Transoral odontoid process release, partial resection and antedisplacement for basilar invagination: a novel technique and preliminary results
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Published on: August 15, 2025
ShengLi Guo1, YaKun Chen1, LuoKai Huangfu1
1Department of Neurosurgery, First Medical Center, Chinese PLA General Hospital, Beijing, China.
Objective:
Symptomatic basilar invagination (BI) is a complex craniovertebral junction malformation often accompanied by atlantoaxial dislocation (AAD). While posterior reduction and fixation is widely used, anterior odontoidectomy remains essential for decompression. However, conventional odontoidectomy carries a high risk of cerebrospinal fluid (CSF) leakage. We present a novel technique-Transoral Odontoid Process Release, Partial Resection, and Antedisplacement (TOPRA)-designed to achieve effective decompression while reducing CSF leakage risk.
Methods:
Between April 2020 and September 2024, 31 consecutive patients (22 females, 9 males; mean age 40.0 ± 12.92 years) with symptomatic BI underwent the TOPRA procedure. Neurological function was assessed using the Japanese Orthopedic Association (JOA) score. The vertical distance from the odontoid tip to the Chamberlain line (CL) measured on 3D-CT and the cervico-medullary angle (CMA) measured on MRI, were used to assess the degree of compression at the medulla oblongata and upper cervical cord.
Results:
All patients successfully underwent TOPRA without intraoperative or postoperative CSF leakage. 29 patients with AAD underwent additional posterior reduction and fixation during the same surgical stage. The mean vertical distance from the odontoid tip to the CL decreased significantly from 14.8 ± 3.07 mm preoperatively to 9.8 ± 2.14 mm postoperatively (p < 0.01). The mean JOA score improved from 11.6 ± 3.49 to 13.6 ± 3.32 at final follow-up (p < 0.01). Follow-up MRI indicated that the CMA increased significantly from 123.0° ± 8.09° preoperatively to 152.8° ± 6.70° (p < 0.01).
Conclusion:
This study demonstrates that the TOPRA technique can serve as a viable surgical treatment option for symptomatic BI. By preserving the odontoid tip with its ligamentous attachments and displacing the tip anterior-inferiorly, it achieves significant neural decompression while substantially reducing the risk of CSF leakage.
