Experimental And Clinical Research Of Pedicle Screw And Bone Grafting For Denis Type B Thoracolumbar Burst Fracture

PartⅠ Experimental research of monosegmental pediclescrew and bone grafting for Denis type B thoracolumbar burstfractureObjectiveThe study made animal model building with pig spine. To evaluate and compare thebiomechanical stability properties of mono-segmental pedicle screw and bone graftingwith traditional short-segmental pedicle screw for Denis type B thoracolumbar burstfracture. So as to provide theoretical basis and experimental guidance in treatment ofthoracolumbar burst fracture with posterior mono-segmental pedicle screw fixation andbone grafting.Methods1. Chose12fresh adult pigs, separated the lumbarvertebrae involved4vertebraesegments (T11-L3). After took the posteroanterior and lateral radiograph, removingmuscles tissue carefully with the ligament and disc reserved. According to Panjabi’s highspeed trauma apparatus, the specimens were made into the burst fracture specimen.2.12burst fracture specimens are divided into two groups randomly, every grouphas been setted four status：A：intact；B：fractured；C：fixated；D：fixated and bonegrafting，specimens were used repeatedly.The ROMs of mearsured segment were noted. With the ROMs of intact，injury sepcimens， fixated specimens，fixated plus bonegrafting sepcimens were compared each other, the stability of mearsured motionsegments in different status was analyzed. Stiffness under flexion-compression weremeasured on the MTS testing system，to measure the deformation capacity of specimento resist different axial load. Data are analyzed and processed in Spss16.0.Results1. In the biomechanical experiment，the stability of two groups by segment posteriorinstrumentation combined with discectomy and bone grafting are enhanced remarkablyafter operation（P＜0.05）.2. Although ROM of mono-segmental fixation was increased compared withshort-segmental fixation in all directions, there was no significant difference inbetweentwo group(P>0.05). ROM was increased in pedicle fixation combined with discectomyand bone grafting compared just only pedicle fixation, but there was no significantdifference inbetween two group(P>0.05).ConclusionBiomechanical study indicate that mono-segmental and short-segmental pediclescrew fixation can provide the good biomechanical initial stability properties,transpedicular fixation with bone fusion can reconstruct the support force of anterior andmiddle colum in fracture vertebral body， diminish the stress load of internalinstrumentation in treat of Denis type B fracture.PartⅡ Denis type B thoracolumbar burst fractures treatedwith transpedicular fixation and intracorporal bone grafting infracture vertebral bodyObjectiveTo explore the outcomes of transpedicular fixation and intracorporal bone grafting infarcture vertebral body in treatment of Denis type B thoracolumbar burst fractures.MethodsA retrospective study was carried out from Jan2005to Jun2009，42cases of Denis type B thoracolumbar burst fractures,21treated with transpedicular fixation through thepedicle of fractured vertebra and21treated with traditional short-segment pedicleinstrumentation. All patients underwent X-ray and spiral CT scan preoperatively,postoperaively, before and after implant removal, we analysed the results, meanwhileevaluated neurological functions, postoperative pain and recovery work of patients.ResultsAll cases had been followed up from18months to36months, average23.6months.Neurological status improved on average of1.8ASIA grade after operation,83%ofpatients felt good after operation. Kyphosis was corrected postoperatively in two groups,the correction was14.1°in experiment group,13.8°in control group (P>0.05), at finalfollow-up loss of kyphosis correction was3.5°in experiment group,6.2°in controlgroup（P<0.05）. Correction loss was most evident at fractured vertebrae and upper discspace. Degeneration and narrowing of upper intervertebral disc was very common,intervertebral disc degeneration of two groups showed no statistically significant effect(P>0.05). The improvement to Spinal Canal Midsagittal Diameter(SCMD) in two groupshad no statistically significant effect (P>0.05).ConclusionTranspedicular fixation provides satisfying stability for Denis type Bthoracolumbar fractures and restore vertebral height. It reduce spinal canal stenosis andfacilitates neural recovery. Transpedicular fixation through the pedicle of fracturedvertebra provides more stability, and reduce the loss of correction. But there are stillproblems loss of correction, correction loss was most evident at fractured vertebrae andupper disc space. Combied with intrabody and Interbody fusion can reconstruct theanterior and middle columns, it helps to reduce the incidence of kyphosis.