Biomechanical Evaluation of Anterior Plate Fixation With Cage for Basilar Invagination With Atlantoaxial Dislocation: A Cadaveric Study

Sep 30, 2026

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Biomechanical characteristics of two anterior fixation techniques—clival plate fixation (CPF) and transoral atlantoaxial reduction plate (TARP)—were assessed against posterior occipitocervical fixation (POCF) for basilar invagination with atlantoaxial dislocation (BIAAD). Seven fresh cadaveric specimens (Oc–C3) underwent testing in intact, BI-AAD, BI-AAD+CPF, BI-AAD+TARP, and BI-AAD+POCF conditions across atlantoaxial lateral mass cage heights of 4–10 mm, using 1.5 N·m moments to compare range of motion and neutral zone at Oc–C2. All internal fixations reduced Oc–C2 ROM versus BI-AAD; TARP showed greater flexion-extension ROM, and anterior constructs were more limited than POCF in lateral bending and axial rotation. Cage height changes did not significantly affect overall stability, and clival plate fixation provided optimal biomechanical stability for BI-AAD.

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CategoryHealthcare

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Neurospine 2025;22(4):974-986. [https://doi.org/10.14245/ns.2550694.347](https://doi.org/10.14245/ns.2550694.347) Original Article Corresponding Author Wei Ji [https://orcid.org/0000-0001-8271-9411](https://orcid.org/0000-0001-8271-9411) Division of Spine Surgery, Department of Orthopedics, Nanfang Hospital, Southern Medical University, Guangzhou, China Email: [spineji@126.com](spineji@126.com) Co-corresponding Author Zhongmin Zhang [https://orcid.org/0000-0002-6761-6120](https://orcid.org/0000-0002-6761-6120) Division of Spine Surgery, Department of Orthopedics, Nanfang Hospital, Southern Medical University, Guangzhou, China [Email: nfzzm@163.com](Email: nfzzm@163.com) Received: April 26, 2025 Revised: July 1, 2025 Accepted: July 7, 2025 *Jianying Zheng and Zhiping Huang contributed equally to this study asco-first authors. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ([https://creativecom](https://creativecom)[mons.org/licenses/by-nc/4.0/](mons.org/licenses/by-nc/4.0/)) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright © 2025 by the Korean Spinal Neurosurgery Society Neurospine pISSN 2586-6583 eISSN 2586-6591 Biomechanical Evaluation of Anterior Plate Fixation With Cage for Basilar Invagination With Atlantoaxial Dislocation: A Cadaveric Study Jianying Zheng*, Zhiping Huang*, Kunqi Li, Xuanhang Zhang, Jian Xiong, Yu Wang, Jiahao Xie, Panjie Xu, Zhongmin Zhang, Wei Ji Division of Spine Surgery, Department of Orthopedics, Nanfang Hospital, Southern Medical University, Guangzhou, China Objective: To evaluate the biomechanical characteristics of 2 anterior fixation techniques (clival plate fixation [CPF], transoral atlantoaxial reduction plate [TARP]) versus posterior occipitocervical fixation (POCF) for basilar invagination with atlantoaxial dislocation (BIAAD), under varying atlantoaxial lateral mass cage heights (4–10 mm) . Methods: Seven fresh cadaveric specimens (occiput to C3, Oc–C3) were tested in the following conditions: (1) intact state; (2) BI-AAD state; (3) BI-AAD+CPF; (4) BI-AAD+TARP fixation; (5) BI-AAD+POCF. A pure 1.5 N·m moment loads to specimens in flexion/extension, lateral bending and axial rotation . Range of motion (ROM) and neutral zone (NZ) values at Oc–C2 were calculated and compared. Results: ROM of the C1–2 segment under the intact and BI-AAD states were as follows: 9. 3° ± 4 . 6° versus 21 . 3° ± 8 . 3° in flexion, 4. 6° ± 1 . 9° versus 9 . 3° ± 3 . 8° in extension, 3. 6° ± 2.2° versus 12.0° ± 6.5° in lateral bending, and 68.9° ± 14.4° versus 76.6° ± 6.6° in axial rotation, respectively. Compared with BI-AAD states, all internal fixation techniques significantly reduced the ROM of the Oc–C2 segment. TARP fixation exhibited larger ROM in flexion-extension . While in lateral bending and axial rotation, the ROM values for the anterior plate constructs were smaller than that of POCF, with a statistically significant difference observed between CPF and POCF. Cage height variations showed no significant impact on overall biomechanical stability. Conclusion: Anterior plate fixation techniques demonstrated superior resistance to lateral bending and rotational forces compared to posterior approaches, with clival plate fixation exhibiting optimal biomechanical stability for BI-AAD. Variations in cage height exhibited negligible impact on stability when internal fixation achieved adequate rigidity. Keywords: Basilar invagination, Atlantoaxial dislocation, Internal fixation, Biomechanics, Fusion cage INTRODUCTION Basilar invagination combined with atlantoaxial dislocation (BI-AAD) represents a complex craniocervical junction deformity characterized by progressive dorsocranial migration of theodontoid process, which can lead to severe compression of the brainstem and spinal cord, resulting

FAQs

What was the main objective of the study?

To compare the biomechanical characteristics of two anterior fixation methods (CPF and TARP) with posterior occipitocervical fixation (POCF) for basilar invagination with atlantoaxial dislocation (BIAAD).

How were the cadaveric specimens tested?

Seven fresh cadaveric specimens (Oc–C3) were evaluated in intact, BI-AAD, BI-AAD+CPF, BI-AAD+TARP fixation, and BI-AAD+POCF conditions. A 1.5 N·m moment load was applied for flexion/extension, lateral bending, and axial rotation, and ROM and neutral zone were calculated at Oc–C2.

Did changing cage height (4–10 mm) affect stability?

No. Variations in cage height showed no significant impact on overall biomechanical stability in the measured outcomes.

Sep 30, 2026

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