【作者】 唐明星；

【导师】 张宏其；

【作者基本信息】 中南大学 ， 外科学， 2009， 博士

【摘要】 背景青少年特发性脊柱侧凸(adolescent idiopathic scoliosis,AIS)在青少年中的发病率约为2%～3%,严重威胁着青少年的身心健康。其治疗方法较前大有改进,疗效也明显提升。但是,很多问题仍有待进一步研究,其中脊柱侧凸的生物力学研究是最为重要的一方面。脊柱生物力学研究方法有多种,包括动物实验、物理实验、尸体实验等。脊柱侧凸在自然界的动物中尚未发现,模型选材困难,而脊柱侧凸的人体标本获取更是困难。随着电子计算机的发展,有限元法已经迅速发展成为一种现代计算方法。其可在研究中重复,并可改变任何质量与定量变化,同时提供了局部以及内部的反应机制。Hueter-Volkmann定律认为:骨骼所受到的应力增加,骨的生长就会受到抑制;骨骼所受到的应力减小,骨的生长就会加速。上述定律可解释AIS在生长高峰时侧凸的进展。而支具就是通过施加矫形力将凸侧和凹侧的椎间盘应力平衡,从而达到治疗效果的。在本次研究中我们选取一名青少年特发性脊柱侧凸患者,Lenke分型1A-型(PUMC分型Ⅱa型),Risser征3级,通过建立特发性脊柱侧凸的有限元模型,研究不同矫形力的生物力学特性,并模拟支具治疗后椎间盘凸侧、凹侧应力的分布变化,预测支具治疗的效果,为AIS的生物力学研究提供一个量化指标。第一章目的:建立青少年特发性脊柱侧凸的三维有限元模型,并验证模型的有效性,为下一步研究提供平台。方法:选取一名青少年特发性脊柱侧凸患者,螺旋CT对其脊柱进行层厚1mm的连续扫描,以Dicom格式文件储存所得的扫描图像。用Mimics软件生成脊柱侧凸的三维几何模型,导入Hypermesh软件进行网格划分,并对网格赋予特定的材料属性。将患者建立的模型与仰卧位、站立位、仰卧左右侧屈位X线片进行比较,并选取T12-L2、L3-S1节段与相关的生物力学实验研究相比较。结果:1、仰卧位、站立位、仰卧左、右侧屈位X线片的Cobb角分别为31°、40°、44°、19°,而有限元模型中相应的角度分别为30°、41°、40°、20°。2、椎体质心偏离骶骨中线的距离:仰卧位、站立位、仰卧左右侧屈位X线片与有限元模型相比较,P>0.10,可以认为两者没有差别。3、T12-L2、L3-S1节段与相关的生物力学实验研究相比较,平均刚度均在相关生物力学实验研究的范围内。结论:1、基于CT扫描的Dicom格式文件,采用Mimics及Hypermesh软件,构建了T1至骶骨的青少年脊柱侧凸有限元模型,该模型包括了T1至骶骨的所有椎体、椎间盘、韧带,同时还包括了胸廓的肋骨、肋软骨及胸骨。2、将该模型与临床仰卧位、站立位、仰卧左、右侧屈位X线片及体外生物力学实验结果相对比,验证结果显示X线片与模型符合程度高,充分说明了该模型的可靠性和有效性,为脊柱侧凸生物力学的进一步研究提供了数值化平台。第二章目的:利用上一章节所建立的脊柱侧凸有限元模型,研究不同矫形力的生物力学特性。方法:1、胸1椎体约束X、Y方向的移动,固定骨盆,限制其X、Y、Z三个方向的移动。于顶椎凸侧所对应的三根肋骨侧面均匀施加20N,40N,60N大小的力,观察矫形效果。2、限制胸1椎体约束X、Y方向的移动,固定骨盆,限制其X、Y、Z三个方向的移动。在胸1椎体上加载100N,200N,400N的撑开力,观察矫形效果。3、限制胸1椎体约束X、Y方向的移动,固定骨盆,限制其X、Y、Z三个方向的移动。在胸8、胸9椎体上加载总共大小为10N.m,20N.m,40N.m的旋转力矩,观察矫形效果。结果:1、施加20N、40N、60N的横向矫正力时,胸弯的Cobb角度由最初仰卧位的31度分别减少至26°、20°、15°,顶椎旋转角度减小了1.234°、2.501°、3.674°。2、加载100N、200N、400N撑开力后,侧弯的Cobb角度分别减少至25°、18°、13°,顶椎旋转角度减小了0.09°、0.21°、0.33°。3、在T8至T9这两个椎体加载总共大小为10N.m、20N.m、40N.m的旋转力矩后,脊柱的Cobb角度分别减少至26°、24°、25°,顶椎旋转角度减小了10.781°、18.423°、30.795°。结论:(1)利用有限元方法分析不同矫形力的生物力学特点,为临床器械矫形及支具治疗提供生物力学依据。(2)利用有限元方法研究脊柱侧凸的矫形力,为脊柱侧凸三维矫形提供了全域性和区域性的量化指标。(3)侧凸畸形的Cobb角度较小时,横向矫形力对侧凸畸形矫正效率高于撑开力。(4)三种不同矫形力对三维矫形的效率不相同:施加撑开力、横向矫形力主要起脊柱去旋转的作用,而旋转力主要起椎体去旋转的作用。第三章目的:利用已建立的脊柱侧凸模型,分析支具治疗后椎间盘凸侧、凹侧椎间盘应力分布的变化,预测支具治疗效果。方法:1、站立位下脊柱生物力学特点约束条件:固定骨盆,限制其在各个方向的活动,在椎体各个节段施加相应的重力载荷。观察并测量椎间盘应力、韧带应力分布情况,预测1年后椎体增加的高度及椎体契形病变角度。2、支具矫形效果约束条件:为达到较好的模拟佩戴支具条件下的工况,需固定骨盆,约束其X、Y、Z轴三个方向的活动,限制T3、T4的肋骨在X、Y方向的活动。施加载荷:在椎体各个节段施加相应的重力载荷,再在T8、T9、T10椎体凸侧的肋骨上施加横向力,力的大小分别为0N、10N、20N、30N、40N、60N、80N、100N。观察并计算凸侧和凹侧椎间盘平均应力变化、凸/凹应力比值,预测1年后椎体增加的高度及椎体契形病变角度。结果:1、站立位下,患者T6-T11之间的椎间盘凹侧应力值高于凸侧,凸/凹侧应力比值均小于1,T8/9椎间盘凸/凹侧应力比值最小,为0.23。2、随着施加横向矫形力的增加,T6-T11之间的椎间盘凸/凹侧应力比值也相应的增加,当施加的力达到30N时,T6/7椎间盘凸/凹侧应力比值达到了1.00,而T8/9、T9/10椎间盘凸/凹侧应力比值在施加100N力时,仍小于1。3、随着横向矫形力的增加,T6-T11之间椎体的契形病变逐渐减小,预计1年后总的椎体契形病变也呈减小趋势。其中在加载100N矫形力后,主胸弯椎体契形病变角度总和被逆转为负数。结论:(1)首次利用有限元方法研究脊柱侧凸椎间盘凸、凹侧应力值,并应用凸、凹侧应力值预测支具治疗的效果,为预测支具治疗效果提供了一种新的方法。(2)有限元方法对椎间盘凸、凹侧应力值的研究,为支具的改良设计提供了一个新的量化指标。(3)站立位下,脊柱侧凸项椎附近椎间盘应力值凹侧高于凸侧,凸/凹侧应力比值有向顶椎逐渐减小的趋势。更多还原

【Abstract】 BackgroundAdolescent idiopathic scoliosis(AIS) has a morbility of 2%～3%in teenagers,which threatens physical and mental health of teenagers seriously.And the therapic method has been improved greatly,the curative effect has raised a lot.But there are many problems that wait us for studying,in which the biomechanics study of scoliosis is the most important aspect.Spinal biomechanical research methods include animal experiment,physical experiment,cadaver experiment,and so on.The model of scoliosis had not been found in natural animals,and it is difficult to select material.And it is very difficult to get human specimen of scoliosis.With the development of computer,finite element method has been becoming a modern computing method,which can be repeated in study,and it can change any quality and quantitation,and also can provid local and internal reaction mechanismHueter-Volkmann law presumes that the growth of the bone will be suppressed when the stress adding to the bone increases,and the growth of the bone will be accelerated when the stress adding to the bone decreases.The law can explain the progression of AIS in the period of growth peak.The brace can get therapic effect through balancing the stress of convex and concave disc by exerting orthopedic force.In our research,we chose a patients of AIS with Risser sign 3 degree,whose AIS type is Lenk type IA-and PUMC typeⅡa.We construct a FEM of AIS,and research the characteristics of different orthopedic force,and also research distribution change of disc stress after brace treatment in order to predict the effect of brace therapy,which provides a quantization index for AIS biomechanical study.Part oneObjective:Construct a 3-diamensions finite element model of AIS and check the validity of the model,which provides a platform for the next study.Methods:Chose a patient with AIS,and used spiral CT to get spinal successive scanning with layer thickness of 1 millimeter.And the images were saved as a form of DICOM.Used the Mimics to form a 3-diamensions geometric model of AIS,and divided mesh in Hypermesh, and assign the mesh with specific materials attribute.Compared the model with upstanding posterior-anterior X-Ray,supine posterior-anterior X-Ray and lateral flexion X-Ray of supine posterior-anterior position.Chose T12-L2 and L3-S1 to compare with related results of biomechanics empirical study.Results:1.The Cobb’angle of upstanding posterior-anterior X-Ray,supine posterior-anterior X-Ray and lateral flexion X-Ray in left and right supine position were 40°,31°,44°,19°,and 41°,30°,40°,20°in finite element model corresponding.2.Compared the center of mass deviated from sacral middle line between X-Ray and finite element model,P＞0.10,which considered no differences between them.3.Chose T12-L2 and L3-S1 to compare with related results of biomechanics empirical study,the stiffness of the model was in the boundary of related results.Conclusions:1.Based on Dicom document with CT scanning,used software of Mimics and Hypermesh,we constructed a finite element model of AIS from T1 to sacral bone.The model included vertebral body,intervertebral discs,ligaments,costal bone,costal cartilage and sternum from T1 to sacral bone.2.Compared the model with X-Ray and related results of biomechanics,the model meet them very well,which demonstrated the reliability and validity of the model,and it provides a digital platform for the next study. Part twoObjective:To make use of the model constructed in upper chapter in researching characteristics of different orthopedic forces.Methods:1.Limitate the movement of T1 in X and Y orientation,fix the pelvis,and exert 20N,40N,60N at three costal bones in convex side of apex vertebrae,and compare the reshaping effect.2.Limitate the movement of T1 in X and Y orientation,fix the pelvis,exert longitudinal force of 100N,200N,400N at the upper surface of T1 vertebrae,and compare the reshaping effect.3.Limitate the movement of T1 in X and Y orientation,fix the pelvis,exert torque of 10N.m,20N.m,40N.m at T8 and T9,and compare the reshaping effect.Results:1.After exerting transversal force of 20N,40N and 60N,the Cobb’s degree change from 31°initially to be 26°,20°and 15°correspondingly, and the rotational angle of T9 decreased by 1.234°,2.501°,3.674°.2.After exerting longitudinal force of 100N,200N and 400N,the Cobb’s degree change from 31°initially to be 25°,18°and 13°correspondingly,and the rotational angle of T9 decreased by 0.09°、0.21°、0.33. 3.After exerting torque of 10N.m,20N.m and 40N.m in vertebraes of T8 and T9,the Cobb’s degree change from 31°initially to be 26°,24°and 22°correspondingly,and the rotational angle of T9 decreased by 10.781°、18.423°、30.795°.Conclusions:1.Analyzing biomechanical characterastics of different orthopedic force using finite element method,which provides biomechanical basis for deformity correction with instrument and brace therapy.2.Analyzing scoliotic orthopedic force using finite element method, which provides general and local quantization index for 3D correction of scoliosis.3.The reshaping effect of transversal force is much more great than longitudinal force when the Cobb’s degree is small.4.The efficiency of orthopedic forces are different:transversal force and longitudinal force perform spinal derotation function mainly,and rotary strength perform vertebral derotation function mainly.Part threeObjective:Make use of the FEM of AIS in part one to analyse distribution change of disc stress in the convex side and concave side in order to predict curative effect of brace. Methods:1.Characteristic of spinal biomechanics in standing positionConstrained condition:fix the pelvis and restrict its movement,and exert gravity load correspondingly.Measure the distribution of disc stress and ligament stress,and predict the increasing height of vertebrae and wedge angle of vertebrae after one year.2.Reshaping effect of braceConstrained condition:fix the pelvis and restrict its movement,and restrict T3 and T4 movement in X-axis and Y-axis.Loading:exert gravity load in each segment of spine correspondingly,and exert lateral force of 0N,10N,20N,30N,40N,60N, 80N,100N at three costal bones in convex side of apex vertebrae.Calculate the mean stress in convex side and concave side,and also the stress ratio between the convex side and the concave side,and predict the increasing height of vertebrae and wedge angle of vertebrae after one year.Results:1.In up standing position,the stress in concave side is higher than the convex side in the discs between T6 to T11 segment,and the stress ratio between the convex side and the concave side is smaller than one. And the ratio in the disc of T8/9 is the most smallest,which is 0.23.2.The stress ratio between the convex side and the concave side is increasing following with the increasement of orthopedic force.When the orthopedic force increases to 30N,the stress ratio between the convex side and the concave side get to 1.00 in T6/7 disc.But when the orthopedic force increases to 100N,the stress ratio between the convex side and the concave side is still smaller than one.3.With the increasing of orthopedic force,the wedge angle in T6-T11 are decreasing gradually,and the total wedge angle change predicted in one year is becoming decrease.And when the force adds up to 100N, the total wedge angle change predicted in one year becomes negative number.Conclusions:1.It is the first time we use finite element method to research the disc stress in the convex side and concave side,and use the disc stress in the convex side and concave side to predict therapeutic efficacy of the brace,which provides a new method for predicting therapeutic efficacy of the brace.2.The study of the disc stress in the convex side and concave side using finite element method provides a new quantization index for improvement of the brace.3.In standing position,the stress in the concave side is much more higher than the convex side,and the ratio of disc stress in the convex side to the concave side has a tendency of becoming small towards apex vertebrae.更多还原