Vertebral Artery Variations at the Craniovertebral Junction in “Sandwich” Atlantoaxial Dislocation Patients

OBJECTIVE: To summarize the vertebral artery (VA) pattern of 96 “sandwich” atlantoaxial dislocation (AAD) patients and to describe the strategies of reducing the injury of VA during surgery. METHODS: From 2009 to 2020, we retrospectively reviewed the 3-dimensional computed tomography angiography data of 96 AAD patients combined with atlas occipitalization and C2–3 fusion, which were diagnosed as “sandwich” AAD and 96 patients as control group patients who were without atlas occipitalization, C2–3 fusion and any other cervical bone deformity at our institution. The variations of each side of VA were described in 3 different parts (C0–1, C1–2, and C2–3) according to the characteristics of the 3-part pathological structures in “sandwich” subgroup. RESULTS: One hundred ninety-two sides of VAs in every group of patients were analyzed and every VA was described separately at 3 different level regions. There were different variations in these 3 different regions: 4 variations in the upper fusion region, 5 variations in the sandwiched region, and 6 variations in the lower fusion region in sandwich AAD patients. And the rate of VA deformity in sandwich AAD patients was much higher and more types of VA variations existed. CONCLUSION: In “sandwich” AAD patients, deformities of vertebral arteries in craniovertebral junction are more common, and the same VA may have deformities at different levels that severely affect surgical procedures. Therefore, preoperative imaging examination of VA for “sandwich” AAD patients is vital of guiding surgeons to avoid injury of VA during surgery.