Department of Biomedical Engineering, Binghamton University, NY 13902, USA.
Department of Physics, Yale University, CT 06520, USA; Department of Radiology & Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center, NY 10065, USA.
Acta Biomater. 2019 Apr 1;88:141-148. doi: 10.1016/j.actbio.2019.02.003. Epub 2019 Feb 5.
Human skin is a composite tissue that exhibits anisotropic mechanical properties. This anisotropy arises primarily from the alignment of collagen and elastin fibers in the dermis, which causes the skin to exhibit greater tension in one direction, making it appear stiffer. A diverse number of skin tension guidelines have been developed to assist surgeons in making incisions that produce the least conspicuous scars. However, skin anisotropy is believed to vary from subject to subject, and no single guideline is universally recognized as the best to implement for surgical applications. To date, no system exists that can rapidly and non-invasively measure lines of skin tension in vivo. In this article, we evaluate the ability of a new aspiration system to measure the anisotropy of human skin. The device painlessly applies a radial stress of 17 kPa to a region of skin, and captures radially asymmetric skin deformations via a dermal camera. These deformations are used to quantify orientations of strain extrema and the direction of greatest skin stiffness. The ratio of these asymmetric strains varies between 1 and -0.75. A simple 2D transverse isotropic model captures this behavior for multiple anatomical sites. Clinical trials reveal that skin tension line orientations are comparable with existing skin tension maps and generally agree across subjects, however orientations statistically differ between individuals. As such, existing guidelines appear to provide only approximate estimates of skin tension orientation. STATEMENT OF SIGNIFICANCE: Skin tension lines (STL) in human skin arise primarily from collagen fiber alignment in the dermis. These lines are used by surgeons to guide incisions that produce the least conspicuous scars. While numerous anatomical STL maps exist, no single guideline is universally recognized as the most reliable. Moreover, manual methods of quantifying STL are imprecise. For the first time, we have developed a device capable of rapidly and non-invasively measuring STL orientations in vivo, using a single test. Our results are used to establish a simple constitutive model of mechanical skin anisotropy. Clinical trials further reveal STL orientations are comparable with existing maps, but statistically differ between individuals. Existing guidelines therefore appear to provide only approximate estimates of STL orientation.
人类皮肤是一种复合组织，具有各向异性的机械性能。这种各向异性主要源于真皮中胶原纤维和弹性纤维的排列，这使得皮肤在一个方向上表现出更大的张力，从而使其显得更硬。已经开发出许多种皮肤张力指南，以帮助外科医生进行切口，从而产生最不明显的疤痕。然而，人们认为皮肤各向异性因个体而异，没有一种指南被普遍认为是最适合手术应用的。迄今为止，还没有一种系统能够快速、非侵入性地测量体内皮肤张力线。在本文中，我们评估了一种新的抽吸系统测量人体皮肤各向异性的能力。该设备无痛地向皮肤区域施加 17 kPa 的径向应力，并通过真皮相机捕获径向不对称的皮肤变形。这些变形用于量化应变极值的方向和最大皮肤硬度的方向。这些不对称应变的比值在 1 和-0.75 之间变化。一个简单的二维横向各向同性模型可以捕捉到多个解剖部位的这种行为。临床试验表明，皮肤张力线方向与现有的皮肤张力图相似，并且在不同个体之间基本一致，然而方向在个体之间存在统计学差异。因此，现有的指南似乎只能提供皮肤张力方向的近似估计。
人类皮肤的皮肤张力线（STL）主要源于真皮中胶原纤维的排列。这些线被外科医生用来指导切口，以产生最不明显的疤痕。虽然存在许多解剖学 STL 图谱，但没有一种指南被普遍认为是最可靠的。此外，量化 STL 的手动方法不够精确。我们首次开发了一种能够快速、非侵入性地测量体内 STL 方向的设备，只需进行一次测试。我们的结果用于建立一个简单的皮肤各向异性力学模型。临床试验进一步表明，STL 方向与现有的图谱相似，但在个体之间存在统计学差异。因此，现有的指南似乎只能提供皮肤张力线方向的近似估计。
