Endoscopic-assisted anterior transarticular screw fixation and arthrodesis for atlantoaxial instability via a retropharyngeal approach: technical note and preliminary clinical outcomes.

Background: Atlantoaxial instability (AAI) is complex and challenging to manage due to the biomechanical and neurovascular significance of the craniocervical junction. Posterior fixation remains the gold standard but may be contraindicated or infeasible in select patients. Although anterior transoral/transnasal approaches provide adequate access to the atlantoaxial joints, their deep, narrow, and contaminated surgical corridor may reduce visualization and increase postoperative infection risks. Full-endoscopic anterior retropharyngeal procedures also have blind zones that limit visualization, prevent complete joint decortication, and often require posterior fixation to ensure adequate cervical stabilization. A hybrid open Smith-Robinson exposure augmented by endoscopy and anterior transarticular screw (ATS) fixation may provide a wide, clean surgical corridor with improved visualization and high maneuverability that addresses these limitations. The main aim of this prospective study is to describe and evaluate the preliminary clinical outcomes of EATS (endoscopic-assisted anterior transarticular screw fixation) for managing AAIs. Case Description: Thirteen patients with radiographically confirmed AAI underwent EATS between April 2024 and December 2025. The procedure consists of anterior Smith-Robinson exposure, fluoroscopic localization, endoscopic-assisted subchondral decortication and bone grafting, and fluoroscopy-guided ATS fixation. Measured outcomes included screw placement accuracy, neurological improvement (American Spinal Injury Association [ASIA] grade and myelopathic symptoms), and time to radiographic arthrodesis. Outcome: All procedures were completed successfully without any neurovascular complications. Postoperative computer tomography (CT) confirmed accurate screw positioning and satisfactory reduction in all patients. Solid arthrodesis was achieved within 12.4 ± 3.8 weeks. Neck pain, myelopathic symptoms, and ASIA (American Spinal Injury Association) scores significantly improved during follow-up. One postoperative cervical hematoma occurred in a patient receiving low-molecular-weight (LMW) heparin for thromboprophylaxis was recorded. No infections or implant-related complications occurred. Conclusions: EATS is a safe and effective anterior alternative for AAI management. It combines the advantages of the Smith-Robinson approach with enhanced endoscopic visualization and fluoroscopic precision, enabling accurate joint decortication, stable fixation, and early arthrodesis. Larger studies with longer follow-up may be required to validate the overall long-term outcomes and biomechanical efficacy.