C5-6、T12-L1、L4-5椎间盘与相邻椎体的压缩力学特性

对比分析C5-6、T12-L1、L4-5椎间盘与相邻椎体的压缩力学性质,确定不同部位的椎间盘与相邻椎体是否具有不同的压缩力学性质.人死后1 h内解剖取出死者C1-S1脊柱标本,以线锯切取C5-6、T12-L1、L4-5椎间盘与相邻椎体标本各13个.在日本岛津电子万能实验机上进行实验.实验速度为5 mm/min,以统计分析和t检验的方法处理实验数据.L4-5组椎间盘与相邻椎体最大载荷大于T12-L1和C5-6组,差异显著(P＜0.01);C5-6组最大位移大于L4-5组和T12-L1组,差异显著(P＜0.01);L4-5组椎间盘与相邻椎体最大应力大于C5-6和T12-L1组,差异显著(P＜0.01);C5-6组椎间盘与相邻椎体最大应变大于L4-5和T12-L1组,差异显著(P＜0.01).C5-6、T12-L1、L4-5椎间盘与相邻椎体标本的压缩力学性质有一定区别.     

CT后处理技术重建CT值与终板抗压强度的相关性研究

目的 探讨CT后处理技术重建CT值与终板抗压强度的相关性。方法 采用常规CT扫描5具小牛腰椎后,利用CT后处理技术重建终板并测量5个标准化测试位点的平均CT值,接着将腰椎分解成30个游离椎体,在骨性终板的标准化测试位点上使用直径5 mm的平底压头,以12 mm/min的速率进行单轴压缩实验,并根据载荷位移曲线确定每个测试位点的失效载荷值以计算抗压强度,使用组内相关系数验证测量结果一致性,应用相关性检验分析重建CT值与终板抗压强度的相关性。结果 小牛椎体测试位点的重建CT值与抗压强度的观察者内和观察者间的组内相关性系数均大于0.9,对应测试位点的重建CT值和抗压强度具有强相关性（r>0.8, P<0.01）。结论 CT后处理技术重建终板CT值与终板抗压强度之间存在显著的相关性,可以作为术前评估终板强度的参考指标。     

中国人腰椎间盘结构与人工椎间盘置换相关的参数测量

背景：全椎间盘置换已应用多年,但国内鲜见对人腰椎间盘结构测量的大样本系统研究。 目的：为中国人腰椎间盘假体置换手术和设计提供参考数据。 方法：选取中国成年尸体41具(男22例,女19例),解剖获得完整的腰椎标本。测量椎体软骨板断面厚度。随机抽取正常成年人标准腰椎正侧位X射线片157例(男89例,女68例)。测量椎体上/下横径、上/下矢状径和椎间隙高度。 结果与结论：成年尸体及正常成年人标准腰椎正侧位X射线片显示腰椎间盘软骨板厚度、椎体上/下横径、矢状径和椎间隙高度均不存在性别差异(P > 0.05)。除L1/2相邻椎体矢状径、L3/4相邻椎体横径和L4/5相邻椎体矢状径外,其余椎间盘相邻椎体横径或矢状径的差异有显著性意义(P < 0.05),但各径线实测数值之间差距均较小。腰椎间隙自L1/2至L4/5逐渐增宽,前缘高度大于后缘高度。L5/S1椎间隙与其他腰椎间隙存在较大差异,其相邻终板间夹角明显增大。     

椎体截面的数理学原理分析与脊柱病变的探讨

目的　测量脊柱椎体终板截面的横径与矢径,利用数理学原理分析脊柱椎体-椎间盘受力传递规律,分析人体脊柱椎体-椎间盘的受力规律与临床病理联系。 方法　测量10具完整脊柱标本C2~S1各椎体上下截面的横径（L）、矢径（H）,运用几何学相似原理:椎体/椎间盘上下截面面积变化可近似用数学方程表达,S1/S2=(a*b)/(A*B),S=π/4*L*H,分析椎体上下截面的结构规律;根据椎间盘的结构,利用物理学静水液压原理：F1/F2=S1/S2,分析椎间盘压力变化规律;根据数理学原理推测脊柱椎体-椎间盘的结构与力学规律。 结果　脊柱椎体截面的结构从C2下截面到L4下截面面积呈“S”形曲线递增,L4下截面面积最大,L4下截面到S1上截面递减;椎体-椎间盘间截面横径矢径决定其椎体截面面积、压力系数K,K=L*H。 结论　脊柱椎体-椎间盘自身结构决定了脊柱特有的力学传递与分布规律;建立数理学方程来认识脊柱的结构与力学传递规律能更直观的理解与观察脊柱力学特性与临床脊柱病变规律。     

椎基静脉孔及椎体静脉解剖在椎体成形术中的意义

目的　为胸腰椎（T8～L5）椎体成形术减少骨水泥渗漏等并发症提供解剖学依据。 方法　对40例健康成人胸腰椎螺旋CT薄层扫描和重建,观察每节段正中矢状位和横断位图像上椎基静脉孔（basivertebral foramen, BF）和椎体静脉孔道(vertebral vein, VV)出现的频率;测量椎体正中矢状径（VD）和BF宽（BFW）、深（BFD）高（BFH）;测量BF距椎体左右缘距离（VW1和VW2）和距上下终板的距离（VH1和VH2）,应用Stata7.0统计学软件包对上述数据进行统计学分析。 结果 BF及VV出现的频率从T8到L5逐渐增大,BF和VV观察到的频率在性别间差异无统计学意义（P＞0.05）。BFW、BFH、BFD从T8至L5随椎体增大相应增大。在不同椎体上BFD约为VD的1/3。VW1和VW2之间差异无统计学意义（P＞0.05）;VH1和VH2之间差异有统计学差异(P＜0.05)。BF更接近椎体上终板。 结论 熟悉BF和VV在椎体内的分布有助于减少椎体成形术中骨水泥渗漏等并发症的发生。     

椎体后凸成形后相邻椎体生物力学的有限元分析

背景:椎体后凸成形后相邻椎体新发骨折的发生率为2.4%～23%,并且6个月内2/3骨折发生于邻近椎体,其原因是骨质疏松的发展,还是骨水泥强化的结果,目前存有争论。目的:应用脊柱有限元分析方法分析生理载荷作用下,椎体后凸成形后相邻椎体终板的应力变化与相邻椎体新发骨折的相关性。方法:收集老年骨质疏松女性胸腰椎CT扫描资料,利用一系列计算机辅助设计软件构造相对应的T12-L1-L2骨质疏松性椎体的三维有限元模型。模拟L1椎体为楔形压缩骨折椎体(前缘高度较正常降低60%),模拟经皮椎体后凸成形模型,复位骨折椎体(L1椎体高度较正常降低10%,代表骨折椎体复位),在L1椎体内置入2个对称的圆柱体PMMA骨水泥块共约4mL。分析轴向压缩、前屈和后伸3种加载状态下正常椎体、手术前后相邻椎体的应力变化情况。结果与结论:与正常椎体比较,L1压缩性骨折模型和椎体后凸成形后模型相邻椎体终板最大应力值分别增高76%和27%;椎体后凸成形模型后部结构的应力水平较正常椎体平均增加13.2%,其中椎弓根增加4.5%,峡部增加6.15%和关节点增加25.6%。与L1椎体压缩性骨折模型相比,L1椎体后凸成形后椎弓根、峡部和关节突应力均有所降低。结果说明椎体后凸成形后,T12椎体下位终板和L2椎体上位终板的应力值在各种状态下均较正常椎体增加,应力增加可能导致终板骨折可能性增加,进而导致相邻椎体骨折的风险性增加,这一观点尚需进一步研究的支持。     

C2-3、T10-11和L3-4椎间盘段弯曲力学特性

预防和治疗椎间盘脱出等退行性改变需要了解C2-3、T10-11、L3-4椎间盘与相邻椎体的弯曲力学特性,本文对人体C2-3、T10-11、L3-4椎间盘与相邻椎体进行弯曲试验,为临床提供生物力学参数.实验标本取自正常人新鲜尸体脊柱标本,男性,年龄20～30岁,人死后1h内解剖尸体取出C1-S1脊柱标本,以线锯切取C2-3、T10-11、L3-4椎间盘与相邻椎体各13个标本,在日本岛津电子万能测试机上以5 mm/min的实验速度进行弯曲实验,得出C2-3、T10-11、L3-4组标本的最大载荷、最大弯矩、最大应力等力学参数.实验结果得出,C2-3组标本最大载荷、最大弯矩小于T10-11组和L3-4组,有显著性差异（p〈0.05）;C2-3组标本最大应力小于T10-11组,有显著性差异（p〈0.05）;L3-4组最大应力大于T10-11组和C2-3组,有显著性差异（p〈0.05）.此结果说明C2-3、T10-11、L3-4椎间盘与相邻椎体具有不同的抗弯曲力学特性,可对了解腰椎间盘的损伤机理提供生物力学参.     

椎体后凸成形对邻近节段力学影响的有限元分析

背景:椎体后凸成形术自应用临床以来取得了令人鼓舞的临床效果,但是术后邻近椎体发生骨折时有报道。从生物力学角度来分析邻近椎体发生骨折的可能原因具有重要价值。目的:以有限元方法观察椎体后凸成形术对相邻椎体生物力学的影响,分析相邻椎体继发骨折的原因。方法:利用MIMICS软件对1例T12压缩骨折椎体后凸成形术前后的CT图片进行预处理,后导入ABAQUS软件中建立T10~L2的三维有限元模型,设置0.3,1.0,4.0MPa三种轴向载荷进行生物力学分析,观察不同载荷下模型整体及各部分的Von Mises应力,重点评价椎体后凸成形术对骨折相邻椎体生物力学的影响。结果与结论:成功建立了椎体后凸成形术前后的三维有限元模型,当轴向压力以0.3,1.0,4.0MPa增加后,椎间盘、软骨终板和椎体整体的应力也成比例增加。椎体后凸成形术后脊柱胸腰段各部位的应力开始重新分布,增强椎体(T12)的相邻椎间盘(T11~12、T12~L1)及相邻终板(T11下终板、L1上终板)的应力增强区域增加;T12相邻椎体(T11,L1)所受最大应力明显增加,但远端椎体(T10,L2)的最大应力明显减少。提示椎体后凸成形术后引起上下相邻椎体继发骨折可能与术后生物力学行为的改变有关。     

经皮椎体成形术的实验研究及临床应用

目的 :完善经皮椎体成形术的方法并对其临床疗效进行评价。方法 :5具新鲜胸腰段脊柱 (T9～L5)标本随机选取 1 0个椎体节段行椎体成形术 ,观察PMMA在椎体内分布并进行椎体压缩试验。临床选择 4例骨质疏松腰椎压缩性骨折患者行经皮椎体成形术 ,观察其临床效果。结果 :1 0个椎体节段均穿刺顺利 ;PMMA骨水泥在椎体内沿骨小梁分布至整个椎体 ,有 1例出现椎体后静脉窦渗漏 ;椎体成形术后抗压强度由 (2 1 97± 355)N增加至 (4861 1 1 0 9)N ;临床治疗 4例患者疗效好 ,未出现椎体外漏导致的并发症。结论 :在C臂X线机透视引导下经皮椎体成形术安全、可靠 ;对骨质疏松椎体压缩性骨折具有良好疗效     

椎体强化术后恢复高度对邻近椎体的影响:一项有限元分析

背景:椎体压缩骨折是当前骨科领域中常见的疾病,椎体强化术后邻近椎体发生再骨折是一个不可忽视的问题,这对患者的正常生活产生了严重的影响。目的:旨在利用CT图像,建立不同恢复高度的椎体强化后模型。采用有限元分析的方法得出不同恢复高度下邻近椎体的应力情况,并进一步探讨椎体强化术后伤椎高度恢复的重要性。方法:建立并验证了胸腰椎(T_(11)-L3)有限元模型,并在此基础上构建了4种不同恢复高度(100%,80%,60%,40%)的L1术后有限元模型,其中骨水泥容量随着恢复高度的变化而变化。具体模型如下:Model 1为正常恢复高度的术后模型,骨水泥容量为8.3 mL;Model 2为L1前部高度切除20%,后凸角变为10.41°的术后模型,骨水泥容量为6.9 mL;Model 3为L1前部高度切除40%,后凸角变为20.17°的术后模型,骨水泥容量为4.7 mL;Model 4为L1前部高度切除60%,后凸角变为28.85°的术后模型,骨水泥容量为3.6 mL。对术后模型进行评估时,施加了7Nm的力矩和500N的轴向力,记录并分析L2上终板和T12下终板的峰值应力,以及L2和T12松质骨的峰值应力。结果与结论:①L2上终板、T12下终板、L2松质骨、T12松质骨各工况的最高峰值应力都出现在Model 1和Model 4,特别是T12下终板(除后伸工况外),前屈、左右侧弯和左右旋转工况都在Model 4达到了最高峰值应力,应力分别为50.3,33.1,44.9,34.3,31.9 MPa;②根据邻近椎体终板和松质骨的峰值应力,排除Model 1和Model 4两个模型后,大部分工况的最小峰值应力都是出现在Model 2模型上,且Model 2模型出现最小峰值应力的情况占据了66.6%,尤其是在L2的上终板和松质骨(除后伸工况外),最小峰值应力都是出现在了Mode 2上;③因此将恢复高度控制在原高度的100%和40%左右是比较危险的恢复高度,对邻近椎体的影响较大;将恢复高度控制在原高度的80%左右可能是一个较为理想的选择;恢复高度在原高度的80%左右,邻近椎体所承受的应力较小,从而减小了患者发生邻近椎体再骨折的风险。     

颈脊柱姿势及椎间盘水化状态对颈脊柱运动单位整体压缩强度影响——体外力学分析

目的通过体外力学分析,研究颈脊柱姿势及椎间盘水化状态对颈脊柱运动单位整体压缩强度的影响。方法选用12具成人健康新鲜尸体颈段脊柱,解剖出C3-4、C5-6共24个运动单位(包括上下两个椎体和椎间盘)。施以压缩负荷,观察两种预负荷?状态(脱水和高度水化状态)和两种姿势(中立位和屈曲位)下颈段脊柱的极限压缩强度。通过解剖来明确颈椎的损伤。结果标本屈曲位时极限压缩强度比中立位时小(27%42%,P<0.001);在中立位外来负荷下,高度水化状态标本的极限压缩强度小于脱水状态的标本(29%,P<0.01)。结论晨起椎间盘高度水化状态下以及颈脊柱屈曲位时,受到外来负荷颈脊柱易损伤。     

腰椎爆裂骨折椎体松质骨内力学分布特点的有限元研究

目的运用有限元方法模拟腰椎爆裂骨折的过程,观察腰椎在轴向压缩载荷作用下松质骨内的应力分布情况。方法建立正常人体胸腰段(T12~L2)运动节段的三维有限元模型,在T12椎体上表面施加不同等级的压力(0.4、0.6、0.8、1.0、1.2 k N),模拟腰椎爆裂骨折发生时椎体承受的不同等级的轴向压缩载荷。将连接椎体上下终板凹面顶点的连线7等分,在此基础上将L1椎体中的松质骨划分为7个具有统计节点的层面,每个统计层面划分成6个统计区。分别测量L1椎体松质骨内3个层面(第1、4、7层面)18个统计区的平均应力。在同一等级载荷下对3个层面内的平均应力进行单因素方差分析,分析腰椎椎体松质骨内不同载荷作用下的应力分布情况。结果在5个不同等级载荷下,第1、7层松质骨平均应力分别与第4层比较有统计学意义(P0.05),而第1、7层平均应力比较无统计学意义(P0.05)。轴向加载时,相比第1、7层应力,椎体松质骨中间层面(第4层)应力最小。结论腰椎在轴向压缩载荷作用下,椎体松质骨内存在应力集中的现象,接近椎体上下软骨板的松质骨应力较大,而椎体松质骨中间层面应力较小,椎体内应力集中分布在上下软骨板的特点与腰椎爆裂骨折所致终板破裂的生物力学机制相一致,提示腰椎椎体骨结构损伤可能与椎体内应力集中有关。     

Biomechanical modeling of brace treatment of scoliosis: effects of gravitational loads

The biomechanics of bracing in adolescent idiopathic scoliosis is still not fully understood. Finite element models (FEM) have been used but the gravity forces were not included and the production of spinal stresses not evaluated. An improved FEM to simulate brace treatment was thus developed. The 3D geometry of the spine, rib cage, pelvis, and of the trunk external surface of five scoliotic patients was acquired using a multi-view X-ray technique and surface topography. A FEM of the patient’s trunk including gravity forces was created. Custom-fit braces were modeled and their installation simulated. Immediate geometrical corrections and pressures were computed and validated. The resulting compressive loads on the vertebral endplates were quantified. The influence of the strap tension, spine stiffness, and of the gravity forces was evaluated. Results showed that the brace biomechanical action was importantly to prevent the scoliotic spine from bending under the gravity forces. The immediate correction depended on the strap tension and spine stiffness. The distribution and amplitude of computed pressures were similar to those measured with the real braces. After the brace installation, the coronal asymmetrical compressive loading on the vertebral endplates was significantly reduced. In conclusion, the model developed presents improvements over previous models and could be used to better understand and optimize brace treatment.     

骨密度与颈椎终板结构生物力学性质的关系

目的 :研究椎体骨密度 (bonemineraldensity ,BMD)与颈椎终板不同位点力学特性之间的关系。方法 :5 0个颈椎椎体标本 ,用DEXA测试每个椎体的BMD后 ,采用逐步聚类法将标本分为三组 ,高骨密度组 (n =16)、中骨密度组 (n =2 4)、低骨密度组 (n =10 ) ,对每一终板平面上 2 0个特定的测试点进行压缩实验 ,直径 2mm的半球形压头以 0 .0 3mm/s的速度垂直于终板平面下压 2mm ,由所得的力─位移曲线计算出最大压缩力及刚度 ,采用单因素方差分析、析因分析、SNK检验及相关分析对实验数据进行统计学分析。结果 :三组之间的最大压缩力、刚度均存在显著性差异 (P <0 .0 1) ,且最大压缩力、刚度与BMD呈正相关关系 ;BMD对颈椎终板力学强度有显著影响 ,但对其力学分布无明显影响。结论 :椎体BMD是预测终板力学性能的重要指标 ,术前应测量BMD以减少植入物沉陷的发生。     

The clustering of acetylcholine receptors and formation of neuromuscular junctions in regenerating mammalian muscle grafts

The present investigation was undertaken to study the relationship between acetylcholine receptor (AchR) clustering and endplate formation within regenerating skeletal muscle grafts. Silver staining of nerves was combined with rhodamine-alpha-bungarotoxin labeling of AchR clusters in heterotopic grafts of the rat soleus muscle. Two major graft procedures were used: whole muscle grafts and grafts which lacked the zone of original motor endplates (MEP-less grafts). These categories were subdivided into standard grafts, where subsequent innervation was allowed, and noninnervated grafts, which were experimentally deprived of innervation. Grafting brought about the death and removal of muscle fibers, followed by regeneration of myotubes within surviving basal lamina sheaths. A transient population of small extra-junctinal AchR clusters spontaneously appears shortly after myotube formation in all four muscle graft types. Early myotubes of whole muscle grafts (both innervated and standard grafts, prior to the time of innervation) also develop presumptive secondary synaptic clefts and large, organized aggregations of AchRs at original synaptic sites. At later times, nerves regenerating into standard whole muscle and MEP-less grafts lead to the formation of numerous ectopic endplates. In whole muscle grafts, endplates may also form at original synaptic sites. Functional graft innervation is achieved in whole muscle and MEP-less grafts as early as 20 days postgrafting. The results of this study support the existence of still-unknown factors associated with the original synaptic site which can direct postsynaptic differentiation independent of innervation. They also demonstrate that functional endplates may form in mammalian muscle grafts at both original synaptic sites and ectopic locations, thus indicating that the zone of original synaptic sites is not necessary for the establishment of numerous functional and morphologically well-differentiated endplates.     

Spinal muscles can create compressive follower loads in the lumbar spine in a neutral standing posture

The ligamentous spinal column buckles under compressive loads of even less than 100N. Experimental results showed that under the follower load constraint, the ligamentous lumbar spine can sustain large compressive loads without buckling, while at the same time maintaining its flexibility reasonably well. The purpose of this study was to investigate the feasibility of follower loads produced by spinal muscles in the lumbar spine in a quiet standing posture. A three-dimensional static model of the lumbar spine incorporating 232 back muscles was developed and utilized to perform the optimization analysis in order to find the muscle forces, and compressive follower loads (CFLs) along optimum follower load paths (FLPs). The effect of increasing external loads on CFLs was also investigated. An optimum solution was found which is feasible for muscle forces producing minimum CFLs along the FLP located 11 mm posterior to the curve connecting the geometrical centers of the vertebral bodies. Activation of 30 muscles was found to create CFLs with zero joint moments in all intervertebral joints. CFLs increased with increasing external loads including FLP deviations from the optimum location. Our results demonstrate that spinal muscles can create CFLs in the lumbar spine in a neutral standing posture in vivo to sustain stability. Therefore, its application in experimental and numerical studies concerning loading conditions seems to be suitable for the attainment of realistic results.     

Influence of anteroposterior shifting of trunk mass centroid on vibrational configuration of human spine

This study attempts to determine the influence of anteroposterior (A-P) shifting of trunk mass from the upright sedentary posture on dynamic characteristics of the human lumbar spine. A three-dimensional finite element (FE) model comprising of the T12-Pelvis spine unit was used to mimic the human spine system. It is not clear how the A-P shifting of the upper part of human upper body affect on vibrational modality of the human lumbar spine under whole body vibration. Five trunk mass point locations were assumed by 2.0cm anterior, 1.0cm anterior, 1.0cm posterior and 2.0cm posterior to the upright sedentary posture including no shifting posture. FE modal analysis was used to extract the resonant frequencies and vibration modes of the human spine. The analytical results indicate that trunk mass centroid shifting onwards or rearwards may result in a reduction of vertical resonant frequency of the human spine. The human spine has the highest vertical resonant frequency at the normal upright sedentary posture with the trunk mass locating around 1.0cm anterior to the L3-L4 vertebral centroid. Larger A-P deformations and rotational deformations were also found at the spine motion segments L3-L4 and L4-L5, which imply higher compressive stress and shear stress at the disc annulus of those spinal motion segments. The findings in this study may explain why long-term whole body vibration might induce the degeneration of human spine at the relevant spinal motion segments.     

Effect of orientation on measured failure strengths of thoracic and lumbar spine segments

Substantial research has been performed over many years to determine the compressive failure limits of spinal motion segments. However, the majority of studies have not considered the natural alignment of the spine, testing only for pure compression loads. This study tested 27 motion segments, ranging from the T6/T7 to L4/L5 levels, from 13 human cadaveric spines. The segments were oriented in either the neutral position, based on Harrison posterior tangent angles, or in-line axially. Load was applied at a low rate, reducing dynamic effects and in contrast to previous studies, until failure was observed. Force and deformation were measured during testing, with the normalized parameters of stress and strain calculated post-test. Failure forces, adjusted for bone mineral density, were found to decrease by 11% in lumbar segments when oriented while thoracic segment adjusted failure force also decreased by 4.5%. Similarly, orientation decreased failure stress by 12% for lumbar segments and increased it by 25% for thoracic segments. Some correlation was found between failure strength and bone mineral density. After testing, all segments were visually examined to determine the failure mode, and DXA and radiographic scans were performed. Oriented segments exhibited different fracture characteristics than non-oriented segments. The results indicate that segment orientation has a significant effect on failure strength, stress, and strain, and should be considered when determining appropriate load limits.     

Design and mechanical evaluation of a novel fiber-reinforced scaffold for meniscus replacement

A fiber-reinforced degradable scaffold for replacement of meniscal tissue was designed, fabricated, and mechanically evaluated. The hypotheses were that (1) the fiber network design would share a portion of compressive loads via the generation of circumferential tensile loads, and (2) the scaffold tensile properties would be similar to those of the meniscus. Two meniscus scaffold designs varying in fiber content (1000 or 500 fibers: MS1000, MS500) underwent cyclic compressive loading up to 100 and 250N, with resultant tensile loads measured at the anterior and posterior anchors. Standard tensile testing was also performed on each device and ovine menisci. Both scaffolds generated tensile loads directly proportional to the applied compressive loads, with MS1000 scaffolds generating approximately twice the tensile loads of MS500 scaffolds. The tensile strength of MS1000 scaffolds was significantly higher than that of the medial and lateral ovine menisci, and approximately twice that of the MS500 scaffolds. The stiffness of MS1000 scaffolds was lower than that of the lateral meniscus, but not statistically different from that of the medial meniscus. These results support our hypotheses that this novel fiber-reinforced scaffold can mimic the tensile and hoop stress behavior of normal meniscal tissue under compressive loading. The circumferential tensile strength and stiffness are appropriate for a meniscus replacement device.     

Evaluation of biomechanical strength,stability, bioactivity,and in vivo biocompatibility of a novel calcium deficient hydroxyapatite/poly(amino acid) composite cervical vertebra cage

A new type of cervical vertebra cage was prepared using a novel composite, calcium deficient hydroxyapatite/poly(amino acid) (HA/PAA), and its mechanical properties, in vitro stability and bioactivity, and in vivo biocompatibility were characterized. The results showed that the axial compressive loads of the HA/PAA cage were in the range of 10058–10612 N and the lateral compressive loads were in the range of 1180–2363 N, and varied with the height of the cervical vertebra cages. After immersion in simulated body fluid (SBF) for 16 weeks, the axial compressive loads of the cage decreased from 10058 to 7131 N and the lateral compressive loads decreased from 1180 to 479 N. In addition, the weight loss decreased 6.01%, showing that HA/PAA composites had good stability during the incubation period. The pH value of SBF was also monitored during the whole soaking period; it fluctuated in the range of 6.9–7.4. Scanning electron microscope and energy dispersive spectrometer results showed the cage was bioactive with a new apatite layer attached on the surface. The histological evaluation revealed that new bone tissue bonded tightly with the surfaces of the implants, showing excellent biocompatibility. In conclusion, the HA/PAA cage showed sufficient strength, good stability, bioactivity, and biocompatibility, and has potential applications for clinical cervical vertebrae repair.