Dynamic-nondynamic Transpedicular Screw System For Lumbar Spine Fixation: A Finite Element Analysis And Preliminary Clinical Application

Objective：Using three dimensional finite element model to simulat Dynamic-Nondynamic pedicle fixation system and traditional posterior fixation system, tocompare the stress distribution, and mechanical characteristics;And to explore the value of Dynamic-Nondynamic fixation system in lumbosacralvertebral disease in clinical practice.Methods：A healthy male volunteer, aged45-years, was underwent CTscanning and finite element analysis software constructing, to establish a3-dimension lumbo-sacral section finite element model. After effective validation,a Dynamic–Nondynamic internal fixation system model (experiment group) andcommon pedicle screws fixation system model (control group) were established.Stress of screws, longitudinal connection rods as well as discs of adjacent levelwere analyzed and compared after loading application. From October2011toApril2012, clinical data of8cases of vertebral degenerative disease patients in ourhospital, who received decompression and dynamic-None dynamic internal fixationimplantation surgery, were retrospective analyzed. Clinical efficacy and safety wereevaluated using ODI and VAS score, as well as lumbar radiography.Results：There are no significant differences of maximum stress in upright, prone,extension, left and right latero-flexion position. Stress of the topmost screw isalways greater than others, and mainly focuses on the six tails of the screws.Maximum stress of the longitudinal connection rods in the experiment and controlgroups, were focused on the site of screw-rod connection. However, the stress issmaller in the experiment group than that in control group. Stress nearby thepedicle screw was greater than that in the vertebral. The topmost one underwent maximum stress. Stress from adjacent level discs was smaller in the dynamicgroup than that in the common fixation group.Clinical symptoms in the dynamic group were improved obviously in3~4months’ Follow-up. VAS and ODI score were declined. Lumbar mobility wasretained through radiography analysis in unfusion group. No instrumentationloosening and disruption were found during follow-up, which demonstratingedsatisfactory and effective preliminary clinical application.Conclusion1. Finite element analysis demonstrating that Dynamic-Nondynamic pediclefixation system can retain a better mobility range, also can be reduce the stessconcentration of disc.This may be slow down adjacent intervertebral discdegeneration.2.. Preliminarily confirmed using Dynamic-Nonedynamic pedicle fixation systemoperation method can be the safe and it is way for lumbar degenerative diseasesadministration. Further long-term multi-center with large sample study andfollow-up were in need to prove the clinical efficacy, though the previouslyfollow-up was satisfied.