Spatial variations in Achilles tendon shear wave speed

Supersonic shear imaging (SSI) is an ultrasound imaging modality that can provide insight into tissue mechanics by measuring shear wave propagation speed, a property that depends on tissue elasticity. SSI has previously been used to characterize the increase in Achilles tendon shear wave speed that occurs with loading, an effect attributable to the strain-stiffening behavior of the tissue. However, little is known about how shear wave speed varies spatially, which is important, given the anatomical variation that occurs between the calcaneus insertion and the gastrocnemius musculotendon junction. The purpose of this study was to investigate spatial variations in shear wave speed along medial and lateral paths of the Achilles tendon for three different ankle postures: resting ankle angle (R, i.e. neutral), plantarflexed (P; R – 15°), and dorsiflexed (D; R+15°). We observed significant spatial and posture variations in tendon shear wave speed in ten healthy young adults. Shear wave speeds in the Achilles free tendon averaged 12±1.2 m/s in a resting position, but decreased to 7.2±1.8 m/s with passive plantarflexion. Distal tendon shear wave speeds often reached the maximum tracking limit (16.3 m/s) of the system when the ankle was in the passively dorsiflexed posture (+15° from R). At a fixed posture, shear wave speeds decreased significantly from the free tendon to the gastrocnemius musculotendon junction, with slightly higher speeds measured on the medial side than on the lateral side. Shear wave speeds were only weakly correlated with the thickness and depth of the tendon, suggesting that the distal-to-proximal variations may reflect greater compliance in the aponeurosis relative to the free tendon. The results highlight the importance of considering both limb posture and transducer positioning when using SSI for biomechanical and clinical assessments of the Achilles tendon.     

Non-invasive in vivo measurement of the shear modulus of human vocal fold tissue

Voice is the essential part of singing and speech communication. Voice disorders significantly affect the quality of life. The viscoelastic mechanical properties of the vocal fold mucosa determine the characteristics of the vocal folds oscillations, and thereby voice quality. In the present study, a non-invasive method was developed to determine the shear modulus of human vocal fold tissue in vivo via measurements of the mucosal wave propagation speed during phonation. Images of four human subjects' vocal folds were captured using high speed digital imaging (HSDI) and magnetic resonance imaging (MRI) for different phonation pitches, specifically fundamental frequencies between 110 and 440 Hz. The MRI images were used to obtain the morphometric dimensions of each subject's vocal folds in order to determine the pixel size in the high-speed images. The mucosal wave propagation speed was determined for each subject and at each pitch value using an automated image processing algorithm. The transverse shear modulus of the vocal fold mucosa was then calculated from a surface (Rayleigh) wave propagation dispersion equation using the measured wave speeds. It was found that the mucosal wave propagation speed and therefore the shear modulus of the vocal fold tissue were generally greater at higher pitches. The results were in good agreement with those from other studies obtained via in vitro measurements, thereby supporting the validity of the proposed measurement method. This method offers the potential for in vivo clinical assessments of vocal folds viscoelasticity from HSDI.     

An ultrasonic technique for the measurement of the elastic moduli of human cornea

In the hopes of reducing the unpredictability associated with refractive surgical procedures and ultimately improving surgical techniques, many investigators have attempted to determine the elastic moduli of the cornea. Techniques such as stress-strain tests of corneal strips and the measurement of mercury drop displacement in a whole eye under increasing pressure have resulted in a range of values for Young's modulus from 10⁵ to 10⁷ N m⁻². Both of these methods are limited because these mechanical tests cannot be performed in the physiological state and because of the large amount of force applied during testing. We used an ultrasonic technique to determine the elastic moduli of the human cornea. Two groups of six corneas prepared under different conditions (in saline and in dextran) were examined separately and the shear waves were generated and detected in these 12 human eye bank eyes. All the waveforms were digitized and saved in files of binary format. Fast Fourier transformation (FFT) was applied to calculate the speed and attenuation of the shear wave. Using the resulting wave speeds and attenuation coefficients, the Young's moduli of the corneal samples were calculated as (5.3±1.1)×10⁶ N m⁻² and (2.0±1.0)×10⁷ N m⁻² for cornea samples prepared in saline and in dextran at 2.25 MHz, respectively.     

The use of 2D ultrasound elastography for measuring tendon motion and strain

The goal of the current study was to investigate the fidelity of a 2D ultrasound elastography method for the measurement of tendon motion and strain. Ultrasound phantoms and ex vivo porcine flexor tendons were cyclically stretched to 4% strain while cine ultrasound radiofrequency (RF) data and video data were simultaneously collected. 2D ultrasound elastography was used to estimate tissue motion and strain from RF data, and surface tissue motion and strain were separately estimated using digital image correlation (DIC). There were strong correlations (R²>0.97) between DIC and RF measurements of phantom displacement and strain, and good agreement in estimates of peak phantom strain (DIC: 3.5±0.2%; RF: 3.7±0.1%). For tendon, elastographic estimates of displacement profiles also correlated well with DIC measurements (R²>0.92), and exhibited similar estimated peak tendon strain (DIC: 2.6±1.4%; RF: 2.2±1.3%). Elastographic tracking with B-Mode images tended to under-predict peak strain for both the phantom and tendon. This study demonstrates the capacity to use quantitative elastographic techniques to measure tendon displacement and strain within an ultrasound image window. The approach may be extendible to in vivo use on humans, which would allow for the non-invasive analysis of tendon deformation in both normal and pathological states.     

前臂屈指肌腱修复术后功能恢复的影响因素分析

目的:探讨影响前臂屈指肌腱修复术后功能恢复效果的因素,以利于制定合理的手术及康复方案。方法:对2011年1月~2012年10月解放军第401医院手外科收治的58例(其中男性41例,女性17例,年龄13-62岁,平均33.8岁)屈指肌腱在前臂损伤患者的伤因及手术方式进行回顾、分析总结并进行随访,分析其受伤严重程度、手术方式、术后功能锻炼情况。结果:术后随访54例,失访4例,随访时间为术后3~6个月。根据中华医学会手外科学会手功能评定试用标准评定54例前臂屈指肌腱损伤修复术后的患手的恢复情况,其中优31例,良16例,中5例,差2例。指浅、深屈肌腱同时损伤较单纯指浅屈肌腱损伤修复术后粘连发生率较高,手功能的优良率较低(P0.05),合理应用防粘连技术和术后进行系统功能锻炼的患者术后手功能的优良率分别较未合理应用防粘连技术和术后未进行系统功能锻炼的患者显著升高(P0.05)。结论:手术切口是否合理的延长,术中操作是否重视无创操作,是否合理的应用防粘连技术以及缺乏系统的功能锻炼以及肌腱断端吻合质量是影响前臂屈指肌腱修复术后功能恢复的重要因素。     

前臂屈指肌腱修复术后功能恢复的影响因素分析

目的：探讨影响前臂屈指肌腱修复术后功能恢复效果的因素,以利于制定合理的手术及康复方案。方法：对2011年1月～2012年10月解放军第401医院手外科收治的58例（其中男性41例,女性17例,年龄13．62岁,平均33．8岁）屈指肌腱在前臂损伤患者的伤因及手术方式进行回顾、分析总结并进行随访,分析其受伤严重程度、手术方式、术后功能锻炼情况。结果：术后随访54例,失访4例,随访时间为术后3-6个月。根据中华医学会手外科学会手功能评定试用标准评定54例前臂屈指肌腱损伤修复术后的患手的恢复情况,其中优31例,良16例,中5例,差2例。指浅、深屈肌腱同时损伤较单纯指浅屈肌腱损伤修复术后粘连发生率较高,手功能的优良率较低（P〈0．05）,合理应用防粘连技术和术后进行系统功能锻炼的患者术后手功能的优良率分别较未合理应用防粘连技术和术后未进行系统功能锻炼的患者显著升高（P〈0．05）。结论：手术切口是否合理的延长,术中操作是否重视无创操作,是否合理的应用防粘连技术以及缺乏系统的功能锻炼以及肌腱断端吻合质量是影响前臂屈指肌腱修复术后功能恢复的重要因素。     

Gastric emptying in soldiers during and after field exercise in the heat measured with the [13C]acetate breath test method

The effects of exercise on gastric emptying remain controversial, with some workers reporting that heavy exercise inhibits it to varying degrees whereas others report no effects up to an intensity of 70% maximal oxygen consumption (O_2max). The state of hydration of the subjects and the environmental conditions may influence the rate of gastric emptying during exercise. To understand further the effects of a 3-h, 16-km walk/run carrying 30 kg of equipment under field conditions at 39°C, we estimated gastric emptying using a [¹³C]acetate breath test method. Breath samples were collected at intervals after giving 150 mg of [¹³C]acetate. The effects of giving a standard volume (530 ml) of water or dextrose (7.5 g · 100 ml⁻¹) with electrolytes or fructose/corn solids (7.5 g · 100 ml⁻¹) at rest before exercise were compared with those of exercise and of recovery after exercise with or without extra fluids (400 ml each 20 min). At rest, after a standard 530-ml load, gastric emptying times [mean (SE)] were: 37 (2) min (water), 46 (3) min (dextrose/electrolytes) and 47 (5) min (fructose/corn solids) and were significantly slower (P < 0.05) than those occurring after extra fluid ingestion, i.e. 32 (3), 39 (2) and 41 (3) min respectively. After a standard 530-ml load, emptying times during exercise were almost identical to those at rest but, during exercise, extra fluid speeded up gastric emptying more than at rest to 24 (2), 26 (1) and 27 (5) min (P < 0.05) respectively. During resting recovery without extra fluids, gastric emptying was significantly slowed to 60 (2), 71 (5) and 78 (3) min, respectively. Although emptying times during recovery from exercise with extra fluid were faster [49 (6), 55 (2) and 58 (4) min, respectively], they were still slower than before exercise. The results suggest that: (1) extra fluid increases gastric emptying more during exercise than at rest, and (2) gastric emptying during resting recovery from exercise is slower than at rest before exercise whether or not fluid has previously been taken. Accepted: 17 June 1996     

Different regions of bovine deep digital flexor tendon exhibit distinct elastic,but not viscous,mechanical properties under both compression and shear loading

Tendons in different locations function in unique, and at times complex, invivo loading environments. Specifically, some tendons are subjected to compression, shear and/or torsion in addition to tensile loading, which play an important role in regulating tendon properties. To date, there have been few studies evaluating tendon mechanics when loaded in compression and shear, which are particularly relevant for understanding tendon regions that experience such non-tensile loading during normal physiologic function. The objective of this study was to evaluate mechanical responses of different regions of bovine deep digital flexor tendons (DDFT) under compressive and shear loading, and correlate structural characteristics to functional mechanical properties. Distal and proximal regions of DDFT were evaluated in a custom-made loading system via three-step incremental stress-relaxation tests. A two-relaxation-time solid linear model was used to describe the viscoelastic response. Results showed large differences in the elastic behavior between regions: distal region stresses were 4–5 times larger than proximal region stresses during compression and 2–3 times larger during shear. Surprisingly, the viscous (i.e., relaxation) behavior was not different between regions for either compression or shear. Histological analysis showed that collagen and proteoglycan in the distal region distributed differently from the proximal region. Results demonstrate mechanical differences between two regions of DDFT under compression and shear loading, which are attributed to variations of composition and microstructural organization. These findings deepen our understanding of structure–function relationships of tendon, particularly for tissues adapted to supporting combinations of tension, compression, and shear in physiological loading environments.     

衰逝波探测川芎嗪与剪应力对内皮细胞膜PS异位的影响

为探讨川芎嗪和剪应力对血管内皮细胞凋亡的影响,以锥-板旋转式剪切装置提供剪应力,与川芎嗪共同作用于大鼠微血管内皮细胞(rCMEC),采用Annexin V-FITC染色标记,利用全内反射衰逝波激发ICCD成像技术,探测川芎嗪和剪应力对rCMEC磷脂酰丝氨酸(PS)异位的影响。结果表明,培养的内皮细胞膜表面PS异位具有普遍性,静态培养内皮细胞的PS异位率(异位程度)为9.97％。作为单因素,剪应力(6×10~(-5)、12×10~(-5)、24×10~(-5)N/cm~2)或川芎嗪(31.5、63.0、126.0μg/ml)均可使PS异位率明显下降(P<0.001)。在同一剪应力水平条件下,川芎嗪的给予可使内皮细胞的PS异位率进一步降低。中等水平的两因素组合降低异位率的效果较突出。结果提示,适当水平的剪应力与川芎嗪联合作用有可能明显抑制rCMEC凋亡。     

转化人胚肌腱细胞力学特性研究

探讨转化人胚腱细胞９Ｔｒａｎｓｆｏｒｍｅｄ ｈｕｍａｎ ｅｍｂｒｙｏｎｉｃ ｔｅｎｄｏｎ ｅｅｌｌｓ,ＴＨＥＴＣｓ）力学特性,以阐明在应变条件下进行细胞－支架材料复合培养时腱铁力学相容性。取人腱细胞（Ｈｕｍａｎ ｅｍｂｒｙｏｎｉｃ ｔｅｎｄｏｎ ｃｅｌｌｓ,ＨＥＴＣｓ）和ＴＨＥＴＣｓ,采用微吸管吸吮实验技术,测量单个细胞的粘生及其对聚乳酸（Ｐｏｌｙｌａｃｔｉｃ ａｃｉｄ,ＰＬＡ）和聚乳酸羟基乙酸共     

关节镜下应用带跟骨异体跟腱一期联合治疗膝关节脱位合并不稳定

目的：探讨关节镜下应用带跟骨异体跟腱一期联合重建治疗膝关节脱位合并不稳定的治疗效果。方法：2008年1月至2010年1月,我们于关节镜下应用带跟骨异体跟腱一期联合重建治疗膝关节脱位合并不稳定患者11例,男9例,女2例;年龄17～45岁,平均22.3岁;右膝6例,左膝5例。患者在排除手术禁忌后,分别在关节镜下采用带跟骨异体跟腱一期联合重建后交叉韧带（PCL）、内侧副韧带（MCL）、前交叉韧带（ACL）和外侧副韧带（LCL）。结果：术后所有切口均于2周后I期愈合。10例获得随访,随访时间24～36个月,平均30个月。术后24个月,Lysholm评分由术前的42.2±3.5,升至84.5±6.2分,其中A级9例,B级1例,C级0例;国际膝关节文献委员会（IKDC）评分有术前的41.7±6.5分,升至82.3±10.3分。术前与术后Lysholm评分及IKDC评分有显著差别（P〈0.05）。术后膝关节活动范围,与术前相比具有显著性差异（P〈0.05）。结论：关节镜下应用带跟骨异体跟腱一期联合重建治疗膝关节脱位能够较好的恢复患者膝关节稳定和活动范围,具有令人满意的临床效果。     

Perivascular cells of the supraspinatus tendon express both tendon- and stem cell-related markers

Tendons and ligaments are often affected by mechanical injuries or chronic impairment but other than muscle or bone they possess a low healing capacity. So far, little is known about regeneration of tendons and the role of tendon precursor cells in that process. We hypothesize that perivascular cells of tendon capillaries are progenitors for functional tendon cells and are characterized by expression of marker genes and proteins typical for mesenchymal stem cells and functional tendon cells. Immunohistochemical characterization of biopsies derived from intact human supraspinatus tendons was performed. From these biopsies perivascular cells were isolated, cultured, and characterized using RT-PCR and Western blotting. We have shown for the first time that perivascular cells within tendon tissue express both tendon- and stem/precursor cell-like characteristics. These findings were confirmed by results from in vitro studies focusing on cultured perivascular cells isolated from human supraspinatus tendon biopsies. The results suggest that the perivascular niche may be considered a source for tendon precursor cells. This study provides further information about the molecular nature and localization of tendon precursor cells, which is the basis for developing novel strategies towards tendon healing and facilitated regeneration. H. Tempfer and A. Wagner have contributed equally to this paper.     

Atomic force microscopy determination of Young׳s modulus of bovine extra-ocular tendon fiber bundles

Extra-ocular tendons (EOTs) transmit the oculorotary force of the muscles to the eyeball to generate dynamic eye movements and align the eyes, yet the mechanical properties of the EOTs remain undefined. The EOTs are known to be composed of parallel bundles of small fibers whose mechanical properties must be determined in order to characterize the overall behavior of EOTs. The current study aimed to investigate the transverse Young?s modulus of EOT fiber bundles using atomic force microscopy (AFM).