牵伸应力对肌腱延长区生物力学特性的影响

目的:观察肌腱切断后形成的肌腱延长区在牵伸应力作用下生物力学强度的变化,探讨用于治疗肌腱缺损的可行性。方法:取健康成年日本大耳白兔36只,建立肌腱牵伸延长的动物模型,设实验组、对照组和空白对照组,术后第1周开始延长,速度为1mm/d分早晚两次进行,术后4周停止延长,开始被动活动距小腿关节,2次/d,以增加局部的应力刺激,术后分别于3,6,9,12周取材,检测形成的肌腱延长区的生物力学强度。结果:实验组经牵伸后明显长于对照组,12周时的最大断裂载荷为58N,对照组为32N,经非配对t检验,t=27.6,P<0.01,二者差异具有显著性意义,空白对照组218N。结论:肌腱切断后在缓慢牵伸应力作用下不断延长,形成的肌腱延长区的断裂载荷明显大于对照组,超过了正常肌腱最大断裂载荷的1/4,能够满足其日常生活的生理需要。     

牵伸应力对肌腱延长区生物力学特性的影响

目的：观察肌腱切断后形成的肌腱延长区在牵伸应力作用下生物力学强度的变化，探讨用于治疗肌腱缺损的可行性。方法：取健康成年日本大耳白兔36只，建立肌腱牵伸延长的动物模型，设实验组、对照组和空白对照组，术后第1周开始延长，速度为1mm／d分早晚两次进行，术后4周停止延长，开始被动活动距小腿关节，2次／d，以增加局部的应力刺激，术后分别于3，6，9，12周取材，检测形成的肌腱延长区的生物力学强度。结果：实验组经牵伸后明显长于对照组，12周时的最大断裂载荷为58N，对照组为32N，经非配对t检验，t=27．6，P&;lt;0．01，二者差异具有显著性意义，空白对照组218N。结论：肌腱切断后在缓慢牵伸应力作用下不断延长，形成的肌腱延长区的断裂载荷明显大于对照组，超过了正常肌腱最大断裂载荷的1／4，能够满足其日常生活的生理需要。     

弹性成像在肌骨超声中的应用

硬度属于肌腱、肌肉和神经等软组织的力学特性,当发生肌腱病或撕裂时,组织的力学特性会随之变化。近年来弹性成像在肌腱、肌肉和神经等软组织病变的诊断、鉴别诊断以及疗效随访中的应用日益增多。本文就弹性成像在肌骨超声中的应用现状和前景做一述评。     

肌腱的生物学特性及缺损后修复材料的性能评价

目的:探讨肌腱的生物学特性及肌腱缺损修复材料的性能.方法:用计算机检索中国期刊全文数据库(CNKI:1985/2009)和Medline database(1985/2009),纳入主题内容与肌腱生物学特性和肌腱缺损修复材料联系紧密的文章;排除Meta分析、与主题无关的文章及重复性研究.对文献进行筛选、资料收集和质量评价,共纳入29篇文章,其中中文文献16篇,英文文献13篇.从肌腱的生物学特性及肌腱缺损修复材料的性能进行总结.结果:肌腱的营养主要由肌腱当中的血管通过血液供给,肌腱在重复性载荷下会发生疲劳,但和其他工程材料不同之处在于肌腱具有自我修复能力;肌腱的生物力学特性与胶原纤维密切相关,应力应变曲线与胶原纤维基本相同,表现出明显的黏弹性体特性--滞后、蠕变和应力松弛.当前对肌腱缺损的修复材料主要有自体肌腱、同种异体肌腱、异种肌腱、人工肌腱替代物及组织工程化人工肌腱.结论:虽然肌腱缺损的修复材料较多,但是均具有其优缺点,目前仍未找到一种最理想的修复方法.目前对肌健的研究已进入分子水平,相信在不久的将来,组织工程和基因工程将制造出理想的肌腱替代品.     

分米波辐射后肌腱愈合的早期生物力学研究

目的探讨分米波辐射后肌腱愈合早期生物力学变化并观察分米波对主动活动运动的影响。 方法选用Leghorn鸡56只,随机分为治疗组和对照组,每组28只。取Leghorn鸡左足第Ⅲ、Ⅳ趾为肌腱损伤模型趾。将趾深屈肌腱切断、修复,术后石膏托固定,手术部位暴露。治疗组术后1 d～3周局部用分米波辐射治疗,对照组行空白对照。术后1,7,10,14,18,21,28 d取材进行生物力学检测,观察2组肌腱最大拉伸断裂强度(Pmax)、肌腱最大延伸率(δmax)、拉断肌腱粘连带功耗(W0)。 结果治疗组术后7,10,14,18,21,28 d Pmax、δmax、W0均明显优于对照组,差异有统计学意义（P<0.05）。 结论分米波能抑制肌腱外源性愈合、促进内源性愈合,增加肌腱弹性变形能力和坚韧程度,缩短水肿期并减轻疼痛,为早期主动运动提供了必要条件。     

在体乳腺组织非线性变形特征及其在静态超声弹性成像中的影响

目的通过剪切波弹性成像定量研究在体乳腺组织非线性变形特征,评价非线性变形特征对乳腺组织静态超声弹性成像测量的影响,以指导和规范乳腺超声弹性成像操作方法。 方法前瞻性选取自2014年1月至2014年5月于北京友谊医院超声科进行体检的女性26例。其中14例女性（8例双侧乳腺,6例单侧乳腺）纳入乳腺组织非线性变形特征的研究,12例女性（8例双侧乳腺,4例单侧乳腺）纳入乳腺组织非线性变形特征在静态超声弹性成像中的影响相关研究。采用超声剪切波弹性成像功能对乳腺组织非线性变形特征进行研究,采用超声静态弹性成像功能对乳腺组织非线性变形特征在静态超声弹性成像中的影响进行研究。计算乳腺组织的非线性参数硬化系数（b）、初始未受压状态下的剪切模量（μ₀）及伸长比（λ）,并绘制乳腺非线性变形特征曲线。在体乳腺组织非线性变形特征研究中,将8例受试者双侧乳腺的b及μ₀按照左右两侧分组,并进行比较;将14例受试者所有乳腺的b及μ₀按照相对位置不同分为乳头上方组、乳头内侧组、乳头下方组、乳头外侧组、外上象限组,并进行比较。 结果14例受试者的乳腺非线性参数b=6.36±1.74,μ₀=（3.01±0.47）kPa,据此绘制出反映乳腺非线性特征的曲线图,其反映乳腺组织形变与剪切模量的关系为伸长比λ值越小（乳腺的形变越大）,剪切模量μ值变化越显著。8例受试者左右两侧乳腺的非线性参数b及μ₀比较,差异均无统计学意义（t=0.520、0.437,P均>0.05）。14例受试者乳腺不同相对位置的非线性参数b及μ₀比较,差异均无统计学意义（F=1.339、1.916,P均>0.05）。静态超声弹性成像中12例受试者,计算得出乳腺组织的最小伸长比λ=0.75±0.05,绘制反映乳腺组织形变和弹性模量增加倍数之间关系的曲线图,其反映在乳腺非线性变形达到25%时,剪切模量达到初始剪切模量的5.72倍,在变形程度达到5%时,剪切模量为未受压状态的1.10倍。 结论乳腺组织的弹性模量随变形程度的增大而呈非线性增加。乳腺两侧及不同相对位置非线性弹性性质无明显差异。应用乳腺静态超声弹性成像时,需将超声探头加压导致的压缩变形控制在5%以内。     

机械载荷对肌肉和肌腱硬度影响的研究进展

硬度可以客观反映肌肉、肌腱的功能状态。抗阻训练可导致肌肉、肌腱硬度发生改变,不同训练方式和强度对肌肉、肌腱硬度的影响不尽相同。本文综述机械载荷对健康人肌肉、肌腱硬度的影响,以及肌肉、肌腱对机械载荷的适应机制。     

超声弹性成像技术在肌腱疾病诊断中的应用

正由于外伤、过度使用或随着年龄的增长,肌腱将产生不同程度的急性或慢性损伤。损伤的肌腱修复后可能会出现粘连、僵硬、收缩性差等问题,影响肌腱的功能,因此,对受损肌腱的早期诊断及修复后随访有重要意义[1]。二维超声和多普勒超声技术是肌肉骨骼系统的常规检查方法,尤其是高频超声探头的应用,使浅表组织结构得到了较好的评估,评价肌腱结构及功能的常用方法[2]。超声弹性成像技术是最近迅猛发展的超声技术,其在二维超声检查的基础上,进一步对组织的弹性进行评估[3],提供更准确的诊断依据[4]。随着技术的不断发展与成熟,超声弹性成像技术逐渐开始应用于肌肉骨骼系统检查,现对超     

腰椎“U”型弹性内固定棒的有限元分析

将自行研制的弹簧状镍钛记忆合金棒与钛合金椎弓根钉相结合组成生物弹性内固定系统,采用螺旋CT对弹性内固定器进行层厚1.0mm的连续水平扫描,将所得的图像进行轮廓提取和阈值分割后,借助ANSYS8.0软件,建它弹性内固定棒的实体模型与有限元模型,分别施加压缩、前屈及拉伸等各种生理载荷,观察各模型不同载荷下弹性内固定器的应力分布,并与传统的钛合金内固定棒进行比较.建立了"U"型弹性内固定棒的有限元模型,可以预测内固定棒在变形过程中其本身结构中各节点、单元的受力、位移情况.在垂直压缩、前屈和后伸状态下内固定棒应力分布合理,在3种状态下应力集中的部位主要在"U"型弹性内固定棒的中部.提示在加载相同的纵向载荷条件下,"U"型弹性内固定器的应力分布在"U"型连接棒的"U"型区上,应力应变曲线表现出较好的弹性作用,该内固定棒可能成为治疗下腰痛的新型节段内固定器.     

CO_2激光辅助接合屈肌腱的动物实验研究

目的　通过观察CO2 激光辅助接合屈肌腱后腱组织的愈合过程 ,为临床应用提供实验基础。方法　选用 2 0只雌性成年京白鸡 ,建成双侧多趾屈趾深肌腱损伤模型 ,并随机分为实验侧和对照侧。实验侧 ,应用CO2 激光焊接 ;对照侧 ,行改良Kessler法缝合。分别于术后 1、2、3、4、6和 8周对修复肌腱行大体观察及光、电镜组织形态学观察。结果　术后 4周 ,实验组与对照组损伤肌腱均基本愈合。两组对照比较显示 ,实验组中所修复肌腱 ,表面较光滑 ,与周围组织粘连少 ,腱周径近于正常 ;修复组织中无明显异物反应 ;腱内膜和腱外膜再生明显 ,腱纤维形态接近正常。电镜下 ,肌腱断端间纤维母细胞增生活跃。结论　激光辅助接合屈肌腱能够保护屈肌腱的血供、可促进肌腱的内源性愈合 ,减轻与周围组织的粘连 ,不失为一种有临床应用价值的肌腱修复新方法     

Effect of cyclic stretching on the tensile properties of patellar tendon and medial collateral ligament in rat

BACKGROUND: Although dynamic stretching is often prescribed before exercise is undertaken, research has rarely been conducted to determine what effects dynamic stretching has on tendon and ligament injury prevention. The hypothesis is that the mechanical properties of tendon and ligament will increase in an ultimate tensile loading test after sinusoid cyclic stretching. METHODS: Ten paired rat medial collateral ligaments and patellar tendons were used with and without 150 sinusoid cyclic stretching in either side to determine the influence of cyclic stretching on the mechanical behavior of the tendons and ligaments. FINDINGS: The increase in ultimate stress and elastic modulus was significant after sinusoid cycling in both the medial collateral ligaments and the patellar tendons. An adequate sinusoid cyclic stretching could increase the mechanical properties of tendon and ligament under optimization of cyclic strain. INTERPRETATION: A better understanding of the mechanical behavior of tendon and ligament after a series of dynamic stretching prior to exercise may lead to the development of training strategies that could reduce the incidence of injury during sports activities.     

Biomechanical study on the effect of twisted human patellar tendon

Objective. To compare the stiffness and maximum strength between the untwisted and twisted free-tendon.

Design. 22 twisted and untwisted sectioned-specimens of human cadaver patellar tendons were used and pulled to failure to obtain load-deformation profiles from which stiffness, maximum load to failure and elastic elongation limit were derived.

Background. In the reconstruction of the deficient anterior cruciate ligament, the use of the central one-third of the patellar tendon is a well-established procedure in which, prior to insertion, the tendon graft may be twisted to mimic the natural orientation of the anterior cruciate ligament in the knee joint.

Results. The untwisted tendons had a mean stiffness of 36.5 kg/mm (SD, 16.6 kg/mm) and maximum load of 165.9 kg (SD, 86.8 kg). With a 90° twist, the average stiffness of the twisted tendon was 66.5 kg/mm (SD, 25.4 kg/mm), with maximum load at 364.5 kg (SD, 109.9 kg), an increase of over 100%. The elastic elongation limit, or allowable elongation before permanent deformation or failure, was significantly larger in twisted tendons by 35%.

Conclusion. Twisting increased the resistance to deformation of the tendon in this study.

Relevance

The finding supports the surgical practice of pre-twisting tendon grafts for anterior cruciate ligament reconstruction, based on the premise that a stronger and stiffer graft provides a more favourable outcome.     

Temporary tendon strengthening by preconditioning

BACKGROUND: Tendon is frequently injured structure in sports activities. Stretching before activities has been recommended to prevent athletes from injuries. Clinical studies reported that stretching had effects to reduce passive muscle stiffness and leads to an increased range of motion. Recent biomechanical studies suggested that stretching might also temporary affect tensile property of tendon. However, the detailed information regarding optimizing this preconditioning has not been defined. The purpose of this study is to investigate time-dependent effect of preconditioning on the mechanical strength of tendon, and to determine an optimal duration of preconditioning for tendon strengthening. METHODS: Forty eight Achilles tendons from euthanized Sprague-Dawley rats were used. The specimens were randomly divided into six groups. The specimens in control group were tested to failure without preconditioning. In preconditioning groups, 30, 100, 300, 600, and 1000 s stretching at 2% strain were performed. The specimens were subsequently loaded to failure. FINDINGS: Preconditioning from 30s to 600 s significantly increased the ultimate failure load and strength. Ultimate failure load was significantly different between control and each of 30, 100, 300, and 600 s stretching groups (P=0.033, 0.031, 0.004, and 0.029, respectively). There was no significant difference between control and 1000 s stretching group. Ultimate strength was significantly different between control and each of 30, 100, 300, and 600 s stretching groups (P=0.007, 0.008, <0.001, and 0.006, respectively), but not between control and 1000 s stretching group. INTERPRETATION: The time-dependent effect of preconditioning on the mechanical strength of tendon may be due to progressive collagen fibre recruitment and subsequent fatigues at the micro-level.     

Mechanochemistry of single red blood cells monitored using Raman tweezers

Two microparticles were biochemically attached to a red blood cell at diametrically opposite parts and held by optical traps allowing to impose deformations. The cell deformation was monitored from the microscopy images. Raman spectra of the cell under tunable deformations were studied. Vibrational spectra analysis at different stretching states was supported with two statistical methods. Principal Component Analysis distinguishes the most prominent changes in spectra while 2D correlation technique monitors the evolution of Raman bands during stretching. The measurements show significant changes in the cell chemical structure with stretching however the changes saturate above 20% of cell deformation. Mechanical deformation of the cell mainly affects the bands corresponding to hemoglobin but contributions from spectrin and membrane proteins can not be excluded. The saturation of bands at higher deformations suggests some structural relaxation that RBC has to undergo to bear extra load. The results confirm widely accepted belief that spectrin released from membrane proteins allows for significant shape changes of the cells. We therefore tentatively suggest that interaction between membrane and cytoskeleton during deformation can be efficiently probed by confocal Raman spectroscopy, in particular via the peak around 1035 cm(-1).     

Effect of Achilles tendon loading on plantar fascia tension in the standing foot

BACKGROUND: The plantar fascia, which is one of the major arch-supporting structures of the human foot, sustains high tensions during weight-bearing. A positive correlation between Achilles tendon loading and plantar fascia tension has been reported. Excessive stretching and tightness of the Achilles tendon are thought to be the risk factors of plantar fasciitis but their biomechanical effects on the plantar fascia have not been fully addressed. METHODS: A three-dimensional finite element model of the human foot and ankle, incorporating geometrical and material nonlinearity, was employed to investigate the loading response of the plantar fascia in the standing foot with different magnitudes of Achilles tendon loading. FINDINGS: With the total ground reaction forces of one foot maintained at 350 N to represent half body weight, an increase in Achilles tendon load from (0-700 N) resulted in a general increase in total force and peak plantar pressure at the forefoot of up to about 250%. There was a lateral and anterior shift of the centre of pressure and a reduction in the arch height with an increasing Achilles tendon load as a result of the plantar flexion moment on the calcaneus. From the finite element predictions of simulated balanced standing, Achilles tendon forces of 75% of the total weight on the foot (350 N) were found to provide the closest match of the measured centre of pressure of the subject during balanced standing. Both the weight on the foot and Achilles tendon loading resulted in an increase in tension of the plantar fascia with the latter showing a two-times larger straining effect. INTERPRETATION: Increasing tension on the Achilles tendon is coupled with an increasing strain on the plantar fascia. Overstretching of the Achilles tendon resulting from intense muscle contraction and passive stretching of tight Achilles tendon are plausible mechanical factors for overstraining of the plantar fascia.     

Viscoplasticity of rabbit skeletal muscle under dynamic cyclic loading

To elucidate the strain effects of dynamic cyclic loading on the skeletal muscle-tendon unit, the muscle-tendon unit of New Zealand white rabbits were tested with different strains and strain rates under ketamine general anaesthesia. The results indicated that the dynamic responses of muscular tissues were both strain and strain-rate dependent with appreciably non-linear characteristic. The muscle-tendon unit behaved viscoelastically below 12% strain; but when stretching more than 16% strain it began to behave plastically. The loading energies and unloading energy are more dependent on strain than on strainrate. RELEVANCE: This study offers firm evidence that plasticity may be one of the important biomechanical properties of the skeletal muscle. The findings in this report imply that the expression of skeletal muscle mechanical behaviour may not be limited to phenomena represented by a composition of elastic and viscous elements. The elongation of skeletal muscle under sustained stretching might be explained by the plastic property. Elucidation of the existence of viscoplasticity in skeletal muscle gives a good reference point to determine the functional capabilities and limitation of muscular tissue.     

The effects of dynamic stretching on plantar flexor muscle-tendon tissue properties

Dynamic stretching is commonly used in warm-up routines for athletic activities. Even though several positive effects of dynamic stretching on athletic performance have been reported, the effects on the muscle–tendon unit (MTU) itself are still unclear. The objective of this study is to determine the effects of dynamic stretching on the ankle plantar flexor muscle–tendon properties by use of ultrasonography. Twenty healthy male subjects participated in the present study. The subjects were asked to engage in dynamic stretching of plantar flexors for 30 s and to repeat for 5 sets. Ankle dorsiflexion ROM was measured before and after the dynamic stretching. Changes in the displacement of the myotendinous junction (MTJ), pennation angle, and fascicle length were also determined by using ultrasonography. Ankle dorsiflexion ROM increased significantly after the dynamic stretching (p < 0.0001). A significant distal displacement of the MTJ was observed until the second stretching set (p < 0.001) with no significant changes thereafter. Pennation angle, and fascicle length were unaffected by the dynamic stretching. Dynamic stretching was shown to be effective in increasing ankle joint flexibility. Outcomes that could have indicated changes in muscle tissue (such as the pennation angle and fascicle length) were unaltered. However, a significant displacement of the MTJ was found, indicating some change in the tendon tissues. Therefore, dynamic stretching of the plantar flexors was considered an effective means of lengthening the tendon tissues.     

Effects of static stretching on mechanical properties and collagen fiber orientation of the Achilles tendon in vivo

BackgroundThe study was designed to examine changes in tendon properties measured during ramp and ballistic contractions after static stretching and to elucidate the relationship between stretching-induced changes in tendon properties (particularly hysteresis) and collagen fiber orientation.MethodsThirteen males performed static stretching, in which the ankle was passively flexed to 36° dorsiflexion and remained stationary for 10 min. Before and after stretching, the stiffness and hysteresis of tendon structures in the medial gastrocnemius muscle were measured using ultrasonography during ramp and ballistic contractions. Tendon collagen fiber orientation was also estimated from the coefficient of variation (CV) of echogenicity on transverse ultrasonic images of the Achilles tendon.Findings.The hysteresis of tendon structures significantly decreased by 15.5% (p = 0.005) during ramp contractions and by 15.3% (p = 0.003) during ballistic contractions after stretching, whereas stiffness did not. The mean echogenicity of the Achilles tendon significantly increased by 6.0% (p = 0.002) after stretching, whereas the CV of echogenicity did not (p = 0.148). Furthermore, the relative change in mean echogenicity, which reflected interstitial fluid movement within tendons, tended to be correlated to that in hysteresis measured during ballistic contractions (r = 0.439, p = 0.133).InterpretationThese results suggest that the hysteresis, but not stiffness, of tendon structures measured during ramp and ballistic contractions significantly decreased after stretching. Furthermore, a decline in the hysteresis of tendon structures after static stretching was associated with interstitial fluid movement within tendons, but not to changes in collagen fiber orientation.     

Effects of repeated ankle stretching on calf muscle-tendon and ankle biomechanical properties in stroke survivors

Background

The objective of this study was to investigate changes in active and passive biomechanical properties of the calf muscle–tendon unit induced by controlled ankle stretching in stroke survivors.

Methods

Ten stroke survivors with ankle spasticity/contracture and ten healthy control subjects received intervention of 60-min ankle stretching. Joint biomechanical properties including resistance torque, stiffness and index of hysteresis were evaluated pre- and post-intervention. Achilles tendon length was measured using ultrasonography. The force output of the triceps surae muscles was characterized via the torque–angle relationship, by stimulating the calf muscles at a controlled intensity across different ankle positions.

Findings

Compared to healthy controls, the ankle position corresponding to the peak torque of the stroke survivors was shifted towards plantar flexion (P < 0.001). Stroke survivors showed significantly higher resistance torques and joint stiffness (P < 0.05), and these higher resistances were reduced significantly after the stretching intervention, especially in dorsiflexion (P = 0.013). Stretching significantly improved the force output of the impaired calf muscles in stroke survivors under matched stimulations (P < 0.05). Ankle range of motion was also increased by stretching (P < 0.001).

Interpretation

At the joint level, repeated stretching loosened the ankle joint with increased passive joint range of motion and decreased joint stiffness. At the muscle–tendon level, repeated stretching improved calf muscle force output, which might be associated with decreased muscle fascicle stiffness, increased fascicle length and shortening of the Achilles tendon. The study provided evidence of improvement in muscle tendon properties through stretching intervention.     

局部注射肝素钠免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件的改变,日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存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.