Comparative analysis of the biomechanics of anterior cervical discectomy and fusion with multiple segmental plates fixation versus single multilevel plate fixation: a finite element study

Abstract

Background: This study aimed to compare the biomechanical differences between anterior cervical discectomy and fusion (ACDF) with multiple-level separate plates and conventional long plates by using finite element analysis.

Methods: The following four finite element models were created to simulate various fixations: (1) C4-6 ACDF with multiple plates, (2) C4-6 ACDF with a single plate, (3) C3-6 ACDF with multiple plates, and (4) C3-6 ACDF with a single plate. The maximum Von-mises stress of the cage and fixation, compressive force of the adjacent intervertebral discs and range of motion (ROM) of different segments in the four models were calculated and analyzed.

Results: For C4-6 ACDF, the maximum Von-mises stress of the cage and fixation was lower in the multiple plate fixation model in all motion states. Similarly, for the C3-6 ACDF models, the peak stress of the C3-4 and C5-6 cages was lower with multiple plates fixation in all motions but the stress of the C4-5 cage in the multiple plates model was slightly higher in flexion, bending and rotation. Besides, applying multiple plates in C3-6 ACDF models resulted in a decreased maximum stress of the fixation under different motions except for bending. In both the C4-6 ACDF and C3-6 ACDF models, the ROM values of the adjacent motion segments were lower in the multiple plates models in extension, bending and rotation. In the C4-6 ACDF models, the peak stress on the adjacent intervertebral discs in the multiple plates models was slightly smaller. In C3-6 ACDF models, the maximum stress on the adjacent intervertebral discs was larger in the single-plate model under flexion, bending and rotation movements.

Conclusion: Multiple plates fixation has a positive effect on increasing stiffness and maintaining the ROM of adjacent segments, indicating lower risk of construct failure and adjacent segment degeneration. Further studies are required to confirm its efficacy in clinical practice.

Keywords: Adjacent segment degeneration; Anterior cervical discectomy and fusion; Construct failure; Finite element study; Internal fixation.