椎体成形在胸腰椎压缩性骨折后的三维稳定性测试

目的评估在胸腰椎骨折后椎体成形术对恢复脊柱单元即刻三维稳定性的作用。方法7具新鲜胸腰段脊柱标本。测试前屈、后伸、左侧弯、右侧弯、左旋转、右旋转的中性区（neutral zone,NZ）和运动范围（range of motion,ROM）。程序：①完整状态;②骨折后状态;③椎体成形后;④3000次循环疲劳后。结果骨折后中性区和运动范围均明显增大。椎体成形后屈伸、侧弯、旋转在NZ及ROM均明显减少。疲劳后虽然有增加,但较骨折后明显减少。运动范围在椎体成形后和损伤前完整时比较无差别。结论骨水泥椎体成形在离体常规负荷下可恢复脊柱运动单元的三维稳定性。     

低温等离子体消融术对山羊胸椎前路松解的生物力学观察

目的:比较低温等离子体消融术去除胸椎间盘和传统胸椎间盘切除术对山羊胸椎生物力学的影响,评估低温等离子体消融术前路松解的可行性和有效性.方法:将16只2～2.5月龄的健康雌性山羊随机分为低温等离子体消融组(6只)、传统胸椎间盘切除组(6只)、空白对照组(4只,其椎间盘未做任何处理),手术组动物均经前路处理中段6个胸椎间盘(T5～T11),术后处死动物,所有动物均取下完整的T4～T12胸段脊柱标本,应用TMT 858型生物力学试验机测试标本柔韧度和运动范围(ROM),包括中性区(NZ)和弹性区(EZ).结果:松解后脊柱标本的柔韧度和ROM与对照组相比均有显著增加(P<0.05);消融组左、右侧弯和左、右旋转的柔韧度与传统组比较无显著性差异(P>0.05),但前屈、后伸时两组之间有显著性差异(P<0.05);消融组后伸、左侧弯和左、右旋转的ROM与传统组比较无显著性差异(P>0.05).前屈、右侧弯时两组之间有显著性差异(P<0.05);松解组后伸,左、右侧弯和左、右旋转的NZ与对照组比较有显著性差异(P<0.05),而消融组前屈、后伸、左侧弯和左、右旋转的NZ与传统组比较无显著性差异(P>0.05),消融组右侧弯的NZ与传统组比较有显著性差异(P<0.05);消融组后伸、传统组右侧旋转的EZ与对照组比较均有显著性差异(P<0.05),而消融组的EZ与传统组比较无显著性差异(P>0.05).结论:采用低温等离子体消融术去除胸椎间盘可以获得和传统胸椎间盘切除术对胸椎前路松解相似的效果.     

改进型EdWards器械固定不稳定胸腰椎骨折的生物力学评价

目的评价改进型Edwards器械modifiedEdwardsinstrumentationMEI固定不稳定胸腰椎骨折即刻和承受周期性载荷后的稳定性,并与CCD器械相比较。方法在12具新鲜成人胸腰椎标本T9～L5的L1椎体上制备楔形骨折模型,分为两组,分别采用MEI和CCD内固定器恢复脊柱的稳定性。对固定后的脊柱施加0.5Hz的疲劳载荷共1500次,然后评价正常、损伤、固定和周期性加载后胸腰椎节段进行前屈/后伸、左/右侧弯和左/右旋转等运动时的稳定性,经脊柱三维运动测量系统测出脊柱节段的运动范围。结果1L1椎体压缩骨折后,胸腰椎在6个运动方向上均出现不稳。2MEI固定后,T12～L2节段前屈、后伸和侧弯运动的范围均小于对照组,但轴向旋转运动范围大于对照组;周期性加载后胸腰椎节段在所有方向上的运动范围均有所增加,以右侧弯最为明显P<0.01。3CCD固定后,T12～L2节段在6个方向上的运动范围均显著减小;与对照组相比,周期性加载后胸腰椎节段的运动范围也显著减小均P<0.05,但右侧弯除外。4CCD固定后,T12～L2节段左旋、疲劳后侧弯及旋转运动范围明显小于MEI固定组P<0.01或P<0.05。结论MEI固定可为脊柱前屈、后伸和侧弯运动提供即刻稳定性,但不能恢复旋转运动的稳定性;在周期性加载后,胸腰椎节段侧弯运动的稳定性丧失。而经CCD固定后,侧弯和旋转运     

单节段腰椎后部结构逐级切除对脊柱三维运动稳定性的影响

目的 观察单节段脊柱后部结构对腰椎三维运动稳定性的影响。方法 选用6具成人新鲜尸体脊柱标本腰1-骶1(L1～S1)，采用单节段逐步切除腰椎后部结构的方法，形成7种状态，通过脊柱三维运动试验机施加10N．m的载荷，使脊柱产生前屈／后仲，左／右侧屈和左／右轴向旋转运动。结果 切除脊柱的后部结构后，在脊柱的三维稳定性中，前屈及轴向旋转运动的稳定性最易受到破坏，前屈平均运动范围增加5．1度，旋转增加3．4度。结论 除小关节骨性结构及关节囊外，后部结构对维持腰椎的稳定性具有重要作用，特别是对前屈及轴向旋转运动。     

胸腰段脊柱韧带分级切断对脊柱稳定性影响实验研究

目的：研究胸腰段脊柱韧带逐级切断对脊柱节段稳定性影响的三维运动变化。方法：采用７ 具新鲜胸腰段脊柱通过脊柱三维运动试验机施加最大载荷为１０．０Ｎ．ｍ 的６ 种力偶,使脊柱产生前屈、后伸、左／右侧屈和左／右轴向旋转运动。经立体摄像计算机图像处理得到Ｔ１２ ～Ｌ１ 节段的运动范围。先对完整标本进行测量,其结果为自身对照组（Ⅰ组）。然后在Ｔ１２～Ｌ１ 节段依次切断棘上韧带（Ⅱ组）,棘间、黄韧带（Ⅲ组）,关节囊韧带（Ⅳ组）后纵韧带、椎间盘后１／３（Ⅴ组）。结果：切除棘上、棘间韧带后活动范围均有增加,但和对照组相比差异无显著性（Ｐ＞ ０．０５）。切除关节囊韧带后前屈运动和左／右旋转运动范围显著增大和对照组相比差异有显著性（Ｐ＜ ０．０５）,切除后纵韧带、椎间盘后１／３,在Ⅳ组基础上活动范略有增大和正常组相比差异有显著性（Ｐ＜ ０．０５）。结论：胸腰段脊柱关节囊韧带可提供该节段的前屈,左／右旋转运动的内在稳定性。     

合并胸腰段后凸的青少年特发性脊柱侧凸的临床研究

目的 探讨合并胸腰段后凸的青少年特发性脊柱侧凸(AIS)的临床特点和手术治疗策略. 方法对2001年1月至2007年1月收治的413例AIS患者进行回顾性分析,合并胸腰段后凸者共10例,其中男2例,女8例;年龄12～18岁,平均14.3岁.侧凸类型包括PUMC Ⅱb2型3例,Ⅱc 3型4例,Ⅱd2型1例,Ⅲb型2例.单纯后路内固定术8例,前路松解+后路内固定术2例.术前、术后及随访时摄X线片,对侧凸类型、Cobb角、顶椎旋转度、顶椎偏距、侧凸柔韧性、胸腰段后凸、冠状面及矢状面躯干偏移进行评测和分析.结果 本组患者中双弯8例,三弯2例;胸腰弯/腰弯Cobb角≥45°者7例,柔韧性指数≤70%者6例,顶椎旋转度≥Ⅱ度者9例.所有病例的融合范围均符合PUMC分型原则.手术前后平均胸弯冠状面Cobb角分别为71.7°和37.4°,平均矫正率为47.8%;手术前后平均胸腰弯/腰弯冠状面Cobb角分别为65.0°和27.8°,平均矫正率为57.2%;手术前后平均胸腰段后凸分别为35.5°和4.2°,平均矫正率为88.2%.全部病例随访12～72个月,平均23.1个月;最终随访时无躯干失平衡发生. 结论 合并胸腰段后凸的AIS一般多为双弯或三弯,胸腰弯/腰弯畸形往往比较严重,并有明显的旋转畸形.对合并胸腰段后凸的AIS,应融合胸腰弯/腰弯以防止术后发生失代偿或后凸加重, PUMC分型可以有效识别病变类型并指导融合范围的选择.     

颈椎爆裂型骨折模型的建立及其生物力学研究

[目的]建立C4颈椎爆裂骨折的实验模型,初步探讨其发生机理和气维运动变化.[方法]收集新鲜人颈椎标本(C(2-6))共6具,在脊柱三维运动测量仪上测定C(3-4)及C(4-5)节段的三维运动范围,然后在SWD-10型万能材料试验机上予以轴向垂直压缩(5mm/min),产生C4爆裂型骨折,并重复测量C(3-4)和C(4-5)节段的三维运动变化.[结果]6例标本C4均产生爆裂型骨折,骨折后C(3-4)在前屈/后伸、左/右侧弯、左/右旋转方向上的运动范围(ROM)分别增加34%/58%、116%/124%、214%/265%,中性区(NZ)分别增加185%、633%、938%;C(4-5)在前屈/后伸、左/右侧弯、左/右旋转方向上的运动范围(ROM)分别增加45%/58%、130%/133%、259%/238%,中性区(NZ)分别增加173%、816%、907%.骨折后颈椎的运动范围和中性区均有显著增加,其中以侧弯和旋转更为明显.中性区的增加比运动范围更为显著.[结论]颈椎爆裂骨折后各个方向上具有显著的急性不稳定性,其中以侧弯和旋转更为明显;在评价脊柱稳定性时,中性区比运动范围具有更高的敏感性.     

胸腰段后凸畸形影响腰椎诸节段矢状面稳定性的研究进展

胸腰段后凸畸形的病因主要有先天性脊柱畸形、胸腰段脊柱骨折、强直性脊柱炎、Scheuermann s病、老年性脊柱后凸、脊柱结核椎体破坏、椎体肿瘤、软骨发育不全等〔1、2〕,除了脊柱本身的因素外,胸腰段后凸畸形可由腹部肿瘤引起〔3〕。脊柱曲度正常时,身体重力线应通过各节段生理弯曲的交界处。胸腰段以上重心位于胸椎的前部,胸腰段后凸畸形所造成的成角的或短弧形后凸畸形使损伤平面以上躯体的重心更趋前移,必将进一步加重后凸畸形〔4〕。随着我国进入老龄化社会,胸腰段后凸畸形的患者不断增多,胸腰段后凸畸形常出现局部不稳定,脊柱支撑功能…     

单节段与双节段椎弓根螺钉固定胸腰椎单椎体骨折的生物力学比较

目的:比较单节段与双节段椎弓根螺钉固定术固定胸腰椎单椎体骨折的生物力学效果。方法:在16具新鲜小牛胸腰椎标本(T11-L3)的L1椎体上制作不完全爆裂骨折模型,分为两组,分别行单节段与双节段椎弓根螺钉固定,对固定后的标本施加扭矩为4Nm的疲劳载荷共2000次,加载频率为0.5Hz,经脊柱三维运动测量系统测量正常、损伤、固定和周期性加载后固定节段前屈/后伸、左/右侧弯和左/右旋转运动时固定节段的运动范围。结果:单节段固定组前屈、后伸、侧屈、旋转稳定指数(SPI)分别为0.78、0.80、0.92、0.83,双节段固定组SPI分别为0.88、0.89、0.95、0.85,在前屈方向单节段固定组明显小于双节段固定组(P<0.01);疲劳后,单节段固定组SPI在前屈、后伸、侧屈、旋转方向分别降低0.05、0.03、0.05、0.11,降低值均大于双节段固定组,且在旋转和侧屈方向有显著性差异(旋转:P<0.01;侧屈:P<0.05)。结论:两种术式均可重建脊柱骨折即刻稳定性,效果无明显差异。在旋转、侧屈方向,双节段椎弓根螺钉固定术抗疲劳载荷效果优于单节段固定术。     

马凡综合征伴脊柱畸形患者脊柱-骨盆矢状面的形态特征

目的:探索马凡综合征伴脊柱畸形患者脊柱-骨盆矢状面的形态特征。方法:收集以脊柱畸形来我院就诊的马凡综合征患者35例,男18例,女17例,年龄10~20岁,平均14.4±2.3岁。在站立位全脊柱侧位X线片上测量脊柱及骨盆矢状面参数,包括:(1)胸椎后凸角(thoracic kyphosis,TK),(2)胸腰段后凸角(thoracolumbar kyphosis,TL),(3)腰椎前凸角(lumbar lodorsis,LL),(4)骨盆入射角(pelvic incidence,PI),(5)骨盆倾斜角(pelvic tilt,PT),(6)骶骨倾斜角(sacral slope,SS),(7)矢状面平衡(sagittal vertical axis,SVA)。定义顶椎在T12、L1或者T12/L1椎间盘,后凸角度10°的后凸为胸腰段后凸;顶椎在L1/2椎间盘或以下椎体、椎间盘,后凸角度10°的后凸为腰椎后凸。采用Sponseller分型方法对患者脊柱矢状面形态进行分型,比较不同分型患者脊柱-骨盆矢状面形态。结果:本组患者在冠状面上以胸腰双弯(40.0%)、单胸弯(22.8%)以及三弯(20.0%)最常见,最大Cobb角43°~165°,平均75.2°±26.0°。在脊柱矢状面上,TK为-25°~73°(19.0°±24.1°),其中胸椎后凸正常者(20°≤TK≤50°)10例(28.6%);胸椎后凸增大患者(TK50°)5例(14.3%);胸椎后凸减小者(0°≤TK20°)13例(37.1%);另有7例(20.0%)患者表现为胸椎前凸。TL为-25°~73°(14.0°±19.0°);LL为-17°~70°(37.1°±23.3°);SVA为-9.0~7.2cm(-2.0±4.3cm)。15例(42.9%)患者表现为胸腰段后凸或腰椎后凸(9例ⅡA型,6例ⅡB型),5例患者表现为后凸区明显的椎体楔形变。骨盆矢状面上,PI为25°~74°(40.1°±12.7°);PT为-12°~34°(6.9°±9.6°);SS为14°~68°(33.3°±12.6°)。Sponseller分型Ⅰ型患者TK、LL、PI、SS明显大于Ⅱ型患者,而Ⅱ型患者TL明显大于Ⅰ型患者。未见腰椎滑脱现象。结论:马凡综合征伴脊柱畸形患者脊柱-骨盆矢状面形态差异较大,手术医生应该根据不同分型制定不同的手术策略。     

Stability of ventral,dorsal and combined spondylodesis in vertebral body prosthesis implantation

The purpose of this study was to evaluate the biomechanical characteristics of short-segment anterior, posterior, and combined instrumentations in lumbar spine vertebral body replacement surgery. Eight fresh frozen human cadaveric thoracolumbar spine specimens (T12-L4) were prepared for biomechanical testing. Pure moments (2.5, 5, and 7.5 Nm) of flexion-extension, left-right axial torsion, and left-right lateral bending were applied to the top vertebra in a flexibility machine and the motions of L1 vertebra with respect to L3 were recorded with an optoelectronic motion measurement system after preconditioning. One anterior, two posterior pedicle screw systems, and two combined instrumentations were tested. Load-displacement curves were recorded and neutral zone (NZ) and range of motion (ROM) were determined. The anterior instrumentation, after vertebral body replacement, showed greater motion than the intact spine, especially in axial torsion. Posterior instrumentation provided greater rigidity than the anterior instrumentation, especially in flexion-extension. The combined instrumentation provided superior rigidity in all directions compared to all other instrumentations.     

聚乙烯醇水凝胶人工髓核置入对腰椎运动影响的生物力学研究

目的：研究髓核摘除后聚乙烯醇水凝胶人工髓核置入对腰椎活动度和椎间隙高度的影响.方法：对7具新鲜成人尸体L4/5正常椎间隙、髓核摘除后和置入人工髓核后在8.0Nm扭矩下的屈伸、侧弯和旋转的活动度（ROM）、中性区（NZ）和椎间隙高度变化进行测试、比较.结果：髓核摘除后,L4/5椎间屈伸、侧弯、旋转的ROM和NZ较正常组显著增加（P＜0.05或0.01）,在0和200N的负荷下椎间隙高度较相同情况下正常组分别下降1.2mm和1.7mm;置入人工髓核后,相对于正常椎间隙,L4/5椎间屈伸、侧弯、旋转的ROM和NZ无明显差异,较髓核摘除组明显下降（P＜0.05或0.01）,在0N和200N的负荷下椎间隙高度较相同情况下髓核摘除组分别增加1.6mm和2.0mm.结论：聚乙烯醇水凝胶人工髓核置入椎间盘切除后的椎间隙可有效恢复椎间隙高度,维持腰椎节段正常的三维运动功能稳定性.     

下腰椎不同融合方法的即刻与疲劳后稳定性

目的:观察下腰椎后路不同融合方法的即刻与疲劳后稳定性。方法:9具新鲜L1~S1尸体标本分别头尾端固定,在脊柱三维运动实验机上模拟人体行屈伸、左右侧弯及旋转活动,观察L4~L5节段运动范围(ROM),随后进行各种模拟手术并安装内固定,依次测定失稳腰椎、CD内固定(CD)、CD加椎体间植骨(CD-骨块)、CD加TFC(CD-TFC)状态下L4~L5的ROM值。随后在868Mini-MTS多轴生物力学实验机上对三种术式腰椎进行1500次疲劳加载,再观察L4~L5节段的ROM。结果:①失稳腰椎与正常腰椎比较在各运动方向上ROM均明显增加;②单纯CD内固定即刻稳定性好,但疲劳后呈不稳趋势,在屈伸及左右旋转方向明显失稳;③CD-骨块、CD-TFC稳定性好,疲劳后仍能维持良好的稳定性;④CD-骨块与CD-TFC疲劳组比较在屈伸及左右侧弯时ROM无明显差异,但CD-TFC在抗旋转方向优于CD-骨块组。结论:单纯后路短节段CD内固定和/或椎体间植骨融合均能提供良好的稳定性,但单纯后路短节段CD内固定抗疲劳性差,辅以椎间支撑(植骨或TFC)可有效提高抗疲劳稳定性。     

Interbody device endplate engagement effects on motion segment biomechanics

Background ContextStand-alone nonbiologic interbody fusion devices for the lumbar spine have been used for interbody fusion since the early 1990s. However, most devices lack the stability found in clinically successful circumferential fusion constructs. Stability results from cage geometry and device/vertebral endplate interface integrity. To date, there has not been a published comparative biomechanical study specifically evaluating the effects of endplate engagement of interbody devices.PurposeLumbar motion segments implanted with three different interbody devices were tested biomechanically to compare the effects of endplate engagement on motion segment rigidity. The degree of additional effect of supplemental posterior and anterior fixation was also investigated.Study Design/SettingA cadaveric study of interbody fusion devices with varying degrees of endplate interdigitation.Outcome MeasuresImplanted motion segment range of motion (ROM), neutral zone (NZ), stiffness, and disc height.MethodsEighteen human L23 and L45 motion segments were distributed into three interbody groups (n=6 each) receiving a polymeric (polyetheretherketone) interbody spacer with small ridges; a modular interbody device with endplate spikes (InFix, Abbott Spine, Austin, TX, USA); or dual tapered threaded interbody cages (LT [Lordotic tapered] cage; Medtronic, Memphis, TN, USA). Specimens were tested intact using a 7.5-Nm flexion-extension, lateral bending, and axial torsion flexibility protocol. Testing was repeated after implantation of the interbody device, anterior plate fixation, and posterior interpedicular fixation. Radiographic measurements determined changes in disc height and intervertebral lordosis. ROM and NZ were calculated and compared using analysis of variance.ResultsThe interbody cages with endplate spikes or threads provided a statistically greater increase in disc height versus the polymer spacer (p=.01). Relative to intact, all stand-alone devices significantly reduced ROM in lateral bending by a mean 37% to 61% (p≤.001). The cages with endplate spikes or threads reduced ROM by ～50% and NZ by ～60% in flexion-extension (p≤.02). Only the cage with endplate spikes provided a statistically significant reduction in axial torsion ROM compared with the intact state (50% decrease, p<.001). Posterior fixation provided a significant reduction in ROM in all directions versus the interbody device alone (p<.001). Anterior plating decreased ROM over interbody device alone in flexion-extension and torsion but did not have additional effect on lateral bending ROM.ConclusionThe cages with endplate spikes or threads provide substantial motion segment rigidity compared with intact in bending modes. Only the cages with endplate spikes were more rigid than intact in torsion. All devices experienced increased rigidity with anterior plating and even greater rigidity with posterior fixation. It appears that the endplate engagement with spikes may be beneficial in limiting torsion, which is generally difficult with other “stand-alone” devices tested in the current and prior reports.     

腰椎新型钛合金动态内固定系统的稳定性研究

目的 检测由新型钛合金制成的非融合腰椎动态内固定系统的稳定性.方法 收集6具平均6月龄的新鲜小牛腰椎标本,在连续的5种状态下,即完整状态、失稳状态、使用DIFS Ⅰ系统(椎弓根螺钉的弹性模量为75GPa,由新型钛合金制成,其连接棒弹性模量为43GPa,直径为3.5mm)动态固定状态、使用DIFS Ⅱ系统(椎弓根螺钉的弹性模量为75GPa,由新型钛合金制成,其连接棒弹性模量为72GPa,直径为3.5mm)动态固定状态、使用对照组SINO系统(短尾"U"形椎弓根系统,连接棒直径为5.5mm)坚固固定状态,对小牛L2-6施加10N·m的纯力矩,测量标本在三维6个方向前屈、后伸、左右侧屈和左右旋转的活动范围(ROM)和中性区(NZ).结果 在失稳状态下L3,46个方向的ROM和NZ与其他各状态比较,差异均有统计学意义(P<0.05).DIFS Ⅰ系统动态同定与完整状态和SINO系统固定比较差异均无统计学意义.DIFS Ⅱ系统动态固定与完整状态各方向的ROM和NZ比较差异有统计学意义(P<0.05),DIFS Ⅱ系统动态固定与SINO系统固定的各方向ROM和NZ比较差异无统计学意义.L2,3和L4,5的各种状态下6个方向的ROM和NZ比较差异无统计学意义.结论 DIFS Ⅰ系统动态固定既可以维持腰椎的活动性,又可以获得坚强固定的稳定性;DIFS Ⅱ系统动态固定性质更接近坚强固定.     

Two in vivo surgical approaches for lumbar corpectomy using allograft and a metallic implant: a controlled clinical and biomechanical study

BACKGROUND CONTEXT: Both bone graft and metallic implants have been used in combination with the necessary anterior rod or plate instrumentation to fill the voids left by vertebral body removal, with the ultimate goal of restoring stability. One type of device that has recently been introduced is an expandable titanium telescoping cage that is designed to be used as a strut implant to fill corpectomy defects. The use of these devices has met varying success. Acceptance by surgeons and spine biomechanicians has been limited by clinical failure with subsequent loss of reduction and increase in kyphosis. In order to further improve patient care, it is critical to evaluate the use of these implants through biomechanical as well as other modes of testing. PURPOSE: To compare and contrast the spinal fusion outcome of using allograft bone versus the expandable vertebral body replacement titanium implant in a lumbar corpectomy procedure. STUDY DESIGN: Controlled biomechanical study of lumbar spine fusion using bone graft and the expandable cage in an in vivo bovine model after a 4-month postoperative healing period (n=6). ANIMAL MODEL: Twelve Holstein calves aged 4-6 months with L3 and adjacent discs removed to create a simulated lumbar corpectomy defect. OUTCOME MEASURES: Lumbar spine stability after corpectomy repair was quantified by biomechanical parameters. Strength of fusion was assessed by stiffness of ex vivo spine specimens in flexion-extension, lateral bending, and torsion obtained from biomechanical testing. Uniaxial strain at various positions on the surface of the anterior plate was measured during loading as an additional stability parameter. Loading tests were repeated after removal of the anterior instrumentation (plate and the screws). METHODS: The calves were randomly allocated to groups for corpectomy defect repair with 1) Allograft metatarsal bone and thoracolumbar spine locking plate, n=6; or 2) Expandable vertebral body replacement device, and thoracolumbar spine locking plate, n=6. After a 4-month postoperative period, anterior-posterior and lateral radiographs were taken of the spine, followed by animal sacrifice and harvesting of the lumbar spine for biomechanical and histological testing. For biomechanical testing, uniaxial strain gauges were applied to the thoracolumbar spine locking plate to measure plate deformation during loading in a custom built fixture for application of flexion-extension, lateral bending, and torsion moments in an Instron materials testing machine. These loading tests were repeated with the thoracolumbar spine locking plate removed, thereby loading solely the fused segment. RESULTS: At 4 months postoperative, the stiffness of the calf spines repaired by the metatarsal allograft and thoracolumbar spine locking plate was significantly greater than that of the spines repaired by the expandable cage and thoracolumbar spine locking plate. This finding was true for all three directions of loading (flexion-extension, left-right lateral bending, and torsion). Concordantly, the neutral zone, elastic zone, and range of motion of the spines repaired with the allograft bone were less than that of the spines repaired with the expandable cage. Greater strain values were observed from the gauges on the thoracolumbar spine locking plate of the spines using the expandable cage than the spines using allograft bone. This finding held for all gauge positions (anterior edge, anterior face, posterior edge, and posterior face at the longitudinal midpoint of the plate). After thoracolumbar spine locking plate removal and a repeat of the loading tests, a decrease in stiffness of the construct and a rise in the motion parameters were observed for both the allograft and cage groups. CONCLUSIONS: The use of allograft bone for corpectomy defect repair in the lumbar spine appears to contribute to a stiffer and perhaps more stable spine segment compared with using the expandable cage device for such a repair after a 4-month healing period in this in vivo calf model. These findings thus far are based upon the biomechanical data gathered.     

In vitro comparison of bioresorbable and titanium anterior cervical plates in the immediate postoperative condition

Bioresorbable plates have recently been used with anterior cervical discectomy and fusion (ACDF). Compared with metallic plates, bioresorbable plates provide segmental stabilization with minimal imaging artifact, eventual resorption, and increased load sharing. The objectives of the present study were to determine whether a bioresorbable plate can withstand simulated physiologic static and cyclic loading, to compare the reduction in flexibility provided by bioresorbable and titanium plates, and to quantify load sharing between the plate and spine with graft. Sixteen human cervical motion segments were tested to +/-2.5 Nm in flexion-extension, lateral bending, and axial rotation. Range of motion (ROM) was measured (1) in the intact state, (2) with ACDF without plating, (3) after addition of either a bioresorbable or titanium plate, and (4) after 500 cycles of combined flexion-extension and axial torsion. Load sharing was evaluated by applying the same fixed rotation both without and with the plate, and was calculated as the moment resisted by the uninstrumented ACDF expressed as a percentage of the plated ACDF state. No plate failures or graft migration occurred during testing. Compared with the uninstrumented ACDF, bioresorbable plates reduced mean ROM by 49% in flexion-extension and 25% in lateral bending, with very little change in torsion. Titanium plates reduced uninstrumented ACDF ROM by 69% in flexion-extension, 45% in lateral bending, and 27% in torsion. Differences between bioresorbable and titanium plates were significant in flexion-extension and lateral bending. Cyclic loading did not significantly change ROM for either plate. More moment was shared in lateral bending by the spine/graft with bioresorbable plates (78%) compared with titanium plating (63%). Bioresorbable plates contained an intervertebral graft, provided some stabilization, remained intact throughout the simulated immediate postoperative loading, and shared more load with the graft and osteoligamentous spine than titanium plates.     

经皮椎弓根螺钉内固定治疗胸腰椎骨折的生物力学及临床研究

 目的 通过生物力学测试及临床应用对经皮跨伤椎四钉内固定(万向钉固定)与开放手术四钉内固定(单向钉固定)进行比较。方法 取 12具新鲜冰冻小牛腰椎标本 L1~L5节段,随机分为单向钉固定组与万向钉固定组。制备腰椎前中柱损伤模型,比较两组在模型上的运动范围。分别应用 Sextant经皮跨伤椎四钉内固定与开放跨伤椎四钉内固定治疗无神经功能损伤的胸腰椎骨折 25例和 35例,观察其中随访超过 12个月的 11例和 18例的即时复位效果、矫正度丢失情况。结果 (1)生物力学试验院万向钉固定组在各个方向的运动范围均大于单向钉固定组,其中在前屈、后伸方向的差异有统计学意义; 单向钉固定组在前屈、后伸、侧屈方向上的稳定性较完整标本大,差异有统计学意义; 万向钉固定组在前屈、后伸方向上的稳定性与完整标本比较差异无统计学意义。(2)临床应用院两组术前、术后伤椎前缘高度、矢状位 Cobb角的组间差异均无统计学意义; 两组术后伤椎前缘高度、矢状面 Cobb角与术前比较差异均有统计学意义; 末次随访时经皮跨伤椎四钉内固定组伤椎前缘高度丢失(9.9%±5.1%)大于开放跨伤椎四钉内固定组(5.3%±6.8%)。结论 应用 Sextant系统经皮椎弓根螺钉内固定治疗无须神经减压的胸腰椎骨折较开放手术创伤小,但随访中伤椎前缘高度丢失明显。生物力学试验显示其在前屈、后伸运动方向上的强度较弱。     

Biomechanical comparison of semirigid junctional fixation techniques to prevent proximal junctional failure after thoracolumbar adult spinal deformity correction

BACKGROUND CONTEXTAdult spinal deformity patients treated operatively by long-segment instrumented spinal fusion are prone to develop proximal junctional kyphosis (PJK) and failure (PJF). A gradual transition in range of motion (ROM) at the proximal end of spinal instrumentation may reduce the incidence of PJK and PJF, however, previously evaluated techniques have not directly been compared.PURPOSETo determine the biomechanical characteristics of five different posterior spinal instrumentation techniques to achieve semirigid junctional fixation, or “topping-off,” between the rigid pedicle screw fixation (PSF) and the proximal uninstrumented spine.STUDY DESIGNBiomechanical cadaveric study.METHODSSeven fresh-frozen human cadaveric spine segments (T8–L3) were subjected to ex vivo pure moment loading in flexion-extension, lateral bending and axial rotation up to 5 Nm. The native condition, three-level PSF (T11–L2), PSF with supplemental transverse process hooks at T10 (TPH), and two sublaminar taping techniques (knotted and clamped) as one- (T10) or two-level (T9, T10) semirigid junctional fixation techniques were compared. The ROM and neutral zone (NZ) of the segments were normalized to the native condition. The linearity of the transition zones over three or four segments was determined through linear regression analysis.RESULTSAll techniques achieved a significantly reduced ROM at T10-T11 in flexion-extension and axial rotation relative to the PSF condition. Additionally, both two-level sublaminar taping techniques (CT2, KT2) had a significantly reduced ROM at T9-T10. One-level clamped sublaminar tape (CT1) had a significantly lower ROM and NZ compared with one-level knotted sublaminar tape (KT1) at T10-T11. Linear regression analysis showed the highest linear correlation between ROM and vertebral level for TPH and the lowest linear correlation for CT2.CONCLUSIONSAll studied semirigid junctional fixation techniques significantly reduced the ROM at the junctional levels and thus provide a more gradual transition than pedicle screws. TPH achieves the most linear transition over three vertebrae, whereas KT2 achieves that over four vertebrae. In contrast, CT2 effectively is a one-level semirigid junctional fixation technique with a shift in the upper rigid fixation level. Clamped sublaminar tape reduces the NZ greatly, whereas knotted sublaminar tape and TPH maintain a more physiologic NZ. Clinical validation is ultimately required to translate the biomechanics of various semirigid junctional fixation techniques into the clinical goal of reducing the incidence of proximal junctional kyphosis and failure.CLINICAL SIGNIFICANCEThe direct biomechanical comparison of multiple instrumentation techniques that aim to reduce the incidence of PJK after thoracolumbar spinal fusion surgery provides a basis upon which clinical studies could be designed. Furthermore, the data provided in this study can be used to further analyze the biomechanical effects of the studied techniques using finite element models to better predict their post-operative effectiveness.     

胸腰段僵硬性角状后凸畸形对下腰椎的影响及外科治疗

目的 探讨胸腰段僵硬性后凸畸形对腰椎的影响及其临床意义。方法 测量１４例后凸畸形截骨手术治疗前后的胸腰段后凸角和Ｌ２－５、Ｌ２～Ｓ１、Ｌ２－３、Ｌ３－４、Ｌ４－５、Ｌ５～Ｓ１的前凸角以及椎体滑移的情况,对所得结果与正常组进行对比分析。结果畸形组腰椎前凸及Ｌ２－３、Ｌ３－４、Ｌ４－５前凸角明显大于正常组,而且Ｌ２－３、Ｌ３－４前凸增加幅度更大,术后腰椎过度前凸有明显矫正,但仍然大于正常组;畸形组有