear nerve at risk of iatrogenic injury. Proper placement of anterior halo orthosis pins is approximately 1 cm above the superior orbital rim (below the equator of the skull) and over the LATERAL third of the orbit. Staying lateral is critical to avoid the supraorbital and supratrochlear nerves which are located more medially. Injury to the supratrochlear nerve may present with loss of sensation to the medial eyelid, conjunctiva, and some of the forehead. Injury to the supraorbital nerve may present with loss of sensation over the upper eyelid, forehead, scalp, as well as weakness of the upper eyelid. Bono presents a review article on the use of halo fixators for cervical trauma. He recommends placing anterior pins within a region approximately 1 cm above the eye brow (which should be at or below the equator), and over the lateral third of the orbit. He provides further detail on appropriate indications and techniques. Garfin et al. present a retrospective review of 179 patients treated with a halo fixator to identify common complications. Complications included pin loosening (36%), pin-site infection (20%), pressure sores under the vest (11%), dysphagia (2%), and nerve injury (2%). Of note, injury to the supraorbital or supratrochlear nerve occured in 3 patients, all of whom had pins placed over the medial third of the orbit. They recommend anterior pin placement of the lateral third of the orbit to avoid this complication. Illustration A is a drawing to show the safe zone for anterior pin placement relative to the temporalis muscle, supraorbital nerve, and supratrochlear nerve. Illustration B shows a surgical dissection of the Supraorbital nerve and Supratrochlear nerve. Incorrect answers: Answers 1 and 2: The optic nerve is not known to be at risk from a medially placed pin. Answers 3, 4: Cranial nerve VI is not known to be at risk from a medially placed pin
3.2
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