Clinical outcomes of preoperative skull traction combined with intraoperative two-step reduction and occipitocervical fusion for type a basilar invagination with atlantoaxial dislocation.

OBJECTIVE: To evaluate the clinical and radiological outcomes of a staged reduction strategy combining preoperative skull traction with intraoperative two-step reduction and occipitocervical fusion in patients with type A basilar invagination with atlantoaxial dislocation (BI-AAD). METHODS: A retrospective study was conducted on 27 patients with reducible type A BI-AAD who underwent posterior occipitocervical fusion with foramen magnum decompression between January 2019 and April 2025. All patients received preoperative skull traction followed by a staged two-step reduction strategy. Radiological parameters, including the atlantodental interval (ADI), the distance from the odontoid process to the Chamberlain line (DOCL), and the cervicomedullary angle (CMA), were evaluated preoperatively and at postoperative follow-up. Clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA) score and visual analogue scale (VAS). Fusion status and perioperative complications were also recorded. RESULTS: All patients successfully underwent surgery. The mean operative time was 122.63 ± 17.59 min, and the mean intraoperative blood loss was 237.04 ± 89.43 mL. The mean follow-up duration was 19.93 ± 7.27 months. Significant improvements in radiological parameters were observed at the final follow-up, with ADI decreasing from 10.60 ± 0.94 mm to 1.20 ± 0.11 mm, DOCL from 11.70 ± 2.14 mm to 2.67 ± 0.27 mm, and CMA increasing from 116.96 ± 10.54° to 143.84 ± 2.69° (P < 0.05). Clinical outcomes also improved significantly, with the JOA score increasing from 8.56 ± 1.01 to 15.04 ± 0.71 and the VAS score decreasing from 6.59 ± 0.89 to 1.48 ± 0.51. Solid bone fusion was achieved in all patients. Two perioperative complications occurred (one dural tear and one wound infection), both of which resolved after appropriate treatment. CONCLUSION: The staged reduction strategy combining preoperative skull traction with intraoperative two-step reduction and occipitocervical fusion appears to be an effective and safe approach for the treatment of reducible type A BI-AAD. This technique may facilitate a gradual and more controllable reduction process, while achieving satisfactory radiological realignment and clinical improvement. Further prospective and comparative studies are warranted to validate these findings.