[Direct intraoperative two-step distraction and reduction for basilar invagination with atlantoaxial dislocation]

Objective: To assess the clinical impact of direct two-step distraction reduction (TSDR) for basilar invagination (BI) with atlantoaxial dislocation (AAD). Methods: Retrospective analysis was conducted on the clinical data of patients who underwent TSDR and occipitocervical fusion in West China Hospital between October 2013 and March 2021. Depending on whether the preoperative decrease was greater than 50% on preoperative hyperextension X-rays, the patients were split into two groups. The neurological function [Japanese Orthopedic Association (JOA) score], atlantodens interval (ADI), the distance of odontoid process beyond McRae Line (ML) and Wackenheim Line (WL), cervicomedullary angle (CMA), O-C₂ angle (OC2A), and complications incidence were compared between two groups preoperatively and postoperatively. Results: There were 12 men and 23 women among the 35 patients with BI and AAD, and the age ranged from 28 to 71 years, with an mean age of (52.0±13.4) years. In the preoperative reduction ≥50% group, there were 4 males and 9 females with an average age of (54.0±13.8) years; in the preoperative reduction <50% group, there were 8 males and 14 females with a mean age of (50.9±13.4) years. All the patients were followed-up for a mean time of (23.3±13.4) months. There was no significant difference in age, gender, bleeding, length of hospital stay and follow-up time between the two groups (all P>0.05). The JOA score, ADI, WL, ML and CMA of 35 patients were significantly improved when compared with those before operation (all P<0.05). The reduction degree of ADI, ML and WL was more than 80% in 31 cases (88.57%), 30 cases (85.71%) and 31 cases (88.57%), respectively. There was no significant difference in postoperative ADI, ML and WL between the two groups (all P>0.05). All patients had no incision infection, no loosening or breakage of the internal fixators. Dysphagia occurred in 3 patients, non-fusion happened in 1 patient, but no instability in X-ray of cervical dynamic position was found, no loosening or displacement occurred in internal fixators, and partial spontaneous fusion occurred between atlantoaxial lateral mass joints. Conclusions: For BI with AAD without atlantoaxial bony connection or serious atlantoaxial facet joint inclination, TSDR could obtain satisfactory reduction degree. The reduction degree on preoperative hyperextension X-ray doesn't affect the degree of intraoperative reduction.