| Part one: Biomechanical study of the influence of the different length of the injured vertebra pedicle screw combined with the transpedicular bone graft on the thoracolumbar burst fracture.Objective: To investigate the effect of different lengths of pedicle screws combined with transpedicular bone graft on stability and stiffness of thoracolumbar burst fractures through biomechanical test.Methods: A total of 18 fresh calf thoracolumbar(T11-L3)specimens were made into thoracolumbar burst fracture models.They were randomly divided into 3 groups according to different ways of placing screws,6 in each group.The specimens of each group were prebored,and the L1 vertebral burst fracture model was made by constant pressure.The 15cm3 bone particles are implanted into the vertebral body through the injured vertebral pedicle on both sides of the vertebral body and are placed below the upper endplate of the vertebral collapse.The specimens were fixed by the general internal fixation system of the spine.In group A,4 screws were fixed with cross wound vertebra;group B was fixed with 6 screws of the injured vertebra and 35 mm short nail was used in the injured vertebra;group C was fixed with 6 screws of the injured vertebra and 50 mm long nail was adopted in the injured vertebra.The axial deformability and stiffness of specimens in different states were tested.Three dimensional mobility of specimens was measured,namely,the 6 directions of anteflexion,extension,left and right bending,left and right rotation.Results: There was no significant difference in activity and axial displacement in normal state and fracture state among the three groups(P>0.05),indicating that the specimens in each group were balanced,and the stability and stiffness of each group could be improved after fixation.In the axial displacement comparison with different fixation methods,the A group was larger than the B and C group,the difference was statistically significant.Compared with the two groups of B and C,the B group was larger than that of the C group,the difference was statistically significant.In the comparison of range of motion,the range of motion of anteflexion and left and right rotation of group A is larger than that of B and C group.The difference is statistically significant.Between B and C group comparison,B group is larger than C group,the difference is statistically significant.In the range of motion of extension and lateral anteflexion,group A was larger than that of B and C groups,and the difference was statistically significant,but there was no statistical difference between B and C group.Conclusion: The biomechanical test of thoracolumbar burst fracture,vertebral bone grafting and pedicle screw fixation can significantly improve the axial stiffness and stability,on the basis of transpedicular bone grafting,the vertebral implantation of long screw fixation can further improve the spine axial stiffness,anteflexion and rotation stability.Part two:Finite element method analysis of thoracolumbar burst fracture with different injured vertebral pedicle length combined with transpedicular bone graftObjective: To analyze the internal fixation stress distribution,upper plate displacement,the range of motion of fixed segment and the stress of injured vertebrae with different length of vertebral pedicle screw fixation combined with bone grafting for thoracolumbar burst fracture by finite element method.Methods: A case of L1 vertebral burst fracture,used spiral CT thin layer of thoracolumbar spine continuous scanning,scanning the image slice thickness was 0.625 mm,spacing 0.625 mm,512x512 pixels.The image series of Dicom format were obtained in 569,and introduced to engineering software to establish a three-dimensional finite element model.The simulated injured vertebral bone graft combined with pedicle screw fixation,and the collapse upper end plate was reset before the nail placement.The 15cm3 bone particles are implanted into the vertebral body through the injured vertebral pedicle on both sides of the vertebral body and are placed below the upper endplate of the vertebral collapse.A was treated with 4 pedicle screws across the injured vertebra.The B was fixed with 6 screws through the injured vertebra,and the 35 mm was used for the injured vertebrae.The C was fixed with 6 screws through the injured vertebra.The pedicle screws of the injured vertebra were 50 mm long nails,which were parallel to the upper endplate and twisted into the bone graft area.The lower end of the L3 vertebral body is fixed,and the 400 N load is applied continuously on the surface of the T11 vertebral body to simulate the standing condition of the body.At the same time,the 7.5Nm torque on the surface of the T11 vertebral body is applied to simulate 6 kinds of working conditions,such as the flexion of the human body,the extension,the left and right flexion,the left and right rotation.Through the finite element analysis,the stress and displacement cloud maps of the nail rod system,the upper endplate and the segmental vertebral body are obtained.The displacement of 10 fixed points on the upper endplate of L1 was measured under the flexion load.The stress distribution of internal fixation screws and connecting rods under various loads,the stress changes of injured vertebrae and the range of motion of fixed segments were measured.Results: 1.Under the flexion load,the deformation of the 10 points on the L1 endplate in the three internal fixation methods: The A was 0.74 ± 0.14 mm,the B was 0.51 ± 0.14 mm.and the C was 0.37 ± 0.11 mm.The A was larger than the B and C,and the difference was statistically significant,the B was larger than the C,and the difference was statistically significant.2.The internal fixation stress was concentrated at the root of the screw,and the stress of the upper screw was the most in the three internal fixation methods after the bone grafting with the injured vertebra.Under axial,anteflexion and rotation loads,the three groups of upper screw stress were more than those in A and B and C,P<0.05,the difference was statistically significant,and B was larger than C,P<0.05,which had statistically significant difference.In the extension and lateral bending load,the stress of the upper screws of the A was higher than that of the B and the C.The difference was statistically significant,but there was no significant difference between the B and C.The stress comparison of the injured vertebra was compared with the B and C,under the axial,anterior flexion and rotation load,and the difference was statistically significant.There was no statistical difference between the two conditionss of B and C,P>0.05 in the extension and lateral bending load.3.In the range of motion of fixed segment,the fracture model was the largest,after that,the A was larger than B,and the B was larger than the C.4.The stress changes of injured vertebrae: under all kinds of active state loads,the three groups of injured vertebrae all had the biggest stress when rotating,followed by anteflexion and up-right.The stress of the injured vertebra is the least in the extension.In the three fixed methods,A was close to B,and C was significantly greater than A and B.Conclusion: The finite element analysis method can simulate the biomechanical characteristics of spine,reflecting the stress distribution,the endplate deformation,the range of motion of segments and the stress changes of injured vertebrae.The bone grafting and screw fixation of the injured vertebra can increase the stability of the fixed segment and disperse the stress of the upper pedicle screw.Vertebral bone graft and long screw fixation can effectively support the endplate,further reduce endplate deformation,bear and dispersed in the internal fixation stress,increase vertebral stress support,to reduce the incidence of upper endplate collapse,loss of reduction and fixation of complications in the later period.Part three:Clinical study on the treatment of thoracolumbar burst fracture with the length of different injured vertebra fixed and pedicle bone graftObjective: To evaluate the effect of different length of vertebral pedicle screw fixation combined with injured vertebral bone graft on the clinical effect of thoracolumbar burst fracture.Methods: From January 2012 to June 2016,a retrospective analysis of surgical treatment of thoracolumbar burst fracture patients.All patients underwent three surgical treatment,respectively: inter vertebral 4 screws fixation cross injured vertebra with transpedicular bone grafting(A group),6 screws with injured vertebral short nail and vertebral bone graft(B group),6 screws with injured vertebral long nail and vertebral bone graft(group C).The three groups were compared and analyzed.A total of 94 patients were enrolled in the study,including 45 male and 49 female cases,with an average age of 30-65 years and an average of 48.82 ± 9.07 years old,including 30 cases in group A,31 in group B and 33 in group C.The perioperative period of operation,blood loss and the number of complications were counted in three groups.Before surgery and after surgery7 d,30d,3 months,6 months and 12 months by visual analogue scale(VAS)assessment of pain to improve the situation,the Oswestry disability index(ODI)evaluation function;using Frankel nerve function classification to assess the recovery of nerve function;imaging evaluation of vertebral Cobb angle and the anterior height of vertebral body compression rate;at the last follow-up,the statistical number of complications of internal fixation.Result:1.All patients were followed up for a period of 12-18 months,with an average of 13.51 ± 1.63 months.2.Three groups of patients in age,gender,injury segment,preoperative VAS score,Frankel nerve function classification,Oswestry disability index(ODI),vertebral height compression ratio,Cobb angle and other aspects,there was no significant difference(P > 0.05).3.The main indicators of preoperative and postoperative VAS score,Frankel nerve function grading,Oswestry disability index(ODI),Cobb angle and vertebral anterior border height compression rate of all operative patients were significantly improved compared with those before operation,and the difference was statistically significant.4.The operation time A group was 89.67 ± 12.79 min,B group was 99.87 ± 12.20 min,C group was 101.51 ± 13.98 min,the difference between groups is statistically significant,compared A with B and C,the difference is statistically significant,there is no significant difference between B groups and C groups.The blood loss in the A group A was 419.66 ± 113.64 ml,the group B was 399.03 ± 125.20 ml,and the group C was 377.87 ± 86.45 ml,and the difference was not statistically significant in the three groups.Perioperative complications,group A was one case of incision infection and one case of incision hematoma,group B was 1 cases of incision hematoma,all cases were cured within three weeks,C group was not perioperative complications,there was no significant difference in three groups.5.VAS scores were compared in 7d,6 months,and 12 months after operation,and there was no statistical difference in the three groups.In the comparison of 30 d and 3 months after operation,the difference in three groups was statistically significant,and the A group was larger than that of the B groups and C groups.The difference was statistically significant.Compared with B groups and C group,the B group was larger than that of the C group,and the difference was statistically significant.In the 6 months and 12 months after the operation,ODI was compared to three groups,with no statistical difference.The Cobb angle of the injured vertebra was compared in the 7d,30 d,and 3 months after the operation,and the difference was not statistically significant in the three groups.In the 6 months and 12 months after operation,the difference between the three groups was statistically significant,and the difference between the three groups was statistically significant.The difference between the three groups was statistically significant.Compared with the C group,the difference between the three groups was statistically significant.The difference between the three groups was statistically significant.The anterior height of vertebral body compression rate in postoperative 7d,30 d,3 months,three groups had no significant difference;in 6 months,12 months after surgery,there was significant difference between the three groups,A group than B group and C group,the difference was statistically significant;compared with B group and C group.B group than in the C group,the difference was statistically significant.At 12 months after operation,there were 2 cases of broken nails and 2 cases of screw loosening in group A.There were 1 cases of screw loosening in group B and group C,and there was no significant difference between three groups.There was no statistical difference between the three groups of Frankel nerve function classification.Conclusion: 1.Thoracolumbar burst fracture by posterior reduction pedicle screw fixation plus transpedicular bone graft can effectively repair bone defect of vertebral fracture after reduction,increase bone strength of the vertebral body,restore and maintain vertebral height,the vertebral bony healing,sequence and reconstruction of spinal stability.The operation is safe and effective.2.On the basis of injured vertebral pedicle bone graft,the pedicle screw fixation can improve the stability of internal fixation,distract the fixation stress of fixation screws,,improve symptoms in early stage,promote functional recovery of patients,and reduce the incidence of complications of internal fixation.3.The longer pedicle screw was inserted into the injured vertebra to form effective support under the endplate,further strengthening the bone grafting of the injured vertebra,improving the immediate stability of spinal fixation,dispersing the internal fixation stress,reducing the late reduction loss,the upper end plate collapse and kyphosis.It can also promote the early rehabilitation,improve the symptoms and improve the patient's satisfaction with the operation. |
PDF Full Text Request