Biomechanical Evaluation of Intervertebral Fusion Process After Anterior Cervical Discectomy and Fusion: A Finite Element Study

Abstract

Introduction: Anterior cervical discectomy and fusion (ACDF) is a widely accepted surgical procedure in the treatment of cervical radiculopathy and myelopathy. A solid interbody fusion is of critical significance in achieving satisfactory outcomes after ACDF. However, the current radiographic techniques to determine the degree of fusion are inaccurate and radiative. Several animal experiments suggested that the mechanical load on the spinal instrumentation could reflect the fusion process and evaluated the stability of implant. This study aims to investigate the biomechanical changes during the fusion process and explore the feasibility of reflecting the fusion status after ACDF through the load changes borne by the interbody fusion cage.Methods: The computed tomography (CT) scans preoperatively, immediately after surgery, at 3 months, and 6 months follow-up of patients who underwent ACDF at C5/6 were used to construct the C2–C7 finite element (FE) models representing different courses of fusion stages. A 75-N follower load with 1.0-Nm moments was applied to the top of C2 vertebra in the models to simulate flexion, extension, lateral bending, and axial rotation with the C7 vertebra fixed. The Von Mises stress at the surfaces of instrumentation and the adjacent intervertebral disc and force at the facet joints were analyzed.Results: The facet contact force at C5/6 suggested a significantly stepwise reduction as the fusion proceeded while the intradiscal pressure and facet contact force of adjacent levels changed slightly. The stress on the surfaces of titanium plate and screws significantly decreased at 3 and 6 months follow-up. A markedly changed stress distribution in extension among three models was noted in different fusion stages. After solid fusion is achieved, the stress was more uniformly distributed interbody fusion in all loading conditions.Conclusions: Through a follow-up study of 6 months, the stress on the surfaces of cervical instrumentation remarkably decreased in all loading conditions. After solid intervertebral fusion formed, the stress distributions on the surfaces of interbody cage and screws were more uniform. The stress distribution in extension altered significantly in different fusion status. Future studies are needed to develop the interbody fusion device with wireless sensors to achieve longitudinal real-time monitoring of the stress distribution during the course of fusion.

Biomechanical performance of the novel assembled uncovertebral joint fusion cage in single-level anterior cervical discectomy and fusion: A finite element analysis

“…As shown in Figure 2, the predicted segmental ROM of the present intact cervical spine model was within the standard deviation of the previous experimental data (Panjabi et al, 2001;Lee et al, 2016;Liu et al, 2016). The maximal intradiscal pressure of adjacent levels was consistent with in vitro experiments and previous finite element results (Welke et al, 2016;Zhou et al, 2021), and the facet contact force (FCF) of the model was also in agreement with the literature (Wu et al, 2019;Shen et al, 2022). All indicated that the present model was reliable in representing a healthy individual and could be used for further experiments.…”

“…Fourth, this study simplifies the musculoskeletal system, and the results under this ideal condition did not fully reflect the actual postoperative situation. Although this study aimed to provide a biomechanical reference for clinics, the manipulation of the muscular–ligamentous system in this finite analysis was based on previous literature ( Fu et al, 2022 ; Huang et al, 2022 ; Shen et al, 2022 ; Zhang et al, 2022b ). Last, linear elastic materials were adopted for the cervical vertebral body and intervertebral disc.…”

“…The material properties should be re-assessed if the objective of the study changes. Analogously, several recent studies have adopted similar methods for developing a finite element cervical spine model and provided satisfactory results ( He et al, 2021 ; Hua et al, 2020a ; Hua et al, 2020b ; Lin et al, 2021 ; Wo et al, 2021 ; Shen et al, 2022 ; Zhang et al, 2022b ). Given that material properties such as hyperelastic, viscoelastic, or poroelastic materials within the intervertebral disc can result in better biomechanical predictions, a more realistic model has to be developed in future studies.…”

Changes in cervical alignment of Zero-profile device versus conventional cage-plate construct after anterior cervical discectomy and fusion: a meta-analysis

“…Meanwhile, biomechanical research works found that the plate could provide better segmental stability than Zero-profile spacer [27,28], which was consistent with our findings. Loss of CL is often considered to cause progressive degenerative cervical spondylosis (DCS) and also be responsible for neck pain and neurological dysfunction [5,[29][30][31][32]. However, the higher LOC after ACDF with ZP device, especially the data of LOC in CL as high as 48.13% given by Sun et al [13] in the 5-year followup, makes us worry about the condition of patients in the longer term.…”

Comparison of Anterior Cervical Discectomy and Fusion and Anterior Cervical Corpectomy and Fusion in Localized Ossification of the Posterior Longitudinal Ligament

“…The success of cervical surgery often depends directly on the progress of fusion [27]. From a biomechanical point of view, additional external or internal support should be employed to prevent excessive movement of cervical cages[28].…”