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。     

短期局部注射激素大鼠肌腱的生物力学和病理学变化

背景:研究证实激素长期局部注射对肌腱是有负面影响的,但短期应用激素对肌腱的影响仍存在争议.目的:观察短期激素局部注射后大鼠肌腱生物力学和病理方面的变化.方法:激素封闭对照组、激素封闭训练组大鼠均按人体局部封闭疗程进行治疗,于双侧跟腱的腱周部位注射与人体相当剂量地塞米松0.025 mg,1次/周,3次为1个疗程方法.激素封闭训练组保证跑步训练,跑步强度为25 m/min,30 min/次,3次/周.正常对照组大鼠自由活动,无任何处理.分别于第4,7周取肌腱行苏木精-伊红染色和MASSON染色,观察炎细胞浸润及胶原纤维排列情况,并进行跟腱拉伸实验以观察其生物力学变化.结果与结论:激素封闭对照组力学性能呈明显先增强后下降的趋势,并出现1例肌腱断裂实例,而激素封闭训练组力学性能呈明显先下降后恢复的趋势,两组病理均表现为肌腱退变.提示短期激素局部注射对肌腱是一种刺激,可使肌腱的适应性下降,应用时需避免强体力劳动,可进行适度功能锻炼.     

两种不同弹性模量聚乙烯醇水凝胶人工髓核的黏弹性性质评估

背景:人工髓核假体在理论上能够恢复脊柱的稳定性,减少椎间盘髓核摘除后的并发症,但目前对其黏弹性的研究却甚少.目的:与正常腰椎间盘的黏弹性特性对比,评估两种不同弹性模量(3 MPa和1 MPa)水凝胶人工髓核对黏弹性变化的影响.设计、时间及地点:自身对照实验,于2002-11/2003-03在上海大学生物力学研究所试验室完成.材料:弹性模量为3MPa和1MPa的两种聚乙烯醇水凝胶人工髓核由美国Everblooming公司提供.7具新鲜青壮年腰椎脊柱标本L4-5脊柱功能单元方法:在完整椎间盘和分别植入两组不同的水凝胶人工髓核.3种状态下,利用实验应力分析方法进行蠕变和松弛特性研究,并通过建立三参数力学模型计算蠕变和应力松弛方程.主要观察指标:①完整椎间盘和分别植入两组不同的水凝胶人工髓核后脊柱功能单元的蠕变和应力松弛曲线.②三参数力学模型的数学公式.结果:蠕变和应力松弛曲线变化和数学公式均表明弹性模量为3MPa和1MPa的人工髓核植入后的椎间盘均与正常椎间盘有相似的蠕变和应力松弛规律,其中3MPa假体与正常椎间盘更为接近.结论:水凝胶人工髓核具有良好的黏弹性特性,弹性模量为3MPa的髓核假体更加适合.     

猪气管黏弹性的实验研究

目的对猪气管进行黏弹性测试实验研究,为研究人体气管及人工气管提供生物力学参数。方法对猪气管膜部和软骨环部应用50~5 000 N伺服控制拉力试验机分别进行拉伸,分析其应力松弛、蠕变性质。用MATLAB软件仿真处理实验数据,得出两组数据拟合的方程,并根据方程绘制曲线。结果得出的猪气管膜部和软骨环两组数据的方程和曲线显示:应变恒定时,应力随时间的增加呈指数衰减;应力恒定时,应变随时间的增加呈指数增加。结论猪气管符合应力松弛和蠕变特性,为生物黏弹性软组织材料。     

兔挛缩跟腱的组织形态和力学特性改变

目的:观察制动后兔挛缩跟腱的组织形态和生物力学特性的改变.方法:16只新西兰大白兔随机分为造模组和正常组.造模组大白兔右踝石膏固定6周.观察2组跟腱光镜和电镜下的组织形态学、蠕变率和最大断裂应力.结果:与正常组比较,造模组跟腱胶原纤维排列明显紊乱,细小纤维比例升高,粗大纤维比例下降,蠕变率增高,最大断裂应力显著下降.结论:制动6周后跟腱的组织形态和生物力学特征均发生显著改变.     

以函数为描述方式观察实验动物臂丛神经的应力松弛特性

背景:臂丛神经损伤缝合吻接有必要了解臂丛神经应力松弛力学特性.以往的研究多以臂丛神经的单项拉伸力学性质研究居多,关于臂从神经应力松弛、蠕变黏弹性力学性质的报道较少.目的:以函数为描述方式观察分析实验动物臂从神经的应力松弛力学特性,为临床提供实验参数.设计、时间与地点:以函数为描述方式的单因素观察性实验,于2007-03-01/10在吉林大学力学实验中心完成.材料:雄性6月龄SD大鼠由长春市高新医学动物实验中心提供.方法:在日本岛津电子万能试验机上对大鼠臂丛神经进行应力松弛实验,应变增加速度为1%/s,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:应力松弛数据和曲线,应力与时间的变化规律.结果:实验动物臂丛神经试样7 200 s应力松弛量为0.316 MPa.应力松弛曲线是以对数关系变化的,应力松弛最初600 s变化较快,之后应力缓慢下降,达到7 200s曲线基本平衡.结论:应力松弛曲线是以对数关系变化的,臂从神经具有黏弹性力学特性.     

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0.01MPa/s的蠕变实验,在7200s采集100个数据。结果与结论:大鼠L4椎骨对照组7200s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。     

运动锻炼后免胫骨扭转载荷下的蠕变特性

背景:运动中骨组织的蠕变以微应变方式进行,且全骨的扭转能较为全面地反映骨组织的生物力学特性.目的:观察运动训练状态后兔胫骨扭转载荷下的蠕变特点.设计、时间及地点:平行对照动物观察性实验,于2005-05/2007-07在四川省骨科医院生物力学实验室完成.材料:6月龄日本大白兔32只,雌雄各半,分为实验组(n=24)和对照组(n=8).方法:将实验组放入电刺激笼,训练量为每20 s刺激1次,刺激时间为0.1-0.2s,动物受刺激后沿刺激笼跑跳数步并转弯,45min/d,分3次进行,15min/次,间隔15min,每周训练5d,连续训练4周.对照组饲养条件同实验组,不做训练.主要观察指标:取兔胫骨样本,在其前、后、左、右4面各粘贴应变计,在0.52 N·m转矩载荷下测试500s内胫骨的微应变随时间的变化,即胫骨的蠕变.结果:在扭转载荷下,兔胫骨表现出明显的蠕变现象,在约2s时间内迅速达到蠕变曲线的拐点,然后以较为缓慢的速率发生蠕变.训练4周后,实验组胫骨前后侧蠕变明显小于对照组;对照组前侧蠕变最大,明显大于内侧,训练后实验组前侧蠕变最小,明显小于外侧蠕变(P＜0.05).结论:胫骨各向蠕变特性不同,胫骨前后侧变形较内外侧大,经过一段时间运动训练后,兔胫骨蠕变特性发生了变化,其前后侧蠕变明显减小.     

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:实验标奉取自正常国人急性头部创伤致岁匕的新鲜尸体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2h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O.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粜.结果:手指屈肌腱应力松弛、蠕变最初600s变化较快,之后应力缓慢下降,应变缓慢上升,7200 s应力松弛量为0.219MPa,7022s 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.     

去卵巢骨质疏松模型大鼠L_4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0.01MPa/s的蠕变实验,在7200s采集100个数据。结果与结论：大鼠L4椎骨对照组7200s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。     

Static and dynamic biomechanical properties of the regenerating rabbit Achilles tendon

BACKGROUND: Since tendons show viscoelastic behavior, dynamic viscoelastic properties should be assessed in addition to static biomechanical properties. We evaluated differences between static and dynamic biomechanical properties of the regenerating rabbit Achilles tendon following tenotomy. METHODS: At 3, 6, or 12 weeks after right Achilles tenotomy, the right (regenerating) and left (control) tendons were collected with the calcaneus from 49 rabbits. A unidirectional failure test and a dynamic viscoelastic test were conducted. FINDINGS: Tensile strength and Young's modulus (static biomechanical properties) in the regenerating group at Week 6 were significantly greater than at Week 3, while at Week 12, these were significantly greater than at Week 6. However, even at Week 12, both parameters were less than in the control group. The value of tan delta represents dynamic viscoelasticity, a smaller tan delta indicates greater elasticity. tan delta for the regenerating group was significantly greater than for the control group at Week 3, but regenerating and control groups did not significantly differ at Week 6. No marked change was seen from Weeks 6 to 12 in the regenerating group, and no significant difference in tan delta was evident between the regenerating and control groups at Week 12. INTERPRETATION: Dynamic biomechanical properties of regenerating rabbit Achilles tendons may improve more rapidly than static biomechanical properties. Ability to tolerate dynamic movement in the healing Achilles tendon may improve more rapidly than ability to withstand static stresses.     

Relationship between recovery of calf-muscle biomechanical properties and gait pattern following surgery for achilles tendon rupture

BACKGROUND: The relationship between ankle plantar flexor biomechanical properties and gait pattern following surgery for acute rupture of the Achilles tendon has not yet been fully investigated. METHODS: Forty-nine young adults (27 men and 22 women) who underwent surgical repair of a complete Achilles tendon rupture were evaluated at 3, 6, 12 and 24 months by clinical assessment, biomechanical evaluation and gait analysis. FINDINGS: Ankle range of motion, plantar flexor passive stiffness and concentric strength were recovered within 12 months. Gait abnormalities related to these factors took longer to disappear owing to the presence of anomalous muscle patterns. At 24 months, a deficit in calf-muscle eccentric strength was still present, determining adaptive changes in gait strategy that involved ankle motion and coordinated muscular activity. INTERPRETATION: Improvement of gait pattern is slower than recovery of plantar flexor mechanical properties. Persisting mechanical impairment resulting in gait adaptations may be detrimental to the healing structures by increasing stress on the Achilles tendon. Restoration of calf-muscle eccentric strength and coordinated antagonist muscle activity should be key points in postoperative rehabilitation following surgical repair of Achilles tendon rupture.     

应用改良的环扣式传感器进行在体跟腱生物力学测试

背景在体肌腱的生物力学测试国内报道较少.目的探讨在体跟腱的生物力学行为.设计随机对照实验研究.地点和对象实验在武汉大学生物医学工程实验室完成,对象为新西兰大耳白兔45只,雌雄不限,体质量1.85～3.25kg(由武汉大学医学院动物室提供).干预对环扣式传感器进行改良,选择45只兔随机分3组,正常左侧跟腱组,正常右侧跟腱组,失胫神经支配的左侧跟腱组,以改良环式传感器分别对3组的跟腱进行生物学测试.实验和结果由两位有经验的专家检测.主要观察指标跟腱张力曲线,张力波峰值,时间,冲量.结果家兔跑跳时的张力曲线主要有4种即Ⅰ,Ⅱ,Ⅲ,Ⅳ,失胫神经失配状态下的一侧跟腱的生物力学参数[F3=(8.82±3.75)N,冲量=(37.95±14.86)N·ms]明显低于常态[F3=(16.75±5.65)N,冲量=(110.20±62.96)N·ms,P＜0.05].结论改良环扣式传感器用于在体跟腱的生物力学测试具有可行、稳定、灵敏等优点.     

Effect of injected versus iontophoretic corticosteroid on the rabbit tendon.

BACKGROUND: The etiologic role of corticosteroid therapy in tendon rupture is controversial. This study compared the effects of injected versus iontophoretically delivered corticosteroid on the normal rabbit Achilles tendon. METHODS: Rabbits were divided into three treatment groups: (1) corticosteroid injections, (2) iontophoretically delivered corticosteroid, and (3) no treatment. One tendon of each rabbit in the treatment groups was treated with either drug injection or iontophoresis; the tendon of the other leg served as a control. Some tendons were used for testing elastic modulus, ultimate load, and ultimate stress, while the remaining tendons were evaluated histologically. RESULTS: Injections of either corticosteroid or saline into the tendon sheath resulted in short-term changes in tendon biomechanical characteristics and somewhat higher histologic severity scores; however, iontophoretic delivery of corticosteroid or saline did not affect either significantly. CONCLUSIONS: Iontophoresis using sterile water or corticosteroid resulted in minimal or no biochemical and histologic changes in the tendon compared with injection of either substance. The method of corticosteroid delivery may be as important as the actual drug effects on the biomechanical and histologic properties of tendons.     

Effects of growth on the response of the rabbit patellar tendon to stress shielding: a biomechanical study

OBJECTIVE: To know the effect of stress deprivation on the dimensions and mechanical properties of the patellar tendon during growth. DESIGN: The dimensions and tensile properties of stress-shielded patellar tendons were studied in growing rabbits and compared to those in mature animals. BACKGROUND: Although the effects of stress deprivation on the remodeling of ligaments and tendons have been studied in various animal models, the effect of growth on the remodeling has not been studied well. METHOD: A stress shielding technique was applied to 1-, 2-, and 3-month-old Japanese white rabbits to completely remove stress in the patellar tendons for 4, 7, and 14 days. Changes in the dimensions and mechanical properties as well as fibroblast density of the tendon were determined. RESULTS: The tensile strength and tangent modulus of the patellar tendons were markedly decreased by stress shielding, while the cross-sectional area was significantly increased, with the largest changes in 1-month-old rabbits. Fibroblast density also increased; however, the degree of increase was highest in 3-month-old rabbits. CONCLUSION: The changes in the dimensions and mechanical properties of the patellar tendons induced by stress shielding were greater in younger animals. RELEVANCE: The biomechanical response of tendons and ligaments to stress deprivation induced by, for example, limb immobilization is greater and occurs earlier in younger subjects, which is important for the surgical treatment and rehabilitation protocol of joint diseases in young subjects.     

Mechanical properties of the human Achilles tendon, in vivo

Background

Ultrasonography has been widely applied for in vivo measurements of tendon mechanical properties. Assessments of human Achilles tendon mechanical properties have received great interest. Achilles tendon injuries predominantly occur in the tendon region between the Achilles-soleus myotendinous junction and Achilles-calcaneus osteotendinous junction i.e. in the free Achilles tendon. However, there has been no adequate ultrasound based method for quantifying the mechanical properties of the free human Achilles tendon. This study aimed to: 1) examine the mechanical properties of the free human Achilles tendon in vivo by the use of ultrasonography and 2) assess the between-day reproducibility of these measurements.

Methods

Ten male subjects had the Achilles tendon moment arm length, Achilles tendon cross sectional area and free Achilles tendon length determined. All subjects performed isometric plantarflexion ramp contractions to assess between-day reproducibility on two separate days. Simultaneous ultrasonography based measurements of Achilles-soleus myotendinous junction and Achilles-calcaneus osteotendinous junction displacement together with Achilles tendon force estimates yielded free Achilles tendon mechanical properties.

Findings

Free Achilles tendon maximal force, deformation and stiffness were 1924 (SD 229) N, 2.2 (SD 0.6) mm and 2622 (SD 534) N/mm on day 1. For between-day reproducibility there were no significant differences between days for free Achilles tendon mechanical properties. The between-day correlation coefficient and typical error percent were 0.81 and 5.3% for maximal Achilles tendon force, 0.85 and 11.8% for maximal Achilles tendon deformation and 0.84 and 8.8% for Achilles tendon stiffness respectively. Last, osteotendinous junction proximal displacement on average contributed with 71 (SD 12) % of proximal myotendinous junction displacement.

Interpretation

This study, for the first time, presents an ultrasonography based in vivo method for measurement of free AT mechanical properties. The method is applicable for evaluation of free human Achilles tendon mechanical properties in relation to training, injury and rehabilitation.     

制动对兔跟腱力学特性的影响

目的 探讨制动对兔跟腱力学特性的影响。方法 将兔踝关节制动 4周,然后对其本构方程、材料常数等进行了对照研究。结果 兔跟腱的应力一应变关系可用指数函数曲线来描述。与正常组相比,制动组跟腱的两个材料常数均有显著性差异,应力-应变关系理论曲线亦显著不同。结论 踝关节制动,使得跟腱所受应力下降,从而导致其力学特性的改变。在临床工作中,应尽可能地减少制动时间。     

Sonographic evaluation of the size of Achilles tendon: the effect of exercise and dominance of the ankle

This study was undertaken to measure and compare the thickness and cross-sectional area of the Achilles tendon between frequent- and infrequent-exercise subjects, and between the dominant and nondominant ankles in an asymptomatic Chinese population. Interobserver variability in the measurement of the size of Achilles tendon was also evaluated. High-resolution ultrasound (US) examination of Achilles tendons was performed in 40 healthy subjects (20 who frequently exercised, had exercise at least 3 days per week and at least 2 h per session; and 20 who infrequently exercised); their age range was 19 to 25 years. The thickness and cross-sectional area of the Achilles tendons were measured in a transverse scan at the level of medial malleolus. For each subject, the Achilles tendons were measured by five operators to evaluate the interobserver variability in the measurements. The mean thickness and cross-sectional areas of the Achilles tendon in a healthy Chinese population are 5.23 mm(2) and 56.91 mm(2)(2), respectively. The mean thickness of the Achilles tendon of frequent-exercise subjects (dominant ankle 5.43 mm, nondominant ankle 5.38 mm) was significantly greater than that of infrequent-exercise subjects (dominant ankle 5.08 mm, nondominant ankle 5.04 mm) (p < 0.05). The cross-sectional area of the tendons was also larger in frequent-exercise subjects but, whereas a significant result was found in dominant ankles (frequent-exercise subjects 60.46 mm(2)(2), infrequent-exercise subjects 54.71 mm(2)(2)) (p < 0.05), this was not the case for the nondominant ankles (frequent-exercise subjects 57.09 mm(2)(2), infrequent-exercise subjects 55.4 mm(2)(2)) (p > 0.05). In both frequent- and infrequent-exercise subjects, there was no significant difference in the mean thickness and cross-sectional area of Achilles tendon between dominant and nondominant ankles (p > 0.05). There was a high reproducibility in the sonographic measurement of the thickness (68%) and cross-sectional area (81%) of Achilles tendons. Results suggested that exercise would cause increase in the thickness and cross-sectional area of Achilles tendon. Interobserver variability is not significant in the sonographic measurement of Achilles tendons.     

Loading rate and contraction duration effects on in vivo human Achilles tendon mechanical properties

Tendons are viscoelastic, which implies loading rate dependency, but loading rates of contractions are often not controlled during assessment of human tendon mechanical properties in vivo. We investigated the effects of sustained submaximal isometric plantarflexion contractions, which potentially negate loading rate dependency, on the stiffness of the human Achilles tendon in vivo using dynamometry and ultrasonography. Maximum voluntary contractions (high loading rate), ramp maximum force contractions with 3 s loading (lower loading rate) and sustained contractions (held for 3 s) at 25%, 50% and 80% of maximal tendon force were conducted. No loading rate effect on stiffness (25–80% max. tendon force) was found. However, loading rate effects were seen up to 25% of maximum tendon force, which were reduced by the sustained method. Sustained plantarflexion contractions may negate loading rate effects on tendon mechanical properties and appear suitable for assessing human Achilles tendon stiffness in vivo.     

Mechanical properties of the human achilles tendon

OBJECTIVE: To determine whether the human Achilles tendon has higher material properties than other tendons and to test for strain rate sensitivity of the tendon. DESIGN: Mechanical testing of excised tendons. BACKGROUND: While the human Achilles tendon appears to experience higher in vivo stresses than other tendons, it is not known how the Achilles tendon's material properties compare with the properties of other tendons. METHODS: Modulus, failure stress, and failure strain were measured for excised human Achilles tendons loaded at strain rates of 1% s(-1) and 10% s(-1). Paired t-tests were used to examine strain rate effects, and average properties from grouped data were used to compare the Achilles tendon's properties with properties reported in the literature for other tendons. RESULTS: Failure stress and failure strain were higher at the faster strain rate, but no significant difference in modulus was observed. At the 1% s(-1)rate, the mean modulus and failure stress were 816 MPa (SD, 218) and 71 MPa (SD, 17), respectively. The failure strain was 12.8% (SD, 1.7) for the bone-tendon complex and 7.5% (SD, 1.1) for the tendon substance. At the 10% s(-1) rate, the mean modulus and failure stress were 822 MPa (SD, 211) and 86 MPa (SD, 24), respectively. The mean failure strain was 16.1% (SD, 3.6) for the bone-tendon complex and 9.9% (SD, 1.9) for the tendon substance. These properties fall within the range of properties reported in the literature for other tendons. CONCLUSIONS: The material properties of the human Achilles tendon measured in this study are similar to the properties of other tendons reported in the literature despite higher stresses imposed on the Achilles tendon in vivo.