【作者】 王鹏；

【导师】 余新光；

【作者基本信息】 中国人民解放军军医进修学院 ， 外科学， 2008， 博士

【摘要】 目的:建立具有精细解剖结构并通过验证的枕寰枢复合体有限元模型,对正常情况下生物力学特性如运动学、韧带应变、关节应力等进行预测。预测齿突游离小骨、齿突缺如畸形时的生物力学改变。预测前后路减压手术操作后的生物力学改变。预测寰椎椎管环形结构完整对维持枕枢间距的意义。评估新的手术方式-寰枢关节撑开牵引复位及内固定术。研究背景:外伤、先天畸形、手术操作、肿瘤、退行性变、炎性关节病常累及枕寰枢复合体。然而,对于上述病理状态的生物力学改变及变化过程尚不清楚。尽管大量的体内、体外试验用于评估运动学、融合固定方法、脊柱标本和固定装置稳定性,但这些研究手段很难对一些力学参数尤其是结构内部的应力应变,先天畸形和进展性疾病的发病过程进行研究。无论是运动学、动力学、还是结构内部应力应变都可以通过有限元法进行研究。作为一种数学模型,有限元模型可模拟外伤、退行性变、肿瘤、手术(设计新的固定装置),也可以研究关节面角度改变对生物力学的影响。作者通过有限元法模拟和分析先天畸形,减压手术,寰椎椎管环形结构完整对维持枕枢间距的意义,以及新的手术方式-寰枢关节撑开牵引复位及内固定术。方法:根据层厚0.625mmCT扫描原始数据建立包括骨骼、韧带、关节结构的非线性、三维枕寰枢有限元模型,通过和尸体试验运动学数据对比对模型进行验证。建立齿突游离骨、齿突缺如畸形,在屈曲载荷下,和正常模型对比分析运动学,关节应力和韧带应变。建立前路减压(经口齿突切除术)和后路减压模型,同样在屈曲载荷下和正常模型对比分析上述参数改变。对建立的各种减压手术模型进行垂直方向加载,比较两侧寰椎侧块分离移位(侧方位移)和枕枢间垂直距离缩短情况。对一种新的手术方式寰枢关节撑开牵引复位及内固定术的垂直复位和水平复位进行评估,比较两种载荷类型:关节前方间隙增大超过后方(AI＞PI)和后方间隙增大超过前方(AI＜PI)。结果:本模型和尸体试验结果在绝大多数载荷方式下基本一致。屈曲载荷下,和正常模型比,齿突游离骨和齿突缺如模型寰枢间运动角度、关节应力、韧带应变和前后移位均增加明显,上述参数在寰枕间轻度减少。前路减压模型的寰枕、寰枢间运动角度、关节应力、韧带应变和前后移位都增大,但后者变化更明显;后路减压模型的寰枕、寰枢间运动角度、关节应力、韧带应变和前后移位亦都增大,但前者变化更明显。垂直加载60N时,正常模型和前、后路减压同时切除横韧带模型(AD&PD&TL)侧块水平移位距离分别是0.04mm和0.79mm,枕枢间减少的垂直距离分别是0.46mm和0.91mm。垂直加载0.9mm位移载荷时,与正常模型比,横韧带以及前弓部分切除的前路减压(Part_C1_AD&TL)侧块移位最小,然后是后路减压(PD,PD&TL),最大的是前后弓均完全切断的模型(AD&PD,AD&PD&TL)。前弓部分切除,后弓完全切除同时切除横韧带的前后路减压模型(Part_C1_AD&PD&TL)侧块移位明显小于前后弓完全切断同时切除横韧带的模型(AD&PD&TL)。寰枢侧方关节间隙增加可以获得垂直方向的复位,当关节间隙前方增加大于后方时还可获得前后方水平复位。结论:具有精细解剖结构的该枕寰枢有限元模型可以较为真实的模拟此区各种复杂运动。齿突畸形如齿突游离骨和齿突缺如患者潜在有继发寰枢脱位和神经组织受压的危险。前后路减压手术均破坏了枕寰枢复合体稳定性,且前路的稳定性更差,当寰枢正中关节已经受损时行单纯的后路减压而不行固定术是危险的。为避免发生与颅底陷入加重有关的情况,建议经口齿突切除术时尽可能保留寰椎前弓的完整性如仅切除寰椎前弓下缘。对于寰椎完整性已经破坏但局部缺乏牢固的融合固定患者,建议避免头部负重和直立姿势。寰枢侧方关节撑开牵引对于部分颅底陷入病例是有效的垂直复位手段,撑开关节同时应注意前方间隙要大于后方间隙以同时获得水平复位。更多还原

【Abstract】 Objectives.To develop and validate an anatomic detailed finite element model of the occipitoatlantoaxial(C0-C1-C2)complex and to predict biomechanical behavior including kinematics,strain in ligaments,and forces across facets.To predict alterations in biomechanical behavior of os odontoideum and aplasia of odontoid.To predict alterations in biomechanical behavior of decompression procedures including anterior and posterior ones.To predict whether ring of atlas integrity is important in maintaining normal occipitoaxial distance.To assess a novel operation procedure-atlantoaxial joint distraction and fixation.Summary of background.Pathologic occipitoatlantoaxial complex instability due to trauma,congenital anomalies,operation procedures,neoplasms, degenerative disorders,or inflammatory arthropathies is commonly seen. However,the biomechanical contribution to the development and progression of the above involvements is neither well understood nor quantified.Although a large number of biomechanical studies using in vitro and in vivo models are applied to determine the kinematic motion,to predict fusion techniques,to assess stability of the spine specimen or the spinal construct,the biomechanical parameters alterations,especially internal stresses and strains,the modeling of congenital anomalies and progressive disease states,are not easily accomplished using these methods.For FEM(finite element model),kinematics,kinetics,and internal strains and stresses are all possible subjects for study.Mathematical models such as FEM can simulate the effects of injury,degeneration,tumor and operation procedures(e.g.new spinal instrumentation without actually manufacturing it),etc.Mathematical models can also study spine behavior as a function of altering facet orientation.However,there are no studies using FEM to simulate congenital anomalies and other alterations that involve in this region. The author conducted FEM to simulate and assess congenital anomalies, decompression procedures,and the significance of maintaining ring of atlas to maintaining normal occipitoaxial distance,and a novel operation procedure, atlantoaxial joint distraction and direct lateral mass fixation.Methods.A nonlinear,three-dimensional finite-element model that includes bony-ligamentous-articular structures of the C0-C1-C2 complex was generated from 0.625 mm thick serial computed tomography scans.Validation of the model was accomplished by comparing kinematic predictions with cadaveric experimental data.Finite element models representing os odontoideum and aplasia of odontoid were evaluated by comparison the kinematics,joint loading, and strain in ligaments with normal conditions under pure flexion load.Finite element models representing anterior decompression(e.g.odontoidectomy)and posterior decompression were evaluated by comparison the above parameters also under flexion load.Models representing various types of decompression and fusion procedures were loading under axial compression,the bilateral horizontal separation of the C1 lateral masses(e.g.lateral offset)and the vertical compression of the occiput relative to axis were evaluated.Vertical and horizontal reduction of a novel operation procedure,atlantoaxial joint distraction and direct lateral mass direct lateral mass fixation,were assessed by comparison two load types:anterior increases of lateral atlantoaxial joint space exceeding posterior ones(AI＞PI)vs.posterior increases exceeding anterior ones(AI＜PI).Results.The model correlated with experimental data for most of load cases. The range of motion,joint loading,strain in ligaments and anterior-posterior translation under flexion load of both os odontoideum and aplasia of odontoid increased significant in atlaoaxial level(C1-C2)and decreased slightly in occipitoatlantal level(C1-C2).The range of motion,joint loading,strain in ligaments and anterior-posterior translation under flexion load of anterior decompression were increased both in C0-C1 and C1-C2 levels,and the later was more significant.The range of motion,joint loading,strain in ligaments and anterior-posterior translation under flexion load of posterior decompression were increased both in C0-C1 and C1-C2 levels,and the former was more significant. The C1 lateral masses spread horizontally 0.04mm in normal model and 0.79mm in decompression model after anterior and posterior arch and transverse ligament transection(AD&PD&TL),resulting in 0.46mm and 0.91mm decreased in the occipitoaxial(C0-C2)vertical distance(60N axial compression).Compare with the normal model(0.9mm vertical direction load),the minimum lateral mass offset occurred in anterior decompression with resection transverse ligament and only inferior part of anterior arch(Part_C1_AD&TL),followed by posterior decompression(PD,PD&TL),and the maximum occurred in the model after both anterior and post arches transection(AD&PD&TL,AD&PD).There was no difference between transverse ligament resection or not(AD vs.AD&TL,PD Vs. PD&TL).The lateral offset was signiticant smaller in anterior and posterior arch and transverse ligament resection with resection only inferior part of anterior arch (Part_C1_AD&PD&TL)than anterior and posterior arch and transverse ligament resection with complete resection anterior arch(AD&PD&TL). Increases of the lateral atlantoaxial(C1-C2)joint spaces obtained vertical reduction and when anterior increases of joint spaces exceeded posterior ones, horizontal reduction were attained also.Conclusions.The anatomic detailed finite element model of the occipitoatlantoaxial realistically simulates the complex kinematics of the occipitocervical region.Patients with anomalies of the odontoid process such as os odontoideum and aplasia of odontoid have potential risks of subsequent atlantoaxial dislocation and compression of neurological structures.Both anterior and posterior decompression procedures can compromise the stability of occipitoatlantoaxial complex,and the alteration is more significant in the anterior procedure,posterior decompression without fusion is dangerous when the median atlantoaxial joints have already compromised.To prevent the subsequent development diseases related to cranial settling,only resection part of C1 anterior arch(i.e.inferior or superior portion)is recommended during odontoidectomy. Before regional solid fusion,patients with loss integrity of C1 ring should prevent axial compression on head and upright posture.Lateral C1-C2 joints distraction in selected cases of basilar invagination is a reasonable surgical treatment for vertical reduction;and at the same time(i.e.distracting the joints)anterior increases of joint spaces should exceed posterior ones for horizontal reduction.更多还原