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Biomechanical Evaluation of Anterior Plate Fixation With Cage for Basilar Invagination With Atlantoaxial Dislocation:
Jianying Zheng1, Zhiping Huang1, Kunqi Li1
1Division 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 (BI-AAD), 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.
