两种前路减压融合术治疗颈椎间盘突出症的比较

目的对前路颈椎间盘切除减压的碳纤维椎间融合器(cage)植入术与自体髂骨块植骨加钛板固定术治疗单节段颈椎间盘突出症(CDH)进行临床疗效及影像学评估。方法需要手术治疗的单节段CDH患者60例,其中前路减压cage植入术31例,自体髂骨块植骨加钛板固定术29例。术前、术后及随访期间摄X线片,比较两组病例的手术时间、术中出血量、术后并发症、症状改善率、融合时间、融合率、融合节段椎体间高度的维持情况。结果cage植入术较自体髂骨块植骨加钛板固定术手术时间短,出血少(P<0.01)。两组融合节段椎体间高度较术前均明显改善(P<0.01)。两组间症状改善率、融合率无统计学意义(P>0.05)。cage植入术较自体髂骨块植骨加钛板固定术并发症少。结论cage植入术和自体髂骨块植骨加钛板固定术都是前路减压治疗单节段CDH的重要而有效的方法。而cage植入术在减小手术创伤的同时,可以获得同样的临床效果,是治疗单节段CDH理想的术式之一。     

可生物降解聚-DL-乳酸腰椎间融合器的设计及生物力学研究

目的:探讨矩形和圆形两种可生物降解材料制成的腰椎间融合器的生物力学特性。方法:应用可生物降解聚-DL-乳酸材料制成两种腰椎间融合器,矩形融合器前高后低,四壁上下方均呈齿状,内外侧壁上有数个小孔;圆形融合器,圆柱状中空,壁外面有深螺纹,螺纹的凹槽内开有数个小孔。依次在以下六种L4～L5节段新鲜牛标本模型上进行生物力学测试:(1)正常组(完整节段标本模型);(2)单纯椎间盘摘除模型组;(3)椎间髂骨块植入组(植骨块为牛髂骨块制成矩形骨块);(4)椎间置入钛矩形融合器组;(5)椎间置入圆形融合器组(圆形组);(6)椎间置入矩形融合器组(矩形组)。每组均进行前屈、后伸、左右侧弯及左右旋转情况下椎体位移测定。对圆形和矩形融合器在离体装载骨和未装载骨的状态下进行压缩载荷实验。结果:生物力学测试结果表明,与正常组活动范围比较,圆形组背伸时和矩形组左侧弯时活动度有显著性差异(P<0.05);与髂骨植骨组比较,圆形组在背伸时有显著统计学差别(P<0.05),矩形组各方向没有统计学差别(P>0.05);圆形组与矩形组之间比较,圆形组背伸时不稳定;与其他各组间比较,钛cage组各方向运动范围均减小,有明显统计学差异(P<0.05)。矩形和圆形融合器未装载骨组最大压缩载荷分别为8000±215N、900±118N,装载骨组最大压缩载荷分别为8300±223N,1000±95N。结论:聚-DL-乳酸生物降解材料制成的腰椎间融合器能够满足腰椎生物力学稳定性要求,且矩形融合器在性能上优于圆形融合器。     

碳纳米管/羟基磷灰石/聚乳酸椎间融合器力学研究

目的 观察碳纳米管(CNTs)、羟基磷灰石(HA)和聚乳酸(PLLA)制成的增强可吸收椎间融合器力学性能.方法 将形状相同的HA/PLLA cage和CNTs/HA/PLLA椎间融合器分成a、b两组,每组12枚,4枚直接压缩为初始抗压缩力,其余植入山羊体内3、6个月后压缩.结果 A组三个不同时间的压缩力分别为:(6.54±0.36)、(4.71±0.28)、(4.12±0.17)kN;B组(8.45±0.85)、(6.76±0.72)、(6.47±0.45)KN.B组椎间融合器在各个不同时间的抗压缩力较A组大,差异有统计学意义(P<0.05). 结论 CNTs/HA/PLLA 椎间融合器有较强的初始力学强度,在动物体内是一种理想的腰椎融合器.     

髂骨钉置入深度对腰椎-骨盆重建结构的生物力学影响

目的 比较髂骨长钉和短钉对腰椎-骨盆重建结构的生物力学影响.方法 7具成年防腐尸体L3-骨盆标本用于实验.使用脊柱椎弓根钉后路系统对L4-S1椎间活动度进行固定,并将这一状态定义为骶髂关节完整状态.完整状态测试后,将骶骨全部切除,联合髂骨钉行L4-L5-骨盆的稳定重建.根据髂骨钉置入长度顺序分为短钉组和长钉组.其中短钉长度定义为过坐骨切迹水平2 mm,长钉长度定义为穿透髂前下棘前方皮质2 mm.在858型MTS材料实验机上,给标本施加800N轴向压缩和7 Nm轴向旋转载荷后,行髂骨钉轴向拔出实验,记录压缩和旋转刚度、最大拔出力,并加以分析.结果 髂骨短钉和长钉的置入长度分别为(70±2)mm和(138±4)mm.髂骨短钉和长钉的重建结构,在压缩实验中分别获得脊柱.骨盆间初始刚度的53.3%±13.6%和57.6%±16.2%;在旋转实验中,分别恢复脊柱-骨盆间初始刚度的55.1%±11.9%和62.5%±9.2%;长钉和短钉结构间的压缩和旋转刚度均无显著差异(P>0.05);但是,两者的轴向压缩及旋转刚度均显著低于完整状态组(P<0.05).髂骨长钉的最大拔出力显著高于髂骨短钉(P<0.05).结论 在生理载荷下,髂骨短钉的脊柱-骨盆重建结构可获得与髂骨长钉同等的力学稳定性;髂骨短钉的置入深度仅为长钉的一半,可降低置入的风险.但是,无论髂骨长钉或短钉的脊柱.骨盆重建装置均难以恢复局部的初始稳定性.     

帽式颈椎椎间融合器的生物力学性能研究

目的：测试自行研制的帽式颈椎椎间融合器(HCIFC)的生物力学性能，探讨其用于颈椎椎间融合的可行性。方法：48个羊颈椎标本随机分为6组，A组，完整颈椎节段；B组，自体三面皮质髂骨；C组，Harms cage；D组，Syncage C；E组，Carhon cage；F组，HCIFC。除A组外均完全切除C3／4椎间盘后置入以上颈椎内置物，进行生物力学测定．计算出各组平均刚度及体积相关刚度，并行统计学比较。结果：置入HCIFC后颈椎屈曲刚度显著增大，而伸展、侧屈和轴向旋转刚度无变化；Syncage C在各方向上的刚度均最大，HCIFC与Carboncage相似；HCIFC在屈曲、伸展和侧屈刚度上小于Harms cage，而轴向旋转刚度显著大于Harms cage。与移植的三面皮质髂骨相比，所有cage在体积相关刚度上均有显著增加。Harms cage在各个方向上的体积相关刚度显著大于其它cage，其次为Syncage C、HCIFC及Carbon cage。结论：HCIFC可为颈椎椎间融合提供足够的初始生物力学稳定性．     

颈椎前路不同术式对颈椎术后即刻稳定性的影响

目的评价颈椎前路单节段椎间盘髓核切除术后,颈椎间融合器(cage)植入和颈椎间植骨加颈前路钛板内固定的稳定性。方法取8具山羊颈椎标本(C2~C7),先后制成:C4/C5椎间盘髓核切除、C4/C5Solis颈椎间融合器(cage)植入、C4/C5椎间植骨加颈前路钛板内固定模型。在非破坏方式下依次检测和评价颈椎在前屈、后伸、左侧弯方向的载荷及移位情况,计算位移-载荷均值并绘图比较。结果C4/C5椎间盘髓核切除后颈椎的前屈运动增加40%(P<0.05),后伸运动增加31%(P<0.05),侧弯运动增加32%(P<0.05);C4/C5Solis颈椎融合器(cage)植入和C4/C5椎间植骨加颈前路钛板内固定后各方向运动均明显减少,增强了这三个方向上的稳定性。结论在单节段颈椎前路手术时,椎间植骨加颈前路钛板内固定和Solis颈椎间融合器(cage)植入均能够提供良好的颈椎稳定性,但后者有利于减少术后并发症,故基本可以替代钛板内固定方法。     

髂骨不同置钉方式在腰-髂重建结构中稳定性的生物力学研究

目的 评价髂骨单枚短钉、单枚长钉和双枚短钉技术对腰-髂固定结构稳定性的生物力学影响.方法 7具成人新鲜尸体L_(2-)骨盆标本用于实验.于L_(3-5)间行椎弓根钉固定,并将该结构定义为本研究的完整状态.完整状念测试后,制作骶骨全切的失稳模型,并进行三种髂骨钉技术的L_(3-)髂骨间钉-棒稳定重建,A组:双侧单枚髂骨短钉;B组:双侧单枚髂骨长钉;C组:双侧双枚髂骨短钉.三种髂骨置钉技术均在同一标本上按随机顺序建立,短钉和长钉的长度分别为70 mm和130 mm.在MTS材料实验机上,给标本施加800 N压缩和7 N·m扭转载荷,记录L_(3-)髂骨间的结构刚度并比较.结果 A、B、C组的结构压缩刚度分别是完整状态的73%、76%和108%,A组与B组间差异无统计学意义(P>0.05),然而A和B组的结构压缩刚度低于完整状态和C组,差异有统计学意义(P<0.05). A、B、C组的结构扭转刚度分别占初始状态的72%、79%和109%,A、B两组间、完整状态与C组间差异均无统计学意义(P>0.05);但是,A、B组的结构扭转刚度低于完整状态和C组,差异有统计学意义(P<0.05).结论骶骨完全切除后,单枚髂骨长钉难以恢复局部的初始稳定性,双侧双枚髂骨短钉在抗压缩和扭转方面均显著高于双侧单枚髂骨钉结构,并且可获得与初始状态同等的稳定性.     

新型后路腰椎椎间融合器的研制和动物实验研究

目的研制一种新型镍钛形状记忆合金腰椎椎体间融合器,通过动物实验了解其生物力学和组织学性能。方法本研究分为三个步骤。第一步将12个绵羊腰椎功能单位随机分成四组,每组3个,分别为对照组、髂骨植骨组(IG组)、interfix-lumbarcage组(cage组)和镍钛融合器组(NT组),进行生物力学测试,并检测镍钛融合器的力学性能;第二步将15只成年绵羊随机分为对照组、Interfix-lum-barcage组(cage组)和镍钛融合器组(NT组),每组5只,术后定期摄X线片了解椎间隙高度变化及融合进程;第三步将上述动物在术后6个月处死进行组织学观察以了解融合情况。所有数据采用统计学分析软件处理。结果对照组和髂骨植骨组与cage组和NT组在腰椎强度和轴向刚度方面相比,差异均有统计学意义(P<0.05)。镍钛融合器的最大破坏载荷可达11200N,安全系数达到1.2以上。cage组和NT组手术6个月时手术节段高度分别丧失16%和16.5%,但仍高于正常椎间隙高度(P<0.05)。光镜下可见新生骨小梁与宿主骨小梁发生连接。结论镍钛融合器的力学性能良好,可以作为腰椎椎间融合装置应用于临床。     

髂骨双钉在腰-髂重建结构中的生物力学优势

目的 评价髂骨单钉与髂骨双钉技术对腰-髂重建结构稳定性的影响.方法 7具成人新鲜尸体L2-骨盆标本,于L3-L5行椎弓根钉固定,将该结构定义为完整状态.对完整状态进行测试后制作骶骨全切失稳模型,每一标本均应用四种髂骨钉技术行L3-髂骨钉-棒稳定重建:A组,髂骨单枚短钉;B组,髂骨单枚长钉;C组,置入髂骨上、下柱的髂骨双枚短钉;D组,置入髂骨下柱的髂骨双枚短钉.髂骨钉的安装及测试顺序随机产生.在MTS材料试验机上,对标本施加800 N压缩和7 N·m扭转载荷,记录L3-髂骨的结构刚度.结果 (1)轴向压缩下,四组的压缩刚度依次为完整状态的73%、76%、98%和112%,A组和B组低于完整状态及C组和D组(P<0.05).其中A组与B组差异无统计学意义,D组与C组差异有统计学意义(P<0.05).(2)在扭转测试中,四组的扭转刚度依次为完整状态的72%、79%、105%和109%,A组和B组低于其他三组(P<0.05).其中A组与B组,完整状态、C组与D组间的差异无统计学意义.结论 对骶骨完全切除所导致的失稳,单枚髂骨短钉与长钉均难以恢复局部的初始稳定性;而双枚髂骨短钉在抗压缩与抗扭转能力方面均高于单枚髂骨钉,可获得与初始状态等同的稳定性.     

碳纤维椎间融合器在单节段颈椎间盘突出症中的应用及近期疗效观察

目的探讨保留终板的颈前路椎间盘切除减压、碳纤维椎间融合器(cage)植入治疗单节段颈椎间盘突出症(CDH)的短期疗效。方法对28例单节段CDH患者行颈前路椎间盘切除减压、保留终板、碳纤维cage植骨融合术,术前、术后1周、3个月、6个月、1年进行JOA评分、摄X线片,观察植骨融合率、椎间高度、Cobb角及功能恢复情况。结果24例获得随访,平均随访13.2月。植骨融合率100%,平均融合时间3.4月。椎间高度、Cobb角维持满意。症状改善率75%。本组病例未见脊髓、神经损伤及cage移位、下沉,1例髂骨供骨区短期疼痛。结论碳纤维cage能有效恢复和维持椎间高度和颈椎生理弧度,融合率高,近期疗效满意。     

颈椎椎间融合器融合效果的在体动物研究

目的在活体山羊颈椎上比较三面皮质自体骨、垂直圆柱体Harmscage及方盒形Carboncage的椎间融合效果。方法取24只成年雄性山羊,随机分为三组:自体骨组、Harmscage组及Car-boncage组。所有动物均行C3-4椎间盘切除术并分别植入以上内植物。于术前、术后即刻及术后1、2、4、8、12周摄颈椎正侧位X线片,于侧位X线片上测量平均椎间高度、椎间角及前凸角;术后12周处死动物,取C3,4节段标本进行组织学评估。结果术后1周Carboncage组的平均椎间高度、椎间角及前凸角大于Harmscage组和自体骨组(P<0.05);术后12周两个cage组的平均椎间高度、椎间角及前凸角均大于自体骨组,差异有统计学意义(P<0.05)。术后12周依据融合分级标准对三组进行影像学评估,和自体骨组比较,两个cage组的骨融合效果略好,但无统计学意义;组织形态学亦发现两个cage组的椎间融合效果较好,但与自体骨组比较差异无统计学意义。垂直圆柱体Harmscage中形成的新生骨量多于方盒形Carboncage。结论方盒形Carboncage具有良好的椎间支撑能力,而垂直圆柱体Harmscage的椎间融合效果更好。     

In vivo experimental study of hat type cervical intervertebral fusion cage (HCIFC)

The purpose of this study was to compare the characteristics of interbody fusion achieved using the hat type cervical intervertebral fusion cage (HCIFC) with those of an autologous tricortical iliac crest graft, Harms cage and the carbon cage in a goat cervical spine model. Thirty-two goats underwent C3-4 discectomy and fusion. They were subdivided into four groups of eight goats each: group 1, autologous tricortical iliac crest bone graft; group 2, Harms cage filled with autologous iliac crest graft; group 3, carbon cage filled with autologous iliac bone; and group 4, HCIFC filled with autologous iliac graft. Radiography was performed pre- and postoperatively and after one, two, four, eight and 12 weeks. At the same time points, disc space height, intervertebral angle, and lordosis angle were measured. After 12 weeks, the goats were killed and fusion sites were harvested. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine the stiffness and range of motion. All cervical fusion specimens underwent histomorphological analyses. One week after operation, the disc space height (DSH), intervertebral angle (IVA) and lordosis angle (LA) of HCIFC and carbon cage were statistically greater than those of autologous iliac bone graft and Harms cage. Significantly higher values for DSH, IVA and LA were shown in cage-treated goats than in those that received bone graft over a 12-week period. The stiffness of Harms cage in axial rotation and lateral bending were statistically greater than that of other groups. Radiographic and histomorphological evaluation showed better fusion results in the cage groups than in the autologous bone group. HCIFC can provide a good intervertebral distractability and sufficient biomechanical stability for cervical fusion.     

Subsidence resulting from simulated postoperative neck movements: an in vitro investigation with a new cervical fusion cage

STUDY DESIGN: A biomechanical in vitro subsidence test of different cervical interbody fusion devices was performed using a new testing protocol that simulates physiologic conditions. OBJECTIVES: To investigate the effect of simulated postoperative neck movements on the subsidence of the new WING cervical interbody fusion cage in comparison with two other cages and bone cement. SUMMARY OF BACKGROUND DATA: Cervical interbody fusion cages sometimes cause complications because of subsidence into the adjacent vertebrae with collapse of the intervertebral space. Complications such as cage dislocation or nonunion with instability also have been reported. To prevent such complications, the new WING cervical interbody fusion cage (Medinorm AG, Quierschied, Germany) has been developed. Its area of contact with the adjacent vertebrae is supposed to be large enough to resist excessive subsidence and small enough to prevent stress protection of the tissue growing in the cage. METHODS: In this study, 24 human cervical spine specimens were tested after stabilization with either a WING, BAK/C, AcroMed I/F cage or bone cement. Then, in a new testing protocol, 700 pure-moment loading cycles (+/-2 Nm) were applied in randomized directions (lateral bending, flexion-extension, and axial rotation alone or in combination with each other) to simulate the patient's neck movements during the first few postoperative days. Measurements of the subsidence depth (total height loss) in combination with flexibility tests (+/-2.5 Nm) were performed before cyclic loading and after 50, 100, 200, 300, 500, and 700 loading cycles. RESULTS: Cyclic loading caused subsidence in all four device groups, most distinct with BAK/C-cages (1.63 mm after 700 loading cycles) followed by the new WING (0.90 mm) and the AcroMed (0.82 mm) cages. No statistically significant difference could be found among the three cage designs. However, all three cage types showed a significantly higher subsidence depth than bone cement (0.48 mm;P = 0.023 between each of the three cage-types and bone cement). A moderate correlation between bone mineral density and subsidence depth could be found only in the BAK/C group (r2 = 0.495). A large subsidence depth after 700 loading cycles was associated with a large flexibility increase in the WING (r2 = 0.786) and AcroMed groups (r2 = 0.21), but with a small flexibility increase in the BAK/C group (r2 = 0.58). CONCLUSIONS: Postoperative neck movements caused subsidence in all cervical interbody implant types. The new WING cage and the AcroMed cage seemed to have a better resistance against subsidence than the BAK/C cage. However, all three cage types had a significantly higher subsidence tendency than bone cement.     

帽式颈椎椎间融合器的活体实验研究

目的 本研究在活体山羊颈椎上从椎间支撑能力、二期生物力学稳定性及椎间融合组织学方面比较三面皮质骨、Harms椎间融合器（cage）、Carboncage及自行所研制的帽式颈椎椎间融合器（hat　type　cervical　intervertebral　fusion　cage,HCIFC）的术后效果。方法　取32头山羊随机平均分为4组：第1组自体三面皮质髂骨;第2组Harmscage;第3组Carboncage;第4组HCIFC。分别行C3,4椎间盘切除术并分别植入以上内植物。术后共观察12周并测量平均椎间高度（DSH）、椎间角（IVA）及前凸角（LA）,处死后进行影像学、生物力学及组织学评估。结果 术后1周方盒形HCIFC、Carboncage组的平均DSH、IVA及LA要显著大于垂直圆柱体Harmscage和三面皮质骨组（P〈0．05）;术后12周时3个cage组的平均DSH、IVA及LA显著高于三面皮质骨组（P〈0．05）。垂直圆柱体Harmscage轴向旋转和侧屈时平均刚度显著大于其他组（P〈0．001）,轴向旋转时的最大活动度要显著低于其他组（P〈0．05）。与三面皮质骨组相比,3个cage组的椎间融合效果略好。结论HCIFC的椎间支撑能力、生物力学性能及椎间融合效果均适合于临床使用。     

Experimentelle Spondylodese der Schafshalswirbelsäule Teil 1: Der Effekt des Cage-Designs auf die intervertebrale Fusion

INTRODUCTION: There has been a rapid increase in the use of interbody fusion cages as an adjunct to spondylodesis, although experimental data are lacking. A sheep cervical spine interbody fusion model was used to determine the effect of different cage design parameters (endplate-implant contact area, maximum contiguous pore) on interbody fusion. MATERIAL AND METHOD: IN VITRO EVALUATION: 24 sheep cadaver specimens (C2-C5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive flexibility method using a nonconstrained testing apparatus. Four different groups were examined: (1) control group (intact) ( n=24), (2) autologous tricortical iliac crest bone graft ( n=8), (3) Harms cage ( n=8), and (4) SynCage-C ( n=8). IN VIVO EVALUATION: 24 sheep underwent C3/4 discectomy and fusion: group 1: autologous tricortical iliac crest bone graft ( n=8), group 2: Harms cage filled with autologous cancellous iliac crest bone grafts ( n=8), and group 3: SynCage-C filled with autologous cancellous iliac crest bone grafts ( n=8). Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8, and 12 weeks, respectively. At the same time points, disc space height (DSH), height index (HI), intervertebral angle (IVA), and endplate angle (EA) were measured. After 12 weeks the animals were killed and fusion sites were evaluated using biomechanical testing in flexion, extension, axial rotation, and lateral bending. Additionally, histomorphological and histomorphometrical analyses were performed. RESULTS: Over a 12-week period the cage groups showed significantly higher values for DSH, HI, IVA, and EA compared to the bone graft. In vivo stiffness was significantly higher for the tricortical iliac crest bone graft and Harms cage than in vitro stiffness. However, there was no difference between in vitro and in vivo stiffness of the SynCage-C. Histomorphometrical evaluation showed a more progressed bone matrix formation in the Harms cage group than in both other groups. CONCLUSION: The parameter endplate-implant contact area was not able to determine subsidence of cages. In contrast, the maximum contiguous pore of a cage significantly correlates with interbody bone matrix formation inside the cage. Additionally, there was no correlation between in vitro and in vivo stiffness of interbody fusion cages. Therefore, biomechanical in vitro studies are not able to determine in vivo outcome of fusion cages. Animal experimental evaluations of interbody fusion cages are essential prior to clinical use.     

Preparation and physicochemical properties of scaffold materials of heterogeneous deproteinized bone

Objective:To prepare and observe the physicochemical properties of scaffold materials of heterogeneous deproteinized tissue-engineered bone. Methods: Deproteinized bone was made through a series of physicochemical treatments in pig ribs and analyzed with histological observation, scanning electron microscopy, infrared spectrum, X-ray diffraction and energy dispersive analysis, Kjeldahl determination and mechanics analysis. Results: Interstitial collagen fiber was positive and mucin was negative in deproteinized bone, but, both were positive in fresh bone. Deproteinized bone maintained natural pore network. Its pore size was 472.51μm±7.02μm and the porosity was 78.15%±6.45%. The results of infrared spectrum showed that collagen was present in deproteinized bone. Both fresh and deproteinized bone had curve of hydroxyapatite. The Ca/P ratios were 1.71±0. 95 and 1. 68±0. 76 ( P > 0. 05 ), and the protein contents were 26.6%±2.23% and 19.1%±2.14% (P < 0.05) in fresh and deproteinized bone, respectively. There was no significant difference of destruction load under compression and maximal destruction load between fresh and deproteinized bone (P > 0. 05). The elastic modulus was higher in deproteinized bone than that in fresh bone (P < 0.05). Conclusions:Physicochemical properties and mechanic strength of deproteinized tissue-engineered bone meet the demands of ideal scaffold materials. But, its immunogenicity should be observed through further experiments for its clinical applications.     

Restoring geometric and loading alignment of the thoracic spine with a vertebral compression fracture: effects of balloon (bone tamp) inflation and spinal extension.

BACKGROUND CONTEXT: In patients with osteoporosis, changes in spinal alignment after a vertebral compression fracture (VCF) are believed to increase the risk of fracture of the adjacent vertebrae. The alterations in spinal biomechanics as a result of osteoporotic VCF and the effects of deformity correction on the loads in the adjacent vertebral bodies are not fully understood. PURPOSE: To measure 1) the effect of thoracic VCFs on kyphosis (geometric alignment) and the shift of the physiologic compressive load path (loading alignment), 2) the effect of fracture reduction by balloon (bone tamp) inflation in restoring normal geometric and loading alignment and 3) the effect of spinal extension alone on fracture reduction and restoration of normal geometric and loading alignment. STUDY DESIGN/SETTING: A biomechanical study using six fresh human thoracic specimens, each consisting of three adjacent vertebrae with all soft tissues and bony structures intact. METHODS: In order to reliably create fracture, cancellous bone in the middle vertebral body was disrupted by inflation of bone tamps. After removal of the bone tamps, the specimen was compressed using bilateral loading cables until a fracture was observed with anterior vertebral body height loss of >/=25%. Fracture reduction was performed under a compressive preload of 250 N first under the application of extension moments, and then using inflatable bone tamps. The vertebral body heights, kyphotic deformity of the fractured vertebra and adjacent segments and location of compressive load (cable) path in the fractured and adjacent vertebral bodies were measured on video-fluoroscopic images. RESULTS: The VCF caused anterior wall height loss of 37+/-15%, middle-height loss of 34+/-16%, segmental kyphosis increase of 14+/-7.0 degrees and vertebral kyphosis increase of 13+/-5.5 degrees (p<.05). The compressive load path shifted anteriorly by about 20% of anteroposterior end plate width in the fractured and adjacent vertebrae (p=.008). Bone tamp inflation restored the anterior wall height to 91+/-8.9%, middle-height to 91+/-14% and segmental kyphosis to within 5.6+/-5.9 degrees of prefracture values. The compressive load path returned posteriorly relative to the postfracture location in all three vertebrae (p=.004): the load path remained anterior to the prefracture location by about 9% to 11% of the anteroposterior end plate width. With application of extension moment (6.3+/-2.2 Nm) until segmental kyphosis and compressive load path were fully restored, anterior vertebral body heights were improved to 85+/-8.6% of prefracture values. However, the middle vertebral body height was not restored and vertebral kyphotic deformity remained significantly larger than the prefracture values (p<.05). CONCLUSIONS: The anterior shift of the compressive load path in vertebral bodies adjacent to VCF can induce additional flexion moments on these vertebrae. This eccentric loading may contribute to the increased risk of new fractures in osteoporotic vertebrae adjacent to an uncorrected VCF deformity. Bone tamp inflation under a physiologic preload significantly reduced the VCF deformity (anterior and middle vertebral body heights, segmental and vertebral kyphosis) and returned the compressive load path posteriorly, approaching the prefracture alignment. Application of extension moments also was effective in restoring the prefracture geometric and loading alignment of adjacent segments, but the middle height of the fractured vertebra and vertebral kyphotic deformity were not restored with spinal extension alone.