Different techniques of atlantoaxial posterior screw fixation with a special attention to high riding vertebral artery

Abstract

Background: Posterior atlantoaxial fixation (AAF) is a standard surgical procedure for atlantoaxial joint instability (AAI). C1 lateral mass-C2 pedicle screw fixation is the most common adopted technique with high fusion rate, High riding vertebral artery (HRVA) represents a challenge in atlantoaxial fixation..Aim: to evaluate AAF in patients with AAI, assessing treatment outcomes, and complication,s especially with HRVA.Materials and Methods: Retrospective study of 174 patients with AAI, aged 11-68 years old underwent posterior AAF between March 2011 and July 2023 with a minimal follow up period of 1 year. Patients’ demographics, clinical presentation, HRVA presence, operative data, and treatment outcomes will be tabulated and analyzed.Results: 58 patients underwent AAF. HRVA was noted in 10 patients (17.2%). 4 patients had bilateral HRVA, and 6 patients had unilateral HRVA. In cases with bilateral HRVA, 3 cases used bilateral C2 laminar screws, and 1 case used bilateral C2 pars screws. In cases with unilateral HRVA, 3 patients had unilateral pars screws, 2 patients had unilateral laminar screws, and 1 patient had C2 pedicle clamp. Postoperatively, there were statistically significant clinical and functional improvements. Fusion was achieved in 98.3%. Complications were venous bleeding in 6 patients, infection in 1 case, irritation of the C2 root in 1patient. Vertebral artery injury occurred in 1 case.Conclusions: Careful preoperative radiological studies are crucial for identifying HRVA. Different techniques of atlantoaxial posterior fixation are used to reduce VA injury. The selection of fixation techniques with HRVA must be individualized based on the patient's anatomical challenges.