Treatment of Basilar Invagination by Joint Remodeling and Cage Implantation Combined with Intraoperative Cervical Traction

Abstract Objective:This study aimed to explore the clinical and imaging results of lateral atlantoaxial joint remodeling, cage placement, and intraoperative traction in the treatment of basilar invagination. Methods: The clinical data of 11 patients with basilar invagination treated by lateral atlantoaxial joint remodeling, cage placement, and intraoperative traction were analyzed retrospectively. The lateral atlantoaxial joint surface was remodeled to form an inclined surface between the joints, and a cage was then placed. The combined use of these techniques corrects the clivus canal angle and simultaneously moves the dentate process downward, thus reducing the compression on the ventral surface of the brainstem. The Chamberlain line invasion, atlas-dens interval, and clivus-canal angle were measured using a preoperative and postoperative CT scan. In addition, pB-C2 and cervicomedullary angle (CMA) were measured on sagittal magnetic resonance imaging pre- and postoperatively. The clinical outcomes of all patients were assessed using the Japanese Orthopedic Association (JOA) scale. Wilcoxon test was used to compare the pre- and postoperative measurements. Results:Clinical symptoms of all patients significantly improved. The mean JOA score increased from 11.73 ± 2.45 preoperatively to 15.09 ± 1.22 postoperatively (z = –2.956, P = 0.003). No vertebral artery or dura mater injury was observed. The ventral compression of the brainstem was relieved after the operation. The mean pB-C2 decreased from 10.85 ± 2.96 postoperatively to 7.13 ± 1.38 preoperatively (z = –2.936, P = 0.003), and mean clivus-carnal angle and mean CMA increased from 137.25 ± 8.38 and 131.58 ± 9.17 preoperatively to 147.35 ± 7.55 (z = –2.934, P = 0.003) and 146.05 ± 6.36 (z = –2.934, P = 0.003) postoperatively, respectively. There were two cases of collapse of the C1 inferior articular process and one case of avulsion fracture of the C1 anterior arch. All patients achieved interarticular bone fusion. Conclusion: The cases demonstrated a safe and effective method for treating basilar invagination when atlantoaxial joint reduction is difficult during surgery.