Clinical Application and Efficacy Analysis of 3D Navigation Module in the Treatment of Atlantoaxial Instability

Background: Posterior cervical atlantoaxial pedicle screw fixation is a very effective treatment for atlantoaxial instability (AAI). However, due to the complex anatomy of the cranial-cervical junction, the accuracy and safety of posterior atlantoaxial pedicle screw placement remains extremely challenging. Objective: To quantitatively evaluate the safety and accuracy of the 3D navigation module to assist the posterior atlantoaxial fixation. Methods: A total of 20 AAI patients were selected between June 2014 and September 2015. The Mimics v10.1 and 3-matic software were used. The 3D navigation module was designed as a double-sided positioning hole guide with a guide rod. All patients underwent posterior atlantoaxial posterior pedicle screw fixation with 3D navigation module. The actual entry point and screw trajectory were measured after operation, which were compared with the ideal entry point and screw trajectory. The Japanese Orthopaedic Association (JOA) score was measured before and after surgery to evaluate the neurological function improvement. The average operation time, blood loss, and frequency of intraoperative fluoroscopy were counted. Results: The posterior atlantoaxial pedicle screw fixation with a 3D navigation module was successfully performed in all patients. A total of 80 atlantoaxial pedicle screws were implanted in the 20 patients. Postoperative CT scan showed that two pedicle screws deviated from the medial aspect of the atlas pedicle cortex and entered the spinal canal approximately 1 mm, without causing neurological complications. There was no significant difference between the ideal and actual entry points or ideal and actual screw trajectories of the atlas and axis (P > 0.05). The preoperative JOA score was 12.45 ± 1.15 and postoperative JOA score was 15.5 ± 0.89, with statistically significant difference (P < 0.05). Conclusion: It was safe and effective to use the 3D navigation module to assist the posterior atlantoaxial pedicle insertion, with a high accuracy of pedicle screw placement. Keywords: atlantoaxial instability, pedicle screw, 3D navigation module, rapid prototyping