枢椎棘突螺钉单侧应用联合对侧椎弓根螺钉固定的有限元分析

目的分析枢椎棘突螺钉单侧应用联合对侧椎弓根螺钉固定在寰枢和枕颈固定中的生物力学稳定性。方法构建正常枢椎解剖、椎板薄和椎动脉变异椎弓根细小3种不同解剖状态下的完整上部颈椎有限元模型作为完整模型组,然后分别模拟齿状突骨折进行寰枢固定和寰椎骨折进行枕颈固定。在寰枢固定中,比较单侧枢椎棘突螺钉+对侧椎弓根螺钉+双侧寰椎侧块螺钉固定组(棘突螺钉组)和枢椎双侧椎弓根螺钉+双侧寰椎侧块螺钉固定组(椎弓根螺钉组);在枕颈固定中,比较单侧枢椎棘突螺钉+对侧椎弓根螺钉+枕骨螺钉固定组(棘突螺钉组)和枢椎双侧椎弓根螺钉+枕骨螺钉固定组(椎弓根螺钉组)。枢椎棘突螺钉分别测试水平、斜向、垂直置钉3种不同的固定技术。模拟颈椎运动,测量枕颈的屈伸、侧屈、旋转的关节活动范围(ROM)。结果在寰枢和枕颈固定中,棘突螺钉组和椎弓根螺钉组的C1~C2屈伸、侧屈、旋转ROM均较完整模型组均明显下降。在寰枢固定中棘突螺钉组C0~C2屈伸、侧屈、旋转的ROM大于椎弓根螺钉组;在枕颈固定中,棘突螺钉组C1~C2侧屈的ROM大于椎弓根螺钉组,棘突螺钉组的C0~C2旋转的ROM大于椎弓根螺钉组。枢椎棘突螺钉分别测试水平、斜向、垂直固定间有差异,但不明显。结论在寰枢和枕颈固定中,枢椎双侧椎弓根螺钉固定和枢椎单侧棘突螺钉联合对侧椎弓根螺钉组合式固定方法均具有良好的稳定性。在寰枢固定中,相对于枢椎棘突螺钉组合式固定,枢椎双侧椎弓根螺钉固定具有更好的寰枢稳定性。在枕颈固定中,枢椎双侧椎弓根螺钉固定在侧屈和旋转活动上较枢椎棘突螺钉组合式固定稳定性更好。枢椎三种棘突螺钉置钉技术间的稳定性差异并不明显。     

经寰枢关节间隙螺钉和寰椎椎板钩内固定的力学稳定性

目的评价双侧经寰枢关节间隙螺钉和寰椎椎板钩内固定的力学稳定性。方法将6具新鲜尸体颈椎标本（包括枕骨基底部和C1-C4颈椎节段）置于1．5Nm载荷下，测量C1，2节段的三维运动范围（range of motion，ROM）。标本依Gallie内固定、双侧经寰枢关节间隙螺钉和Gallie内固定、双侧经寰枢关节间隙螺钉内固定、双侧经寰枢关节间隙螺钉和寰椎椎板钩内固定、双侧寰椎侧块螺钉和枢椎椎弓根螺钉内固定的顺序实施固定，每次固定后测量三维运动范围。结果包含经寰枢关节间隙螺钉的内固定组在旋转和侧屈方向上具有最小的ROM，其中双侧经寰枢关节间隙螺钉和寰椎椎板钩内固定组在屈伸运动方向上也具有最小的ROM。寰椎侧块螺钉和枢椎椎弓根螺钉内固定组在旋转方向上ROM大于单纯经寰枢关节间隙螺钉内固定组，但在侧屈和屈伸方向上接近经寰枢关节间隙螺钉，差异无统计学意义；其在侧屈和旋转方向上ROM均小于Gallie内固定组，差异有统计学意义。结论双侧经寰枢关节间隙螺钉和寰椎椎板钩“三点”内固定具有最强的生物力学稳定性。虽然双侧寰椎侧块螺钉和枢椎椎弓根螺钉内固定在生物力学稳定性上不及“三点”内固定，但明显优于Gallie内固定。     

寰椎一体式椎板钩与枢椎椎板钉组合应用于非对称内固定生物力学研究

目的本文报道设计一新型寰枢椎内固定组合,并在尸体标本进行生物力学试验,有一定的临床指导意义。方法将6具新鲜尸体颈椎标本置于2Nm载荷下,运用脊柱三维运动测量系统测量C1-2节段的三维运动范围(Range Of Motion,ROM),并将之进行两两对比。实验依完整组、失稳组、双侧寰椎侧块螺钉联合枢椎椎弓根螺钉内固定(Harms技术)组、寰椎侧块螺钉联合单侧枢椎椎板螺钉+对侧枢椎椎弓根螺钉固定组、一侧寰椎一体式椎板钩+枢椎椎板钉联合对侧寰椎侧块螺钉+枢椎椎弓根螺钉内固定组的顺序进行。结果失稳组ROM较完整组显著增加,内固定后ROM显著减小,三种内固定组中:寰椎侧块螺钉联合单侧枢椎椎板螺钉+对侧枢椎椎弓根螺钉固定组在旋转和侧屈方向上具有最小的ROM,双侧寰椎侧块螺钉联合枢椎椎弓根螺钉内固定组在屈伸运动方向上有最小的R0M。一侧寰椎一体式椎板钩+枢椎椎板钉联合对侧寰椎侧块螺钉+枢椎椎弓根螺钉内固定组ROM在旋转、侧屈以及屈伸方向上均较另外两组大,但差异均无统计学意义。结论寰椎一体式椎板钩与枢椎椎板钉组合非对称内固定可提供良好的生物力学稳定性。     

不同内固定手术方式治疗寰枢椎复合骨折稳定性的有限元分析

目的:比较寰枢椎椎弓根螺钉固定及枕颈融合术两种内固定方式治疗寰枢椎复合骨折的生物力学稳定性,为临床治疗寰枢椎复合骨折提供理论依据。方法:选择1例27岁健康男性志愿者,采用64排螺旋CT机扫描枕颈部(C0~C3),利用Simpleware 3.0、Geomagic 8.0、Hypermesh 10.0等软件建立C0~C3节段三维有限元(FEM/intact)模型,并与Panjabi等的结果进行对比验证。在经验证的模型基础上断裂C1前弓和后弓及切断齿状突基底部,模拟Jefferson骨折+Ⅱ型齿状突骨折的复合骨折有限元模型(FEM/fracture)。根据内固定系统的大小规格及临床手术方法在FEM/fracture上分别建立寰枢椎椎弓根螺钉固定术模型(FEM/PSF)及枕颈融合术模型(FEM/OCF)。对不同内固定模型加载前屈、后伸、侧屈、旋转工况,分析各模型在不同工况下Von Mises应力云图及各椎节活动度。结果:(1)建立的FEM/intact外观逼真,几何相似性好。各椎节的活动度与Panjabi发表的结果基本吻合。在相同条件下,FEM/fracture各个工况下的活动度均较FEM/intact明显增大,尤其是C1-C2旋转增加了43.7%,屈伸增加了72.1%。(2)两种加载内固定系统的上颈椎有限元模型与临床实际相符。FEM/PSF的C0-C1屈伸和旋转活动度较FEM/intact分别增加59.2%、68.3%;C1-C2屈伸、侧屈、旋转功能受限,分别降低92.2%、31.3%、99.6%;C2-C3屈伸、侧屈工况下活动度分别降低13.6%、0.6%,旋转工况下活动度增加0.7%。FEM/OCF中C0-C3各椎节活动度较FEM/intact均降低,其中C0-C1屈伸、侧屈、旋转工况下活动度分别降低93.8%、90.4%、90.2%;C1-C2分别降低89%、55.7%、97.4%;C2-C3分别降低92.8%、95.2%、90.5%。(3)FEM/PSF在左右旋转工况下应力值最大,为321.19MPa,主要集中在连接棒和螺钉根部。FEM/OCF在左右侧屈工况下应力值最大,为228.84MPa,主要集中在连接棒及螺钉根部。结论:寰枢椎椎弓根螺钉固定及枕颈融合两种手术方式治疗寰枢椎复合骨折均能起到早期稳定的目的,寰枢椎椎弓根螺钉固定后稳定C1-C2的同时能代偿性增加C0-C1的活动度。     

三种后路寰枢椎融合术的离体生物力学研究

目的 通过离体生物力学研究方法,比较3种后路寰枢椎融合技术的力学稳定性.方法 将8具新鲜尸体的颈椎标本(C1～4)置于1.5 Nm载荷下,测量C1、2关节的三维运动范围(ROM).每具标本依双侧经寰枢关节间隙螺钉结合Gallie内固定术、双侧经寰枢关节间隙螺钉结合寰椎椎板钩内固定术、双侧寰椎侧块螺钉结合枢椎椎弓根螺钉内固定术的顺序实施固定,每次固定后测量三维运动范围.结果 包含经寰枢关节间隙螺钉的内固定组在旋转和侧屈方向上具有最小的ROM角度,其中新型的双侧经寰枢关节间隙螺钉结合寰椎椎板钩内固定组在前屈后伸运动方向上也具有最小ROM角度.寰椎侧块螺钉结合枢椎椎弓根螺钉内固定组在旋转方向上ROM角度显著大于单独经寰枢关节螺钉内固定组,但在侧屈和前屈后伸方向上ROM角度近似于经寰枢关节间隙螺钉,差异无统计学意义.结论 双侧经寰枢关节间隙螺钉结合寰椎椎板钩内固定术具有最强的生物力学稳定性;双侧寰椎侧块螺钉结合枢椎椎弓根螺钉内固定术与双侧经寰枢关节间隙螺钉结合寰椎椎板钩内固定技术比较,具有相似的力学稳定性.     

寰椎椎弓根螺钉联合经寰枢关节螺钉内固定稳定性的生物力学研究

【摘要】 目的：评估寰椎椎弓根螺钉联合经寰枢关节螺钉固定技术的力学稳定性。方法：选取成人颈椎新鲜标本6具,解剖剔除肌肉制备上颈椎完整模型（完整组）,用生物力学测试及计算机视觉分析软件测量在1.5Nm力矩下前屈后伸、左右侧弯和左右旋转时C1-C2的活动度（ROM）;破坏寰椎前弓和侧块制备不稳模型（失稳组）,再次测量相同力矩下各运动方向C1-C2的ROM活动度。随后暴露寰枢椎置钉点,根据先后顺序置入寰椎椎弓根螺钉+枢椎椎弓根螺钉固定（C1P+C2P组）、单纯经寰枢关节螺钉固定（TA组）、寰椎椎弓根螺钉+经寰枢关节螺钉固定（C1P+TA组）,依次分别测量相同力矩下各运动方向C1-C2的ROM,比较各组C1-C2 ROM的差异。结果：失稳组相较于完整组在六个方向上有更大的ROM,两组所有方向上的ROM均有显著性差异（P<0.05）;C1P+C2P组、C1P+TA组、TA组与失稳组比较,所有方向上的ROM均有显著性减少（P<0.05）,三组间比较,前屈、后伸、左旋转和右旋转方向上的ROM存在统计学差异（P<0.05）,C1P+TA组相似文献   

寰枢椎后路动态固定系统有效性的实验研究

【摘要】 目的：测试自主设计的寰枢椎后路动态固定系统的有效性。方法：根据寰枢椎的解剖特征及常规寰枢椎后路椎弓根螺钉置钉技术,设计符合寰枢椎运动方式的新型寰枢椎后路动态固定系统,并测试其有效性。将8具成人枕颈标本（C0~C4）依次按完整状态组（A组）、寰枢椎不稳状态组（B组）、寰枢椎后路动态固定状态组（C组）及寰枢椎后路椎弓根螺钉固定状态组（D组）的顺序进行测试。在三维运动试验机（KD-101）上测试4组模型的颈椎运动范围（range of motion,ROM）,所有标本测试时施加1.50N·M力偶矩按前屈/后伸、左/右侧屈、左/右轴向旋转的顺序进行,取其均值,所得结果进行比较。结果：B组与A组在屈伸状态、侧屈状态和轴向旋转状态的ROM分别相差41%、44%、9%,差异有统计学意义（P<0.05）。C组与A组在屈伸、侧屈和轴向旋转状态的ROM分别相差8%、9%、9%,差异无统计学意义（P>0.05）;C组ROM与B组比较分别相差46%、50%、17%,差异有统计学意义（P<0.001）。D组固定后在屈伸、侧屈、轴向旋转状态的ROM与A组分别相差35%、46%、58%,差异有统计学意义（P<0.001）;与B组分别相差62%、70%、61%,差异有统计学意义（P<0.001）;与C组分别相差30%、41%、53%,差异有统计学意义（P<0.001）。结论：寰枢椎后路动态固定系统能够有效地限制寰枢椎的不稳,同时又能保留寰枢椎一定的屈伸、侧屈和旋转活动功能。     

新型寰枢椎固定组合的生物力学测试

[目的]采用尸体标本测试枢椎椎板螺钉联合新型寰椎椎板钩内固定系统的生物力学稳定性。[方法]采用6具新鲜尸体颈椎标本(C_(0～3)),分别测试完整标本模型(完整组)、寰枢椎不稳标本模型(失稳组)、双侧寰枢椎经关节螺钉联合Gallie固定植骨模型(bTFS+G组)、双侧寰枢椎经关节螺钉联合新型寰椎椎板钩固定植骨模型(bTFS+H组)、一侧寰枢椎经关节螺钉与对侧枢椎椎板螺钉联合新型寰椎椎板钩非对称固定植骨模型(非对称组),在1.5 Nm载荷下,C_(1/2)节段的前后屈伸、左右侧(P0.05)。三种内固定组中:bTFS+G固定组在前后屈伸和左右侧屈方向上具有最小的ROM,bTFS+H内固定组在轴向旋转运动方向上有最小的ROM。非对称内固定组ROM在前后屈伸、左右侧屈、轴向旋转方向上均较另外两组大,但差异均无统计学意义(P0.05)。[结论]寰枢椎经关节螺钉与对侧枢椎椎板螺钉联合新型寰椎椎板钩非对称固定植骨可提供良好的生物力学稳定性。     

寰椎椎板钩联合枢椎椎弓根螺钉内固定的力学稳定性评价

目的 评价寰椎椎板钩联合枢椎椎弓根螺钉内固定的生物力学稳定性.方法 取6具新鲜尸体颈椎标本置于1.5 N·m载荷下,测量C_(1-2)节段的三维运动范围(ROM).标本按随机顺序,依次行完整状态(完整状态组)、不稳状态(齿状突周围韧带切除,为不稳状态组)、经寰枢关节间隙螺钉联合Gallic内固定(固定A组)、寰椎椎板钩联合枢椎椎弓根螺钉内固定(固定B组)、寰枢椎椎弓根螺钉内固定(固定C组)5种状态下的三维ROM值测量.比较各组标本的屈伸、侧屈、旋转ROM值.结果 完整状态组、不稳状态组、固定A、B、C组的平均屈伸ROM值分别为17.78°、30.69°、2.25°、2.93°、2.73°,组间比较差异有统计学意义(F=216.69,P=0.000);平均侧屈ROM值分别为9.56°、17.18°、1.91°、2.30°、2.05°,组间比较差异有统计学意义(F=122.75,P=0.000);平均旋转ROM值分别为44.19°、57.30°、1.22°、2.88°、2.07°,组间比较差异有统计学意义(F=154.54,P=0.000).固定A、B、C组较完整状态组和不稳状态组各个方向的ROM值均明显减少,差异均有统计学意义(P<0.05),但固定A、B、C组之间符个方向的ROM值比较差异均无统计学意义(P>0.05).结论 寰椎椎板钩联合枢椎椎弓根螺钉内固定可提供与经寰枢关节间隙螺钉联合Gallic内固定和寰枢椎椎弓根螺钉内固定相当的力学稳定性.在以上两种方法无法实施时,可作为一种安全的替代.     

一种新型后路寰枢椎固定系统的设计及有限元分析

目的:基于影像学参数设计一种新型后路寰枢椎固定系统,运用有限元方法评价该系统固定的生物力学稳定性。方法:运用医学影像存档与通信系统测量工具对后弓发育正常且结构完整的成人寰椎CT进行解剖学参数测量,依据寰椎影像学测量参数设计出一种符合寰椎解剖结构的新型后路寰枢椎固定系统。对1例健康志愿者上颈椎进行薄层CT扫描,对其CT图片数字图像处理,进行网格划分、设置材料属性及载荷与边界条件,建立正常上颈椎有限元模型(正常模型),并与已发表文献对比验证其有效性;在正常模型基础上通过修改材料属性及去除横韧带构建寰枢椎失稳有限元模型(失稳模型),加载新型后路寰枢椎内固定系统至失稳模型上建立新型后路寰枢椎固定系统固定有限元模型(新型模型);运用Abaqus 2019对新型模型施加扭矩为1.5N·m,对该模型C0-C3节段屈伸、侧屈、旋转活动度进行计算分析,并与寰枢椎椎弓根螺钉固定有限元模型(椎弓根螺钉模型)对比。结果:设计出的新型后路寰枢椎固定系统符合寰椎的解剖结构,此系统由新型寰椎后弓钢板、连接棒及枢椎椎弓根螺钉组成。与以往文献对比,建立的正常模型验证有效。新型模型与正常模型相比减少了屈伸95.3%、侧屈92.6%、旋转99.0%的活动度,在各状态明显减少置入节段(C1-2)的活动度。有限元分析得出新型模型在屈伸、侧屈、旋转状态下C1-2节段活动度分别为1.10°、0.49°、0.59°,与椎弓根螺钉模型活动度相近;新型模型C2/3椎间盘最大应力在前屈、后伸、左侧屈、右侧屈、左旋转、右旋转状态下分别为3.71MPa、5.84MPa、3.09MPa、3.43MPa、2.65MPa、3.59MPa,与正常模型最大应力一致;新型后路寰枢椎固定系统固定的应力主要集中于枢椎椎弓根螺钉根部及连接棒。结论:新型后路寰枢椎固定系统固定具有良好的生物力学稳定性,可作为寰枢椎失稳内固定的补充方式。     

A finite element investigation of upper cervical instrumentation.

STUDY DESIGN: The finite element technique was used to predict changes in biomechanics that accompany the application of a novel instrumentation system designed for use in the upper cervical spine. OBJECTIVE: To determine alterations in joint loading, kinematics, and instrumentation stresses in the craniovertebral junction after application of a novel instrumentation system. Specifically, this design was used to assess the changes in these parameters brought about by two different cervical anchor types: C2 pedicle versus C2-C1 transarticular screws, and unilateral versus bilateral instrumentation. SUMMARY OF BACKGROUND DATA: Arthrodesis procedures can be difficult to obtain in the highly mobile craniovertebral junction. Solid fusion is most likely achieved when motion is eliminated. Biomechanical studies have shown that C1-C2 transarticular screws provide good stability in craniovertebral constructs; however, implantation of these screws is accompanied by risk of vertebral artery injury. A novel instrumentation system that can be used with transarticular screws or with C2 pedicle screws has been developed. This design also allows for unilateral or bilateral implantation. However, the authors are unaware of any reports to date on the changes in joint loading or instrumentation stresses that are associated with the choice of C2 anchor or unilateral/bilateral use. METHODS: A ligamentous, nonlinear, sliding contact, three-dimensional finite element model of the C0-C1-C2 complex and a novel instrumentation system was developed. Validation of the model has been previously reported. Finite element models representing combinations of cervical anchor type (C1-C2 transarticular screws vs. C2 pedicle screws) and unilateral versus bilateral instrumentation were evaluated. All models were subjected to compression with pure moments in either flexion, extension, or lateral bending. Kinematic reductions with respect to the intact (uninjured and without instrumentation) case caused by instrumentation use were reported. Changes in loading profiles through the right and left C0-C1 and C1-C2 facets, transverse ligament-dens, and dens-anterior ring of C1 articulations were calculated by the finite element model. Maximum von Mises stresses within the instrumentation were predicted for each model variant and loading scenario. RESULTS: Bilateral instrumentation provided greater motion reductions than the unilateral instrumentation. When used bilaterally, C2 pedicle screws approximate the kinematic reductions and instrumentation stresses (except in lateral bending) that are seen with C1-C2 transarticular screws. The finite element model predicted that the maximum stress was always in the region in which the plate transformed into the rod. CONCLUSIONS: To the best of the authors' knowledge, this is the first report of predicting changes in loading in the upper cervical spine caused by instrumentation. The most significant conclusion that can be drawn from the finite element model predictions is that C2 pedicle screw fixation provides the same relative stability and instrumentation stresses as C1-C2 transarticular screw use. C2 pedicle screws can be a good alternative to C2-C1 transarticular screws when bilateral instrumentation is applied.     

双节段后路腰椎椎体间融合术单侧椎弓根钉固定的生物力学稳定性

目的 分析对模拟双节段腰椎后路椎体间融合术(PLIF)采用单侧椎弓根钉固定(单侧固定)的生物力学稳定性.方法 将6具新鲜成人尸体腰椎标本(L2～S2)分别制备成L4～S1的PLIF模型,应用MTS 858实验机模拟产生屈伸、侧弯、轴向旋转,并按初始状态、单侧不稳、单侧不稳-单侧固定、双侧不稳-单侧固定、双侧不稳-双侧固定、双侧不稳的顺序进行测试,动态摄取记录各个节段角位移运动范围(ROM)与中性区值(NZ).结果 单侧不稳-单侧固定屈伸、侧弯、轴向旋转方向ROM值依次为2.53±1.12、4.03±2.19、2.78±1.00,NZ值依次为1.14±0.70、1.96±1.13、1.28±0.71,均显著小于初始状态(P<0.05),相比双侧不稳-双侧固定,各方向ROM与NZ值分别增加60.13%与17.52%、315.46%与243.86%、8.17%与6.20%,但差异无统计学意义(P>0.05).双侧不稳-单侧固定侧弯与旋转状态ROM与NZ值较双侧不稳-双侧固定显著增加(P<0.05).结论 单侧固定对人腰椎标本模拟双节段单侧PLIF可提供与双侧固定相似的生物力学稳定性,而对于模拟双节段双侧PLIF则单侧固定在大多数三维运动方向上不能提供足够的力学稳定性.

Abstract：

Objective To analyze the biomechanical efficacy of unilateral pedicle screw fixation on human cadaveric lumbar spine model simulated by two-level posterior lumbar interbody fusion (PLIF). Methods Six fresh-frozen adult human cadaveric lumbar spine motion segments (L2-S2) were simulated to unilateral/bilateral L4-S1 PLIF constructs augmented by unilateral/bilateral pedicle screw fixation sequentially and respectively. All configurations were tested by MTS 858 in the following sequential construct order: the intact, UI (unilateral instability), UIUF1C (unilateral instability via unilateral pedicle screw fixation plus one cage) , BIUF1C (bilateral instability via unilateral pedicle screw fixation plus one cage) , BIBF1C (bilateral instability via bilateral pedicle screw fixation plus one cage) and BI (bilateral instability without pedicle screw and cage). Each specimen was nondestructively tested in flexion/extension, lateral performed between different simulated constructs with One Way of ANOVA and Post hoc LSD tests. Results BIBF1C had the lowest ROM and NZ of L4-S1 fusion segments in all loading models, which were significantly lower than those of any uninstmmented construct (the intact, UI and BI) (P < 0. 05). In flexion/extension, lateral bending, and axial rotation, the ROM of UIUF1C was respectively 2.53 ± 1. 12, 4.03 ± 2. 19, 2. 78 ±1.00 and the NZ of UIUF1C was respectively 1.14 ±0.70, 1.96 ±1. 13, 1.28 ±0.71, which were significantly lower than those of the intact (P <0. 05). Compared to BIBF1C, the ROM and NZ were respectively increased 60.13% and 17.52% in flexion/extension, 315.46% and 243.86% in lateral bending, 8. 17% and 6. 20% in axial rotation, however, there were no significant differences between these two constructs (P > 0. 05). In lateral-bending and axial rotation, the ROM and NZ of BIUF1C were significantly higher than those of BIBF1C (P < 0. 05). In flexion/extension, the ROM and NZ of BIUF1C were higher than those of BIBF1C but there were no significant differences (P >0. 05). Compared to the intact, BIUF1C had lower ROM and NZ except for higher NZ in axial rotation, and there were significant differences only in flexion/extension (P < 0. 05). Conclusions All tested two-level unilateral fixation on simulated human cadaveric model with unilateral PLIF can achieve similar initial biomechanical stability in comparison with two-level bilateral pedicle screw fixation. However in most test modes, two-level unilateral pedicle screw fixation on simulated human cadaveric model with bilateral PLIF can not achieve enough biomechanical efficacy in comparison with two-level bilateral pedicle screw fixation.     

A Biomechanical Comparison of Three Different Posterior Fixation Constructs Used for C6–C7 Cervical Spine Immobilization: A Finite Element Study

The intralaminar screw construct has been recently introduced in C6–C7 fixation. The aim of the study is to compare the stability afforded by three different C7 posterior fixation techniques using a three-dimensional finite element model of a C6–C7 cervical spine motion segment. Finite element models representing three different cervical anchor types (C7 intralaminar screw, C7 lateral mass screw, and C7 pedicle screw) were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the three screw techniques were compared under pure moments in flexion, extension, lateral bending, and axial rotation. ROM for pedicle screw construct was less than the lateral mass screw construct and intralaminar screw construct in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in all the three screw constructs. Maximum von Mises stress in pedicle screw construct was less than the lateral mass screw construct and intralaminar screw construct in all loading modes. This study demonstrated that the pedicle screw fixation is the strongest instrumentation method for C6–C7 fixation. Pedicle screw fixation resulted in least stresses around the C7 pedicle-vertebral body complex. However, if pedicle fixation is not favorable, the laminar screw can be a better option compared to the lateral mass screw because the stress around the pedicle-vertebral body complex and ROM predicted for laminar screw construct was smaller than those of lateral mass screw construct.     

寰枢椎后路椎弓根螺钉固定的生物力学评价

目的：评价寰枢椎后路椎弓根螺钉固定的生物力学稳定性。方法：6具新鲜颈椎标本，按随机顺序，对每一标本先后行C1-C2椎弓根螺钉、Magerl螺钉、Brooks钢丝以及螺钉联合钢丝固定，在脊柱三维运动实验机上测量其三维运动范围。结果：Magerl螺钉或C1-C2椎弓根螺钉联合Brooks钢丝组成的固定系统的三维运动范围最小。C1-C2椎弓根螺钉固定的前后屈伸运动范围与Brooks钢丝固定无差异，但大于Magerl螺钉；其左右侧屈运动范围小于Brooks钢丝固定，大于Magerl螺钉；其轴向旋转角度明显小于Brooks钢丝固定，但与Magerl螺钉无统计学差异。结论：C1-C2椎弓根螺钉的三维稳定性与Magerl螺钉相当，联合Brooks钢丝固定可进一步提高其稳定性。     

Pedicle screw fixation in the cervical spine

Pedicle screw fixation of the lower cervical spine is a new technique that provides an alternative to posterior lateral mass plating. Although biomechanical studies support the use of pedicle screws to reconstruct the cervical spine, placing screws into the small cervical pedicle poses a technical challenge. Penetration of the pedicle is the primary complication associated with screw insertion in the lower cervical spine. Pedicle screw fixation at the C2 and C7 pedicles in conjunction with use of plates for occipitocervical or cervicothoracic plating is becoming an accepted technique; however, pedicle screw fixation should not be routinely used at the C3-C6 levels. It may be indicated in patients who have osteoporotic bone or when rigid internal fixation cannot be achieved by conventional techniques.     

Hangman骨折及其内固定三维有限元模型的建立

目的建立C2~4节段Hangman骨折和应用内固定技术固定骨折的三维有限元模型,探讨三维有限元方法在研究Hangman骨折治疗中的应用价值。方法选择一名成年男性志愿者进行C2~4节段CT扫描,以所得CT扫描图像为基础,利用ANSYS 6.1等有限元分析软件,建立C2~4节段颈椎三维有限元模型(包括椎体和椎弓、椎间盘、韧带成分)。结果对各组有限元模型设定边界条件后予以模拟加载后,C2、3节段:Hangman骨折加韧带椎间盘切除模型在各个方向上均较固定模型ROM增大,在屈伸运动时增大最明显。椎弓根钉固定模型在屈伸运动时ROM小于Hangman骨折模型。C2、3和C2~4钢板固定组在各个方向的ROM较其他组小,两组之间相差很小,相差最大值为0.07°。C3、4节段:C2~4钢板固定组各向ROM均较其他组明显小,而其余各组间的ROM相差不超过0.16°。在对三组固定器械的应力进行计算时,各个方向上应力大小顺序均为椎弓根钉相似文献   

下腰椎不同固定方式的生物力学对比研究

目的 观察下腰椎不同固定方式对腰椎稳定性的影响.方法 新鲜成人尸体下腰椎标本6具,测定L4/5节段屈伸、左右侧屈、左右旋转6个方向ROM和刚度值的变化,按5组顺序依次测试:A组(正常下腰椎标本组);B组(单侧椎板关节突螺钉固定+椎间单枚Cage);C组(单侧椎弓根螺钉固定+椎间单枚Cage);D组(单侧椎弓根螺钉联合对侧椎板关节突螺钉固定+椎间单枚Cage);E组(双侧椎弓根螺钉固定+椎间单枚Cage).结果 与A组比较,B组各运动状态ROM有减少,而刚度明显增加,差异有统计学意义(P＜0.05);与B组比较,C组各运动方向ROM与刚度,差异无统计学意义(P＞0.05);与C组比较,D组各运动状态ROM有减少,而刚度增加,差异有统计学意义(P＜0.05);与E组比较,D组各运动方向ROM与刚度,差异无统计学意义(P＞0.05);与E组比较,C组各运动状态ROM有增加,而刚度减少,差异有统计学意义(P＜0.05).结论 单侧椎板关节突螺钉固定并椎间融合器植骨方法提供了一定的稳定性,而单侧椎弓根螺钉联合对侧椎板关节突螺钉固定并椎间融合器植骨具有与双侧椎弓根螺钉固定相同的稳定性,临床上可根据病例的具体情况,如身高体质量指数、病变类型及病变节段稳定程度选择性地应用上述两种固定融合方法.