| ObjectiveThe clinical incidence of thoracolumbar burst fracture is higher,as it is often caused by axial load fall from height injury and have some disability rate.there are many treatment methods for thoracolumbar burst fractures,and the results reported are various in clinical. Short-segment posterior instrumentation has become a generally accepted method of academia in treatment of thoracolumbar burst fractures,as reported it had a higher implant failure rate as a result of the lack of anterior support which was caused by the defect of fractured vertebtal body,many authors had made a large number of attempt and exploration for the treatment of thoracolumbar burst fracture,and put forward many improved methods,some new technologies has been applicated in clinic one after another. However, the efficacy of this different treatment still need to be observed.We make some new reforms for short-segment posterior instrumentation : We take unilateral transpedicular fixation with screw and supplemented with autologous bone grafting by another transpedicular passage in fracture vertebral body for thoracolumbar burst fractures,it is unclearly about the stability after unilateral transpedicular fixation and autologous bone grafting in fracture vertebral body, the related biomechanical study has not been reported, The clinical application of this method is not extensive. The purpose of this article study on biomechanics and clinical cases are as follows:â‘ to study the change of range of motion(ROM) in several different states after unilateral transpedicular fixation and autologous bone grafting in fracture vertebral body,and evaluate the stability of spine after operation from the view of biomechanics.â‘¡To explore the validity and reliability of the surgical operation and how to avoid complication.â‘¢To advance the operation indications of this surgical operation.Methods1. 12 fresh calf thoracolumbar spine specimens involved five vertebrae segements(T11-L3) were obtained,take the postero-anterior and lateral radiograph to exclude bone diseases,then remove muscle tissue carefully,the integrity of ligment and disc are reserved. According to Panjabi's high speed trauma apparatus,the specimens were made into the burst fracture specimen.2. 12 burst fracture specimens are divided into two groups randomly , every group has been setted four status:A:intact;B:fractured;C:fixated;D:fixated and bone grafting,specimens were used repeatedly.The ROMs of mearsured segment were noted. With the ROMs of intact,injury sepcimens, fixated specimens,fixated plus bone grafting sepcimens were compared each other, the stability of mearsured motion segments in different status was analyzed. Stiffness under flexion-compression were measured on the MTS testing system,to measure the deformation capacity of specimen to resist different axial load. Data are analyzed and processed in Spss 13.0.3.According to Denis classification of thoracolumbar burst fracture,52 patients with monomer burst fracture were adopted into our series,we make an retrospective analysis of 25 cases treated with short-segment posterior fixation combined with bone grafting and 27cases treated with short-segment posterior fixation supplemented with unilateral transpedicular fixation and bone grafting in fracture vertebral body. We make an evaluation on cobb angle ,anterior vertebral compression rate,vertebral body translation percentage in pre-,post-operation and last follow-up respectively,the recovery of pain and work afer surgery are evaluated by Denis Pain and Work Scale,Functional recovery of spinal cord are evaluated in the light of American Spinal Injury Association (ASIA)Results1. In the biomechanical experiment,the stability of two groups by short-segment posterior instrumentation combined with transpedicular fixation and bone grafting are enhanced remarkably after operation(P<0.05).2. The supplemented unilateral transpedicular fixation and bone grafting in the fracture vertebral body can enhance the stability in anteflexion and axial rotation better than traditional short-segment posterior instrumentation(P<0.05),there is no significant difference in extension and lateral bending between the two group(sP>0.05),there is no significant difference before and after transpedicular bone grafting in the fracture vertebral body(P>0.05).3. There are significant difference among cobb angle , anterior vertebral compression rate and vertebral body translation percentage compare with preopration in these two groups(P<0.05),there are no significant difference between the two groups(P>0.05).In the last follow up after operation, there are significant difference in cobb angle and vertebral body translation percentage between the two groups(P<0.05),and all patients with incomplete neurologic deficits had improvement 1.7 grades on average by ASIA grade.Conclusion1. Biomechanical study indicate that transpedicular unilateral pedicle screw fixation and bone grafting in the fracture vertebral body can enhance the stability of spine better than traditional instrumentation,reconstruct the support force of anterior colum in fracture vertebral body,diminish the stress load of internal instrumentation.2. In control of indications appropriately, short-segment posterior instrumentation combined with spinal decompression supplemented with transpedicular unilateral pedicle screw fixation and bone grafting in the fracture vertebral body are safe and feasible which can restore the height and load intensity of fractured vertebral body,conducive to the stability of pedicle screw rod system.In the meantime reposition the vertebral body of fracture dislocation and maintain its stability,diminish the probability of the injury of nerve and spinal cord induced by latent instability of the fractured vertebral body after laminectomy.This surgical approach have a good prevention to the incidence of implant failure after short-segment posterior instrumentation. |
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