| Background Percutaneous vertebroplasty is widely used in the treatment of osteoporotic vertebral compression fracture(OVCF),because of its good analgesic effect and rapid improvement of the quality of life of the elderly.However,during the follow-up,it is found that the incidence of postoperative vertebral collapse is very high,and there may be more serious complications,seriously affecting the health of patients,so spinal surgeons pay more and more attention to it.There are many influencing factors of vertebral body collapse.recent studies have found that the distribution of bone cement is closely related to vertebral collapse.in clinic,we use improved cross-puncture technique to control the distribution of bone cement.to obtain a good distribution of bone cement to reduce the occurrence of postoperative vertebral collapse,but there is a lack of relevant research basis and experience summary.This study analyzes the improved cross-puncture technique from two aspects of biomechanics and clinical application,and explores the feasibility and curative effect of this improved puncture method,as well as its role in improving vertebral collapse after vertebroplasty,so as to provide new ideas and theoretical basis for clinical work.Part ? Establishment of in vitro animal model of low bone mass vertebral compression fracture(pig)Objective The traditional chemical decalcification method of EDTA solution was improved to establish an in vitro animal model of low bone mass vertebral compression fracture(pig)and to verify the multi-dimensional low bone mass,so as to provide a model for later biomechanical research.Subjects and Methods Twenty-four thoracolumbar vertebrae of mature pigs were obtained.Decalcification in vitro(EDTA solution)was used to reduce the bone mineral density(BMD)of pig spine.The regional BMD,was measured by dual energy X-ray absorptiometry.The volume was evaluated by QCT scanning.The trabecular morphology was evaluated by Micro-CT.The histological characteristics of the tissues before and after decalcification were observed by HE staining and calcium salt staining.The specimens were tested by uniaxial compression test machine and Young's modulus,yield strain,final strain,yield pressure and final pressure were recorded.Finally,the low bone mass vertebral fracture model was established by vertebral body destruction,and the fracture model was verified by X-ray.Descriptive analysis,t-test and Pearson correlation were used in the statistical methods.Results(1)At 4 weeks after decalcification,the bone mineral density of all vertebrae in the experimental group was less than 0.75g/cm2 and was in a state of low bone mass.There was a significant difference in bone mineral density before and after decalcification(1.18±0.12g/cm2,0.58±0.06 g/cm2)(P<0.05).(2)QCT scan showed that after 4 weeks of decalcification,the experimental group(189.2±41.2mg/cm3)(p< 0.01)and 66.3±13.5mg/cm3 were smaller than the control group bone cortex BMD(611.8±31.5mg /cm3)and cancellous bone BMD(329.1±53.1mg/cm3)(P< 0.01).(3)Micro-CT showed that the bone trabeculae became thinner and thinner and the gap widened after decalcification treatment.(4)HE staining tissue sections showed that the volume of bone trabeculae in the experimental group was different from that in the control group,and there were differences in the connection between bone trabeculae.,von Kossa calcium staining showed that the density of black bone trabeculae in the experimental group was significantly lower than that in the control group.(5)In the axial compression test of decalcified vertebrae in the experimental group,compared with the control group,the elastic modulus decreased by 79.1%,the yield stress decreased by 73.2%,and the ultimate stress decreased by 72.2%.There were statistical differences among the three groups(P<0.001).The elastic modulus(R2 = 0.749,P<0.001),yield stress(R2=0.808,P<0.001)and ultimate stress(R2 = 0.753,P<0.001)of porcine vertebrae were positively correlated with BMD.(6)After compression destruction,all vertebral bodies were in a state of fracture. X-ray showed that the anterior edge of vertebral body was compressed and the bone cortex was discontinuous.Conclusion(1)Four weeks after the decalcification of pig vertebrae,the specimens showed strong osteopenia and reached the diagnostic criteria of low bone mass(<0.75g/cm2).(2)By using EDTA decalcification method,a large number of animal models which can satisfy the experiment of low bone mass vertebral fracture can be prepared,and the model shows a significant decrease in bone mineral density,bone morphological characteristics and bone strength.(3)EDTA decalcification is a suitable method for modeling low bone mass,which can basically meet the needs of the experiment from the aspects of imaging,histology and biomechanics.Part ? Biomechanical analysis of modified cross-puncture vertebroplasty in the model of low bone mass vertebral compression fractureObjective Analyze the differences of the distribution shape and biomechanics of bone cement formed by different puncture methods,and explore the ideal distribution shape and puncture method of bone cement,so as to provide biomechanical theoretical support for determining the best distribution form of bone cement.Subjects and Methods The weights of all vertebral bodies were measured and quantitative 5ml bone cement was injected into the model of low bone mass vertebral fracture in pigs by simulating vertebroplasty.Four different puncture methods were set: group 1 was cross puncture to form the distribution of bone cement distributed on the upper and lower edge of the vertebral body,group 2 was the traditional puncture to form the distribution of bone cement distributed on the lower edge of the vertebral body,and group 3 was the traditional puncture to form the distribution of bone cement distributed on the upper edge of the vertebral body.In experiment 4,the distribution of bone cement distributed in the center of vertebral body was formed by traditional puncture.Four types of dispersion distribution of bone cement were established and confirmed by X-ray.Another four OVCF models were selected as the control group without injecting bone cement.All specimens were tested by uniaxial compression test with material testing machine,and the yield load,ultimate load,stress and stiffness were recorded,and the load-displacement curve was established.The diffusion volume of bone cement was measured by CT three-dimensional reconstruction and the diffusion coefficient was calculated.The biomechanics of different bone cement distribution was compared,the three-dimensional reconstruction morphology of CT with different bone cement distribution was observed and analyzed,and the relationship between different indexes of bone cement distribution and biomechanics was studied.Descriptive analysis,independent sample nonparametric test(Mann-Whitney test)and Pearson correlation analysis were used in the statistical methods.Results(1)There was no significant difference in vertebral body weight between the controlgroup and the experimental group before bone cement injection.(2)The diffusion volume and diffusion coefficient of bone cement in group 1 werehigher than those in the other three groups.(3)The load and stress of vertebral body are different under different bone cementdistribution,and the order of ultimate load,yield load and stress from large to small is: fulldistribution type>upper distribution type>middle distribution type>lower distributiontype.In the control group,the yield load was 1.75±0.37 KN,the limit load was1.90±0.36 KN,and the stress was 3.14±0.55 Mpa.In experimental group 1,the yield load,ultimate load and stress were 4.97±0.79 KN,5.24±0.66 KN and 9.43±1.59 Mpa respectively.In experimental group 2,the yield load,ultimate load and stress were 2.28±0.27 KN,2.39±0.26 KN and 3.94±0.64 Mpa respectively.The yield load,ultimate load and stress ofexperimental group 3 were 4.46±0.39 KN,4.69±0.43 KN and 7.9±1.36 Mpa respectively.Inexperimental group 4,the yield load,ultimate load and stress were 2.91±0.42 KN,3.08±0.39 KN and 5.17±0.61 Mpa respectively.(4)In the experimental group,the stiffness of a few models after bone cementinjection was higher than that before bone cement injection,but the stiffness of all modelsin the experimental group did not return to the stiffness of the vertebral body before fracture.The stiffness of the experimental group 1 before and after injection of bone cement was 2.28±0.62KN/mm and 2.55±0.36KN/mm respectively.In experimental group 2,the stiffness of bone cement before and after injection was 2.70±0.42KN/mm and 2.68±0.45KN/mm respectively.The stiffness before and after injection of bone cement in group 3 and 4 were 2.49±0.48KN/mm and 1.77±0.59KN/mm,respectively,and the stiffness of group 4 before and after injection were 2.12±0.20KN/mm and 1.88±0.41KN/mm,respectively,and the stiffness before and after injection of bone cement in group 3 and group 4 were 1.77±0.59 KN/mm and 1.88±0.41KN/mm respectively.(5)The height of bone cement formed by cross puncture is higher P=0.004<0.05,and the total diffusion volume is larger P=0.029<0.05.This may be due to the fact that the two cement outflow channels are established in different positions,resulting in different diffusion directions of bone cement.(6)In the cross puncture group,a higher cement height ratio of P=0.004<0.05 could be obtained,but there was no absolute advantage in the distance between the upper edge of the cement and the superior endplate of the vertebral body P=0.058>0.05.(7)Correlation analysis showed that bone cement height and bone cement height ratio were positively correlated with ultimate load and stress,and negatively correlated with upper endplate distance and ultimate load and stress.There was no significant correlation between bone cement dispersion volume and biomechanics.That is,the higher the distribution of bone cement,the greater the proportion of height,the smaller the distance from the upper endplate,the greater the ultimate load and stress,and the difference in the distribution of bone cement did not affect the stiffness.Conclusion(1)After injection of bone cement into porcine spinal low bone mass vertebral fracture model,all types of bone cement distribution increased the loading force and stress of fracture vertebral body,and all bone cement distribution types did not restore vertebral stiffness.(2)The height and proportion of bone cement were positively correlated with ultimate load and stress,and negatively correlated with upper endplate distance and ultimate load and stress.There was no significant correlation between bone cement dispersion volume and biomechanics.That is,the higher the distribution of bone cement,the larger the proportion of height,and the smaller the distance from the upper endplate,the greater the ultimate load and stress.(3)There is no significant correlation between the difference of bone cement distribution and vertebral stiffness.(4)Cross puncture has a significant advantage in the distribution of bone cement,resulting in the full distribution of bone cement with high load and stress.Part ? Clinical analysis of modified cross-puncture vertebroplasty in the treatment of osteoporotic vertebral compression fractureObjective To compare the clinical efficacy of cross-puncture technique and traditional puncture technique in the treatment of osteoporotic vertebral compression fracture,analyze the difference of bone cement distribution pattern formed by different puncture methods,and explore the high risk factors of vertebral collapse after vertebroplasty.Subjects and Methods In a prospective study,70 cases of cross-punctured vertebroplasty were followed up for more than 1 year and the injection volume of bone cement was 4ml.70 cases of traditional vertebroplasty were selected as the control group.The general data between the two groups were compared: sex,age,fracture segment,bone mineral density,bone cement injection volume,operation time,follow-up time.Imaging: height of injured vertebra,wedge angle,Cobb angle,diffusion volume of bone cement,diffusion coefficient,functional score: VAS,ODI,Odom standard.Complications: bone cement leakage,vertebral collapse,vertebral fracture and so on.The differences of CT three-dimensional reconstruction images of bone cement distribution under different puncture were observed,the correlation between diffusion coefficient and vertebral collapse height was analyzed,the influence of vertebral collapse on patient satisfaction was analyzed,and the high risk factors of vertebral collapse were analyzed.Statistical analysis used t-test,chi-square test and LSD test for comparison,Pearson correlation analysis and Logistic regression analysis.Results(1)General data.a.The comparison between groups showed that there was no significant difference in age,sex,bone mineral density,fracture segment,bone cement injection volume,postoperative bed rest time and high compression ratio(P>0.05).After January 2018,70 patients with OVCF were treated with cross puncture,and 70 patients who used traditional puncture before 2018 were selected.b.There were significant differences in operation time and follow-up time between the two groups(P<0.01).The operation time was 29.0±8.6min in the cross puncture group and 20.7±10.2min in the traditional puncture group.The follow-up time was 15.37±3.9 months in the cross puncture group and 23.5±10.6 months in the traditional puncture group.(2)Image data.a.Intra-group comparison: there were significant differences in kyphosis angle,injured vertebral wedge angle,anterior edge height and middle vertebral body height between the cross puncture group and the traditional puncture group(P<0.05).There was no significant difference in the height of posterior edge of vertebral body between preoperative and postoperative data(P>0.05).In the cross puncture group,there was no significant difference in kyphosis angle,wedge angle,anterior edge height,middle height and trailing edge height between 1 day,3 months,6 months and 12 months after operation(P> 0.05).However,it can be seen from the data that the kyphotic angle and wedge angle gradually increased during follow-up,while the anterior edge height,middle height and trailing edge height decreased gradually during follow-up.In the traditional puncture group,there was no significant difference in kyphosis angle,wedge angle,anterior edge height,middle height and posterior edge height between 1 day and 3 months after operation(P>0.05).However,there were significant differences in kyphosis angle,wedge angle,anterior edge height,middle height and posterior edge height between 3 months,6 months and 12 months after operation(P<0.05).There was no significant difference in the height of the posterior edge of the vertebral body during the follow-up period(P>0.05).b.Comparison between groups: there was no significant difference in preoperative kyphosis angle,spinal wedge angle,anterior edge,middle segment and posterior edge height between the cross puncture group and the traditional puncture group(P>0.05).There was no significant difference in kyphosis angle,spinal wedge angle,anterior edge, middle segment and posterior edge height between the cross puncture group and the traditional puncture group 1 day and 3 months after operation(P>0.05).There were significant differences in kyphosis angle,spinal wedge angle,anterior edge and middle height of injured vertebrae between the two groups 6 months and 12 months after operation(P<0.05).c.There were significant differences in diffusion volume and diffusion coefficient between the two groups(P<0.05).The distribution area of bone cement obtained by cross puncture method was larger than that obtained by traditional puncture method.(3)Functional score: the pain relief and functional improvement of the two surgical methods were similar,and there were significant differences in VAS score and ODI score between the two groups before and 1 day after operation(P<0.05).There was no significant difference in VAS score and ODI score at 3 months,6 months and 12 months after operation(P>0.05).There were differences in the overall efficacy of Odom standard in the last follow-up.The cross-puncture group was better than the traditional group,and the excellent and good in the last follow-up Odom standard in the cross-puncture group was higher than that in the traditional puncture group.(4)Complications: the postoperative complications in the cross puncture group were better than those in the traditional puncture group,and the incidence of vertebral collapse and kyphosis in the cross puncture group was significantly lower than that in the traditional puncture group.There was a significant difference in the incidence of vertebral collapse between the two groups,which were 18.6%(13)and 78.6%(55),P<0.05,respectively.There were also significant differences in kyphosis between the two groups,with a distribution of 17.1%(12 cases)and 78.6%(55 cases),P<0.05).(5)Three-dimensional CT reconstruction of bone cement showed that the height of bone cement formed in the cross-puncture group was higher than that in the traditional puncture group,the bone cement in the cross-puncture group had more pores and larger diffusion volume than that in the traditional puncture group,and the distribution pattern of bone cement formed by traditional puncture and cross-puncture was different.(6)The diffusion coefficient can objectively reflect the distribution of bone cement,and the diffusion coefficient is inversely proportional to the loss rate of vertebral height,that is,the greater the dispersion coefficient,the lower the loss rate of vertebral height.r=-0.713,R2=0.508.(7)There were significant differences in VAS and ODI between the collapse group and the non-collapse group at 3 months,6 months and 12 months after operation(P<0.05).The Odom standard of the last follow-up was 80.9% satisfactory and 19.1% poor in the collapse group.The Odom criteria of the last follow-up were 79.1% excellent and 18.1% good in the non-collapse group.It shows that whether the vertebral body collapses or not will affect the patient's satisfaction,and the patient's satisfaction will decrease significantly after the collapse.(8)Regression analysis showed that patients with traditional puncture methods,bone mineral density?-3,diffusion volume<7.5,diffusion coefficient<1.5,height recovery ratio ?100% and wedge angle recovery ratio?50% were more likely to collapse.(9)The fully distributed bone cement patterns formed by cross-puncture method and traditional puncture method accounted for 97.1%(68/70)and 12.8%(9/70),respectively.There was significant difference in bone cement injection volume and diffusion coefficient between the two groups(P<0.05).There was no significant difference in diffusion volume(P>0.05).There were significant differences in the incidence of vertebral collapse and adjacent vertebral fracture in the cross puncture group(P<0.05).Conclusion(1)Compared with the traditional puncture,the diffusion coefficient of bone cement injected by cross puncture is larger,and the distribution pattern of bone cement is different.The height of bone cement formed in the cross puncture group was higher than that in the traditional puncture group,and there were more pores in the cross puncture group than in the traditional puncture group.(2)The curative effect of cross-puncture PVP in the treatment of OVCF within 3 months was similar to that of traditional puncture.6 months after operation,the cross-puncture group showed good vertebral body anti-compression ability,and the incidence of vertebral collapse in the traditional puncture group was much higher than that in the cross-puncture group.(3)The diffusion coefficient can objectively reflect the distribution of bone cement,and the diffusion coefficient is inversely proportional to the loss rate of vertebral body height,that is,the greater the dispersion coefficient,the lower the loss rate of vertebral body height.(4)The high risk factors of vertebral collapse include bone mineral density,diffusion volume,diffusion coefficient of bone cement,height recovery ratio,wedge angle recovery ratio and puncture mode.(5)In order to form the full distribution pattern of bone cement,the traditional puncture group needs to inject more bone cement,and the collapse rate of vertebral body is lower,but it significantly increases the incidence of clinical vertebral fracture. |
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