Biomechanical analysis of a single-level customized cage screw fixation for anterior cervical discectomy and fusion in the cervical spine: an in-silico study

Abstract

The usual surgical choice of customized cage fixation is anterior cervical discectomy and fusion (ACDF) for cervical spondylosis with disc herniation. The safe and successful cage fixation for ACDF surgery benefits patients with cervical disc degenerative disease by easing their discomfort and regaining function. The cage prevents mobility between the vertebrae by using cage fixation to anchor the neighbouring vertebrae. The goal of the current study is to develop a customized cage-screw implant for single-level cage fixation at C4-C5 level of the cervical spine (C2-C7). The Finite Element Analysis (FEA) is performed for the intact and implanted cervical spine and analysed the flexibility, stress of the implant and implant adjacent bone during three physiological loading conditions being analysed. Lower surface of the C7 vertebrae is fixed and 50 N compressive force with 1 Nm moment are applied on the C2 vertebrae for simulated lateral bending, axial rotation and flexion-extension. The flexibility is decreased at single level of fixation (C4-C5 level) by 64% to 86%, as compared to natural cervical spine. The flexibility is increased 3% to 17% at the nearest levels of fixation. The maximum Von Mises stress in PEEK cage varies from 24 to 59 MPa and for Ti-6Al-4V screw the stress varies from 84MPa to 121MPa which are far below the yield stress of PEEK (95MPa) and Ti-6Al-4V (750MPa).

Finite element analysis of the biomechanical effects of anterior and posterior cervical fusion surgery for bilateral cervical dislocation

“…The results indicated that the stress on Ti screws ranged from 84 MPa to 121 MPa, which is significantly below their yield stress. The study employed an internal fixation method, and the stress results were not compared with relevant approaches for entry route fixation [47]. Duan Y's team compared the postoperative stress levels of three internal fixation techniques.…”

Biomechanical analysis of single and multi-level artificial disc replacement (ADR) in cervical spine using multi-scale loadings: A finite element study

“…15 The intricate geometry of the vertebra necessitated the use of a tetrahedral element for volume meshing, with mesh sensitivity analysis refined to less than 3% error. 29–30…”