Open AccessEffect of Augmentation Material Stiffness on Adjacent Vertebrae after Osteoporotic Vertebroplasty Using Finite Element Analysis with Different Loading Methods
Author(s) -
Ah-Reum Cho
Publication year - 2015
Publication title -
pain physician
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.31
H-Index - 99
eISSN - 2150-1149
pISSN - 1533-3159
DOI - 10.36076/ppj.2015/18/e1101
Subject(s) - medicine , von mises yield criterion , finite element method , vertebra , stiffness , osteoporosis , bone cement , orthodontics , compression (physics) , torsion (gastropod) , biomechanics , displacement (psychology) , structural engineering , materials science , cement , composite material , surgery , anatomy , engineering , psychology , psychotherapist , endocrinology
Background: Vertebroplasty is an effective treatment for osteoporotic vertebral fractures,which are one of the most common fractures associated with osteoporosis. However, clinicalobservation has shown that the risk of adjacent vertebral body fractures may increase aftervertebroplasty. The mechanism underlying adjacent vertebral body fracture after vertebroplastyis not clear; excessive stiffness resulting from polymethyl methacrylate has been suspected asan important mechanism.Objectives: The aim of our study was to compare the effects of bone cement stiffness onadjacent vertebrae after osteoporotic vertebroplasty under load-controlled versus displacementcontrolled conditions.Study Design: An experimental computer study using a finite element analysis.Setting: Medical research institute, university hospital, Korea.Methods: A three-dimensional digital anatomic model of L1/2 bone structure was reconstructedfrom human computed tomographic images. The reconstructed three-dimensional geometrywas processed for finite element analysis such as meshing elements and applying materialproperties. Two boundary conditions, load-controlled and displacement-controlled methods,were applied to each of 5 deformation modes: compression, flexion, extension, lateral bending,and torsion.Results: The adjacent L1 vertebra, irrespective of augmentation, revealed nearly similarmaximum von Mises stresses under the load-controlled condition. However, for the displacementcontrolled condition, the maximum von Mises stresses in the cortical bone and inferior endplateof the adjacent L1 vertebra increased significantly after cement augmentation. This increase wasmore significant than that with stiffer bone cement under all modes, except the torsion mode.Limitations: The finite element model was simplified, excluding muscular forces andincorporating a large volume of bone cement, to more clearly demonstrate effects of bonecement stiffness on adjacent vertebrae after vertebroplasty.Conclusion: Excessive stiffness of augmented bone cement increases the risk of adjacentvertebral fractures after vertebroplasty in an osteoporotic finite element model. This result wasmost prominently observed using the displacement-controlled method.Key words: Bone cements, displacement-controlled method, finite element analysis, loadcontrolled method, osteoporosis, osteoporotic fracture, polymethyl methacrylate, vertebroplasty