| Background:Lumbar spinal stenosis (lumbar spinal stenosis, LSS) is a common clinical spinesurgery diseases, mainly cause the patient back pain, leg pain and other symptoms ofintermittent claudication. There is many surgical approachs to treat the LSS and traditionallaminectomy and fusion surgery is still the gold standard, but for various reasons, thecurative effect is often not satisfactory. Therefore, we conceive lumbar pedicle osteotomyand laminoplasty extend pedicle screw fixation (Extensible pedicle screw, EPS) inside.However, because the lumbar activity after large multi-load bearing internal fixation afterpseudarthrosis, vertebrae gripping force of the screw enough screws loose or prolapsehigher incidence of complications. So we pass from biomechanical testing and mechanicalstrength test body to extend the pedicle fixation device (Novel extensible pedicle fixture,NEPF) in the EPS system testing and evaluation in order to provide a reliable pediclescrew fixation in the method.Objective:Select the67-year-old average age of complete wetting of the spine specimens(L3-L5)7tools.①The specimens were randomly divided into L3, L4and L5threegroups of7vertebrae.②the prone position the lumbar spine specimens fixed, strippedof soft tissue specimen spinal ligaments and spinal nerves and other tissues. Thenconventional lumbar Shape Crest nail into law Under direct vision after bilateral pedicledrilling, cutting device with pedicle and vertebral pedicle saw off the back wall junction,the EPS placed within the vertebral body.③EPS inner side of the nut, mark the outsideof the exit screws, screw on the outer tag corresponding segment smooth adhesive strain gauges and lead around the proximal threaded screw placement while re-fixed on the nut,the last with STSS-1stress detection module is connected, while the STSS synchronousmulti-channel acquisition system connected to the strain.④Then slowly screwing thescrews to pedicle distraction as the initial point of the upcoming recording screwplacement0circle, a circle, and the corresponding strain2laps and3laps. Then mark thecorresponding screw inside smooth gage section after pasting into the screw again, repeatthe process. Finally, the formula derived by the lateral shear forces.⑤Screws throughthe formula deduced moment and transverse shear force.⑥vertebral pedicle screwplacement extend vertebral cancellous bone and axial pull-out strength of pedicleexperiments were conducted.Results:①Extend the process of pedicle screw placement0circle, a circle, and when the twolaps3laps, transverse shear force at L3transverse shear force was0.53±0.06N,1.87±0.08N,2.77±0.05N,4.24±0.04N, the L4was0.63±0.08N,2.44±0.04N,3.75±0.16N,5.37±0.26N, in L5was0.75±0.08N,4.26±0.05N,5.48±0.07N,6.98±0.03N, radiategradually increasing trend,the difference was statistically significant (P <0.05).②andcompared between L3, L4, L5group, screw exit0laps difference was not statisticallysignificant (P>0.05), at exit1lap,2laps when and3laps, transverse shear force tended toincrease, the difference was statistically significant (P <0.05).③Extend the maximumaxial pedicle screw pull-out strength in vertebral cancellous bone was317.20±34.98N,maximum axial pullout force within the pedicle was467.48±33.08N.Conclusions:①Pedicle screws extend transverse shear forces between the process and radiate intothe nail gradually increased in the L3-L5segment.②pedicle screws extend transverseshear force is far less than the maximum axial pullout force, so this screw loosening and screw back after nailing the role of small, is a reliable method of pedicle screw fixation. |
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