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Stress analysis of interbody fusion – finite element modelling of inter-vertebral implant and vertebral body

Adam, Clayton J., Pearcy, Mark J., & McCombe, Peter (2003) Stress analysis of interbody fusion – finite element modelling of inter-vertebral implant and vertebral body. Clinical Biomechanics, 18(4), pp. 265-272.

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Abstract

Objective: To investigate stresses in interbody fusion systems during compressive loading. Design: The study uses finite element methods to investigate predicted stresses. Previously published experimental material properties are used as inputs to the numerical simulation. Background: Interbody spinal fusion procedures using cage style inter-vertebral implants often cause subsidence failure of the vertebral end plate, resulting in potential pain and mechanical instability of the fusion system. Methods: Finite element models were developed to simulate compressive load transfer between interbody implants and adjacent vertebral body. The vertebral body was modelled using tied finite element mesh regions for cancellous core and cortical shell, and non-linear frictional contact between implants and vertebral end plate. Results: Simulation results predicted end plate stresses of approximately twelve times the nominal contact pressure due to differing deformation stiffnesses of the implant and end plate structures. Reduction of the cancellous core elastic modulus to simulate severely osteoporotic bone resulted in end plate stresses up to three times higher than the benchmark values. Conclusions: In this study, finite element analysis was used to investigate the stresses in interbody fusion systems. Published vertebral loads corresponding to certain activities were shown to generate end-plate stresses which approach and exceed the failure stress for cortical bone. Endplate stresses are strongly dependent on the modulus of the underlying cancellous core. Relevance. Endplate subsidence failure can potentially occur at the corners of existing cage-type interbody implants under physiological compressive loads. Matching material properties between cortical endplate and implant does not guarantee optimal contact conditions, and overall bending stiffness should be assessed.

Impact and interest:

24 citations in Web of Science®
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ID Code: 3712
Item Type: Journal Article
Keywords: Spinal fusion, interbody fusion implant, finite element, stress analysis, back pain, vertebrae
DOI: 10.1016/S0268-0033(03)00022-6
ISSN: 0268-0033
Subjects: Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > BIOMEDICAL ENGINEERING (090300) > Biomechanical Engineering (090302)
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Copyright Owner: Copyright 2003 Elsevier
Copyright Statement: Reproduced in accordance with the copyright policy of the publisher.
Deposited On: 21 Nov 2006
Last Modified: 29 Feb 2012 23:03

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