5000/实验动物臂丛神经应力松弛特性研究

背景：臂丛神经损伤缝合吻接术有必要了解臂丛神经应力松弛力学特性。 目的：研究实验动物臂丛神经的应力松弛力学特性,为临床提供应力松弛力学特性参数。 设计、时间与地点：以函数为描述方式的观察实验,于2007年3月1日——3月10日在吉林大学力学实验中心完成BL-1级。 材料：实验用大鼠由长春市高新医学动物实验中心提供,均为6月龄雄性大鼠。 方法：在日本岛津电子万能试验机上对实验动物臂丛神经进行应力松弛实验。应力松弛实验应变增加速度为1%/s,实验设定时间为7200s,采集100个实验数据,以一元线性回归分析的方法处理实验数据。 主要观察指标：观察应力松弛数据和曲线,应力与时间的变化规律。 结果：动物臂丛神经试样7200s应力松弛量为0.316MPa。 结论：应力松弛曲线是以对数关系变化的,应力松弛最初600s变化较快,之后应力缓慢下降,达到7200s曲线基本平衡。臂丛神经具有粘弹性力学特性。     

手指屈肌腱应力松弛的蠕变实验

背景：屈肌腱损伤都要进行吻接修复。 目的：通过实验定量得出手指屈肌腱应力松弛和蠕变与时间的变化规律,为人工屈肌腱和临床外科吻接术提供黏弹性力学参数。 设计、时间及地点：单因素实验,于2006-06-20/30在吉林大学力学实验中心完成。 材料：实验标本取自正常国人急性头部创伤致死的新鲜尸体4具由白求恩医科大学解剖教研室提供,均为男性,年龄19~28岁。于死亡2 h之内解剖尸体取下屈肌腱。 方法：在日本岛津电子万能试验机上对手指屈肌腱各8个试样进行应力松弛、蠕变实验。模拟人体体温36.5 ℃的温度场下进行实验,应力松弛的应变增加速度为5%/s,蠕变实验的应力增加速度为0.05 GPa/min。设定实验时间为7 200 s,采集100个数据以一元线性回归分析的方法处理实验数据。 主要观察指标：①应力松弛曲线。②归一化应力松弛函数方程的计算。③蠕变实验曲线结果。④归一化蠕变函数方程计算结果。 结果：手指屈肌腱应力松弛、蠕变最初600 s变化较快,之后应力缓慢下降,应变缓慢上升,7 200 s应力松弛量为0.219 MPa,7 200 s蠕变量为3.1%。 结论：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,其具有很好的黏弹性力学特性。     

骨性关节炎动物模型内侧副韧带的应力松弛☆

背景：韧带和其他生物软组织一样,具有黏弹性特性,其应力松弛和蠕变黏弹性特性是为适应人的生理功能需要而存在的。研究说明骨性关节炎对韧带力学性能具有一定影响。 目的：比较正常和骨性关节炎动物模型内侧副韧带的应力松弛流变特性,确定骨性关节炎对内侧副韧带应力松弛特性的影响。 方法：以闭合关节刻痕法复制骨性关节炎动物模型,取正常和骨性关节炎动物模型大鼠膝关节内侧副韧带各10个试样,进行应力松弛实验。应力松弛实验的应变增加速度为5%/s。设定实验时间为7 200 s,采集100个数据,观察应力松弛数据和曲线、应力与时间的变化规律,以一元线性回归分析的方法处理实验数据。 结果与结论：正常组和病态组试样应力松弛最初600 s变化较快,之后应力缓慢下降,正常组7 200 s应力松弛量0.47 MPa,病态组7 200 s应力松弛量0.29 MPa。模型组7 200 s应力松弛量显著低于正常组(P < 0.05),且应力松弛曲线是以对数关系变化的。说明骨性关节炎时可以使膝关节对内侧副韧带应力松弛量降低,对膝关节应力松弛特性具有一定影响。     

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。     

应用肌膜瓣包裹、羊膜管预置聚乳酸-羟基乙酸微丝模拟周围神经再生

背景：周围神经损伤部位的微环境状况是影响神经再生的重要因素之一。周围神经损伤后，良好的神经再生微环境有利于保护受损神经元、促进轴突的有效再生。 目的：应用肌膜瓣包裹、羊膜管预置聚乳酸-羟基乙酸微丝，充填大鼠自体周围神经组织浆模拟周围神经再生微环境，探讨其修复坐骨神经缺损的可行性。 设计、时间及地点：随机对照动物实验，于2006-06/2007-10在广东医学院实验动物中心完成。 材料：清洁级2月龄SD大鼠30只，随机分为实验组、对照组、标准组3组，每组10只，右侧为实验侧，左侧为正常对照侧。取健康、足月、顺产的新鲜胎儿羊膜(产妇知情同意) 制备羊膜基质膜。用医用Vicryl缝线和羊膜基质膜制备聚乳酸-羟基乙酸微丝桥接物。 方法：大鼠切除坐骨神经6.0 mm，自然回缩建立坐骨神经缺损模型。实验组采用带蒂肌膜瓣、人羊膜管预置Vicryl微丝并充填大鼠自体坐骨神经组织浆；对照组采用单纯人羊膜管充填大鼠自体坐骨神经组织浆；标准组采用自体神经移植，桥接大鼠坐骨神经缺损。 主要观察指标：术后8，12周行大体观察、组织学检查、胫前肌湿质量、有髓神经纤维通过率及神经电生理学检测。 结果：术后12周，实验组、标准组肌萎缩有所恢复，对照组则恢复不明显。实验、标准组患侧胫前肌色泽红润，饱满富有弹性；对照组色泽相对较暗，弹性度较差。术后8，12周3组胫前肌恢复率组间比较，术后12周3组有髓神经纤维总数、截面积，神经移植体血管数和血管截面积组间比较，以及小腿三头肌复合肌动作电位幅值组间比较，差异均有显著性意义(P < 0.05），其中标准组神经纤维再生质量最佳，实验组优于对照组。 结论：肌膜转位、羊膜管预置聚乳酸-羟基乙酸微丝，并填充大鼠自体周围神经组织浆导管能较好的模拟周围神经再生之微环境，促进神经纤维再生，但与自体神经移植尚有差距。     

大鼠臂丛神经的蠕变特性

背景：臂丛神经损伤缝合吻接有必要了解臂丛神经蠕变力学特性。以往的研究多以臂丛神经的单项拉伸力学性质研究居多，关于臂丛神经蠕变黏弹性力学性质的研究鲜有报道。 目的：以函数为研究方式观察分析实验动物臂丛神经的蠕变力学特性，为临床提供蠕变力学特性参数。 方法：采用日本岛津电子万能试验机对SD大鼠臂丛神经进行蠕变实验。蠕变实验应力增加速度为0.01 GPa/s，实验设定时间为7 200 s，采集100个实验数据，以归一化分析的方法处理实验数据。 结果与结论：大鼠臂丛神经试样7 200 s蠕变为5.6%。蠕变最初600 s变化较快，之后应变缓慢上升，达到7 200 s曲线基本平衡。结果表明蠕变曲线是以指数关系变化的，臂丛神经具有黏弹性蠕变力学特性。     

股骨颈松质骨的应力松弛方程

背景：无论是股骨颈骨折内外固定，还是人工关节的研究都需要了解股骨颈松质骨应力松弛特性。股骨颈骨折后都需要以内固定或头固定机械进行固定治疗。 目的：通过实验定量得出股骨颈应力松弛与时间的变化规律，为人工关节研究和内外固定提供黏弹性力学参数。 设计、时间及地点：观察性实验，于2006-09在吉林大学力学实验中心完成。 材料：股骨颈标本8个，由白求恩医科大学解剖室提供。 方法：在日本岛津电子万能试验机上对股骨颈松质骨8个试样进行应力松弛实验。模拟人体体温36.5 ℃的温度场下进行实验，应力松弛实验的应变增加速度为50%/min。设定实验时间为7 200 s，采集100个数据以三参数模型处理实验数据。 主要观察指标：应力松弛曲线，应力松弛与时间的变化规律。 结果：股骨颈松质骨应力松弛，最初600 s变化较快，之后应力缓慢下降，7 200 s应力松弛量为 0.84 MPa。 结论：应力松弛曲线是以对数关系变化的，以三参数模型建立的股骨颈松质骨应力松弛方程能真实地反映其应力松弛特性。     

实验动物臂丛神经的拉伸力学特性

背景：臂丛神经损伤缝合吻接术有必要了解臂丛神经拉伸力学特性。 目的：对大鼠臂丛神经进行拉伸实验,观察其臂丛神经的拉伸力学特性,为临床提供拉伸力学特性参数。 方法：取SD大鼠C6~7臂丛神经40个,随机分为正常对照组20个,模拟臂丛神经损伤吻接组20个,对模拟臂丛神经损伤吻接组以手切在标本中间切开再缝合吻接离断标本。在电子万能试验机上以5 mm/min的实验速度对2组标本进行拉伸实验,以多项式用最小二乘法处理实验数据。拉伸实验力速度为5 mm/min。观察大鼠臂丛神经拉伸最大载荷、最大位移、最大应变、最大应力和应力-应变曲线。 结果与结论：模拟臂丛神经损伤吻接组大鼠臂丛神经拉伸最大载荷为(1.050±0.135) N、最大位移为(3.090±0.356) mm、最大应变为(61.860±7.252)%、最大应力为(5.095±0.647) GPa,正常对照组最大载荷、最大应力大于模拟丛神经损伤吻接组(P < 0.05)。模拟臂丛神经损伤吻接组最大位移和最大应变大于正常对照组(P < 0.05)。拉伸应力-应变曲线是以指数关系变化的。结果显示2组臂丛神经标本具有不同的拉伸力学特性。     

三参数模型计算正常与病态股骨头松质骨的应力松弛方程

背景：为避免人工假体置入后发生松动脱落现象，有必要进行松质骨的力学性质研究。 目的：以三参数模型建立了应力松弛方程，比较正常股骨头和坏死后股骨头应力松弛性质。 设计、时间和地点：观察性实验，于2006-05-15/20在吉林大学力学实验中心完成。 材料：正常和坏死股骨头各8个标本，由白求恩医科大学解剖教研室提供。 方法：在电子万能试验机上对正常与坏死股骨头松质骨各8个试样进行应力松弛实验。模拟人体体温在36.5 ℃的温度场下，以5%/s的应变增加速度对标本施加常应力，设定时间为7 200 s，采集100个实验数据。采用三参数模型计算应力松弛方程。 主要观察指标：①应力松弛曲线。②正常和病态股骨头松质骨应力松弛量。 结果：正常和坏死股骨头应力松弛曲线均以对数关系变化的，在最初600 s应力变化较快，随时间延长应力缓慢下降，最后进入平衡阶段。坏死股骨头松质骨7 200 s应力松弛量小于正常股骨头松质骨。 结论：三参数模型计算简便，能很好地拟合股骨头的应力松弛变化，通过建立这种理想化的方程，可以定量说明坏死股骨头的黏弹性较差。     

局部注射肝素钠兔跟腱系统生物力学性质的变化

背景: 跟腱腱围炎会导致跟腱生物力学特性的改变，目前以局部注射肝素钠治疗较为普遍，但其对跟腱生物力学特性影响的报道甚少。 目的：观察跟腱劳损后生物力学性质及黏弹性的变化，同时验证肝素钠对跟腱生物力学特性及黏弹性的影响。 设计、时间及地点：于2005-03/12在四川省骨科医院生物力学实验室完成随机对照动物实验。 材料：50只成年日本大耳白兔，体质量(4.10±0.23) kg，用于制备跟腱劳损动物模型。 方法：50只动物随机分为对照组(n=20)、训练组(n=12)和肝素钠组(n=18)。动物3周运动训练后继续训练，同时开始跟腱腱围及跟腱止点的肝素局部注射，2次/周。6周后进行跟腱的循环蠕变和应力松弛测定，最后进行跟腱的断裂实验。 主要观察指标：测定不同运动后跟腱的生物力学特性及黏弹性的变化，包括跟腱的横截面积、循环蠕变、滞后环、应力松弛、强度特性和应力-应变。 结果：训练组和肝素钠组动物的滞后环明显减小，应力松弛加快。训练后跟腱的屈服载荷及能量、断裂能量、屈服应力、应变能力明显高于对照组。肝素钠组所有生物力学指标都得到改善。 结论：大强度运动可使跟腱的黏弹性下降，局部注射肝素钠可改善跟腱的强度特性和黏弹性。劳损后跟腱腱围和跟腱止点局部注射肝素钠对改善跟腱系统的强度特性和黏弹性有益。     

Autologous nerve anastomosis versus human amniotic membrane anastomosisA rheological comparison following simulated sciatic nerve injury

The sciatic nerve is biological viscoelastic solid,with stress relaxation and creep characteristics.In this study,a comparative analysis of the stress relaxation and creep characteristics of the sciatic nerve was conducted after simulating sciatic nerve injury and anastomosing with autologous nerve or human amniotic membrane.The results demonstrate that,at the 7 200-second time point,both stress reduction and strain increase in the human amniotic membrane anastomosis group were significantly greater than in...     

Comparison of viscoelasticity between normal human sciatic nerve and amniotic membrane

Sciatic nerve tissue was obtained from the gluteus maximus muscle segment of normal human cadavers and amniotic membrane tissue was obtained from healthy human puerperant placentas.Both tissues were analyzed for their stress relaxation and creep properties to determine suitability for transplantation applications.Human amniotic membrane and sciatic nerve tissues had similar tendencies for stress relaxation and creep properties.The stress value of the amniotic membrane stress relaxation group decreased to a greater extent compared with the sciatic nerve stress relaxation group.Similarly,the stress value of the amniotic membrane creep group increased to a greater extent compared with the sciatic nerve creep group.The stress relaxation curve for human amniotic membrane and sciatic nerve showed a logarithm correlation,while the creep curve showed an exponential correlation.These data indicate that amniotic membrane tissue has better stress relaxation and creep properties compared with sciatic nerve tissue.     

Strain and stress variations in the human amniotic membrane and fresh corpse autologous sciatic nerve anastomosis in a model of sciatic nerve injury

A 10-mm long sciatic nerve injury model was established in fresh normal Chinese patient cadavers. Amniotic membrane was harvested from healthy maternal placentas and was prepared into multilayered,coiled,tubular specimens.Sciatic nerve injury models were respectively anastomosed using the autologous cadaveric sciatic nerve and human amniotic membrane.Tensile test results showed that maximal loading,maximal displacement,maximal stress,and maximal strain of sciatic nerve injury models anastomosed with human amniotic membrane were greater than those in the autologous nerve anastomosis group.The strain-stress curves of the human amniotic membrane and sciatic nerves indicated exponential change at the first phase,which became elastic deformation curves at the second and third phases,and displayed plastic deformation curves at the fourth phase,at which point the specimens lost their bearing capacity.Experimental findings suggested that human amniotic membranes and autologous sciatic nerves exhibit similar stress-strain curves, good elastic properties,and certain strain and stress capabilities in anastomosis of the injured sciatic nerve.     

Viscoelasticity of repaired sciatic nerve by poly（lactic-co-glycolic acid） tubes

Medical-grade synthetic poly（lactic-co-glycolic acid） polymer can be used as a biomaterial for nerve repair because of its good biocompatibility, biodegradability and adjustable degradation rate. The stress relaxation and creep properties of peripheral nerve can be greatly improved by repair with poly（lactic-co-glycolic acid） tubes. ＂Fen sciatic nerve specimens were harvested from fresh corpses within 24 hours of death, and were prepared into sciatic nerve injury models by creating a 10 mm defect in each specimen. Defects were repaired by anastomosis with nerve autografts and poly（lactic-co-glycolic acid） tubes. Stress relaxation and creep testing showed that at 7 200 seconds the sciatic nerve anastomosed by poly（lactic-co-glycolic acid） tubes exhibited a greater decrease in stress and increase in strain than those anastomosed by nerve autografts. These findings suggest that poly（lactic-co-glycolic acid） exhibits good viscoelasticity to meet the biomechanical require- ments for a biomaterial used to repair sciatic nerve injury.     

Biological conduits combining bone marrow mesenchymal stem cells and extracellular matrix to treat long-segment sciatic nerve defects

The transplantation of polylactic glycolic acid conduits combining bone marrow mesenchymal stem cells and extracellular matrix gel for the repair of sciatic nerve injury is effective in some respects, but few data comparing the biomechanical factors related to the sciatic nerve are available. In the present study, rabbit models of 10-mm sciatic nerve defects were prepared. The rabbit models were repaired with autologous nerve, a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells, or a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel. After 24 weeks, mechanical testing was performed to determine the stress relaxation and creep parameters. Following sciatic nerve injury, the magnitudes of the stress decrease and strain increase at 7,200 seconds were largest in the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel group, followed by the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells group, and then the autologous nerve group. Hematoxylin-eosin staining demonstrated that compared with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells group and the autologous nerve group, a more complete sciatic nerve regeneration was found, including good myelination, regularly arranged nerve fibers, and a completely degraded and resorbed conduit, in the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel group. These results indicate that bridging 10-mm sciatic nerve defects with a polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel construct increases the stress relaxation under a constant strain, reducing anastomotic tension. Large elongations under a constant physiological load can limit the anastomotic opening and shift, which is beneficial for the regeneration and functional reconstruction of sciatic nerve. Better regeneration was found with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells + extracellular matrix gel grafts than with the polylactic glycolic acid conduit + bone marrow mesenchymal stem cells grafts and the autologous nerve grafts.     

Chemically extracted aceUular allogeneic nerve graft combined with ciliary neurotrophic factor promotes sciatic nerve repair

A chemically extracted acellular allogeneic nerve graft can reduce postoperative immune rejection, similar to an autologous nerve graft, and can guide neural regeneration. However, it remains poorly understood whether a chemically extracted acellular allogeneic nerve graft combined with neurotrophic factors provides a good local environment for neural regeneration. This study investigated the repair of injured rat sciatic nerve using a chemically extracted acellular allogeneic nerve graft combined with ciliary neurotrophic factor. An autologous nerve anastomosis group and a chemical acellular allogeneic nerve bridging group were prepared as controls. At 8 weeks after repair, sciatic functional index, evoked potential amplitude of the soleus muscle, triceps wet weight recovery rate, total number of myelinated nerve fibers and myelin sheath thickness were measured. For these indices, values in the three groups showed the autologous nerve anastomosis group 〉 chemically extracted acellular nerve graft ＋ ciliary neurotrophic factor group 〉 chemical acellular allogeneic nerve bridging group. These results suggest that chemically extracted acellular nerve grafts combined with ciliary neurotrophic factor can repair sciatic nerve defects, and that this repair is inferior to autologous nerve anastomosis, but superior to chemically extracted acellular allogeneic nerve bridging alone.     

Autologous nerve graft repair of different degrees of sciatic nerve defect: stress and displacement at the anastomosis in a three-dimensional fnite element simulation model

In the repair of peripheral nerve injury using autologous or synthetic nerve grafting, the magnitude of tensile forces at the anastomosis affects its response to physiological stress and the ultimate success of the treatment. One-dimensional stretching is commonly used to measure changes in tensile stress and strain; however, the accuracy of this simple method is limited. Therefore, in the present study, we established three-dimensional finite element models of sciatic nerve defects repaired by autologous nerve grafts. Using PRO E 5.0 finite element simulation software, we calculated the maximum stress and displacement of an anastomosis under a 5 N load in 10-, 20-, 30-, 40-mm long autologous nerve grafts. We found that maximum displacement increased with graft length, consistent with specimen force. These findings indicate that three-dimensional finite element simulation is a feasible method for analyzing stress and displacement at the anastomosis after autologous nerve grafting.     

Human umbilical cord blood-derived stem cells and brain-derived neurotrophic factor protect injured optic nerve：viscoelasticity characterization

The optic nerve is a viscoelastic solid-like biomaterial.Its normal stress relaxation and creep properties enable the nerve to resist constant strain and protect it from injury.We hypothesized that stress relaxation and creep properties of the optic nerve change after injury.Moreover,human brain-derived neurotrophic factor or umbilical cord blood-derived stem cells may restore these changes to normal.To validate this hypothesis,a rabbit model of optic nerve injury was established using a clamp approach.At 7 days after injury,the vitreous body received a one-time injection of 50 μg human brain-derived neurotrophic factor or 1 × 106 human umbilical cord blood-derived stem cells.At 30 days after injury,stress relaxation and creep properties of the optic nerve that received treatment had recovered greatly,with pathological changes in the injured optic nerve also noticeably improved.These results suggest that human brain-derived neurotrophic factor or umbilical cord blood-derived stem cell intervention promotes viscoelasticity recovery of injured optic nerves,and thereby contributes to nerve recovery.     

Stress and strain analysis on the anastomosis site sutured with either epineurial or perineurial sutures after simulation of sciatic nerve injury

The magnitude of tensile stress and tensile strain at an anastomosis site under physiological stress is an important factor for the success of anastomosis following suturing in peripheral nerve injury treatment. Sciatic nerves from fresh adult cadavers were used to create models of sciatic nerve injury. The denervated specimens underwent epineurial and perineurial suturing. The elastic modulus (40.96 ± 2.59 MPa) and Poisson ratio (0.37 ± 0.02) of the normal sciatic nerve were measured by strain electrical measurement. A resistance strain gauge was pasted on the front, back, left, and right of the edge of the anastomosis site after suturing. Strain electrical measurement results showed that the stress and strain values of the sciatic nerve following perineurial suturing were lower than those following epineurial suturing. Scanning electron microscopy revealed that the sciatic nerve fibers were disordered following epineurial compared with perineurial suturing. These results indicate that the effect of perineurial suturing in sciatic nerve injury repair is better than that of epineurial suturing.     

Methylprednisolone microsphere sustained-release membrane inhibits scar formation at the site of peripheral nerve lesion

Corticosteroids are widely used for the treatment of acute central nervous system injury. However, their bioactivity is limited by their short half-life. Sustained release of glucocorticoids can prolong their efifcacy and inhibit scar formation at the site of nerve injury. In the present study, we wrapped the anastomotic ends of the rat sciatic nerve with a methylprednisolone sustained-release membrane. Compared with methylprednisone alone or methylprednisone microspheres, the methylprednisolone microsphere sustained-release membrane reduced tissue adhesion and inhibited scar tissue formation at the site of anastomosis. It also increased sciatic nerve function index and the thick-ness of the myelin sheath. Our ifndings show that the methylprednisolone microsphere sustained-release membrane effectively inhibits scar formation at the site of anastomosis of the peripheral nerve, thereby promoting nerve regeneration.