| Thoracic lumbar spine fractures (T10-L2) is the most common injury in spinal surgery clinical areas, in thoracic lumbar spine, spine by migration of chest smaller section for movement of the movement of larger waist section, stress concentration under external force here, easy to cause the fracture occurred. It is reported that in North America there was about160000patients with thoracic lumbar spinal fracture each year. Due to industry, agriculture and construction industry development in our country, the incidence of thoracic lumbar fracture is higher. Complications of thoracic lumbar fractures including paraplegia, pain, deformity and dysfunction.Usually thoracic lumbar spine fracture was caused by massive violence, mostly because of falling injury and traffic accident injury and fracture is not stable, often because of violent injury is larger, this type of fracture is often combined with other multiple organ damage. Although so far, the treatment of spinal fractures instruments and strategies have been improved, but the ultimate goal of the treatment did not change, namely on the basis of stable fracture protect or promote the recovery of spinal cord function, prevention of spinal deformity, maximum limit to improve the function of clinical prognosis.And if it is a stable fracture of thoracic lumbar segment and not associated with nerve damage, often take and early activities with a conservative treatment. If fracture conbined with nerve injury and/or instability, often need surgery, polytrauma and unstable and not treated with a suitable person, also need surgery. These cases, surgical decompression neural structures, sagittal curvature and early recovery activities. For lumbar instability of chest compression and comminuted fracture of surgical technique correctly, is still controversy. Surgery included anterior anterior column reconstruction, fixed, or joint before and after posterior fixation fusion. Anterior column reconstruction can directly restore vertebral body height, but exists in the related complications. Posterior surgery are more commonly used in fixedClinically and all kinds of works without clear thoracolumbar fractures of posterior pedicle screw fixation segment selection, selection of injured vertebral fixed and increase the segmental fixation, each have advantages and disadvantages.Finite element analysis (FEA), an advanced computer technique for structural analysis, has evolved over the past30years as an indispensable tool for biomechanical researchers to investigate structural behavior of all kinds of human tissues, for example, assessing the redistribution of load in bone tissue after implantation of an implant.This topic through finite element method analysis, to analyze the stress change of internal fixation, and the internal stress distribution and deformation of injured vertebral, to judge the pros and cons of various fixed way, to choose to provide basis for clinical surgery choice of internal fixation implants, this topic first introduced increased the nail long segmental six groups, consistent with the clinical choice, not only to injured vertebral screw fixed6and4screw method comparison. In addition to injured vertebral endplate on deformation is more in line with the injury mechanism, help determine the fixed effect and prognosis, and through this topic research, further to find a suitable finite element modeling method of clinical use. Another part of this article, through the analysis of clinical cases, from the clinical point of view, for the injured vertebra fixed, long segment fixation to analyze clinical effect, from another Angle to part of the validation based on the finite element model.PART ONE Finite element analysis for3kinds of posterior pedicle fixation to treat lumbar vertebral compression fracturesObjective1.Establish a finite element model with3kinds of posterior pedicle fixation which includes with pedicle screws in injured level、short segment4-screws and long segment6-screws.2.To investigate the biomechanical mechanism of the treatment about lumbar vertebral compression fractures with pedicle screws in injured level、short segment4-screws and long segment6-screws by finite element analysis.Methods Select1cases diagnosed as the second lumbar vertebral compression fractures,male patients, CT scan, CT data was input into Mimics software to build a three dimensional bone image, then input a drawing pedicle screw image, build finite element model of lumbar2verteral compression fractures, on the basis of this model simulated group A short segment4screw internal fixation, group B injured vertebral short segment6screw internal fixation, group C long segment6screw internal fixation, the model was input into Ansys products11.0software to mesh, in Mimics software material allocation, to solve products in Ansys software, finite fixed edge of lumbar vertebral body3, on the T12vertebral body surface keep up500n load, in the vertical load of500n load at the same time, the T12vertebral15nm torque applied on the surface, after points forward bends, stretching and lateral load and other three kinds of situation. For three models respectively after applying vertical compression, bending forward, stretch, side bending load, and to measure internal fixation screw, connecting rod under various load stress distribution. In forward bends down and load2on the end plate on10fixed point displacement.Results The largest stress was measured in the screw root for three groups. The stress of the superior screw was larger than that of the subordinate screw (P<0.05). The stress in the A group was larger than that in B and C group (P<0.05). The deflection of the superior endplate in L2under flexion loadings are (0.0001mm)A group87±3.06、B group41±5.33、C group13.8±8.20,the results of B(0.89±0.08MPa)and C (0.8±0.11MPa) group are lesser than it in A (1.12±0.13MPa) group(P <0.05),and C group is C lesser than it in B group(P<0.05).Conlusion It is indicated that it can be optimized to reduce the failure of internal fixation with pedicle screws in injured level and long segment fixation. pedicle screws in injured level and long segment fixation can decrease the deflection of injure vertebra so they are benefit for frcture rescover. PART TWO The clinical application research for treatmentin thoracolumbar fractures with pedicle screws fixationObjective To discuss the efficacy of the pedicle of fractured vertebra for thoracolumbar fractures and the reason of the correction loss.Methods From June2011to July2013,101patients with type B2thoracolumbar fractures according to AO classification were treated. Injury reasons:52cases of falling from height,16cases from heavy objects smashing or crushing,43cases of car accidents. The injured vertebra located at T11in7cases,T12in20cases,Ll in41cases,L2in33cases. Based on ASIA grading system of neurologic deficit, grade A was found in1case, grade B in3cases, grade C in2cases, grade E in95cases. The patients were divided into three groups:in the no via fractured vertebra group, there were23male and12female with an average age of20.2±11.62years(range from22to26years), in the unilateral pedicle screw fixation through the pedicle of fractured vertebra group, there were25male and9female with an average age of42.65±10.71years(range from17to62years), in the bilateral pedicle screw fixation through the pedicle of fractured vertebra group, there were26male and6female with an average age of39±13.96years(range from17to65years).The assessments include the anterior vertebral body height and the sagittal Cobb angle in preoperative and postoperative. Recorded the fracture reduction rate and the correction loss of the final follow-up. Estimated the patients’subjective evaluation according to Denis scale, analysised the difference of reset rate and correction loss of the final follow-up. Analysised the reason of the correction loss comprehensively.Results All the patients were followed up for an average of2years(range from1.5to3.5). In the final follow-up, the loss of the anterior vertebral body heights were:(14.37±13.33)%,(7.16±2.96)%,(6.03±1.72)%. The loss of sagittal Cobb angle degrees were:3.34°±1.59°±1.91°±0.75°±,1.69°±1.72°. The fracture reduction rates were:(83.85±7.43)%,(86.93±19.81)%,(90.65±15.03)%. There were1-2recovery of three groups in Denis pain scales. The no via fractured vertebra group compared with the unilateral or bilateral pedicle screw fixation through the pedicle of fractured vertebra group had statistical significance in the correction loss of Cobb angle degrees and reduction relative height loss(P<0,01). There were no statistical significance in the reduction rate and Denis pain scale (P>0.05). The unilateral pedicle screw fixation through the pedicle of fractured vertebra group comparer with bilateral group had no statistical significance in the correction loss of Cobb angle degrees, reduction relative height loss, reduction rates and Denis pain scale (P>0.05).Conclusion The pedicle screw fixation has better effection of reduction for the type B2thoracolumbar fractures. It can help patients relieve pain, however, unilateral or bilateral pedicle screw fixation through the pedicle of fractured vertebra has better effetion for the biomechanical stability of the spine after the operation. |
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