A Finite Element Analysis Of Dynesys On The Biomechanics Of The Lumbar Spine

Background:Lumbar fusion surgery is considered as the gold standard to treat spinal diseasesuch as spinal stenosis, lumbar instability, spondylolisthesis and lumbar disc diseaseconservative ineffective. Some gradually deepened, long-term efficacy observationwith follow-up imaging studies have shown that the issues about adjacent segmentscompensatory degeneration need more attention. As a result, a large amount ofclinical research about non-fusion technology spring up. Dynamic stabilizationthrough pedicle is a common method applied in posterior lumbar pedicle fixation. Bythe special design of the device,dynamic stablization could retain a certain degree oflumbar physiological activities, as well as reducing the adjacent segmentcompensatory activities to achieve the purpose of reducing the possibility of lumbaradjacent segment forward degeneration. But for now, the clinical research of pedicledynamic stablization is far from statisfied, especially in the biomechanics field. Thisstudy is to choose finite element analysis as typical method to access the effect onimplanted and adjacent segment by the biomechanical outme of DYNESYS system.Objective:1.To establish and validate an anatomic detailed lumbosacral finiteelement model.2.With finite element analysis method, to evaluate the effect ofDYNESYS system on range of motion,intervertebral disc stress and facet jointpressure by comparing with simple decompression model and rigid fixation model.Methods:(1)The lumbosacral spine geometries were determined from CT images of ahealthy volunteer. MIMICS10.0, Abaqus6.10,Geomagic studio9.0software wereused to establish the finite element model. ROM was caculated and compared to theprevious study to validate the model.(2)Three-dimensional model of theDYNESYS system was reconstrued and meshed by the Rhino4.0software.(3)Basedon the finite element model,three new models—simple decompression model,DYNESYS model,and rigid fixed modle--were generated.Under the specific boundary conditions and loads applied to the model,there are calculations and comparisons withthe range of motion, disc stress,facet joint pressure for every model.Results:(1) The entired finite element model includes123,021nodes and344,145elements,evaluation, and is valid by its consitance to literatures.(2) The finite elementmodle of DYNESYS system was established and meshed.(3)It is found that,by thesurgical intervention segments,compared with simple decompression model, Dynesyssystem may constrain the range of motion,however compared with the rigid fixedmodel,it may retain a certain activity while significantly reducing the stress of theintervertebral disc and facet joints. And by the adjacent segments we also found thatthe stress of disc and facet joint on DYNESYS system model,was significantly lowerfixed rigid model.Conclusions:(1) The lumbosacral finite element model is validated and can be used on relatedbiomechanics study.(2)Dynamic fixation may retain part of the intervertebral activity,reduce the small joint pressure,impact the adjacent segments less than spinal fusionsurgery. From this point of view,the short-term clinical effect of dynamic fixationusing DYNESYS system is optional when treating lumbar degeneration disease.