两种不同支抗快速扩弓的三维有限元分析

目的:比较分析两种不同支抗快速扩弓时颅面复合体的生物力学变化,为不同支抗快速扩弓的临床应用提供理论依据。方法:应用Mimics10.0、MSC.Marc.mentat 2005 R3等软件,建立颅面复合体三维有限元模型,加载80N的扩弓力模拟种植体支抗及牙支抗快速扩弓,分析不同加载条件下颅面复合体的应力分布和位移趋势。结果:两种支抗快速扩弓时颅面复合体应力的较大区域均分布在鼻额缝、颧颌缝、鼻上颌缝、翼腭缝,腭中缝呈楔形扩开。快速扩弓时种植体支抗产生的颅面复合体应力值和位移比牙支抗更小。结论:两种支抗扩弓均能有效扩展腭中缝,但种植体支抗快速扩弓时颅面复合体旋转更小,临床扩弓时的开牙合趋势减小。     

唇腭裂上颌复合体不同类型截骨块的抗力中心

目的 探讨唇腭裂上颌复合体不同类型截骨块的抗力中心,以便为临床牵引截骨提供理论指导.方法 采用螺旋CT扫描与三维有限元方法相结合,建立唇腭裂上颌复合体LeFort Ⅰ、Ⅱ、Ⅲ型截骨骨块及相应软组织有限元模型,分别在5个不同垂直高度加载水平向力和4个不同水平距离加载垂直向力,力值均为9.8 N,根据骨块不同观察点位移情况确定不同截骨块的抗力中心.结果 唇腭裂上颌复合体LeFort Ⅱ型截骨骨块的抗力中心前后位置在尖牙与第1双尖牙后缘之间,高度为鼻底与梨状孔中点间.LeFort Ⅲ型截骨骨块的抗力中心前后位置在第1双尖牙后缘与第1磨牙后缘之间,高度为梨状孔中点与鼻前点间.结论 唇腭裂上颌复合体不同截骨块抗力中心的确定,为唇腭裂颅面复合体牵引成骨生物力学研究奠定了基础.     

胫骨平台后外侧骨折带状钢板固定的有限元分析

[目的]研究胫骨平台后外侧骨折不同内固定模型在轴向载荷作用下骨块位移、钢板应力的分布规律,探讨符合力学原理的最佳内固定。[方法]应用有限元相关软件建立胫骨平台后外侧骨折有限元模型,包括Ⅰ、Ⅱ和Ⅲ度骨折,并分别用三种钢板固定方式,包括外侧解剖钢板、带状钢板和后侧支撑钢板。设定边界及载荷条件,模拟体重60 kg的慢跑步(1 200 N)情况下胫骨平台后外侧骨折三种固定方式下胫骨平台位移、应力分布及钢板螺钉承受应力情况。[结果]在有限元软件中构建了胫骨平台后外侧骨折钢板固定三维有限元模型;三种固定模型在轴向载荷为1 200 N时,带状钢板与外侧解剖型钢板及后方重建支撑钢板的轴向位移接近;随着载荷增大,三种固定方式下胫骨与螺钉所承受的应力值也随之增大,但各组总体位移与最大应力值均比较接近。[结论]利用有限元相关软件建立的胫骨平台后外侧骨折有限元模型及钢板内固定有限元模型能有效模拟骨折真实情况。使用带状钢板固定后外侧胫骨平台骨折能达到外侧解剖型钢板后方重建钢板固定的生物力学效果。     

滑槽钉生长棒内固定系统三维有限元的生物力学研究

[目的]建立L3～5有效的三维有限元模型,评价滑槽钉内固定系统生物力学性能.[方法]利用软件建立正常人L3～5有限元模型,对腰椎模型模拟手术过程装配滑槽钉及锁定钉内固定系统;并对模型进行赋值得到最终有限元模型.对模型施加500 N的轴向压缩及15N·m力矩的预载荷,使模型产生前屈、后伸、侧弯、旋转运动,分析滑槽钉及锁定钉内固定系统内部应力分布及大小情况,并计算运动转角度及位移.[结果](1)建立的L3～5三维有限元模型与文献报道相似,装配滑槽钉内固定系统的腰椎三维有限元模型,其运动转角度及位移与锁定钉内固定系统存在一定的差异;(2)滑槽钉组内固定系统在前屈、后伸时较锁定组所受应力值明显增大;旋转时所受应力值明显减少;滑槽钉组内固定系统的螺钉-腰椎骨界面应力值在各种工况下均有不同程度的增大.[结论]滑槽钉内固定系统与锁定钉内固定系统相比具有更好的活动范围,滑槽钉内固定系统钛棒、螺钉及螺钉-腰椎骨界面所受的最大应力值均小于其极限强度,滑槽钉内固定系统具有较好的生物力学特性.     

牙槽嵴裂隙间固定对腭裂上颌复合体内置式牵引成骨生物力学的影响

目的 探讨裂隙间固定对唇腭裂上颌复合体牵引成骨生物力学的影响.方法 采用三维有限元方法,建立唇腭裂上颌复合体LeFort Ⅰ型截骨骨块及相应软组织有限元模型,在保留牙槽嵴裂隙与裂隙两侧钛板固定两种情况下,模拟临床上内置式牵引方式,使截骨块上牵引器固位点沿牵引方向前移10 mm,比较分析其生物力学变化.结果 唇腭裂上颌复合体LeFort Ⅰ型截骨内置式牵引下,腭部出现压缩现象,而裂隙两侧钛板固定腭部压缩现象不明显.矢向位移与垂直向位移在两种工况下比较,位移方向及大小与保留裂隙的前牵引无明显差异.结论 裂隙间固定后唇腭裂上颌复合体内置式牵引成骨,可以避免腭部出现压缩现象,有生物力学指导意义.     

不同方向的中位牵引作用下颅面部的生物力学变化

目的 探讨颅面复合体在不同方向的中位前牵引作用下的生物力学变化.方法 采用三维有限元法测量以梨状孔底骨性承力,不同方向中位前牵引的生物力学变化.结果 随牵拉的角度增大,各观察点的矢向位移逐渐减小.垂直向移位由向上逐渐转为向下,前下20°～30°牵引可整体前移上颌,且各骨缝区应力一致,可避免上颌骨的逆时针旋转.结论 以梨状孔底承力骨性前牵引,牵引方向为前下20°～30°时,可有效地前移上颌复合体.     

上颌骨Le Fort-Ⅰ型截骨术坚强内固定的有限元研究

目的 研究不同接骨板在上颌骨Le Fort-Ⅰ型截骨正颌手术中固定的生物力学特性,以期找出最佳固定方法.方法 建立正颌Le Fort-Ⅰ型截骨9种内固定方式的三维有限元模型,并分为3组,计算不同固定方法在3种咬合情况下上颌骨的应力及截骨段的位移,对比不同内固定系统,不同形状接骨板,以及接骨板不同放置位置的固定效果.结果 前牙咬合时,颅、上颌复合体中应力主要循双侧鼻上颌支柱向上传递,前磨牙和磨牙咬合时,应力先自咬合处向牙槽突两侧传递,再分别循颈上颌支柱和鼻上颌支柱传递;内固定系统中螺钉与接骨板交接处及接骨板近截骨线处,为应力集中部位.前磨牙咬合时,不同固定方法截骨段位移从大到小依次为:组1 生物可吸收小型板系统(0.396 509 mm)、微型钛板(0.148 393 mm)、小型钛板(0.078 436 mm);组2 单纯鼻上颌支柱固定(0.188 791 mm)、颧上颌支柱固定(0.12l 718 mm)、双支柱固定(0.078 436 mm);组3 直形板(0.091 023 mm)、L形板(0.078 436 mm)、Y形板(0.072 450 mm)、T形板(O.065 617 ram).结论 正颌Le Fort-Ⅰ型截骨术生物可吸收接骨板固定的稳定性和强度相对钛板较小;颧上颌支柱固定效果好于鼻上颌支柱固定;不同形状的钛板在鼻上颌支柱固定的稳定性有差异.     

重建颈后方韧带复合体单、双开门椎板成形术的生物力学比较研究

目的：比较重建颈后方韧带复合体单、双开门椎板成形术后生物力学的差异。方法：新鲜山羊颈椎标本24具，随机分成3组，每组8具。A组．完整标本组，保留后方项韧带、伸肌等伸颈结构，切除前方结构；B组，在A组基础上行重建颈后方韧带复合体单开门椎板成形手术；C组，在A组基础上行重建颈后方韧带复合体双开门椎板成形术。在电子万能试验机上行生物力学实验，测试项目包括三点折弯试验、轴向拉伸试验和压缩试验，分析比较三组间的差异性。结果：三点折弯试验中标本变直时的位移、加载力，A、B、C三组间无显著性差异（P〉0．05）。拉伸试验中各拉伸负荷下与变直时的位移，A、B、C三组间无显著性差异（P〉0．05）。压缩试验中，A、B、C三组间位移无显著性差异（P〉0．05）。结论：在对抗颈椎变直和前屈的应力方面，重建颈后方韧带复合体单、双开门颈椎板成形术间无明显差别．都最大限度保留了颈后方韧带复合体的功能。     

唇腭裂上颌复合体在不同类型上颌截骨内置式牵引下生物力学研究

目的 探讨唇腭裂继发上颌发育不全应用不同类型截骨内置式牵引的生物力学变化特点.方法 采用三维有限元方法,建立唇腭裂上颌复合体Le Fort Ⅰ、Ⅱ、Ⅲ型截骨骨块及相应软组织有限元模型,分别模拟临床上新型内置牵引方式,使截骨块上牵引器固位点沿牵引方向前移10mm,比较分析其生物力学变化情况.结果 唇腭裂上颌复合体不同类型截骨内置式牵引下,Le FortⅠ型截骨腭部出现压缩现象,而Le Fort Ⅱ、Ⅲ型截骨腭部压缩现象不明显.矢向位移比较,Le FortⅢ型截骨内置式牵引可以整体前移截骨体,Le Fort Ⅰ、Ⅱ型截骨存在不同程度的旋转.垂直向位移比较Le FortⅡ型截骨出现较多的逆向旋转.结论 三维有限元仿真研究应用于内置式牵引成骨手术,可以较好地反映颌骨位移情况,为手术计划提供理论依据.     

基于有限元模型的单侧唇裂鼻畸形的生物力学分析

目的运用有限元分析的方法,对单侧唇裂鼻畸形患者鼻部进行全面的生物力学分析和研究,从生物力学角度阐述唇裂鼻畸形形成的原因,揭示单侧唇裂鼻畸形形成的力学规律,为单侧唇裂鼻畸形患者的整形外科治疗奠定生物力学理论基础。方法自2007年至2009年,共采集单侧唇裂鼻畸形患者10例,均在术前行CT和MRI扫描,MIMICS软件进行计算机三维重建,建立畸形鼻部三维有限元分析模型,确定有限元分析的边界条件,进行单侧唇裂鼻畸形的鼻部生物力学的测量和分析。结果成功获得单侧唇裂鼻畸形患者的鼻部三维重建模型。分析表明,静态下,畸形鼻部的应力分布值很小,关键应力点的应力分别为鼻中隔部0.009 35±0.002 MPa,鼻小柱底部0.005 9±0.002 1 MPa,鼻翼外侧脚0.006 81±0.001 3 MPa;位移载荷状态下,形变后的畸形鼻部拥有较大的应力分布值,关键应力点的应力分别为鼻小柱患侧25.51±3.98 MPa,鼻中隔部7.882±1.35 MPa,患侧鼻翼8.184±1.58 MPa。结论鼻小柱患侧是畸形整复的力学关键部位,其次是患侧塌陷鼻翼;鼻中隔应力的集中,提示了鼻中隔部位整复的重要性,其整复和固定可能是单侧唇裂鼻畸形整复的重要内容。     

Treatment of thoracolumbar fracture with pedicle screws at injury level: a biomechanical study based on three-dimensional finite element analysis

The aim of this study was to investigate the biomechanical mechanisms of treatment of thoracolumbar compression fracture with pedicle screws at injury level based on a three-dimensional finite element method. We constructed one three-dimensional finite element model of T11-L1 in a patient with a compression fracture of the T12 vertebral body(anterior edges of vertebral body were compressed to 1/2, and kyphosis Cobb angle was 18.6°) fixed by four pedicle screws and another model fixed by six pedicle screws at the injured vertebrae, and then assigned different forces to the two models to account for axial compression, flexion, extension, left lateral bending, and rightward axial rotation by Ansys software. After different loading forces were applied to the models, we recorded stress measurements on the vertebral pedicle screws, as well as the maximum displacement of T11. The stress distribution suggested that stress concentration was appreciable at the root of the pedicle screws under different loading modalities. Under axial compression, flexion, extension, left lateral bending, and rightward axial rotation load, the stress for the superior screw was significantly greater than the stress for the inferior screw (P < 0.05). The stress in the six pedicle screw fixation model was significantly decreased compared to the four screw interbody fusion model (P < 0.05), but the maximum displacement of T11 between two models under different loadings was not statistically different. The use of pedicle screws at injured vertebral bodies may optimize internal fixation load and reduce the incidence of broken screws.     

螺钉固定与Tight-rope固定治疗下胫腓前联合损伤的初步有限元分析

目的 :建立下胫腓前联合损伤(anterior inferior tibiofibular syndesmosis injuries,AITSI)螺钉固定及Tightrope固定(TR)模型,比较其受力及位移情况,为临床诊治提供依据。方法 :选取1例正常人的踝关节CT图像建立3D模型。然后建立AITSI损伤模型,对损伤模型置入螺钉得到螺钉固定模型,使用Tight-rope固定得到TR模型。分析各模型单脚站立时的中立位、踝关节内旋以及外旋3种受力情况,观察胫腓骨及距骨关节面应力变化,以及胫腓骨远端位移情况。结果:AITSI导致胫腓骨及距骨关节面受力增加,胫腓骨位移增加。使用螺钉固定及TR均能有效减少AITSI导致的胫腓骨远端过度位移,但在螺钉固定模型中,胫腓骨位移明显小于正常模型,且胫腓骨远端及距骨关节面受力增大,螺钉受力集中。螺钉固定模型中的胫骨及腓骨最大受力为TR模型的1.3倍以上,距骨关节面接触力为1.8倍,螺钉固定模型中下胫腓前韧带胫骨附着点位移约为正常模型的0.6倍,而TR模型中该数据约为正常模型的1.1倍,但TR对于腓骨位移控制欠佳。结论:严重的下胫腓前联合损伤将改变踝关节受力及位移情况,应该行内固定治疗。下胫腓联合螺钉及TR都能有效地治疗下胫腓前联合分离,Tight-rope固定相较于螺钉固定在骨骼受力、踝关节微动及内固定物断裂方面具有优势,但存在腓骨旋转控制欠佳的劣势。伴有Weber C型踝关节骨折以及肥胖的患者更适合螺钉固定。     

Midfacial fractures: importance of angle of impact to horizontal craniofacial buttresses

The complex nature of midfacial fractures is a result of the interaction of impact forces and inherent resistance of the facial bones to displacement. Analysis of fractures created in cadavers shows that impact forces angled obliquely to the horizontal craniofacial buttresses cause LeFort III fractures with inferior and posterior displacement of the midface. Forces directed head-on to the buttresses cause LeFort II-I fractures with inferior rotation of the midface around the lower ends of the pterygoid plates. It appears that the point of impact is of lesser importance in creating midfacial fractures than is the angle of impact in relation to the horizontal craniofacial buttresses. This may explain why victims of equal impact forces at the same level on the face suffer widely varying injuries.     

A clinical and stress radiographical follow-up investigation after Jones' operation for replacing the anterior cruciate ligament

Measurements have been made on knee radiographs exposed during stress displacement by controlled hydraulic forces using a specially designed apparatus. This accurately records the amount of anterior and posterior tibial displacement (drawer sign) and the degree of medial and lateral collateral ligament laxity on radiographs. The findings in 25 patients have been analysed following the Jones' procedure for the repair of the anterior cruciate ligaments.The operative results were judged to be completely successful in 72 per cent of patients and the value of stress radiographic measurements is discussed.     

Three-dimensional finite element analysis of lumbar vertebra loaded by static stress and its biomechanical significance

To explore the mechanical behavioroflum-bar spine loaded by stress and provide the mechanical ba-sis for clinical analysis and judgement of lumbar spine frac-tare classification, mechanical distribution and static stress. Methods: By means of computer simulation method, the constructed lumbar spine three-dimensional model was introduced into three-dimensional finite element analysis by software Ansys 7.0. The lumbar spine mechanical be-havior in different parts of the stress loading were calculated. Impact load is 0-8000 N. The peak value was 8000 N. The loading time is 0-40 minutes. The values of the main stress, stress distribution and the lumbar spine unit displacement in the direction of main stress were analyzed. Results: The lumbar spine model was divided into a total of 121 239 nodes, 112 491 units. It could objectively reflect the true anatomy of lumbar spine and its biomechani-cal behavior and obtain the end-plate images under differ-ent stress. The stress distribution on the lumbar interverte-bral disc (L<,3>-L<,4>) under the axial, lateral flexion and extension stress, and the displacement trace of the corresponding pro-cessus articularis were analyzed. Conclusion: It is helpful to analyze the stress distribu-tion of lumbar spine and units displacement in static stress loading in the clinical research of lumbar spine injury and the distribution of internal stress.     

Three-dimensional finite element analysis of lumbar vertebra loaded by static stress and its biomechanical significance

To explore the mechanical behavioroflum-bar spine loaded by stress and provide the mechanical ba-sis for clinical analysis and judgement of lumbar spine frac-tare classification, mechanical distribution and static stress. Methods: By means of computer simulation method, the constructed lumbar spine three-dimensional model was introduced into three-dimensional finite element analysis by software Ansys 7.0. The lumbar spine mechanical be-havior in different parts of the stress loading were calculated. Impact load is 0-8000 N. The peak value was 8000 N. The loading time is 0-40 minutes. The values of the main stress, stress distribution and the lumbar spine unit displacement in the direction of main stress were analyzed. Results: The lumbar spine model was divided into a total of 121 239 nodes, 112 491 units. It could objectively reflect the true anatomy of lumbar spine and its biomechani-cal behavior and obtain the end-plate images under differ-ent stress. The stress distribution on the lumbar interverte-bral disc (L<,3>-L<,4>) under the axial, lateral flexion and extension stress, and the displacement trace of the corresponding pro-cessus articularis were analyzed. Conclusion: It is helpful to analyze the stress distribu-tion of lumbar spine and units displacement in static stress loading in the clinical research of lumbar spine injury and the distribution of internal stress.     

Three-dimensional finite element analysis of lumbar vertebra loaded by static stress and its biomechanical significance

To explore the mechanical behavioroflum-bar spine loaded by stress and provide the mechanical ba-sis for clinical analysis and judgement of lumbar spine frac-tare classification, mechanical distribution and static stress. Methods: By means of computer simulation method, the constructed lumbar spine three-dimensional model was introduced into three-dimensional finite element analysis by software Ansys 7.0. The lumbar spine mechanical be-havior in different parts of the stress loading were calculated. Impact load is 0-8000 N. The peak value was 8000 N. The loading time is 0-40 minutes. The values of the main stress, stress distribution and the lumbar spine unit displacement in the direction of main stress were analyzed. Results: The lumbar spine model was divided into a total of 121 239 nodes, 112 491 units. It could objectively reflect the true anatomy of lumbar spine and its biomechani-cal behavior and obtain the end-plate images under differ-ent stress. The stress distribution on the lumbar interverte-bral disc (L<,3>-L<,4>) under the axial, lateral flexion and extension stress, and the displacement trace of the corresponding pro-cessus articularis were analyzed. Conclusion: It is helpful to analyze the stress distribu-tion of lumbar spine and units displacement in static stress loading in the clinical research of lumbar spine injury and the distribution of internal stress.     

Three-dimensional finite element analysis of lumbar vertebra loaded by static stress and its biomechanical significance

To explore the mechanical behavioroflum-bar spine loaded by stress and provide the mechanical ba-sis for clinical analysis and judgement of lumbar spine frac-tare classification, mechanical distribution and static stress. Methods: By means of computer simulation method, the constructed lumbar spine three-dimensional model was introduced into three-dimensional finite element analysis by software Ansys 7.0. The lumbar spine mechanical be-havior in different parts of the stress loading were calculated. Impact load is 0-8000 N. The peak value was 8000 N. The loading time is 0-40 minutes. The values of the main stress, stress distribution and the lumbar spine unit displacement in the direction of main stress were analyzed. Results: The lumbar spine model was divided into a total of 121 239 nodes, 112 491 units. It could objectively reflect the true anatomy of lumbar spine and its biomechani-cal behavior and obtain the end-plate images under differ-ent stress. The stress distribution on the lumbar interverte-bral disc (L<,3>-L<,4>) under the axial, lateral flexion and extension stress, and the displacement trace of the corresponding pro-cessus articularis were analyzed. Conclusion: It is helpful to analyze the stress distribu-tion of lumbar spine and units displacement in static stress loading in the clinical research of lumbar spine injury and the distribution of internal stress.     

Three-dimensional finite element analysis of lumbar vertebra loaded by static stress and its biomechanical significance

To explore the mechanical behavioroflum-bar spine loaded by stress and provide the mechanical ba-sis for clinical analysis and judgement of lumbar spine frac-tare classification, mechanical distribution and static stress. Methods: By means of computer simulation method, the constructed lumbar spine three-dimensional model was introduced into three-dimensional finite element analysis by software Ansys 7.0. The lumbar spine mechanical be-havior in different parts of the stress loading were calculated. Impact load is 0-8000 N. The peak value was 8000 N. The loading time is 0-40 minutes. The values of the main stress, stress distribution and the lumbar spine unit displacement in the direction of main stress were analyzed. Results: The lumbar spine model was divided into a total of 121 239 nodes, 112 491 units. It could objectively reflect the true anatomy of lumbar spine and its biomechani-cal behavior and obtain the end-plate images under differ-ent stress. The stress distribution on the lumbar interverte-bral disc (L<,3>-L<,4>) under the axial, lateral flexion and extension stress, and the displacement trace of the corresponding pro-cessus articularis were analyzed. Conclusion: It is helpful to analyze the stress distribu-tion of lumbar spine and units displacement in static stress loading in the clinical research of lumbar spine injury and the distribution of internal stress.