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。     

带有BMP中空侧孔新型椎弓根钉作用特点的实验研究

目的 探讨带有MBP中空侧孔新型椎弓根钉的作用特点,明确其在腰椎骨折模型中内固定的效果.方法 比较两种不同椎弓根钉的生物力学测试,包括轴向最大拔出力,垂直压缩刚度及极限压缩强度.采用X线摄片及CT观察伤椎内固定后的大体形态,比较两组中伤椎前缘高度及椎管正中矢状径(MD)的差异.结果 新型椎弓根钉组其平均轴向最大拔出力明显高于普通型组,差异有统计学意义(P＜0.05);两种椎弓根钉行椎弓根钉固定后即刻状态的整体刚度差异无统计学意义(P＞0.05),极限抗压强度差异有统计学意义(P＜0.05).普通型与新型椎弓根钉相比较,其平均前缘高度及伤椎平均MD值差异均有统计学意义(P＜0.05).结论 新型椎弓根钉内固定的稳定性明显优于普通型椎弓根钉,值得推广应用.     

不同骨密度绵羊腰椎模型的椎弓根钉道空间结构及其力学性能

目的:应用MicroCT研究在不同骨密度(BMD)情况下椎弓根钉道骨小梁及钉道外口皮质骨空间结构与椎弓根螺钉轴向拔出力的关系。方法:对40个绵羊腰椎标本应用微量注射泵椎体内外盐酸脱钙方法分别建立4组不同BMD水平的生物力学模型,即A组(正常骨质),B组(骨量减少),C组(骨质疏松),D组(严重骨质疏松),生物力学测试各组椎体椎弓根螺钉的最大轴向拔出力(Fmax)。应用MicroCT研究各组椎体椎弓根钉道周围骨小梁参数,包括骨小梁厚度(Tb.th)、骨小梁数量(Tb.N)、骨小梁间隙(Tb.sp)、骨体积分数(BV/TV)及钉道外口皮质骨的厚度(Cor.th),统计分析其与椎弓根螺钉轴向拔出力的关系。结果:成功建立不同BMD下降程度的生物力学模型,B、C、D组BMD下降分别为19%、28%及37%。生物力学测试示B、C、D组椎体的Fmax较A组显著下降,且有统计学意义(P0.05);B、C、D组组间椎体Fmax随BMD下降而下降,各组间具有统计学差异(P0.05)。MicroCT显示各组椎弓根螺钉钉道空间结构参数随BMD下降而变化,且各组组间参数随脱钙时间的延长而变化,各组间有统计学意义(P0.05)。相关性分析发现钉道骨质空间结构参数(Tb.th、Tb.N、Tb.sp、BV/TV、Cor.th)、BMD、脱钙时间与Fmax均存在直线相关关系;多元回归方程(y=1185.658×BMD+153.535×Tb.N-247.037×Tb.sp)可预测椎体椎弓根螺钉的Fmax。结论:椎弓根螺钉的最大轴向拔出力(Fmax)不仅与椎体BMD的变化密切相关,亦与椎弓根钉道松质骨及皮质骨空间结构参数密切相关。     

计算骨丧失量经椎弓根打压植骨治疗胸腰椎压缩性骨折的生物力学研究

[目的]探讨用计算骨丧失量的方法经椎弓根打压植骨(transpedicular impacted grafting,TPIG)治疗胸腰椎压缩性骨折的生物力学性能。[方法]将6具成人新鲜尸体胸腰椎标本,模拟正常组、压缩性骨折损伤组、单纯计算骨丧失量TPIG和单纯经椎弓根植骨组(transpedicular grafting,TPG)、计算骨丧失量TPIG+椎弓根固定和TPG+椎弓根固定组,行生物力学实验应力分析,比较各组的椎体和椎间盘的强度、刚度和稳定性以及扭转生物力学性能。[结果](1)计算骨丧失量TPIG+椎弓根固定组的椎体和椎间盘的强度、刚度和稳定性高于TPG+椎弓根固定组,具有显著性差异(P0.05);(2)单纯计算骨丧失量TPIG组的强度和刚度高于单纯TPG组,并具有显著性差异(P0.05);(3)从扭转生物力学试验中也同样得到了相似的结论。[结论]计算骨丧失量TPIG+椎弓根固定治疗胸腰椎压缩性骨折具有优越的生物力学性能,适合于临床应用。     

磷酸钙复合BMP-2增强骨质疏松椎体椎弓根螺钉内固定

[目的]探讨磷酸钙复合BMP-2对骨质疏松状态下椎弓根螺钉稳定性的影响,评价其临床应用价值。[方法]雌性新西兰大白兔卵巢切除去势法制备骨质疏松模型,测量骨密度。将兔随机分为增强组和常规组,增强组采用磷酸钙复合BMP-2注入增强后置入椎弓钉,而常规组采用常规技术置入椎弓钉。置钉后4、8和12周分别进行骨组织形态计量检查和生物力学检测。[结果]与术前比较,卵巢切除后6个月的BMD显著下降(P0.05),提示骨质疏松模型建立成功。置入L3椎弓螺钉术后4、8和12周,增强组和常规组骨形态计量指标比较,类骨质表面、骨-螺钉接触、骨内生和骨矿物沉积速率,均随时间延长显著增加,相同时间点增强组各项指标优于常规组,差异有统计学意义(P0.05)。生物力学测试表明,置钉后4、8和12周,随着固定时间延长,两组的最大拔出力和最大破坏功耗均显著增加,相同时间点,增强组的最大拔出力和最大破坏功耗均显著大于常规组,差异有统计学意义(P0.05)。[结论]磷酸钙复合BMP-2可以增强椎弓根螺钉在骨质疏松椎体中的稳定性,具有一定的临床应用价值。     

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。     

经椎弓根打压植骨与骨水泥椎体成形术治疗胸腰椎压缩骨折的生物力学比较

目的通过对非内固定状态下经椎弓根打压植骨与骨水泥椎体成形术治疗胸腰椎压缩骨折的标本进行强度和刚度测试数据分析,探讨哪一种方法更符合生物力学,为临床采用经椎弓根打压植骨术治疗胸腰椎压缩骨折提供理论依据,为PVP、PKP慎用提供参考。方法对9具冻干尸体胸腰段椎体(T12~L2)标本随机分成3组,即正常组、造成L1压缩骨折经椎弓根打压植骨和骨水泥椎体成形3组,每组3具标本,通过生物力学测试仪对各组标本在前屈、后伸、侧屈、中立位4种状态下,各组L1椎体、L1、2椎间盘测试其强度和刚度数据进行比较研究。结果椎弓根打压植骨后椎体和相应椎间盘的强度、刚度接近正常组椎体,而骨水泥椎体成形组椎体强度明显增加,刚度则明显下降。这表明目前常用骨水泥椎体成形术可改变伤椎及邻近椎间盘的生物力学特性,增加伤椎再骨折机会和增加邻近椎间盘的应力,加速其退变。结论通过此实验可以说明临床以经椎弓根打压植骨替代骨水泥椎体成形的可行性,可使骨折椎体和相邻椎间盘获得更好的生物力学康复结果。     

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。     

干细胞移植和BMP2基因治疗修复骨损伤和坏死的实验研究

目的:根据老年骨缺损和股骨头坏死实验模型的研究结果来评价干细胞移植和BMP2基因治疗的方法是否可用于一些特殊损伤和疾病的治疗.方法:从不同年龄段大鼠、羊骨髓中分离培养骨髓间充质干细胞,利用含BMP-2基因或βal基因的腺病毒载体感染干细胞,通过酶联免疫测定方法检测基因转染细胞培养上清中BMP-2蛋白的含量.利用基因转染细胞和多孔三磷酸钙复合,回植后修复24月龄老年大鼠股骨干6毫米节段性缺损和实验性羊股骨头坏死.通过组织学观察和生物力学测定来评价比较BMP-2治疗组和βgal对照组的新骨形成情况和修复组织的强度.结果:基因转染细胞培养上清中BMP-2蛋白的含量随时间延长而逐渐上升,不同年龄大鼠干细胞BMP-2转染后蛋白质的分泌水平没有明显差异.组织学观察表明BMP-2基因转染细胞和多孔三磷酸钙复合物已成功修复24月龄老年大鼠股骨干6毫米节段性缺损和实验性羊股骨头坏死,BMP-2治疗组的新骨形成明显多于βgal对照组(P＜0.05).治疗后第16周,BMP-2治疗组股骨头修复组织的最大压缩强度和弹性模量也明显高于Bgal对照组(P＜0.05).结论:BMP-2基因转染的自体骨髓间充质干细胞和多孔三磷酸钙复合后回植可有效修复老年大鼠骨缺损并重建羊坏死股骨头的功能.     

Effect of pilot hole on biomechanical and in vivo pedicle screw–bone interface

Purpose

To experimentally study the influence of pilot hole diameter (smaller than or equal to the internal (core) diameter of the screw) on biomechanical (insertion torque and pullout strength) and histomorphometric parameters of screw–bone interface in the acute phase and 8 weeks after pedicle screw insertion.

Methods

Fifteen sheep were operated upon and pedicle screws inserted in the L1–L3 pedicles bilaterally. The pilot hole was smaller (2.0 mm) than the internal diameter (core) of the screw on the left side pedicle and equal (2.8 mm) to the internal diameter (core) of the screw on the right side pedicle. Ten animals were sacrificed immediately (five animals were assigned to pullout strength tests and five animals were used for histomorphometric bone–screw interface evaluation). Five animals were sacrificed 8 weeks after pedicle screw insertion for histomorphometric bone–screw interface evaluation.

Results

The insertion torque and pullout strength were significantly greater in pedicle screws inserted into pilot holes smaller than internal (core) diameter of the screw. Histomorphometric evaluation of bone–screw interface showed that the percentage of bone-implant contact, the area of bone inside the screw thread and the area of bone outside the screw thread were significantly higher for pilot holes smaller than the internal (core) diameter of the screw immediately after insertion and after 8 weeks.

Conclusion

A pilot diameter smaller than the internal (core) diameter of the screw improved the insertion torque and pullout strength immediately after screw insertion as well the pedicle screw–bone interface contact immediately and 8 weeks after screw placement in sheep with good bone mineral density.     

新型钉道固化方法增强椎弓根螺钉固定强度的体外实验研究

目的评价新型钉道固化方法提高椎弓根螺钉稳定性的效果,并观察钉道界面情况。方法42个新鲜成年山羊腰椎随机分为三组,分别给予3种不同的钉道处理。24h后各组随机选取4个椎体进行Micro-CT重建,对其余30个椎体进行轴向拔出实验。结果Micro-CT三维重建显示:实验组中呈现一种特殊的部分"螺钉-骨质"和部分"螺钉-CSC-骨质"共存的整体界面。生物力学实验表明:新型钉道固化方法可以显著提高椎弓根螺钉的最大轴向拔出力。结论做为一种新型的钉道固化方法,钉道局部固化不仅可以显著提高椎弓根螺钉固定的稳定性,而且形成了一种特殊的部分"螺钉-骨质"和部分"螺钉-CSC-骨质"共存的整体界面,为减少螺钉取出时对周围骨质的破坏提供了一个良好的前提条件。     

医用骨水泥对腰椎椎弓根钉固定的影响

目的探讨医用骨水泥对椎弓根钉固定强度的影响。方法24个新鲜冰冻尸体的腰椎椎体作为实验对象,随机分为3组,第1组为单纯钻孔组,第2组丝锥攻丝组,第3组为扩大钻孔组。每组8个椎体,每个椎体自身对照,两侧的固定方式一样,只是一侧在固定螺钉前加用骨水泥,另一侧不加骨水泥作为对照。固定后分别在万能机上进行轴向拉力测试,比较二者的差异。结果在第1组单纯钻孔组中,骨水泥固定侧拉力范围平均(1988±289)N,对照侧平均(1242±264)N,二者比较有显著差异(P<0001)。第2组丝锥攻丝组骨水泥固定侧拉力范围平均(4553±945)N,对照侧为平均(1303±138)N,二者比较有显著差异(P<0001)。第3组扩大钻孔组骨水泥固定侧拉力范围平均(4653±675)N,对照侧平均1213N,二者比较有显著差异(P<0001)。3组骨水泥固定侧的结果相比,第1组单纯钻孔组与第2组丝锥攻丝组、第3组扩大钻孔组之间有明显差异(P<0001),而第2组与第3组之间无差异(P>005)。结论骨水泥对椎弓根螺钉的固定有明显的增强作用。对于骨质疏松的患者或手术中椎弓根钉固定失败,或二次手术重新固定时,都可以采取骨水泥进行加强固定的方法,且强度可靠。     

Early effect of parathyroid hormone (1-34) on implant fixation.

Intermittent systemic administration of parathyroid hormone increases bone formation by stimulating osteoblastic activity. The current study determined how parathyroid hormone (1-34) administration influences the bony fixation of stainless steel screws with time. A screw was implanted in the left tibia and a metal rod was implanted in the right tibia in 30 adult male rats that then were injected three times a week with human parathyroid hormone (1-34) at 60 microg/kg/injection (n = 15) or saline (n = 15). The animals were euthanized after 1, 2, or 4 weeks of treatment. Eight additional rats received only the screw and were euthanized immediately after implantation. No significant effects of parathyroid hormone on body weight change or ash weight of the femurs were seen. The degree of fixation was assessed by measuring pullout strength of the screws. The mean pullout strength immediately after implantation was 12 N. The pullout strength of the group injected with saline was 33 N after 1 week, 23 N after 2 weeks, and 41 N after 4 weeks. The pullout strength of the group injected with parathyroid hormone increased to 43 N after 1 week, 58 N after 2 weeks, and 100 N after 4 weeks. The increase at 2 and 4 weeks was statistically significant. Strength reflects the mechanical properties of the bone within the screw threads. The contralateral tibia with its metal rod was used for blinded histologic assessment. Parathyroid hormone increased the fraction of the metal surface having contract with bone without an intervening soft tissue layer from 45% to 69% after 1 week. The current results suggest that intermittent parathyroid hormone treatment can enhance early implant fixation by enhancing the density of the surrounding bone and by increasing the implant bone contact.     

Pedicle screw augmentation with bone cement enforced Vicryl mesh

Achieving sufficient mechanical purchase of pedicle screws in osteoporotic or previously instrumented bone is technically and biologically challenging. Techniques using different kinds of pedicle screws or methods of cement augmentation have been used to address this challenge, but are associated with difficult revisions and complications. The purpose of this biomechanical trial was to investigate the use of biocompatible textile materials in combination with bone cement to augment pullout strength of pedicle screws while reducing the risk of cement extrusion. Pedicle screws (6/40 mm) were either augmented with standard bone‐cement (Palacos LV + G) in one group (BC, n = 13) or with bone‐cement enforced by Vicryl mesh in another group (BCVM, n = 13) in osteoporosis‐like saw bone blocks. Pullout testing was subsequently performed. In a second experimental phase, similar experiments were performed using human cadaveric lumbar vertebrae (n = 10). In osteoporosis‐like saw bone blocks, a mean screw pullout force of 350 N (±125) was significantly higher with the Bone cement (BC) compared to bone‐cement enforced by Vicryl mesh (BCVM) technique with 240 N (±64) (p = 0.030). In human cadaveric lumbar vertebrae the mean screw pullout force was 784 ± 366 N with BC and not statistically different to BCVM with 757 ± 303 N (p = 0.836). Importantly, cement extrusion was only observed in the BC group (40%) and never with the BCVM technique. In vitro textile reinforcement of bone cement for pedicle screw augmentation successfully reduced cement extrusion compared to conventionally delivered bone cement. The mechanical strength of textile delivered cement constructs was more reproducible than standard cementing. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:212–216, 2018.     

Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae - A cadaveric study

Background:

The objective of this cadaveric study was to analyze the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of lower thoracic and lumbar pedicle screws. We also investigated the effect of bone mineral density (BMD), diameter of pedicle screws, and the region of spine on the pullout strength of pedicle screws.

Materials and Methods:

Sixty fresh human cadaveric vertebrae (D10–L2) were harvested. Dual-energy X-ray absorptiometry (DEXA) scan of vertebrae was done for BMD. Titanium pedicle screws of different diameters (5.2 and 6.2 mm) were inserted in the thoracic and lumbar segments after dividing the specimens into three groups: a) standard pedicle screw (no cortical perforation); b) screw with medial cortical perforation; and c) screw with lateral cortical perforation. Finally, pullout load of pedicle screws was recorded using INSTRON Universal Testing Machine.

Results:

Compared with standard placement, medially misplaced screws had 9.4% greater mean pullout strength and laterally misplaced screws had 47.3% lesser mean pullout strength. The pullout strength of the 6.2 mm pedicle screws was 33% greater than that of the 5.2 mm pedicle screws. The pullout load of pedicle screws in lumbar vertebra was 13.9% greater than that in the thoracic vertebra (P = 0.105), but it was not statistically significant. There was no significant difference between pullout loads of vertebra with different BMD (P = 0.901).

Conclusion:

The mean pullout strength was less with lateral misplaced pedicle screws while medial misplaced pedicle screw had more pullout strength. The pullout load of 6.2 mm screws was greater than that of 5.2 mm pedicle screws. No significant correlation was found between bone mineral densities and the pullout strength of vertebra. Similarly, the pullout load of screw placed in thoracic and lumbar vertebrae was not significantly different.     

可注射磷酸钙骨水泥对不同骨质椎弓根螺钉的强化作用

目的评价不同骨质疏松程度条件下,可注射性磷酸钙骨水泥对椎弓根螺钉稳定性强化作用,为其应用于合并有骨质疏松症的患者脊柱手术提供力学理论基础。方法采用新鲜尸体脊柱标本,根据骨密度检测结果,按临床诊断标准分成骨质正常、骨量减少、骨质疏松和重度骨质疏松四个水平;然后,每个骨密度水平,分直接置入椎弓根螺钉（对照组）和用可注射性磷酸钙骨水泥强化钉道后置入椎弓根螺钉（钉道强化组）,各12枚,进行螺钉轴向拔出实验,测定最大拔出力、刚度和能量吸收值三项指标,进行组间的对比分析。结果骨密度水平从正常下降到重度疏松程度,最大拔出力、刚度、能量吸收值均随之下降,同种置钉方法组间存在显著性差异（P〈0.05）。骨质疏松条件下钉道强化组最大拔出力、刚度、能量吸收值与骨量减少条件下对照组的比较,两者无显著性差异（P〉0.05）;但是,重度骨质疏松条件下钉道强化组的最大拔出力、刚度、能量吸收值均显著性低于骨量减少条件下对照组的（P〈0.05）。结论可注射性磷酸钙骨水泥强化钉道后可以提高椎弓根螺钉的稳定性,尤其是骨质疏松条件下经钉道强化后可以达到需要固定强度。     

磷酸钙骨水泥强化骨质疏松绵羊腰椎力学强度的动态观察

目的观察磷酸钙骨水泥（calcium phosphate cement,CPC）强化骨质疏松绵羊腰椎生物力学强度的体内动态变化。方法成年雌性绵羊12只行去势手术后饲养1年,测量去势前后腰椎骨密度。取L2~L5为实验对象,空白组不给予任何处理,CPC组中,经椎弓根向椎体内注射CPC 2.0 mL。于术后1 d、6周、12周和24周四个时间点各随机处死3只绵羊,对椎体行压缩实验,分别测量各组中椎体的最大压缩应力（ultimate compressive stress,σult）和能量吸收值（energy absorption value,EAV）,对比分析同一时间点不同方法之间和同一方法的不同时间点之间的力学指标。结果去势1年后绵羊腰椎骨密度显著下降,差异具有统计学意义（P〈0.05）,骨质疏松绵羊模型建立成功。空白组中各时间点之间的σult和EAV均无显著性差异（P〉0.05）,而CPC组中各时间点之间的σult和EAV也均无显著性差异（P〉0.05）;在同一时间点,CPC组螺钉的σult和EAV均显著高于对照组（P〈0.05）。结论 CPC对骨质疏松椎体的即时强度和远期强度均有显著的强化效果,它对椎体的强化效果在体内是动态稳定的,为脊柱达到坚强骨性融合提供了良好的力学环境。CPC作为一种生物相容性好、可降解吸收、可促骨生成和机械强度好的材料具有广阔临床应用前景。