• BaoCheng Zhang, HaiBo Liu, XianHua Cai, ZhiHua Wang, Feng Xu, XiMing Liu, HuaSong Wang, Hui Kang, and Ran Ding.
• *Department of Orthopaedics, Wuhan General Hospital of Guangzhou Command of PLA, Wuhan, China †Southern Medical University, Guangzhou, China ‡Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan, China.
• Spine. 2016 Apr 1; 41 (8): E459-66.

Study DesignA finite element analysis.ObjectiveThe aim of this study was to determine the biomechanical differences between atlantoaxial fusion cage combined with transoral atlantoaxial reduction plate fixation (TARP + Cage, modified TARP technique) and that combined with C1 lateral mass screw and C2 pedicle screw fixation (C1LS + C2PS + Cage, modified Goel technique) in the treatment of basilar invagination (BI) by finite element analysis.Summary Of Background DataClinical studies have shown that transoral anterior atlantoaxial release followed by TARP fixation can achieve reduction, decompression, fixation, and fusion of C1-C2 through a transoral-only approach. Although cage has been used to reduce the BI through posterior approach, there are no studies referred to the cage combined with TARP for C1-C2 fusion.MethodsA finite element model was used to investigate and compare the stability between TARP + Cage fixation and C1LS + C2PS + Cage fixation in the treatment of BI. Vertical load of 40  N was applied on the C0, to simulate head weight, and 1.5  Nm torque was applied to the C0 to simulate flexion, extension, lateral bending, and rotation.ResultsIn comparison with the C1LS + C2PS + Cage model, the TARP + Cage model reduced the ROM by 44.7%, 30.0%, and 10.5% in extension, lateral bending, and axial rotation, while the TARP + Cage model increased the ROM by 30.0% in flexion, and the TARP + Cage model also led to lower screw stress in all motions with one exception (anterior C2PS stress in extension).ConclusionOur results indicate that the TARP + Cage fixation may offer higher stability to C1LS + C2PS + Cage in extension, lateral bending, and axial rotation but lower stability in flexion. Compared with modified Goel technique, the modified TARP technique not only has the capability of transferring the load and distributing the stress but also can provide neural decompression, stabilization and fusion, and restore C1-C2 normal fusion angle.Level Of EvidenceN/A.

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