Effect of side holes in cervical fusion cages: a finite element analysis study

Abstract

The objective of this study was to investigate the effect of side holes on the predicted von Mises stress levels in cervical spinal fusion cages subjected to compressive loading. Models with between zero and ten side holes were developed. Finite element analysis (FEA) was used to simulate compression of the cage, made from the polymer PEEK (polyetheretherketone), between two adjacent vertebrae. The analyses were validated by experimental tests. In all of the models, the von Mises stress was highest at the cage-vertebrae interface with peak stresses of between 14 and 18 MPa. Increasing the Young's modulus of the vertebrae from 12 to 30 GPa increased the peak stress on average by 29 per cent. The stresses in the models were lower than the compressive strength of PEEK (118 MPa), and are well within the PEEK fatigue strength reported (60 MPa at 10 million cycles). This study suggests that the number of side holes had a negligible effect on the stress distribution within the cage; the stress magnitudes were fairly constant across all of the models and did not change substantially with the number of holes. Hence, a cervical cage with side holes is unlikely to fail in compression.

Finite element modeling to predict the influence of anatomic variation and implant placement on performance of biological intervertebral disc implants

“…Computational simulations utilizing finite element (FE) analysis can aid in our understanding of material properties and systems of high complex geometry, 27–29 and provide biomechanical insight into the feasibility of materials as implants 28,30 . FE analysis is particularly attractive in this case to test a range of parameters that may be critical to surgically implanted TE‐IVDs 31,32 . Previous attempts at modeling cage structures with simplified geometries have been performed to analyze stress distribution and displacement, but none have focused on predicting the mechanical performance and failure of cage structures in the cervical spine 27,31–37 .…”

“… 28 , 30 FE analysis is particularly attractive in this case to test a range of parameters that may be critical to surgically implanted TE‐IVDs. 31 , 32 Previous attempts at modeling cage structures with simplified geometries have been performed to analyze stress distribution and displacement, but none have focused on predicting the mechanical performance and failure of cage structures in the cervical spine. 27 , 31 , 32 , 33 , 34 , 35 , 36 , 37 Furthermore, to the best of our knowledge, there has not been any simulations which utilized the unique geometry of the porcine cervical spine to understand the mechanical behavior of the cage in vivo.…”

“… 31 , 32 Previous attempts at modeling cage structures with simplified geometries have been performed to analyze stress distribution and displacement, but none have focused on predicting the mechanical performance and failure of cage structures in the cervical spine. 27 , 31 , 32 , 33 , 34 , 35 , 36 , 37 Furthermore, to the best of our knowledge, there has not been any simulations which utilized the unique geometry of the porcine cervical spine to understand the mechanical behavior of the cage in vivo. Therefore, capturing the anatomical geometry and simulating in vivo loading achieves a model that closely evaluates cage stability under non‐uniform loading.…”

Optimization of cervical cage and analysis of its base material: A finite element study

“…Many researchers have used this method to assess cage-related subjects such as analysis of stresses on lumbar or cervical vertebrae, 20 modeling different types of cages, investigating stress and subsidence, 15 exploring the effect of cages on the upper position of vertebrae, 21 and the effect of a hole on the cage function. 22…”

“…Many researchers have used this method to assess cage-related subjects such as analysis of stresses on lumbar or cervical vertebrae, 20 modeling different types of cages, investigating stress and subsidence, 15 exploring the effect of cages on the upper position of vertebrae, 21 and the effect of a hole on the cage function. 22 The finite element method can be also utilized in cage optimization. In general, cage optimization can be carried out in form of mechanical 23 and design algorithms such as Taguchi 14 and asymptotic homogeneous method 24 or with help of the finite element methods.…”