Unilateral C1 Posterior Arch Screw-C2 Laminar Screw Posterior Fixation for Vertebral Artery Preservation in Bow Hunter's Syndrome.

Pedicle or lateral mass screws, which are usually used to fix atlantoaxial instability, increase the risk of vertebral artery (VA) injury in patients with bone or arterial anomalies or osteoporotic bone. Here, we report the use of a unilateral C1 posterior arch screw-C2 laminar screw posterior fixation with a contralateral C1 lateral mass screw for VA preservation in a patient with bow hunter's syndrome (BHS). A 65-year-old male presented with recurrent loss of consciousness in the right rotational and backward-bending head positions for 1 year. Cerebral angiography in the same head position showed that the left VA was disrupted at C1/2 and the right VA was hypoplastic. The patient was diagnosed with BHS. C1-2 posterior fixation and iliac bone grafting were performed. The left VA was on the dominant side, and the VA was in a high position; thus, a C1 posterior arch screw was selected for the left side, a C1 lateral mass screw was selected for the right side, and a C2 laminar screw with O-arm navigation and a C-arm was used to prevent arterial injury. Intraoperative findings revealed no VA injury, and postoperative computed tomography showed the screw at the planned site. In a patient with BHS, posterior fixation with a unilateral C1 posterior arch screw-C2 laminar screw prevented VA injury because the screw could be inserted while avoiding the VA.