Université François Rabelais de Tours, INSERM, U930, CNRS, ERL 3106, Tours, France.
J Biomech. 2012 Nov 15;45(16):2860-5. doi: 10.1016/j.jbiomech.2012.08.032. Epub 2012 Sep 15.
Most studies on skin anisotropy are carried out in an "average" context, e.g. with an extension/compression test on the skin in vivo, the elastic modulus being estimated for the stretched zone overall. Furthermore, the natural tension of the skin is not taken into account either in the experimental protocols or in the models studied. In this study, a battery of elastographic tests was carried out to investigate forearm skin anisotropy quantitatively by measuring local through-thickness strain in the dermis by means of high frequency elastography. The biaxial tensile effect and influence of the natural forearm skin tension were also analyzed.
The elastographic test was carried out using a combination of an extensiometer device and a real time ultrasound scanner. The extensiometer was used to apply a stress cycle, i.e. stretching, holding and release, on the internal face of the forearm in vivo. Parallel to the mechanical test, 2D real time ultrasound acquisitions were performed to track local displacements and to estimate local through-thickness strain using an elastographic algorithm. Local through-thickness strain kinetics were then extracted and used as a quantified indicator. We studied anisotropy in two stretching situations: stretching parallel and stretching perpendicular to Langer's lines. Elastographic tests were performed for two upper arm/forearm angles, i.e. outstretched and bent forearm, in order to check the natural skin tension effect.
The results showed the effectiveness of elastographic tests to describe and quantify the anisotropic behavior of the forearm skin in vivo. Elastographic results were distinctly different according to forearm positions: the anisotropic behavior was reversed from the bent forearm to the outstretched forearm.
The local anisotropic behavior of the skin in vivo could be easily studied using the elastographic test. Nevertheless, the initial skin tension is an important parameter which strongly affects the mechanical behavior of the skin in vivo, in particular its anisotropic properties.
大多数关于皮肤各向异性的研究都是在“平均”情况下进行的，例如在体内皮肤的拉伸/压缩测试中，整体估计拉伸区域的弹性模量。此外，实验方案或研究的模型都没有考虑到皮肤的自然张力。在这项研究中，通过高频超声弹性成像测量真皮的局部穿透应变，进行了一系列弹性测试，以定量研究前臂皮肤的各向异性。还分析了双轴拉伸效应和自然前臂皮肤张力的影响。
弹性测试使用拉伸计装置和实时超声扫描仪的组合进行。拉伸计用于在体内的前臂内表面施加应力循环，即拉伸、保持和释放。与机械测试平行，进行二维实时超声采集，以跟踪局部位移，并使用弹性算法估计局部穿透应变。然后提取局部穿透应变动力学并用作量化指标。我们在两种拉伸情况下研究了各向异性：平行于朗格线拉伸和垂直于朗格线拉伸。进行了两种上臂/前臂角度的弹性测试，即伸展和弯曲的前臂，以检查自然皮肤张力的影响。
结果表明弹性测试能够有效地描述和量化体内前臂皮肤的各向异性行为。根据前臂位置，弹性测试结果明显不同：从弯曲的前臂到伸展的前臂，各向异性行为发生逆转。
可以使用弹性测试轻松研究体内皮肤的局部各向异性行为。然而，初始皮肤张力是一个重要参数，它强烈影响体内皮肤的力学行为，特别是其各向异性特性。
