Biomechanical Effects of a Novel Anatomic Titanium Mesh Cage for Single-Level Anterior Cervical Corpectomy and Fusion: A Finite Element Analysis

Abstract

Background: The traditional titanium mesh cage (TTMC) has become common as a classical instrument for Anterior Cervical Corpectomy and Fusion (ACCF), but a series of complications such as cage subsidence, adjacent segment degeneration (ASD), and implant-related complications by using the TTMC have often been reported in the previous literature. The aim of this study was to assess whether a novel anatomic titanium mesh cage (NTMC) could improve the biomechanical condition after surgery.Methods: The NTMC model consists of two spacers located on both sides of the TTMC which match the anatomic structure between the endplates by measuring patient preoperative cervical computed tomography (CT) data. The ranges of motion (ROMs) of the surgical segments and the stress peaks in the C6 superior endplates, titanium mesh cage (TMC), screw–bone interface, anterior titanium plate, and adjacent intervertebral disc were compared.Results: Compared with the TTMC, the NTMC reduced the surgical segmental ROMs by 89.4% postoperatively. The C6 superior endplate stress peaks were higher in the TTMC (4.473–23.890 MPa), followed by the NTMC (1.923–5.035 MPa). The stress peaks on the TMC were higher in the TTMC (47.896–349.525 MPa), and the stress peaks on the TMC were lower in the NTMC (17.907–92.799 MPa). TTMC induced higher stress peaks in the screw–bone interface (40.0–153.2 MPa), followed by the NTMC (14.8–67.8 MPa). About the stress peaks on the anterior titanium plate, the stress of TTMC is from 16.499 to 58.432 MPa, and that of the NTMC is from 12.456 to 34.607 MPa. Moreover, the TTMC induced higher stress peaks in the C3/4 and C6/7 intervertebral disc (0.201–6.691 MPa and 0.248–4.735 MPa, respectively), followed by the NTMC (0.227–3.690 MPa and 0.174–3.521 MPa, respectively).Conclusion: First, the application of the NTMC can effectively decrease the risks of TMC subsidence after surgery. Second, in the NTMC, the stresses at the anterior screw-plate, bone–screw, and TMC interface are much less than in the TTMC, which decreased the risks of instrument-related complications after surgery. Finally, increases in IDP at adjacent levels are associated with the internal stresses of adjacent discs which may lead to ASD; therefore, the NTMC can effectively decrease the risks of ASD.

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

“…The self-tapping screws were 16 mm long. Additionally, convergence analysis was performed to ensure that the maximum changes in the strain energy were <3% and showed that when the element size was between 0.1 and 1, the error stabilized at a minimum value, i.e., less than 3%, which is concordant with previous studies ( Jones and Wilcox, 2008 ; Ayturk and Puttlitz, 2011 ; Zhang et al, 2022b ). The material properties of the bone graft and newly formed bone were set as the cortical bone ( Figure 1 ).…”

“…However, the current study aimed to provide a trend instead of natural status. Several recent studies have adopted similar methods in developing the finite element spine model and reported acceptable results ( Wu et al, 2019 ; Liang et al, 2022 ; Zhang et al, 2022b ). Third, the geometry of the human spine varies among individuals, while the model of this present study was developed on the basis of the data from a single patient.…”

“…Due to the progressive enhancement of bony fusion at the inter–end plate and bilateral uncovertebral joint, the stiffness of the anterior column increased, which further improved the stability of the construct ( Zhang et al, 2022b ). It is worth noting that the ROMs of the unfused levels in all models increased by 10.4%–73.2% for all motions when compared to the intact model.…”

“…However, current methods for making reasonable estimates of stress thresholds for subsidence are still limited and not individualized. Because the physiological curvature of the cervical spine is anteriorly convex and loads on the anterior spine are eccentric relative to the posterior spine ( Zhang et al, 2022b ), the failure loads were related to many factors, such as the applied high tensile strains ( Fields et al, 2010 ), bone–end plate contact area or cage shape ( Tan et al, 2005 ), and bone mineral density (BMD) or cage placement ( Labrom et al, 2005 ). Lin et al (2021 , 2022) determined subsidence by measuring the distance that penetrated both the cage and screw into the end plate bone.…”

“…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.…”