复合骨水泥椎体间固定的生物力学研究及临床应用

按一定比例将脱钙骨粒掺入骨水泥，行成年犬椎体间固定。分别于术后２、４、８、１２周时处死。固定段行Ｘ线照片、ＣＴ扫描及生物力学测试。观察不同时相点的生物力学效应。结果显示：术后２、４周时复合骨水泥的抗压强度低于单纯骨水泥，８周时两者相近，１２周时高于单纯骨水泥与正常脊柱功能运动单位。     

注射型磷酸钙骨水泥和PMMA在椎体成形术中的生物力学研究

目的:模仿椎体成形术观察注射型磷酸钙骨水泥(calcium phosphate cement CPC)/聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)植入椎体后的生物力学改变.方法:将PMMA和CPC通过手术植入到犬椎体,经过8周和16周后分别取材,行X线、CT检查,并测定不同时间椎体的轴向抗压强度和抗扭转强度.结果:(1)植入早期,PMMA的抗压强度明显高于正常椎体和CPC(P＜0.01),CPC的抗压强度明显低于正常椎体和PMMA(P＜0.01).术后8周显示,PMMA的抗压强度有所下降(P＜0.01=0.009),CPC的抗压强度有所上升(P＜0.05=0.034),但与正常椎体相比仍差别显著.术后16周显示PMMA抗压强度继续下降(P＞0.05=0.710),CPC的抗压强度继续上升(P＞0.05=0.648),与正常椎体相比无显著性差异.(2)植入早期,PMMA的抗扭转强度明显高于正常椎体和CPC(P＜0.05=0.03),CPC的抗扭强度明显低于正常椎体和PMMA(P＜0.05=0.02).术后8周显示,PMMA的抗扭强度有所下降,但与正常椎体相比仍差别显著(P＜0.05=0.045),CPC的抗压强度有所上升与正常椎体相比差异不显著(P＞0.05=0.078).术后16周显示PMMA抗压强度继续下降(P＞0.05=0.137),CPC的抗压强度继续上升,与正常椎体相比无显著性差异(P＞0.05=0.847).结论:磷酸钙骨水泥是椎体成形术中治疗椎体压缩性骨折和胸腰椎爆裂骨折一种比较理想的材料,注入到椎体后,其生物力学强度有逐渐增强的趋势,而PMMA是机械固定,其生物力学强度有逐渐减弱的趋势.     

注射型磷酸钙骨水泥和PMMA在椎体成形术中的生物力学研究

目的模仿椎体成形术观察注射型磷酸钙骨水泥(calcium phosphate cement CPC)/聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)植入椎体后的生物力学改变.方法将PMMA和CPC通过手术植入到犬椎体,经过8周和16周后分别取材,行X线、CT检查,并测定不同时间椎体的轴向抗压强度和抗扭转强度.结果(1)植入早期,PMMA的抗压强度明显高于正常椎体和CPC(P＜0.01),CPC的抗压强度明显低于正常椎体和PMMA(P＜0.01).术后8周显示,PMMA的抗压强度有所下降(P＜0.01=0.009),CPC的抗压强度有所上升(P＜0.05=0.034),但与正常椎体相比仍差别显著.术后16周显示PMMA抗压强度继续下降(P＞0.05=0.710),CPC的抗压强度继续上升(P＞0.05=0.648),与正常椎体相比无显著性差异.(2)植入早期,PMMA的抗扭转强度明显高于正常椎体和CPC(P＜0.05=0.03),CPC的抗扭强度明显低于正常椎体和PMMA(P＜0.05=0.02).术后8周显示,PMMA的抗扭强度有所下降,但与正常椎体相比仍差别显著(P＜0.05=0.045),CPC的抗压强度有所上升与正常椎体相比差异不显著(P＞0.05=0.078).术后16周显示PMMA抗压强度继续下降(P＞0.05=0.137),CPC的抗压强度继续上升,与正常椎体相比无显著性差异(P＞0.05=0.847).结论磷酸钙骨水泥是椎体成形术中治疗椎体压缩性骨折和胸腰椎爆裂骨折一种比较理想的材料,注入到椎体后,其生物力学强度有逐渐增强的趋势,而PMMA是机械固定,其生物力学强度有逐渐减弱的趋势.     

丝素蛋白/双相磷酸钙/半水硫酸钙/重组人骨形态发生蛋白-2骨水泥的制备及修复椎体骨缺损的实验研究

目的 研制丝素蛋白(SF)/双相磷酸钙(BCP)/半水硫酸钙(CSH)/重组人骨形态发生蛋白-2(rhBMP-2)骨水泥,并探讨其在绵羊椎体内的成骨作用. 方法 制备SF/BCP/CSH/rhBMP-2骨水泥,分别在12只绵羊的L2 L3、L4椎体内制作直径为6.0mm、深度为10 mm的圆柱型骨缺损模型,在3个缺损处随机植入SF/BCP/CSH/rhBMP-2骨水泥作为实验组,植入聚甲基丙烯酸甲酯(PMMP)作为对照组,另一椎体缺损处不植入任何材料作为空白对照组.术后3、6个月分别随机处死6只绵羊进行CT、组织学和生物力学检查.结果 CT和组织学检查显示:术后3个月实验组椎体密度与正常椎体相似,骨缺损修复基本完成,术后6个月骨缺损修复完成;对照组术后3、6个月时PMMP无降解,并与骨之间结合疏松,表面无新骨形成;空白对照组术后3、6个月时骨缺损一直存在.生物力学测试显示:术后3、6个月时实验组椎体抗压强度和刚度与正常椎体相比差异无统计学意义(P＞0.05). 结论 SF/BCP/CSH/rhBMP-2骨水泥具有良好的成骨作用,在成骨过程中能维持椎体的力学性能,有望成为经皮椎体强化术的一种可降解、具成骨作用的填充剂.     

后路椎弓根钉固定结合硫酸钙骨水泥椎体成形术治疗新鲜胸腰椎压缩性骨折

目的探讨后路椎弓根钉固定结合硫酸钙骨水泥椎体成形术治疗新鲜胸腰椎压缩性骨折的临床疗效。方法选择性对70例新鲜胸腰椎压缩性骨折患者采用后路复位椎弓根钉内固定结合硫酸钙骨水泥椎体成形术治疗。分别于术前、术后1周及随访终末观测脊柱后突角、椎体前后缘高度压缩率变化;观察内固定稳定状况及神经损伤的恢复情况。结果 8例发生骨水泥渗漏。57例获得平均17个月随访,1例发生内固定断裂。脊柱后凸角、椎体前后缘高度压缩率:末次随访与术前比较,差异有统计学意义(P0.05);与术后1周比较,差异无统计学意义(P0.05)。术后神经功能按Frankel分级评定:E级54例,D级3例。结论后路椎弓根钉固定结合硫酸钙骨水泥椎体成形术治疗新鲜胸腰椎压缩性骨折,可有效恢复脊柱单元的生物力学稳定性,进而避免后突矫正度丢失、内固定松动断裂等并发症的发生及促进神经功能的恢复。     

BCC骨水泥椎体成形术强化骨质疏松性椎体压缩性骨折的实验研究

目的 比较新型带负电荷硫酸钙/β-磷酸三钙复合骨水泥(BCC骨水泥)与甲基丙烯酸甲酯骨水泥(PMMA骨水泥)用于椎体成形术的生物力学性能,探讨BCC骨水泥用于椎体成形术的可能性.方法 采用4具老年男性骨质疏松性尸体胸腰段脊柱标本,建立椎体压缩性骨折的模型,随机分为2组,每组8例,分别以2 ml/min注入BCC组和PMMA组的骨水泥,测试术前、术后椎体的强度和刚度的变化.结果 BCC组和PMMA组骨折前与骨折治疗后最大载荷间的差异具有统计学意(P＜0.05),且两组治疗后的最大载荷均高于骨折前;而BCC组和PMMA组骨折前与骨折治疗后刚度间的差异均无统计学意义(P＞0.05).结论 BCC骨水泥椎体成形术能强化骨质疏松性椎体压缩性骨折,达到生物力学要求.     

胸腰椎内固定和椎体增强技术对邻近节段影响的生物力学分析

[目的]探讨采用内固定或椎体增强技术后邻近节段生物力学特性的变化.[方法]12具尸体胸腰椎标本,分为正常对照组、椎体压缩骨折后经椎弓根自体骨植骨组、椎体成形术组、RF内固定组分别进行实验应力分析.应力加载方式为轴向压缩、前屈、后伸、侧屈等4种,通过各种工况的生物力学测试,说明采用内固定或椎体增强技术后邻近节段力学特性的变化.[结果]采用椎体内植骨或骨水泥填充的方法,有使邻近节段的刚度降低,应力强度提高的轻微趋势,但无显著性差异（P＞0.05）.而采用内固定后,邻近节段刚度明显降低,应力强度明显提高,呈显著性差异（P＜0.05）.[结论]采用椎体内植骨或骨水泥填充的方法对邻近节段的影响较小,而采用内固定后对邻近节段产生了不利的生物力学影响.     

Genex骨水泥结合短节段椎弓根内固定治疗骨质疏松性骨折伴真空征

目的评估Genex骨水泥椎体成形术结合短节段椎弓根内固定治疗骨质疏松性椎体压缩骨折（osteoporotic vertebral compression fracture,OVCF）伴椎体真空征的疗效。方法 2008年3月至2010年7月,采用Gennex骨水泥椎体成形术结合短节段椎弓根内固定治疗23例OVCF伴椎体真空征患者,其中18例获得随访,男7例,女11例;年龄57～71岁,平均64岁。病程3～14个月,平均8.4个月。根据Kraus5,标准均诊断为椎体真空征。术后定期随访,通过侧位X线片测量伤椎的前、中、后缘高度和局部后凸角,采用SF-36健康调查评分表评估患者术后生活质量的改善。结果所有患者均顺利完成手术,无严重并发症发生。18例术后随访时间9～38个月,平均18个月。Genex骨水泥术后3个月开始吸收,6个月时候完全吸收。椎体骨折愈合时间为4～6个月,平均4.5个月。伤椎前缘、中部高度较术前明显恢复,差异有统计学意义（P〈0.05）,后缘高度手术前后各时间点差异均无统计学意义（P〉0.05）。末次随访时椎体高度维持良好（P〉0.05）。术后SF-36评分表8个分项维度中有7个显著提高,与术前相比,差异有统计学意义（P〈0.05）,末次随访时7个分项维度均得到较好的维持,和术后相比差异无统计学意义（P〉0.05）。术后1周CT复查发现2例发生骨水泥椎间隙渗漏,但均术无临床症状。结论 Genex骨水泥椎体成形术结合短节段椎弓根内固定治疗骨质疏松性椎体压缩骨折伴椎体真空征,术后可即可缓解疼痛,恢复椎体高度,减小后凸畸形,恢复脊柱矢状序列,提高患者的生活质量,并且在椎体骨折愈合后Genex骨水泥在体内完全降解。     

负载重组人骨形态发生蛋白2的α型半水硫酸钙/纳米羟基磷灰石复合植骨材料的成骨性能研究

目的:评价负载重组人骨形态发生蛋白2(rh BMP-2)的α型半水硫酸钙/纳米羟基磷灰石(α-CSH/n HA)复合植骨材料的成骨性能。方法:制备可注射性α-CSH/n HA/rh BMP-2复合材料,取12只成年绵羊,分别经左侧椎弓根在L1~L6椎体上制作直径6mm、深15mm的6个洞形缺损,第一只绵羊的椎体缺损随机分为3组,其余羊的椎体都按此进行分组,即L2、L5为实验组,L1、L4为对照组,L3、L6为空白对照组。实验组植入α-CSH/n HA/rh BMP-2复合材料;对照组植入可注射性磷酸钙骨水泥(CPC);空白对照组不植入任何材料。术后4、8、12周各处死4只动物,取椎体标本分别行X线及micro-CT扫描,观察缺损修复情况;行生物力学检查,测定椎体压缩强度和压缩模量;行组织学观察比较新骨生成率。结果:术后4周时,实验组压缩强度及压缩模量与CPC组的差异无统计学意义(P0.05),实验组和对照组均显著性高于空白对照组(P0.05);术后8周和12周时实验组和对照组均显著性高于空白对照组(P0.05),实验组显著性高于对照组(P0.05)。影像学及组织学结果显示,术后4周时,实验组复合材料大部分已降解,密度稍低于正常骨,可见大量纤细短小、尚未塑形的新生骨小梁,边缘有大量成骨细胞环绕;对照组CPC材料呈高密度充满整个缺损,未见明显降解吸收征象,材料与骨的界限明显,缺损边缘有少量幼稚骨小梁形成;空白对照组缺损较大,边缘整齐,几乎看不到有新骨生成。术后8周时,实验组复合材料完全降解,缺损内新生骨小梁数量增多,增粗变长,且开始早期塑形;对照组材料开始部分降解,在边缘和中心降解区可见明显新骨形成,新生骨小梁数量较实验组少;空白对照组缺损修复不明显,边缘只可见少量新生骨小梁。术后12周时,实验组缺损完全被新生骨小梁充满,骨小梁趋于成熟,结构与正常骨小梁相似,密度与正常骨接近,很难与正常部位区分;对照组CPC大量降解,只残留一小团块状和零星的材料,缺损边缘修复明显,新生骨小梁长入残余材料内,将其分割成岛屿状;空白对照组缺损依然较大,呈低密度影清晰可见,新骨生成很少。结论:α-CSH/n HA/rh BMP-2复合材料在绵羊体内具有良好的成骨活性,是较好的微创植骨材料。     

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。     

Biomechanical effect of vertebropiasty on the adjacent intervertebral levels using a three-dimensional finite element analysis

Objective: To investigate the biomechanical effect of different volume, distribution and leakage to adjacent disc of bone cement on the adjacent vertebral body by three-dimensional osteoporosis finite element model of lumbar. Methods: L4 -L5 motion segment data of the cadaver of an old man who bad no abnormal findings on roentgenograms were obtained from computed tomography (CT) scans. Three-dimensional model of L4-L5 was established with Mimics software, and finite element model of L4-L5 functional spinal unit (FSU) was established by Ansys 7. 0 software. The effect of different loading conditions and distribution of bone cement after vertebroplasty on the adjacent vertebral body was investigated. Results: This study presented a validated finite element model of L4-L5 FSU with a simulated vertebroplasty augmentation to predict stresses and strains of adjacent untreated vertebral bodies. The findings from this FSU study suggested the endplate and disc stress of the adjacent vertebral body was not influenced by filling volume of bone cement but unipedicle injection and leakage to the disc of bone cement could concentrate the stress of adjacent endplate. Conclusions: Asymmetric distributions and leakage of cement into intervertebral disc can improve the stress of endplate in adjacent vertebral body. These results suggest that optimal biomechanical configuration should have symmetric placement and avoid leakage of cement in operation.     

美罗培南骨水泥体外生物力学及洗脱特性研究

目的 研究不同含量的美罗培南骨水泥的体外生物力学特性和药物洗脱特性.方法 40 g骨水泥(Palacos LV,40 g聚合物粉剂+20 ml单体液剂)中分别加入2、4、6 g注射用美罗培南和2、4 g注射用盐酸万古霉素复合,制备成A2、A4、A6、B2、B4和不含抗菌药物的对照组共6组样品.对6组样品分别进行能承受的...     

应用microCT技术对中药干预去卵巢小鼠骨组织微结构的分析

目的应用micro CT技术观察健骨颗粒对C57小鼠去卵巢骨质疏松模型骨组织骨量、骨微结构及生物力学的影响。方法将4周龄清洁级C57小鼠30只随机分为三组(假手术组10只、卵巢切除小鼠两组各10只),两组卵巢切除小鼠术后1周开始,分别用健骨颗粒和生理盐水进行灌胃,假手术组用生理盐水灌胃。2个月后,小鼠左胫骨行micro CT检测及图像分析、右胫骨行生物力学三点抗压最大载荷检测。结果与假手术组比较,去卵巢组BMC、BMD、Mean、BV、BS显著下降(P0.01),TMC下降(0.01P0.05);与去卵巢组比较,去卵巢中药组BMC、BMD、Mean指标显著提高(P0.01);图像分析结果显示去卵巢组较假手术组骨皮质薄,骨小梁数量少,形态细小、不连续呈扭曲或断裂状等明显骨质疏松病理特征,去卵巢中药组介于两者之间。生物力学结果显示三组胫骨三点抗压最大载荷均具有明显差异(P0.01)。结论去卵巢2月成功建立小鼠绝经后骨质疏松症模型;健骨颗粒抗骨质疏松作用明显,主要通过增加骨量和改善骨小梁微结构来最终提高骨强度;micro CT对骨质疏松参数分析简洁、高效,图像多维、全面,与传统的检测方法相比,具有一定的优势。     

Biomechanical effect of vertebroplasty on the adjacent intervertebral levels using a three.dimensional finite element analysis

Objective： To investigate the biomechanical effect of different volume, distribution and leakage to adjacent disc of bone cement on the adjacent vertebral body by threedimensional osteoporosis finite element model of lumbar. Methods ： L4-L5 motion segment data of the cadaver of an old man who had no abnormal findings on roentgenogrmns were obtained from computed tomography （CT） scans. Three-dimensional model of L4-L5 established with Mimics software, and finite element model of L4-L5 functional spinal unit （FSU） was established by Ansys 7. 0 software. The effect of different loading conditions and distribution of bone cement after vertebroplasty on the adjacent vertebral body was investigated. Results： This study presented a validated finite element model of L4-L5 FSU with a simulated vertebroplasty augmentation to predict stresses and strains of adjacent untreated vertebral bodies. The findings from this FSU study suggested the endplate and disc stress of the adjacent vertebral body was not influenced by filling volume of bone cement but unipedicle injection and leakage to the disc of bone cement could concentrate the stress of adjacent endplate. Conclusions： Asymmetric distributions and leakage of cement into intervertebral disc can improve the stress of endplate in adjacent vertebral body. These results suggest that optimal biomechaulcal configuration should have symmetric placement and avoid leakage of cement in operation.     

Experimental study on the repair of tibial plateau defect

Objective: To evaluate the effect of autograft bone,allograft bone,calcium sulfate bone cement,and calcium phosphate bone cement on the repair of tibial plateau defect in rabbits.Methods: We used autog...     

不同年龄尾吊鼠负重骨骨代谢及力学性能变化

目的 比较尾吊脱负荷对不同发育阶段大鼠负重骨骨代谢和生物力学性能的影响程度。方法 将年幼2月龄和成年6月龄雄性SD大鼠分别随机分至尾吊组（S2M，S6M）和对照组（C2M，C6M）。4周后，生物材料试验机测负重骨生物力学性能，灰化法和原子吸收分光光度法测骨矿盐和钙含量。结果 （1）尾吊引起鼠胫骨体积，湿重，干重和骨矿物盐含量明显减少（P＜0．01），其中，胫骨体积，湿重减少与年龄有关（P＜0．05）；（2）2月龄和6月龄尾吊鼠骨矿盐含量分别减少4．32％，2．78％，与骨钙丢失程度0．53％，3．05％并不一致；（3）除弹性负荷外（P＞0．05），尾吊使负重骨各力学指标显著下降（P＜0．01），且最大桡度和最大负荷下降与月龄有关（P＜0．05）。结论 肢体废用对不同发育阶段大鼠负重骨的影响程度并不相同。     

骨水泥在骨质疏松性骨折椎体内分布状态与生物力学性能的关系

 目的 研究骨水泥在腰椎骨质疏松性骨折椎体内不同区域分布状态的生物力学特性,为经皮椎体后凸成形术(percutaneous kyphoplasty,PKP)临床应用提供理论依据。方法 取12具福尔马林固定的老年尸体腰椎标本(包括L1~L5),共筛选49个椎体。对各椎体标本施加轴向压力负载,测量各椎体的原始强度和刚度,并建立椎体压缩骨折模型。按临床PKP手术操作要求根据不同的椎体分区灌注骨水泥,分为对照组和6个实验组,每组7个椎体。测量每组的最大压缩强度和刚度。结果 PKP术后各实验组最大压缩强度较初始强度均明显增强。单侧前2/3灌注组和单侧后2/3灌注组比较,单侧全灌注组、双侧前2/3灌注组和双侧后2/3灌注组比较差异均无统计学意义;椎体最大压缩强度双侧全灌注组>单侧全灌注组、双侧前2/3灌注组和双侧后2/3灌注组>单侧前2/3灌注组和单侧后2/3灌注组。PKP术后双侧全灌注组椎体刚度和初始刚度比较差异无统计学意义,其余各组度均明显小于初始刚度。单侧前2/3灌注组、单侧后2/3灌注组和单侧全灌注组比较,D和双侧后2/3灌注组比较差异无统计学意义;双侧全灌注组>双侧前2/3灌注组和双侧后2/3灌注组> 单侧前2/3灌注组、单侧后2/3灌注组和单侧全灌注组。结论 骨水泥分布在骨质疏松性骨折椎体的不同区域,其生物力学性能存在差异,骨水泥在椎体双侧分布较单侧分布可以获得更好的生物力学效应。骨水泥均匀分布于椎体前2/3区域是较为理想的分布状态,但仍需临床进一步验证。     

Biomechanical evaluation of kyphoplasty with calcium phosphate cement in a 2-functional spinal unit vertebral compression fracture model

BACKGROUND CONTEXT: Kyphoplasty is used to treat vertebral compression fractures (VCFs) by inflating a balloon within the vertebral body (VB) to create a void, thereby reducing the fracture, and then depositing polymethylmethacrylate (PMMA) into that void to augment the VB. Calcium phosphate (CaP) may be preferable to PMMA because it is resorbable and nontoxic, although there are concerns about its compressive strength during the setting process. PURPOSE: To evaluate the ability of a particular self-setting CaP cement to restore the structural integrity of a VCF in a 2-functional spinal unit (2FSU) cadaver model under physiologically relevant loading. STUDY DESIGN/SETTING: Repeated-measures compressive testing on a cadaver thoracolumbar 2FSU VCF model. METHODS: Ten 2FSU thoracolumbar specimens were tested to evaluate structural integrity under compressive loading during initial anterior VCF creation (in the central VB), after fracture, and after kyphoplasty treatment. Bipedicular kyphoplasty treatment was performed in a 37 degrees C chamber to reduce the fracture and create a void, which was filled with CaP (n=5) or PMMA (n=5) and allowed to cure for at least 15 minutes. Using fluoroscopic imaging, the sagittal area of the VB (SAVB), the minimum central VB height (MCVBH), and the wedge angle were measured on the central VB for each condition at a 1,000-N compressive load. A repeated-measures linear model was used to determine if the differences in these parameters among the various experimental conditions were statistically significant (p< .05). RESULTS: Compared with the fractured condition, there was a significant improvement in the SAVB, MCVBH, and wedge angle under a physiologically relevant 1,000-N compressive load applied after kyphoplasty. There was no statistically significant difference between treatment with CaP or PMMA. CONCLUSIONS: The structural properties of CaP-augmented VBs are similar to those of PMMA-augmented VBs. Our study indicated that, after at least 15 minutes of setting, a fractured 2FSU specimen treated with kyphoplasty with PMMA or CaP could withstand physiologically relevant loading.     

Differences in endplate deformation of the adjacent and augmented vertebra following cement augmentation

Vertebral cement augmentation can restore the stiffness and strength of a fractured vertebra and relieve chronic pain. Previous finite element analysis, biomechanical tests and clinical studies have indirectly associated new adjacent vertebral fractures following augmentation to altered loading. The aim of this repeated measures in situ biomechanical study was to determine the changes in the adjacent and augmented endplate deformation following cement augmentation of human cadaveric functional spine units (FSU) using micro-computed tomography (micro-CT). The surrounding soft tissue and posterior elements of 22 cadaveric human FSU were removed. FSU were assigned to two groups, control (n = 8) (loaded on day 1 and day 2) and augmented (n = 14) (loaded on day 1, augmented 20% cement fill, and loaded on day 2). The augmented group was further subdivided into a prophylactic augmentation group (n = 9), and vertebrae which spontaneously fractured during loading on day 1 (n = 5). The FSU were axially loaded (200, 1,000, 1,500–2,000 N) within a custom made radiolucent, saline filled loading device. At each loading step, FSUs were scanned using the micro-CT. Endplate heights were determined using custom software. No significant increase in endplate deformation following cement augmentation was noted for the adjacent endplate (P > 0.05). The deformation of the augmented endplate was significantly reduced following cement augmentation for both the prophylactic and fracture group (P < 0.05, P < 0.01, respectively). Endplate deformation of the controls showed no statistically significant differences between loading on day 1 and day 2. A linear relationship was noted between the applied compressive load and endplate deflection (R ² = 0.58). Evidence of significant endplate deformation differences between unaugmented and augmented FSU, while evident for the augmented endplate, was not present for the adjacent endplate. This non-invasive micro-CT method may also be useful to investigate endplate failure, and parameters that predict vertebral failure.     

Intravertebral body reconstruction with an injectable in situ-setting carbonated apatite: biomechanical evaluation of a minimally invasive technique.

The ability to mechanically reinforce an osteoporotic vertebral body could impede spinal compression fracture and the associated pain and complications. Previous studies have shown that reinforcement of fractured vertebrae with conventional acrylic cement can relieve symptoms and avoid further collapse. In this study, we explored the use of a carbonated apatite cement combined with a minimally invasive injection technique to improve the compressive mechanical properties of cadaveric vertebral bodies. After establishing the biomechanical characteristics of cement formulations intended to have appropriate viscosities, we evaluated the infiltration of the cements into thoracic vertebral bodies using a combined suction-injection technique. The energy-absorption capabilities of the reinforced vertebral bodies were then measured during axial compressive tests and compared with those of nonreinforced vertebrae. The ultimate compressive strength of the cement formulations averaged from 11.6 to 17.7 MPa, depending on curing conditions. The suction-injection technique allowed from one-half to two-thirds of each vertebral body to be infiltrated with cement. Energy absorption was significantly higher (p < 0.05) between 25 and 70% collapse of the vertebral body in the specimens that received the apatite injection as compared with the controls. These results suggest that osteoporotic vertebral-body augmentation with the injection of apatite cement could prevent further collapse after initial failure has occurred. The osteoconductive nature of the cement and its ability to be remodeled by bone, together with its compressive strength, which is higher than that of cancellous bone, could provide better clinical results than those of current treatments with acrylic cement.