Biomechanical Analysis of Two-Level Novel Cage-Type Implant for Anterior Cervical Discectomy and Fusion: A Finite Element Analysis.

One of the standard treatments for spinal diseases is anterior cervical discectomy and fusion (ACDF). ACDF is a secure and successful operation that prevents patients to improve their pain and function. The mechanical goal of the ACDF is to prevent motion between adjoining vertebrae by a novel cage-screw implant. The objective of this study is to analyze the biomechanical flexibility in terms of the range of motion (ROM) of two-level ACDF fixation using the finite element method (FEM). A CT scan-based FEM model of the cervical spine (C2-C7) is used and two-level cage is implanted at C4-C6 segments. A 50-N compressive force and 1-Nm moment are applied on C2 vertebrae and C7 is fixed in all directions. The ROM at two-level fixation (C4-C5-C6) is reduced by 55 to 88% compared with intact spine during all physiological movement. The ROM slightly increase (3-9%) at the adjacent segment. The maximum von Mises stress variations are 25-65 MPa during flexion-extension, lateral bending, and axial rotations under given loading. The maximum von Mises stress found in cage and screw is below the yield stress during all physiological movement.