Biomechanical Comparison of Polymeric Spinal Cages Using Ct Based Finite Element Method

Abstract

Abstract:Interbody fusion devices are gaining acceptance as a treatment method of mainly for disc degeneration diseases and other medical conditions. Posterior lumbar interbody fusion (PLIF) cage is used in the procedure to maintain stability and promote fusion between vertebrae. Poly lactic acid (PLA) is assumed to be the alternative material which could provide cheaper material and lower production cost. However, these implants often cause subsidence failure at the endplate, resulting in injury risk and mechanical instability during fusion. In this study, the stress behavior of PLIF cage made by two different materials, Polyether ether ketone (PEEK) and PLA; was studied using finite element method (FEM). By implementing bilateral cages between vertebral bone L4 and L5, and conducting 6 different motion activities onto the model, the stress distribution of L4-L5, and cage bodies was predicted. Simulation results predicted that the cage subsidence occurred at both materials, with an overall of higher cage-endplate stresses for PEEK, in comparison to PLA and controlled configurations. In addition, the stress distribution in PLA cage was better and the maximum von Mises stress was approximately 3 times lower than PEEK cage. Further investigation of PLA cage's mechanical properties should be done experimentally to determine the accuracy and reliability of the simulation.

Stand-alone lumbar cage subsidence: A biomechanical sensitivity study of cage design and placement.

“…However, none of these outcomes account for bone failure which is the actual cause of Contrary to other studies which found more inelastic strains in extension or lateral bending, in our model plastic 299 strains were more prone to occur in the anterior part of the caudal vertebra during flexion. This difference may 300 be related to the use of posterior fixation by Jalil et al [35] which restricted the flexion motion decreasing the 301 compressive force on the anterior part of the endplates. Regarding the cage parameters, the inelastic strains 302 increased for cages with: high radius, high curvature and an anterior position.…”

Patterns of Vertebral Bone Marrow Edema in the Normal Healing Process of Lumbar Interbody Fusion: Baseline Data for Diagnosis of Pathological Events

“…No cases were localized in the posterior portion, even in the dual cage group. Prior finite element analyses showed stress distribution in interbody cages included axial load stress on interbody cages were concentrated anteriorly [30][31][32][33][34][35] In addition, a cadaveric study by Sengupta et al 36 further demonstrated anterior localization of cage stress. This eccentric distribution might be derived from the stress-shielding effect of the high stiffness of PS-rod fixation.…”

Biomechanical Evaluation of two different types of Interbody Cages in Posterior Lumbar Interbody Fusion

“…It has been reported that the application of PI could significantly reduce the cage-endplate interface stress by 50 to 60% if compared to non-instrumented cage [1]. In addition, the application of PI would also mitigate the risks of cage failure and cage migration by increasing the cage pullout resistance [9][10] [18]. Even though it seems like the increased stress on the pedicle screw would increase the load burden on that area, however we have to bear in mind that the stress generation by the PEEK-based cage was comparably lower than the stress generation produced by titanium-based cage construct.…”