聚甲基丙烯酸甲酯强化对骨质疏松椎弓根螺钉固定的生物力学作用

目的探讨聚甲基丙烯酸甲酯 (polymethylmethacrylate,PMMA)骨水泥强化椎弓根螺钉的方法和评价 PMMA强化骨质疏松椎弓根螺钉后的生物力学性质。方法 6具新鲜老年女性胸腰段骨质疏松脊柱标本 (T10～ L5),使用双能 X线骨密度吸收仪测试每个椎体的骨密度,随机取 16个椎体 (32侧椎弓根 ),一侧椎弓根拧入 CCD螺钉,测量最大旋入力偶矩后拔出螺钉作为正常对照组,用 PMMA骨水泥强化椎弓根螺钉作为修复固定组,行螺钉拔出试验;另一侧经导孔直接强化椎弓根螺钉后拔出作为强化固定组,记录三组螺钉的最大轴向拔出力。结果椎体平均骨密度为 (0.445± 0.019)g/cm2;螺钉最大旋入力偶矩为（ 0.525± 0.104） Nm;正常对照组螺钉最大轴向拔出力为 (271.5± 57.3)N;修复固定组为 (765.9± 130.7)N;强化固定组为 (845.7± 105.0)N。 PMMA骨水泥强化或修复骨质疏松椎弓根螺钉后最大抗压力明显高于强化前,差异有非常显著性意义 (P< 0.01)。结论 PMMA骨水泥强化骨质疏松椎弓根螺钉能显著增加螺钉在椎体内的稳固性。     

geneX骨水泥强化骨质疏松椎体椎弓根钉的生物力学研究

目的评估骨质疏松情况下geneX骨水泥强化椎弓根钉的固定强度。方法应用微量注射泵对30个新鲜小牛腰椎标本注射稀盐酸建立骨质疏松椎体模型。60个椎弓根分为四组:geneX骨水泥组,硫酸钙骨水泥(CSC)组,聚甲基丙烯酸甲酯骨水泥(PMMA)组,对照组。随机选择一侧注射2.5 ml骨水泥,然后置入螺钉;另一侧行正常螺钉固定对照,应用材料试验机进行轴向拔出力测试,记录各组的轴向最大拔出力和能量吸收值并进行比较。结果 geneX组与CSC组两组拔出力及能量吸收值比较,差异无统计学意义(P>0.05),两组均显著低于PMMA组(P<0.05),两组均显著高于对照组(P<0.05)。结论 geneX骨水泥强化椎弓根钉可显著提高椎弓根固定强度,geneX骨水泥可用作椎弓根强化螺钉的填充材料。     

钉道强化提高椎弓根螺钉固定强度的生物力学研究

目的 评价椎弓根钉道局部强化技术及其结合膨胀式椎弓根螺钉提高椎弓根螺钉固定强度的效果.方法 通过自行设计及加工的钉道局部强化装置,向钉道周壁点状注入CaSO4骨水泥以强化椎弓根钉道.5具新鲜冻存人体脊柱标本,每具随机选取4个腰椎共20个腰椎标本,采用随机区组设计方法分为10个区组.设计四种固定方法:A组(普通椎弓根螺钉)、B组(普通椎弓根螺钉+钉道局部强化)、C组(膨胀式椎弓根螺钉+钉道局部强化)、D组(普通椎弓根螺钉+钉道内灌注CaSO4骨水泥),随机应用在每个区组的2个椎体共4个椎弓根钉道.分别测试每个椎弓根螺钉的最大轴向拔出力及能量吸收值.从剩余腰椎标本中任意取两个腰椎,应用钉道局部强化技术后利用Micro-CT观察钉道周壁微观结构变化.结果 C、D两组的最大轴向拔出力均值及能量吸收值均值高于A组(P＜0.01)及B组(P＜0.05),B组最大轴向拔出力均值及能量吸收值均值高于A组(P＜0.01),C、D两组之间的差异无统计学意义(P＞0.05).结论 钉道局部强化技术可显著提高椎弓根螺钉的固定强度,结合使用膨胀式椎弓根螺钉可进一步提高螺钉的固定强度.     

重度骨质疏松条件下椎弓根螺钉内固定的可靠性研究

目的评价重度骨质疏松条件下椎弓根螺钉的稳定性,为椎弓根内固定在合并有重度骨质疏松症的患者中的选用提供力学理论基础。方法采用新鲜尸体脊柱标本,检测骨密度后,根据诊断标准,选用正常骨质的2具尸体标本、重度骨质疏松的4具尸体标本,分离T12~L5节段成单个椎体以备后用;然后在骨质正常椎体置入椎弓根螺钉12枚作对照组;在重度骨质疏松水平,分单纯置入椎弓根螺钉(pedicle screw,PS)、经磷酸钙骨水泥(calcium phosphate cement,CPC)强化钉道后置入椎弓根螺钉、经聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)强化钉道后置入椎弓根螺钉三种方法置钉,依次为PS组、CPC/PS组和PMMA/PS组,进行螺钉轴向拔出实验,测最大拔出力、刚度和能量吸收值,对所测指标进行组间对比分析。结果重度疏松条件下,PS组、CPC/PS组和PMMA/PS各组最大拔出力、刚度、能量吸收值均显著低于对照组(P0.005);但是,PMMA/PS组三项指标均显著高于PS组、CPC/PS组(P0.001);PS组、CPC/PS组之间比较仅最大拔出力存在显著性差异(P0.05),刚度与能量吸收值差异无统计学意义(P0.05)。结论重度骨质疏松条件下,椎弓根螺钉固定强度明显下降,不宜单纯应用普通椎弓根螺钉行脊柱内固定治疗,采用普通骨水泥强化钉道后置钉可以提高椎弓根螺钉稳定性。     

骨水泥强化椎弓根螺钉固定治疗老年退行性腰椎不稳的临床疗效分析

目的:探讨用聚甲基丙烯酸甲(polymethylmethacrylate,PMMA)骨水泥强化椎弓根螺钉内固定治疗老年退行性腰椎不稳的临床疗效.方法:回顾性分析2002年3月～2009年6月收治的23例老年腰椎退行性不稳患者的临床资料,其中:男6例,女17例;年龄62～77岁,平均71岁;均采用PMMA骨水泥强化椎弓根螺钉内固定、椎体间植骨融合治疗,术前测量待置人螺钉之椎体的骨密度,术中测量螺钉的最大旋入力偶矩;取出螺钉后经钉道注入3ml粘稠的PMMA,再拧入螺钉,10min后拧紧螺钉并测量螺钉的最大旋入力偶矩;减压后行植骨融合内固定.结果:所有患者随访7～24个月,平均17个月,腰腿痛治愈好转率达87%,无手术并发症发生.PMMA强化椎弓根螺钉后,螺钉的最大旋入力偶矩由0.591±0.213N·m增至1.332±0.377N·m,差异有显著性(P<0.01):影像学表现为骨水泥分布于钉道周嗣松质骨中,未出现椎体外渗漏.结论:骨水泥强化椎弓根螺钉内固定治疗老年退行性腰椎不稳能明显增强螺钉的稳定性;正确掌握进钉技术及螺钉强化技术是手术成功的关键.     

一种新型钉道强化椎弓根螺钉生物力学研究

[目的]探讨一种新型钉道强化椎弓根螺钉在骨质疏松椎体中的生物力学特性。[方法]从4具老年尸体中选取20个腰椎标本(L_(1～5)),均符合骨质疏松症诊断标准(T-2.5),采用随机分4组,每组5个椎体。分别为单纯普通椎弓根螺钉组(无强化组)、普通椎弓根螺钉强化组(普通强化组)、可注射空心椎弓根螺钉强化组(空心钉强化组)、新型钉道强化椎弓根螺钉强化组(新型强化组)。观察骨水泥分布情况,并测量各组螺钉最大轴向拔出力及不同螺钉的刚度。[结果]三种强化骨水泥的分布不同,普通强化组骨水泥主要分布于椎体前部;空心钉强化组骨水泥主要分布于椎体前部及部分中后部,新型强化组骨水泥主要分布于钉道周围,包括椎体前、中、后部及部分椎弓根部。生物力学测量最大轴向拔出力依次为:新型强化组空心钉强化组普通强化组无强化组,差异具有统计学意义(P0.05)。螺钉刚度依次为普通螺钉新型螺钉空心螺钉,差异有统计学意义(P0.05)。[结论]新型钉道强化椎弓根螺钉能够提高螺钉在骨质疏松椎体固定的稳定性,且骨水泥分布有所改善,螺钉的刚度适中。     

两种不同方法提高椎弓根螺钉稳定性的体外生物力学研究

目的 比较膨胀式椎弓根螺钉(EPS)与骨水泥(PMMA)强化方法在体外提高螺钉稳定性的效果.方法 将60个新鲜成年绵羊腰椎随机分为三组.普通椎弓根螺钉组(CPS组):直接拧入普通椎弓根螺钉;PMMA-PS组:向钉道内注入PMMA(1.0 ml)后拧入CPS;EPS组:直接拧入EPS.24 h后对所有标本进行X线检查,随...     

经椎弓根螺钉内固定翻修术的生物力学研究

目的探讨不同直径与长度螺钉翻修及骨水泥强化后椎弓根固定的强度,评价其生物力学效果.方法采用10具新鲜成人尸体T10～L5节段共80个椎体标本.首先置入5.5mm/45mm椎弓根螺钉作为对照组.再将脊椎标本随机平分为Ⅰ、Ⅱ两大组.Ⅰ组中40个椎体各随机选择一侧椎弓根应用6.25mm/45mm螺钉翻修(Ⅰ a组),另一侧椎弓根应用7.0mm/45mm螺钉翻修(Ⅰ b组);Ⅱ组中40个椎体各随机选择一侧椎弓根应用6.25mm/55mm螺钉翻修(Ⅱa组),另一侧椎弓根应用7.0mm/55mm螺钉翻修(Ⅱb组).再随机选择56个椎弓根分别行细小螺钉及粗大螺钉骨水泥强化固定翻修(Ⅲa组、Ⅲb组).在858Mini-MTS生物力学实验机上测试最大拔出力及最大扭力矩,并进行统计分析.结果①6.25mm/45mm螺钉翻修5.5mm/45mm螺钉置入后的椎弓根,其拔出力及扭力矩无明显增加(P＞0.05);应用7.0mm/45mm、6.25mm/55mm及7.0mm/55mm螺钉翻修,把持力及扭力矩均明显增加(P＜0.05).②骨水泥强化固定后,螺钉把持力远大于单纯螺钉翻修组,且与螺钉粗细无关.③在对照组及螺钉翻修组,螺钉把持力与扭力矩间有明显相关性,相关系数r=.86.结论①椎弓根螺钉翻修时,单纯螺钉直径增加1.5mm或直径增加0.75mm、长度增加l0mm以及骨水泥强化均可达到翻修固定的生物力学要求,以骨水泥强化固定更为明显.②增加螺钉直径与长度的翻修中,把持力与扭力矩是一致的;而应用骨水泥强化固定时,螺钉把持力主要取决于骨水泥本身及添加物-骨界面结合强度.     

椎弓根螺钉骨水泥强化固定治疗腰椎退行性变的临床效果

目的 探讨椎弓根螺钉骨水泥强化固定治疗腰椎退行性变的临床效果.方法 对56例腰椎退行性变患者行椎弓根螺钉骨水泥强化固定、椎间植骨融合,术前测量拟固定椎体的骨密度,术中测量螺钉的最大旋入力偶矩后取出螺钉,钉道注入聚甲基丙烯酸甲酯（PMMA）3ml再次置入螺钉并测量螺钉的最大旋入力偶矩,椎体固定后减压并行椎体间植骨融合.结果 患者均获随访,时间6~24（14.4±3.6）个月,均未发生内固定物松动、断钉及断棒等并发症.影像学评估：骨水泥分布于钉道周围松质骨中无明显椎体外渗.末次随访时按改良Macnab标准评价临床疗效：优27例,良22例,可7例;椎弓根螺钉的最大旋入力偶矩经术中骨水泥强化固定后由（0.61±0.23）N·m增至（1.35±0.32） N·m,差异有统计学意义（P〈0.05）.结论椎弓根螺钉骨水泥强化固定治疗腰椎退行性变可以明显增强螺钉的稳定性.     

可注射硫酸钙MIIGX3与医用骨水泥对椎弓根钉固定作用的比较研究

[目的]用可注射硫酸钙M IIGX3(m in im ally invasive in jectab le graft X3,以下简称M IIGX3)及医用骨水泥分别强化猪腰椎椎弓根钉内固定,测定椎弓根钉最大轴向拔出力,比较两种材料对椎弓根钉固定强度的影响。[方法]8个新鲜猪腰椎作为实验对象,在同一椎体双侧椎弓根制作钉道,一侧在固定螺钉前加用M IIGX3(M IIGX3组),另一侧加用骨水泥(骨水泥组)。24 h后行轴向拔出力测试。[结果]最大轴向拔出力,M IIGX3组1915±375 N,骨水泥组3625±775 N,二者配对t检验有显著差异(P<0.01)。[结论]骨水泥对椎弓根钉的固定作用大于M IIGX3。当存在脊柱滑脱需较大提拉力量或椎弓根钉需承受较大拔出力的节段,使用骨水泥进行强化更为合适。     

可灌注骨水泥椎弓根螺钉的生物力学研究

目的 探讨可灌注骨水泥椎弓根螺钉(novel perfusional pedicle screw,NPPS)在骨质疏松椎体内的生物力学稳定性.方法 选取平均年龄73岁的完整湿润脊柱标本(T11～L5)6具,共42个椎体,平均骨密度为(0.696±0.14)g/cm2.所有椎体均任取一侧椎弓根置入可灌注螺钉后,使用配套的骨水泥推杆和灌注筒向椎体内灌注骨水泥2ml,对侧椎弓根置入常规螺钉,作为对照组.随机选取3个椎体,剖开椎体观察骨水泥分布情况.余39个椎体随机分成3组,每组13个,分别行最大轴向拔出力、最大旋出力矩、周期抗屈试验.另取10个可灌注螺钉和10个对照组螺钉行三点弯曲实验.结果 所有椎体均没有观察到骨水泥渗漏.可灌注螺钉的最大轴向拔出力为(760±178)N,对照组为(355±87)N;可灌注螺钉的最大旋出力矩为(1.347±0.377)N·m,对照组为(0.488±0.205)N·m.4枚(4/13,占30.8%)可灌注螺钉发生松动,其平均载荷为(150±46)N;未松动的螺钉中,松动位移半均(0.661±0.289)mm,对照组中所有的螺钉在最大负荷介于50～200 N时开始松动(位移>2.000 mm),平均载荷(104±35)N.可灌注螺钉的平均极限弯曲载荷为(3082±144)N,对照组螺钉为(3357±263)N.结论 可灌注椎弓根螺钉,结合骨水泥推杆和灌注筒能有效控制骨水泥渗漏,明显增强椎弓根螺钉在骨质疏松椎体内的稳定性.     

Biomechanical comparison of a novel multilevel hex-head pedicle screw design with a conventional head design.

The objective of the study was to determine the biomechanical effect during insertion of multilevel hex-head design pedicle screws compared to a conventional screw-head design. Eighteen lumbar vertebrae and thoracic vertebrae from human cadavers were instrumented with a novel, multilevel hexagonal head pedicle screw on one side and a conventional head pedicle screw on the contralateral side. Screws were inserted at a constant rate and insertion and removal torques were recorded. A further 14 lumbar and thoracic vertebrae were used to test alterability of screw direction and operational effort required. Electromagnetic sensors recorded the change in angular direction for both screw and screwdriver. The force applied through the insertion screwdriver required to produce the directional change was also recorded. No significant differences were found between the two screw types for insertion or removal torque in either lumbar or thoracic vertebrae. Multilevel hex-head screws had significantly greater directional alterability than conventional head screws in both lumbar and thoracic specimens. Multilevel hex-head screws also required less force applied through the screwdriver than conventional screws to alter direction of screw insertion in both lumbar and thoracic specimens. The multilevel hex-head design did not affect the insertion or removal torque in comparison to a conventional head design.     

Characteristics of immediate and fatigue strength of a dual-threaded pedicle screw in cadaveric spines

Background contextNovel dual-threaded screws are configured with overlapping (doubled) threads only in the proximal shaft to improve proximal cortical fixation.PurposeTests were run to determine whether dual-threaded pedicle screws improve pullout resistance and increase fatigue endurance compared with standard pedicle screws.Study design/settingIn vitro strength and fatigue tests were performed in human cadaveric vertebrae and in polyurethane foam test blocks.Patient sampleSeventeen cadaveric lumbar vertebrae (14 pedicles) and 40 test sites in foam blocks were tested.Outcome measuresMeasures for comparison between standard and dual-threaded screws were bone mineral density (BMD), screw insertion torque, ultimate pullout force, peak load at cyclic failure, and pedicular side of first cyclic failure.MethodsFor each vertebral sample, dual-threaded screws were inserted in one pedicle and single-threaded screws were inserted in the opposite pedicle while recording insertion torque. In seven vertebrae, axial pullout tests were performed. In 10 vertebrae, orthogonal loads were cycled at increasing peak values until toggle exceeded threshold for failure. Insertion torque and pullout force were also recorded for screws placed in foam blocks representing healthy or osteoporotic bone porosity.ResultsIn bone, screw insertion torque was 183% greater with dual-threaded than with standard screws (p<.001). Standard screws pulled out at 93% of the force required to pull out dual-threaded screws (p=.42). Of 10 screws, five reached toggle failure first on the standard screw side, two screws failed first on the dual-threaded side, and three screws failed on both sides during the same round of cycling. In the high-porosity foam, screw insertion torque was 60% greater with the dual-threaded screw than with the standard screw (p=.005), but 14% less with the low-porosity foam (p=.07). Pullout force was 19% less with the dual-threaded screw than with the standard screw in the high-porosity foam (p=.115), but 6% greater with the dual-threaded screw in the low-porosity foam (p=.156).ConclusionsAlthough dual-threaded screws required higher insertion torque than standard screws in bone and low density foam, dual-threaded and standard pedicle screws exhibited equivalent axial pullout and cyclic fatigue endurance. Unlike single-threaded screws, the mechanical performance of dual-threaded screws in bone was relatively independent of BMD. In foam, the mechanical performance of both types of screws was highly dependent on porosity.     

骨水泥并椎弓根螺钉脊柱内固定的力学效应

目的通过用骨水泥强化椎弓根螺钉固定新鲜尸体胸腰段脊椎标本,在电子万能力学试验机上进行生物力学测试,探讨骨水泥对椎弓根钉固定强度的影响。方法选用30个新鲜胸腰段椎体作为实验对象,随机分2组,每组15个,每个椎体自身对照,第一组一侧椎弓根用聚甲基丙烯酸甲酯强化椎弓根螺钉固定;另一侧椎弓根作为对照单纯椎弓根螺钉固定,第二组一侧椎弓根扩大钻孔,然后用聚甲基丙烯酸甲酯强化椎弓根螺钉固定（模拟骨水泥强化翻修侧）;另一侧椎弓根作为对照,扩大钻孔后用粗大螺钉固定（模拟粗大螺钉翻修侧）。将标本固定于特制的模具上,用电子万能力学试验机,沿人体纵轴线作向上螺钉受力测试,至椎骨损坏或螺钉拔出时受力即为耐受负荷临界值,对所得数据进行分析。结果骨水泥强化侧耐受负荷临界值为（1 198±122）N,单纯螺钉固定侧耐受负荷临界值为（805±64）N,两组比较存在显著性差异（P〈0.05）;骨水泥强化翻修侧耐受负荷临界值为（1 775±203）N,粗大螺钉翻修侧耐受负荷临界值为（953±97）N,两组比较存在显著性差异（P〈0.05）。说明骨水泥在耐受螺钉对椎体切割破坏方面有明显的加强作用,骨水泥强化翻修的效果优于粗大螺钉翻修的效果。结论经骨水泥强化及强化翻修的椎弓根内固定有更强的力学效应,有一定的防止螺钉对椎骨损坏的作用,可提高骨质疏松患者脊椎内固定及脊椎内固定翻修手术的疗效。     

Biomechanical comparative study of the stability of injectable pedicle screws with different lateral holes augmented with different volumes of polymethylmethacrylate in osteoporotic lumbar vertebrae

Background Context

Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Until now, there had been no studies of the relationship between screw stability and the distribution and volume of PMMA.

Evaluation of calcium sulfate paste for augmentation of lumbar pedicle screw pullout strength.

BACKGROUND CONTEXT: Many authors have evaluated the components responsible for ultimate pullout strength of pedicle screws. In these studies, one important variable has been the screw fixation. Because pedicle screw fixation has increased in popularity over recent years, so has the need for augmentation in difficult situations. Polymethylmethacrylate (PMMA) has been established as the gold standard in terms of strength of fixation but has the potential for severe complications when applied in spine surgery. Calcium sulfate is an alternative to PMMA, because it lacks the exothermic reaction, is potentially osteoconductive and is resorbed by the body in 30 to 60 days. PURPOSE: To determine the strength of a new calcium sulfate cement in terms of pedicle screw augmentation. The purpose was to evaluate calcium sulfate versus PMMA in terms of pullout strength. PMMA was considered the gold standard in terms of strength for this experiment. STUDY DESIGN: Lumbar vertebrae implanted with pedicle screws were subjected to axial pullout tests. The force required to cause implant failure was measured and compared for three methods of fixation. OUTCOME MEASURES: Force to failure (Newtons) for each pedicle test was recorded and analyzed with results from similarly augmented pedicles. METHODS: Lumbar vertebrae were harvested from four cadavers and implanted with pedicle screws. These screws were either placed in native bone or augmented with either calcium sulfate paste or PMMA. In those pedicles that had augmentation, the material was permitted to set for a minimum of 24 hours. Axial pullout tests were then performed using an MTS (Materials Testing System Corporation, Minneapolis, MN) testing machine. The screws were pulled out over a distance of up to 6 mm at 0.25 mm/sec. This rate and distance ensured failure in each case. The load to failure was recorded for each pedicle. RESULTS: Calcium sulfate augmentation improved pedicle screw pullout strength significantly when compared with native bone (p=.0003). This represented an average increase of 167% over the native bone. Likewise, PMMA improved the pullout strength significantly over native bone (p<.0001) for an average increase of 199%. There were no significant differences between the calcium sulfate and PMMA augmentation (p=.0791), although the PMMA averaged 119% of the strength of calcium sulfate. CONCLUSIONS: Although PMMA is considered the gold standard in terms of fixation strength, its use around the spine has been limited because of concern over complications. The calcium sulfate bone paste tested in this study demonstrated strength similar to PMMA without the major risks to the spinal cord. In addition, the calcium sulfate paste allows for possible osteoconduction to aid in spinal fusion. Further study is needed to determine the applicability of this calcium sulfate paste in the clinical setting of spine surgery.     

两种长度的颈椎椎弓根螺钉与侧块螺钉拔出试验比较

目的:比较两种长度的颈椎椎弓根螺钉和侧块螺钉的抗拔出力,探讨颈椎经椎弓根短螺钉固定的可行性。方法:5具C3~C5共15节新鲜颈椎标本,用长度为28mm和20mm的皮质骨螺钉分别置入椎弓根,并用20mm的螺钉行侧块双皮质固定,螺钉进入侧块深度约14mm。行拔出试验,比较螺钉的最大轴向拔出力。结果:椎弓根长螺钉的最大拔出力为650N,椎弓根短螺钉为585N,两者比较无显著性差异(P>0.01);侧块螺钉的最大拔出力为360N,与椎弓根短螺钉比较有显著性差异(P<0.0001)。结论:颈椎椎弓根短螺钉固定可提供足够的稳定性,其安全性相对较高。     

Hole preparation techniques for transpedicle screws. Effect on pull-out strength from human cadaveric vertebrae

In each of eight thoracolumbar human cadaveric vertebrae, a hole was made through one pedicle into the vertebral body with a drill bit and through the contralateral pedicle with a probe. Identical metal screws were implanted into the holes to equal depths, and maximum pull-out force was determined for each screw. Using a paired Student t test, no significant difference (P = 0.87) was found in pull-out strength between the screws implanted into drilled holes and those implanted into probed holes. In fact, the average pull-out strengths for the two groups differed by less than 2%. The pedicular cortex was broken through during hole preparation in 5 of the 16 pedicles: 3 as a result of drilling and 2 secondary to probing. The average pull-out strength of the screws in these five pedicles was 11.0% less than the average pull-out strength of the screws implanted into the contralateral intact pedicles. Although this does not represent a statistically significant difference (P = 0.15), it suggests that damaging the pedicular cortex may weaken pedicle screw fixation.