| Objective1.The incidence of adjacent segmental fractures and related risk factors were calculated by long-term follow-up of cases of large-scale percutaneous vertebral augmentation.2.Under the microscopic syndrome theory system of traditional Chinese medicine,the three-dimensional finite element model of CT was used to test the stress changes of adjacent segments under different loads after vertebral augmentation,and to predict the occurrence of adjacent segmental fractures,fracture line orientation and fracture collapse.3.Based on the thoracolumbar segment finite element model,the effects of different degrees of vertebral fracture reduction on the stress distribution of adjacent segments were tested.4.Based on the finite element model of thoracolumbar segment,simulate the mechanical effects of bone cement leakage on different parts of the vertebral body(intervertebral space,intraspinal canal,nerve hole,paravertebral)on adjacent vertebral bodies.Method1.Part Ⅰ Clinical Research:We retrospectively studied 457 patients who underwent vertebral augmentation in the First Affiliated Hospital of Guangzhou University of Traditional Chinese Medicine from January 1,2007 to December 31,2012 due to painful osteoporotic vertebral compression fractures.There were 75 male patients and 382 female patients.The indications for PVA are severe back pain,local spinous process tenderness,obvious snoring pain,progressively worsened kyphosis,ineffective by conservative treatment,preoperative MRI confirmed acute or subacute vertebral compression fracture or staleness Patients with non-union fractures.There were 323 patients who did not see new fractures during the follow-up period and were assigned to group A.Another 134 patients had new fractures during the follow-up period and were assigned to group B.Observed indicators include:patient gender,age,body mass index,bone density,site of existing fractures,number of fractured vertebral bodies before surgery,segments of vertebral augmentation,number of vertebral bodies treated with vertebral body augmentation,The severity of the fracturedvertebral body,the average amount of cement injection,the way of vertebral augmentation(PVP or PKP),the leakage of cement,and the location of new fractures.The severity of vertebral body intensified treatment is evaluated by Genant semi-quantitative fracture degree,that is,the observation of X-ray film,mild fracture:the height of the vertebral body is reduced by 20%-25%,and the projected area of the vertebral body is reduced by 10%-20%;Moderate fractures:vertebral height is reduced by 26%to 40%,vertebral projection area is reduced by 21%to 40%;severe fractures:vertebral height and vertebral projection area are reduced by>40%.The measurement data is expressed by the mean plus or minus standard deviation,and the count data is expressed by the frequency.Statistical analysis was performed using SPSS22 statisticalsoftware.The measurement data were analyzed by two independent samples t test,and the categorical variables were analyzed by x 2 test.The difference of P<0.05 was significant.Univariate regression analysis was used to analyze single factor analysis,and multivariate linear regression analysis was used to analyze the relationship between various factors and new vertebralfractures.2.Part Ⅱ Finite element analysis:We selected a patient with T12 OVCFs who underwent PKP in our hospital and had an adjacent segment of the T11 vertebral fracture during the follow-up period.The CT data of thethoracolumbar segment were used as the study object.Based on the CT data of the patient’s T12 augmentation thoracolumbar segment,we used the finite element modeling and analysis software Mimics 20.0,Geomagic Studio 2013,SolidWorks 2013,ANSYS16.0 to construct the three-dimensional finite element model of T12 vertebral compression fracture after vertebral augmentation(Model A).At the same time,a three-dimensional finite element model(model B)of T11 recurrent vertebral fracture after T12 vertebral body strengthening was constructed based on CT data of the thoracolumbar segment of the adjacent segment of the T11 fracture.Assuming that a normal adult weighs 60 kg,usually 2/3(40 kg)of the total weight of the human body is applied to the thoracolumbar spine of the human body,and the load is about 400 N.Therefore,this study applied a uniform vertical downward force on the upper surface of the T10 thoracic vertebra,simulating the upper body weight of the human body,a total of 400N,to simulate the load of the human chest and waist when standing upright.We load the 400N load vertically in the erect finite element model,and simulate the human body flexion,extension,side curve,and rotation by loading the torques of the X,Y,and Z axes(10Nm),respectively,specifically the coordinates corresponding to the flexion loading.The axis is the X axis(the description corresponds to the forward flexion of the current human body),the corresponding coordinate axis of the rear extension loading is the X axis(the description corresponds to the extension of the current human body),and the coordinate axis corresponding to the lateral bending loading is the Y axis(corresponding to the current human body)Left side bend),the corresponding coordinate axis of the rotary loading is the Z axis(corresponding to the counterclockwise rotation of the current human body),simulating the human body flexion,extension,side bend,and rotation.Observe the stress cloud of model A under different loads and record the stress distribution and maximum stress value.Comparing the stress cloud of model A with model B,the degree of matching between the stress concentration of the model A and the true fracture line contour of the T11 vertebral body and the fracture of the fracture in the model B is observed.3.Part Ⅲ Finite element analysis:We selected a female patient with osteoporotic vertebral body(L1)compression fracture and obtained CT data of the thoracolumbar region.A finite element modeling and analysis software,Mimics 17.0,Geomagic Studio 2013,SolidWorks 2012,ANSYS 17.0,was used to construct a L1 vertebral fracture without a reduction model(model A).On the basis of model A,the thoracolumbar osteoporosis model(model B)was constructed separately.On the basis of model A,the lower surface of the vertebral body was changed,and the material properties of some cancellous bone units in the vertebral body were changed to PMMA bone cement.The material properties,forming a cylindrical cement block,the amount of 4ml,simulated injection of bone cement,the construction of a fracture-free PVP model(model C):on the basis of model B,the change of part of the cancellous bone unit within the vertebral body The material properties are the material properties of PMMA bone cement,forming a cylindrical cement block of 4 ml,and constructing a complete fracture reduction PKP model(model D).Set the displacement of all nodes in the lower edge of the L2 vertebral body in the three directions of X,Y and Z axes to be zero,and fix the lower surface of L2.Apply a uniform vertical downward force on the upper surface of the T11 thoracic vertebra to simulate the upper body weight of the human body,a total of 400N,to simulate the load of the human chest and waist when standing upright.While the vertical finite element model is loaded with 400N load vertically,lONm moment is applied to the upper surface of the T11 vertebral body,which is divided into four kinds of loads.The directions are flexion,extension,left and right rotation,respectively.Loads for flexion,extension,left and right rotation.We observed the stress distribution of the thoracolumbar segments of the spine in the above model under different loads.4.Part Ⅳ Finite element analysis:We selected a female patient with L1 vertebral osteoporotic compression fracture and obtained CT data of the thoracolumbar region.Using the finite element modeling and analysis software Mimics 17.0,Geomagic Studio 2013,SolidWorks 2012,ANSYS 17.0,we respectively constructed the L1 vertebral bone cement 4 ml enhanced non-leakage model(model A),L1 vertebral bone cement 4.5ml fortification Non-leakage model(model B),intervertebral space cement leakage model above L1(model C),construction of intervertebral space cement leakage model under L1(model D),L1 upper and lower intervertebral space cement leakage model(model E),L1 pedicle leak model(model F),L1 anterior leak model(model G),L1 paraspinal leakage model(model H),L1 intervertebral foramina model(model I),and L1 Intraspinal leakage model(model J).Assuming that a normal adult weighs 60 kg,usually 2/3(40 kg)of the total weight of the human body is applied to the thoracolumbar spine of the human body,and the load is about 400 N.Therefore,this study applied a uniformly distributed vertical downward force on the upper surface of the T11 thoracic vertebra,simulating the upper body weight of the human body,a total of 400N,to simulate the load of the human chest and waist when standing upright.We apply a lONm moment on the upper surface of the T11 vertebral body while loading the 400N load vertically in the erect finite element model.It is divided into four kinds of loads,and the directions are flexion,extension,left and right rotation respectively.Here,only the left and right rotations are studied),simulating the load of the human thoracolumbar flexion,extension,left and right rotation.Observe the stress distribution of the various parts of the bone cement leakage model in different parts of the thoracolumbar segment under different loads.Result1.Part Ⅰ Clinical Research:In all 457 patients,there were 1092 fractured vertebral bodies before operation(431 mild fractures,361 moderate fractures,and 300 severe fractures).Among them,422 vertebral bodies were diagnosed by MRI to diagnose the vertebral body with old fracture healing.670 vertebral bodies were diagnosed as fresh fractures or old fractures without cerebral infarction(332 mild fractures,202 moderate fractures,and 136 severe fractures).Of the 457 patients,295 were treated with PVP,162 were treated with PKP,61 with one-sided puncture,and 396 with bilateral puncture.All patients were followed for at least 24 months.Most of the fractured vertebral bodies and surgically treated vertebral bodies that occurred before the operation occurred in the thoracolumbar region.The pre-operative fractured vertebral body accounted for 56.04%of the thoracolumbar segments.The thoracolumbar segments in the PVA-treated vertebral body accounted for 64.2%.284 patients had no cement leakage,and 173 patients(196 vertebral bodies)had intraoperative cement leakage.Among them,85 vertebral bodies had paraspinal cement leakage,50 vertebral bodies had intervertebral space cement leakage,18 vertebral bodies had puncture channel leakage,1 vertebral body had intervertebral hole leakage,and 23 vertebral bodies Intraspinal leakage occurred in 19 cases of paravertebral venous leakage.According to Yeom et al.,the leakage of bone cement is divided into three types:B-type,C-type and S-type.Among them,B-type leakage is the leakage of bone cement along the vertebral basilarus to the posterior edge of the vertebral body;In order to leak along the vertebral cortical defect;S-type is leakage along the intervertebral vein.In patients with bone cement leakage,one patient required reoperation for surgery due to leakage of cement in the spinal canal and nerve compression.The remaining 172 patients were not treated for further treatment due to leakage of cement.A total of 134 patients(29.3%)developed new vertebral fractures during the follow-up period.Among them,67 patients had new fractures in adjacent segments,and 67 patients had new fractures in non-adjacent segments.Of the patients with new vertebral fractures,19 patients underwent conservative treatment after new fractures,and the remaining 115 patients underwent vertebral augmentation 2 or more due to new fractures.Most of the vertebral bodies with the first new fracture occurred in the thoracolumbar region,accounting for 53.1%.During the follow-up period,33 patients had limb fractures,including 26 hip fractures(9 femoral neck fractures,17 intertrochanteric fractures),4 proximal humeral fractures,and 3 wrist fractures.There were significant differences in mean age,bone mineral density,body mass index,number of fractured vertebral bodies before surgery,average number of vertebral bodies treated with PVA,and amount of bone cement injected between the two groups.Univariate analysis showed that the patient’s age,bone mineral density,body mass index,number of fractured vertebral bodies before surgery,number of vertebral bodies,bone cement injection and new vertebral fractures were correlated(P<0.05).),and the patient’s gender,cement leakage,intervertebral space leakage,surgical vertebral severity,single/double puncture,and surgical approach were not associated with new vertebral fractures(P>0.05).Multivariate analysis showed that the patient’s bone mineral density and the number of existing fractured vertebral bodies were the main factors for new vertebral fractures,and the standardized partial regression coefficients were-0.055 and 0.028,respectively.2.Part Ⅱ Finite element analysis:The maximum stress of the T11 vertebral body under the five loads of erect,flexion,extension,lateral bending and rotation are 19.252Mpa,63.679Mpa,67.387Mpa,76.264Mpa,92.079Mpa,respectively,and the maximum stress of the L1 vertebral body under 5 kinds of loads.They were 17.918Mpa,23.626Mpa,15.402Mpa,23.807Mpa,and 44.049Mpa,respectively.It can be seen that the T11 vertebral body is more stressed than the L1 vertebral body under five different loads.The maximum stress of the T11 vertebral endplate under erect,flexion,extension,lateral bending and rotation was 9.2217Mpa,25.324Mpa,9.0966Mpa,25.479Mpa,11.911Mpa,and the L1 vertebral endplate was 5 The maximum stresses under the load are 2.5117Mpa,4.9306Mpa,4.9695Mpa,4.1593Mpa,and 9.4029Mpa.It can be seen that the stress of the T11 vertebral endplate is greater than that of the L1 vertebral endplate under five different loads.Thus,in adjacent segments of the vertebral strengthening segment(T12),the upper adjacent vertebral bodies and endplates are subjected to greater stress.The T11 vertebral body has a higher risk of secondary fracture than the L1 vertebral body.The end plate stress on T11 is mainly concentrated in the middle of the upper end plate,and the end plate stress under T11 is mainly concentrated in the front part of the lower end plate.Except for the extension load,the cortical bone stress of the T11 vertebral body is larger than the posterior edge of the vertebral body.The upper edge of the T11 vertebral body is mainly concentrated in the middle part.The lower edge of the T11 vertebral body is mainly concentrated in the anterior part of the vertebral body.It is inferred from the T11 stress cloud diagram that if the T11 vertebral body fracture collapses,the upper end of the vertebral body and the upper part of the vertebral body are mainly center collapsed,and the lower end of the vertebral body and the lower part of the vertebral body are mainly collapsed in the middle and the anterior part.The trailing edge is compressed significantly.The real T11 re-fracture model(model B)was reconstructed based on CT data from patients with T11 fracture after T12 vertebral augmentation and compared with model A.The collapse of T11 vertebral body is mainly caused by the collapse of the middle and lower end of the vertebral body.The compression of the anterior edge of the vertebral body is more compressed than the posterior edge of the vertebral body.In the realistic fracture model(model B),the fracture subsidence of the T11 vertebral body matches the stress concentration of the T11 vertebral body and the upper and lower endplates in the model A under standing,flexion and lateral flexion loads,and the buckling compression stress is the most OVCFs.Common damage external forces.Therefore,the stress distribution of adjacent segments after standing,flexion and lateral flexion after PVA can be observed,and the segmentation,fracture morphology and collapse of new fractures in adjacent segments can be predicted.3.Part Ⅲ Finite element analysis:In model B,the buckling,extension,sidebend and rotational loads are applied to the T11-L1 segment with a torque of 7.5 N/m.The experimental angular displacement data are 7.11°,5.09°,7.98°,4.77°,respectively.The literature is relatively close,verifying the validity of the finite element model of this study.Model A,model C and model D had no uniform change in the maximum stress of T12 vertebral body,L2 vertebral body,T12/L1 intervertebral disc and L1/L2 intervertebral disc under various loads,and the stress did not change significantly under each load.In general,there was no significant difference in stress between adjacent vertebral bodies and intervertebral discs before and after vertebral intensive surgery.There was no significant difference in the stress between adjacent vertebral bodies after PVA.4.Part Ⅳ Finite element analysis:Compared with model A(no leakage 4ml)and model B(no leakage 4.5ml),there was no significant difference in the maximum stress between adjacent segments in the two models under erect,flexion,extension and lateral flexion loads.There is no uniform trend in the two models for the maximum stress under rotating load.That is,compared with the non-leakage 4 ml model,the non-leakage 4.5 ml model increases the maximum stress of the T12 vertebral body and the L2 vertebral body under rotating load,but reduces the T12 lower endplate,T12/L1 intervertebral disc,L1/The maximum stress of the L2 intervertebral disc and the L2 upper endplate.Overall,there was no significant difference in the stress effects of models A and B on adjacent vertebral bodies,endplates,and intervertebral discs.The non-leakage model(models A,B)was compared with different models of cement leakage models(model C-J).Except for the maximum stress of the T12 vertebral body under the vertical load,the maximum stress of the adjacent segment of the cement leakage model(except model E)increased under the erect and forward flexion loads under different flexural loads.The increasing trend of adjacent segment stress is more obvious.Model E(upper and lower intervertebral space leakage models)showed no uniform trend of stress changes in adjacent segments under erect and flexural loads.There is no uniform trend in the stress changes of adjacent segments in the different parts of the cement leakage model(model C-J)under the extension,lateral flexion and rotational loads.In general,in addition to the cement leakage in the upper and lower intervertebral space,the leakage of bone cement in other parts increased the maximum stress of adjacent segments under the upright and forward flexural load,and the stress increased under the previous flexural load.Conclusion1.Part Ⅰ Clinical Research:Bone mineral density and the number of vertebral fractures before surgery were independent risk factors for new fractures in patients with PVA2.Part Ⅱ Finite element analysis:Under the theoretical system of microscopic syndrome differentiation of traditional Chinese medicine,we can observe the stress distribution of the adjacent segment finite element model after PVA under standing,flexion and lateral flexion load to predict the segment,fracture morphology and collapse of new fractures in adjacent segments.3.Part Ⅲ Finite element analysis:PVA does not significantly increase the stress of adjacent vertebral bodies,and provides a certain biomechanical evidence for the theory that the adjacent vertebral body secondary fracture is the natural course of osteoporosis.There was no significant difference in the biomechanical changes of adjacent vertebral bodies after PVA for different fracture vertebral body reductions.4.Part Ⅳ Finite element analysis:Increasing the amount of bone cement injected did not significantly increase the maximum stress of adjacent segmental vertebral bodies.Most cement leakage increases the maximum stress of adjacent segmental vertebral bodies under erect and flexion loads,which may increase the incidence of adjacent segmental fractures. |
PDF Full Text Request