Analysis of Surgical Strategies and Efficacy in the Treatment of Os Odontoideum with Atlantoaxial Dislocation

Background: There are many classification systems for atlantoaxial dislocation (AAD). Among these systems, the definitions of irreducible AAD remain vague, and its treatments are not unified. Objective: To explore the surgical strategies and their efficacy for the treatment of os odontoideum (OO) with AAD. Methods: : The clinical data of 56 OO patients with AAD who underwent surgery from January 2017 to June 2021 were retrospectively analyzed. AAD was classified into four types, Type I and type II were treated with posterior fixation and fusion. Type III received posterior fixation and fusion after irreducible dislocations were converted to reducible dislocations by trans lateral mass release or transoral release. Type IV required transoral release for conversion into reducible dislocations before posterior fixation and fusion. The operation time, intraoperative blood loss, and perioperative complications were recorded. The preoperative and postoperative neurological function changes were assessed using the Japanese Orthopedic Association (JOA) score. Postoperative fusion status was assessed by X-ray or CT scan. Results: : There were 40 cases (71%) of type I-II, 14 cases (25%) of type III, and two cases (4%) of type IV AAD. The operation time was 137.5±42.04 min, and the blood loss was 202.85±171.21 mL. One patient with type III died, one with type III underwent revision surgery due to infection, and three patients with type I had further neurological deterioration after operation. Except for the patients who died, all patients were followed up for 12-24 months. The follow-up results showed that sufficient decompression was achieved and that the fixation and fusion were effective. The JOA score increased from 9.58±1.84 points before operation to 13.09±2.68 points at 3 months after operation,14.07±2.83 points at 6 months and 14.25±2.34 at 12 months after operation, all significant differences comparison with preoperative results (P<0.05). Conclusion: OO patients with irreducible AAD can be treated by trans lateral mass release or transoral release combined with posterior fixation and fusion, while some of those with bony fusion can be treated by transoral release combined with posterior fixation and fusion.