四种后巩膜加固材料的生物力学特征

在模拟人体环境的生物环境箱中对人巩膜、兔巩膜、人工心包补片、脱细胞猪真皮进行生理应力下的单轴拉伸、蠕变及极限抗拉强度实验,计算各材料弹性模量,蠕变性能及极限破坏强度.与人巩膜相比,人工心包补片蠕变变形极小,极限强度极大,弹性模量纵向稍大,横向稍小;兔巩膜蠕变变形是人巩膜的两倍以上,弹性模量比人巩膜稍大;脱细胞猪真皮弹性模量与人巩膜接近.     

利用后巩膜加固术治疗家兔近视眼后 成纤维细胞生物力学性能变化

目的 研究后巩膜加固术后家兔眼球不同时期成纤维细胞力学特性的变化,从生物力学的角度探讨后巩膜加固术的作用机制。 方法 3周龄新西兰家兔45只随机选取一侧眼球用眼睑缝合方法制备近视动物模型,建模60天后,眼球随机分为两组,A组行后巩膜加固术（PSR）,B组行相似手术（不放置加固条带）。分别于术后3个月和6个月取材培养培养巩膜加固区及过渡组织的成纤维细胞。用免疫细胞化学法对培养的细胞进行鉴定。利用微管吸吮方法结合半无限体细胞力学模型测定各组成纤维细胞的力学特性（包括成纤维细胞的平衡弹性模量E∞和表观黏性μ）。 结果经统计学分析,两组巩膜成纤维细胞的平衡弹性模量及表观黏性均无统计学意义（P>0.05）。后巩膜加固术6个月,经统计学分析,两组巩膜成纤维细胞的平衡弹性模量及表观黏性均无统计学意义（P>0.05）。后巩膜加固术后3月组与6月组的巩膜成纤维细胞比较,E∞和μ的差异均无统计学意义（P>0.05）。后巩膜加固术后3个月与6个月组的过渡区成纤维细胞的力学特性,E∞分别为（289.2±84.3）,（276.9±113.9）Pa;μ分别为（1 575.2±459）Pa·s,（1 492.2±562.6）Pa·s,其差异均无统计学意义（P>0.05）。结论后巩膜加固术的增强作用并不是原位巩膜成纤维细胞本身生物力学的加强,而是由于加固条带及引起过渡区的存在。     

人眼巩膜归一化松弛函数探讨

本文对软组织材料——巩膜的力学性能进行描述.在单项拉伸状态下,测量了其拟弹性模量、破坏应力及相应的应变值.给出了单向拉伸状态下的应力应变曲线.同时做了常温下的应力松弛实验.测定了巩膜应力和时间相关的不同效应,给出了巩膜的归一化松弛函数和有关参数.     

拇展肌与拇收肌移位吻接术前、后黏弹性实验研究

研究了正常拇展肌、拇收肌拉伸黏弹性力学性质和模拟拇外翻拇展肌、拇收肌移位吻接术后拇展肌和拇收肌的拉伸黏弹性力学性质.取20个足标本,解剖后暴露拇展肌与拇收肌,得出拉伸应力松弛、蠕变等数据.对断裂后的拇收肌和拇展肌模拟临床手术进行移位吻接,对10个拇展肌和10个拇收肌标本做腱与腱吻接,另各取10个拇收肌、拇展肌标本做了腱与骨膜吻接.对吻接后的标本进行拉伸实验,得出了吻接术后各组拉伸应力松弛、蠕变曲线.以回归分析的方法处理实验数据,得出了归一化应力松弛、蠕变曲线及归一化应力松弛函数和归一换化蠕变函数.     

人颈椎后纵韧带黏弹性实验研究

研究了正常国人8具新鲜尸体颈椎后纵韧带C1-C4、C4-T1的黏弹性力学性质.对C1-C4、C4-T1段后纵韧带进行拉伸应力松弛、蠕变实验.得出了C1-C4、C4-T1后纵韧带的应力松弛、蠕变数据和曲线.对应力松弛、蠕变数据进行归一化处理,得出了归一化应力松弛函数蠕变函数及曲线.对实验数据进行回归分析,得出了回归系数.还对后纵韧带C1-C4段、C4-T1段试样进行单向拉伸实验,得出了后纵韧带的拉伸破坏载荷、伸长比、拉应力、拉应变等,对应力应变数据以多项式,用最小二乘法进行拟合,得出其应力应变关系公式及曲线.构建了后纵韧带的松弛函数K(λ、t)=G(t)T(e)(λ)表达式,对实验结果进行分析讨论.     

巩膜的区域性力学性能研究

目的比较不同区域巩膜力学特性的差异。方法以健康家猪眼为材料,将巩膜分为前部、赤道部和后部3个区域,对整体眼球巩膜的不同区域分别进行局部压痕;沿赤道方向对不同区域巩膜进行环切,制成条带状试件,采用INSTRON 5544材料试验机进行单轴拉伸。结果正常生理载荷范围内,局部压痕法测得巩膜前部、赤道部、后部的刚度分别为(0.91±0.21)、(0.6±0.16)、(0.39±0.13)MPa;单轴拉伸测得巩膜前部、赤道部、后部的弹性模量分别为(1.28±0.37)、(0.95±0.31)、(0.72±0.28)MPa。结论局部压痕法能够反映巩膜的区域性力学特性;巩膜前部相比赤道区域及后部具有更强的刚度。实验结果为进一步探讨近视等眼部疾病的发病机理提供参考。     

膝关节前交叉韧带与后交叉韧带粘弹性实验研究

研究了10具新鲜成人尸体膝关节前交叉韧带和后交叉韧带的拉伸力学性质和粘弹性力学性质,对前交叉韧带和后交叉韧带进行单向拉伸实验,得出了破坏载荷,强度极限、最大应变、伸长比、弹性模量.对前交叉韧带和后交叉韧带进行应力松弛,蠕变实验,得出了应力松弛、蠕变实验数据和曲线.对实验数据进行归一化处理,得出了归一化应力松弛函数,蠕变函数,以回归分析的方法处理实验数据,得出了回归系数,很好的拟合了实验曲线.实验结果表明:前交叉韧带的拉伸强度极限、最大应变等大于后交叉韧带,后交叉韧带7200s应力松弛、蠕变量小于前交叉韧带.     

含裂纹缺损关节软骨的单轴准静态拉伸性能

背景:关节软骨一旦出现裂纹缺损其力学性能会发生改变,而先前研究中针对受损关节软骨的探究多集中在压缩,对于拉伸性能的研究较少。目的:预先在软骨层试样上制造裂纹缺损,测试其单轴准静态拉伸性能。方法:选取新鲜成年猪膝关节的关节软骨,制备含裂纹缺损的软骨试样,在不同应力率下(0.001,0.01,和0.1 MPa/s)测试其拉伸性能,在不同恒定应力下(1,2,3 MPa)测试其蠕变性能。结果与结论:①不同应力速率下的拉伸实验中,随着应力速率的增加,达到相同应变所需的应力逐渐增大,且试件的杨氏模量随应力率的增加而增加;②不同应力速率下含裂纹缺损关节软骨的拉伸应力-应变曲线不重合,说明含裂纹缺损关节软骨的拉伸性能具有率相关性;③不同恒定拉应力水平下的蠕变实验中,蠕变应变随着拉应力水平的提高而增大,蠕变柔量随拉应力水平的提高而降低,并且随着蠕变时间的推移蠕变应变先快速增加后缓慢增加;④结果表明,不同应力率和不同恒定应力对含裂纹缺损关节软骨的拉伸力学性能影响较大,该实验结果可为缺损关节软骨的修复提供力学参考。     

股骨上端松质骨拉伸应力松弛及蠕变的实验研究

目的研究正常国人新鲜尸体股骨上端松质骨的拉伸粘弹性力学性质,为临床提供生物力学参数。方法对股上端松质骨试样纵向进行拉伸应力松弛及蠕变实验。得到股骨上端松质骨纵向的应力松弛及蠕变数据和曲线。对实验数据进行归一化处理。结果分别用对数、指数一元回归分析的方法处理数据,得出了归一化应力松弛、归一化蠕变函数及曲线。结论股骨上端松质骨拉伸应力松弛7200s应力松弛量为0.422MPa,7200s蠕变量为0.784%。     

一种眼巩膜生物补片的制备及生物相容性研究

目的 制备一种适用于眼后巩膜加固术的新型生物补片,通过对其生物相容性进行研究,评价其生物安全性.方法 首先采用新鲜的牛心包经去除表面脂肪组织、脱细胞、扩孔和梳整后,与京尼平进行生物交联,制备出一种眼巩膜生物补片.然后进行体外细胞毒性试验、溶血试验、皮内反应试验、皮肤致敏试验、急性全身毒性试验和植入试验,通过检测细胞存活率、溶血率、皮内反应记分、皮肤致敏反应等级、毒性反应和植入刺激指数分析眼巩膜生物补片的生物相容性.结果 眼巩膜生物补片无细胞毒性反应、无潜在的动物皮内刺激和肌肉刺激作用、无皮肤致敏性和无急性全身毒性反应;溶血率符合要求.结论 通过扩孔和梳整工艺等技术所制备的眼巩膜生物补片具有良好的生物相容性,符合国家相关标准要求,为其在临床上眼后巩膜加固术中的安全应用提供参考.     

The inflation response of the posterior bovine sclera

An in vitro inflation test method was developed to characterize the mechanical behavior of the bovine posterior sclera. The method used digital image correlation to provide a spatially resolved, full-field deformation map of the surface of the posterior sclera in response to controlled pressurization. A series of experiments were performed in the range of 2–6 kPa (15–45 mmHg) to characterize the load–unload displacement response at various pressure rates and the time-dependent displacement response at different applied pressures. The magnitude of the displacement was largest in the peripapillary region, mainly between the apex and the optic nerve head. Further, the results showed that bovine scleral tissue exhibited nonlinear and viscoelastic behavior characterized by a rate-dependent displacement response, hysteresis during unloading and creep. The creep rate was insensitive to the applied pressure, suggesting that the tissue can be modeled as a quasilinear viscoelastic material in the physiological pressure range of 2–6 kPa.     

Experimental Models for Culturing of Eye Tissues of <Emphasis Type="Italic">Pleurodeles Waltl</Emphasis> for Evaluation of Specific Effects of Sclera Bioregulator in Ultra-Low Doses

Experiments on stationary culture of posterior eye and roll-bottle culture of the whole eye from adult water lizards Pleurodeles waltl showed that sclera bioregulator produces a stabilizing effects on adhesion interactions between the sclera, choroid, and pigment epithelium and on the maintenance of viability of sclera fi broblasts and pigment epithelium cells.     

仿生UHMWPE关节软骨材料的静态黏弹性研究

目的 通过蠕变、应力松弛和蠕变回复等实验评价多孔梯度UHMWPE仿生软骨材料的静态黏弹性能。方法 采用模板滤取（T-L）法制备多孔梯度UHMWPE仿生软骨材料,扫描电镜观察多孔组织结构,压汞仪测量多孔层的孔隙率和孔径分布特征,平头压痕实验测定多孔梯度UHMWPE材料的蠕变、应力松弛和蠕变回复性能。结果 T-L法制备的UHMWPE梯度多孔层与基体的结合良好,随NaCl含量的增加,孔隙率增大,孔径尺寸分布范围扩大。蠕变变形和模量随时间呈非线性增加,应力松弛应力和模量非线性降低,对冲击载荷的缓冲能力明显高于致密UHMWPE。实验表明,具有合理孔隙率的U50和U60样品与致密UHMWPE材料回复性能相近,但过高的孔隙率造成蠕变回复的塑性变形增加。结论 多孔梯度结构UHMWPE材料的弹性增加,应变响应速度提高,有利于改善摩擦副的接触润滑状态,减轻材料的磨损。     

Experimental Study on Stress Relaxation and Creep Properties of Human Thoracolumbar Vertebral Bodies and Intervertebral Discs

Objective：Underwater shock can produce extremely high accelerations, resulting in severe human injuries on shipboard, and human thoraco lumbar spines are prone to suffer from injuries by ship shock motion. To observe the viscoelasticity of thoracolumbar of young fresh cadavers, and to provide biomechanical parameters for both research and clinical practice. Materials and Methods：5 fresh young male cadavers （aged 22 to 31 years） were provided, and 15 thoracolumbar spinal anatomies of 5 samples were harvested within 1 hour of death. WE-10A universal testing machine was used for creep and relaxation tests.Results：Stress relaxation and creep deformation equations are derived from the biomechanics model and the measured and simulated curves are compared. The creep in vertebral bodies and intervertebral discs exhibited significantly changes in the first 5 min and 10 min, respectively. The stress rapidly decreased in the first 2 min, and then gradually went balance during the relaxation process. Conclusion：The change in creep rate is significant at early stage,and gradually slows down.This indicates that the differences between internal pressure and local pressure are decreased until balance. The simulated curve derived from equation coincides with the experimental data to a large degree, which states that the equation is rational and reliable.     

Ultrastructural changes in scleral proteoglycans precede destruction of the collagen fibril matrix in necrotizing scleritis

Proteoglycans were localized using cuprolinic blue and visualized by electron microscopy in sclera from the eye of a 58-year-old woman with necrotizing scleritis. Samples of sclera taken from clinically normal anterior and posterior sclera and from sites involved in anterior necrotizing scleritis with ulceration and posterior scleritis showed markedly different patterns of proteoglycan distribution. Proteoglycans appeared as stain-positive filaments associated regularly with the 'd/e' bands of the collagen fibrils in normal anterior sclera, but were absent from intact collagen fibrils in the zone of anterior ulcerative scleritis. In posterior sclera including a site of posterior scleritis, proteoglycans were reduced in number with more heterogeneous associations with collagen fibrils. Depletion of scleral proteoglycans therefore precedes the degradation of scleral collagen in necrotizing scleritis, which may also involve the synthesis of atypical proteoglycan types in pathological sclera.     

Nonlinear Viscoelasticity in Rabbit Medial Collateral Ligament

The goal of this study was to characterize the viscoelastic behavior of the rabbit medial collateral ligament (MCL) at multiple levels of strain (between 0% and approximately 5%) and their corresponding stresses (between 0 and approximately 55 MPa) for stress relaxation and creep, respectively. We hypothesized that in the rabbit MCL the rate of stress relaxation would be strain dependent and the rate of creep would be stress dependent. Thirty MCLs from 15 rabbits were tested ex vivo for this study. Results show that within the physiologically relevant region of ligament behavior, the rate of stress relaxation is strain dependent in the rabbit MCL, with the rate of relaxation decreasing with increasing tissue strain. The rate of creep is stress dependent in the rabbit MCL, with the rate of creep decreasing with increasing stress. These results support our hypothesis, with the greatest nonlinearities in a physiologically relevant region of loading. As such, these nonlinearities should be considered when quantifying ligament viscoelastic behavior with a rabbit model.     

去卵巢骨质疏松模型大鼠L4脊椎骨的应力松弛与蠕变

背景：去卵巢大鼠脊椎骨会发生哪些应力松弛与蠕变及时间的变化规律？ 目的：观察去卵巢骨质疏松对雌性大鼠承重骨黏弹性特性的影响。 方法：Wistar雌性大鼠44只随机等分为对去卵巢骨质疏松动物模型组和对照组。模型组大鼠于0周摘除卵巢,14周后对大鼠L4椎骨进行应变增加速度为1%/s的应力松弛实验和应力增加速度为0.01 MPa/s的蠕变实验,在7 200 s采集100个数据。 结果与结论：大鼠L4椎骨对照组7 200 s应力松弛量和蠕变量大于模型组(P < 0.05);同时大鼠L4椎骨应力松弛曲线是以对数关系变化的,蠕变曲线是以指数关系变化的。提示去卵巢骨质疏松大鼠椎骨黏弹性力学特性发生了改变。     

Effect of X-ray irradiation on the elastic strain evolution in the mineral phase of bovine bone under creep and load-free conditions

Both the load partitioning between hydroxyapatite (HAP) and collagen during compressive creep deformation of bone and the HAP residual strain in unloaded bone have been shown in previous synchrotron X-ray diffraction studies to be affected by the X-ray irradiation dose. Here, through detailed analysis of the X-ray diffraction patterns of bovine bone, the effect of X-ray dose on (i) the rate of HAP elastic strain accumulation/shedding under creep conditions and (ii) the HAP lattice spacing and average root mean square (RMS) strain under load-free conditions are examined. These strain measurements exhibit three stages in response to increasing X-ray dose. Up to ～75 kGy (stage I) no effect of dose is observed, indicating a threshold behavior. Between ～75 and ～300 kGy (stage II) in unloaded bone the HAP d-spacing increases and the RMS strain decreases with dose, indicating strain relaxation of HAP. Furthermore, under constant compressive load creep conditions, the rate of compressive elastic strain accumulation in HAP decreases with increasing dose until, at ～115 kGy, it changes sign, indicating that the HAP phase is shedding load during creep deformation. These stage II behaviors are consistent with HAP–collagen interfacial damage, which allows the HAP elastic strain to relax within both the loaded and unloaded samples. Finally, for doses in excess of ～300 kGy (stage III, measured up to 7771 kGy) the HAP lattice spacing and RMS strain for load-free samples and the rate of HAP elastic strain shedding for crept samples remain independent of dose, suggesting a saturation of damage and/or stiffening of the collagen matrix due to intermolecular cross-linking.     

Assessing viscoelastic properties of chitosan scaffolds and validation with cyclical tests

We evaluated and modeled the viscoelastic characteristics of chitosan and chitosan-gelatin scaffolds prepared using a freeze-drying technique. Chitosan and chitosan-gelatin solutions (0.5 and 2 wt.%) were frozen at -80°C and freeze-dried. Using the scaffolds, uniaxial tensile properties were evaluated under physiological conditions (hydrated in phosphate buffered saline at 37°C) at a cross-head speed of 0.17 mms(-1) (10 mm min(-1)). From the break strain, the limit of strain per ramp was calculated to be 5% and the samples were stretched at a strain rate of 2.5%s(-1). The ramp-and-hold type of stress-relaxation test was performed for five successive stages. Chitosan and chitosan-gelatin showed nearly 90% relaxation of stress after each stage. The relaxation behavior was independent of the concentration of chitosan and gelatin. Also, changes in the microstructure of the tested samples were evaluated using an inverted microscope. The micrographs acquired after relaxation experiments showed orientation of pores, suggesting the retention of the stretched state even after many hours of relaxation. Based on these observations, two models (i) containing a hyper-elastic spring (containing two parameters) and (ii) retaining pseudo-components (containing three parameters) were developed in Visual Basic Applications accessed through MS Excel. The models were used to fit the experimental stress-relaxation data and the parameters obtained from modeling were used to predict their respective cyclic behaviors, which were compared with cyclical experimental results. These results showed that the model could be used to predict the cyclical behavior under the tested strain rates. The model predictions were also tested using cyclic properties at a lower strain rate of 0.0867%s(-1) (5%min(-1)) for 0.5 wt.% scaffolds but the model could not predict cyclical behavior at a very slow rate. In summary, the pseudo-component modeling approach can be used to model the sequential strain-and-hold stage and predict cyclical properties for the same strain rate.