Tension Lines of the Skin
Skin tension lines are natural lines of tension that occur within the skin as a result of growth and remodeling mechanisms. Researchers have been aware of their existence and their surgical implications for over 150 years. Research in the twentieth centur
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Abstract Skin tension lines are natural lines of tension that occur within the skin as a result of growth and remodeling mechanisms. Researchers have been aware of their existence and their surgical implications for over 150 years. Research in the twentieth century showed clearly, through destructive mechanical testing, that the orientation of skin tension lines greatly affects the mechanical response of skin in situ. More recent work has determined that this anisotropic response is, at least in part, due to the structural arrangement of collagen fibres within the dermis. This observation can be incorporated into mathematical and mechanical models using the popular Gasser-Ogden-Holzapfel constitutive equation. Advances in noninvasive measurement techniques for the skin, such as those based on elastic wave propagation, have enabled patient-specific identification of skin tension lines in an accurate and rapid manner. Using this technique on humans, we show that there is considerable variation in the level of anisotropy as the skin ages. Furthermore, we identify that both the structural arrangement of fibres and the in vivo levels of pre-strain play a significant role in the anisotropic behavior of skin.
A. Ní Annaidh School of Mechanical & Materials Engineering, University College Dublin, Dublin 4, Ireland UCD Charles Institute of Dermatology, School of Medicine and Medical Science, University College Dublin, Dublin, Ireland e-mail: [email protected] M. Destrade () Stokes Centre for Applied Mathematics, School of Mathematics, Statistics and Applied Mathematics, NUI Galway, Galway, Ireland School of Mechanical & Materials Engineering, University College Dublin, Dublin 4, Ireland e-mail: [email protected] © Springer Nature Switzerland AG 2019 G. Limbert (ed.), Skin Biophysics, Studies in Mechanobiology, Tissue Engineering and Biomaterials 22, https://doi.org/10.1007/978-3-030-13279-8_9
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A. Ní Annaidh and M. Destrade
1 Historical Beginnings and Clinical Significance As is the case for most biological soft tissues, an inherent residual stress exists in the skin [1–3]. It is due to growth and remodelling mechanisms [4] and is, in general, very complex to model and evaluate [5]. In human skin, the presence of residual stress has important implications for surgical planning and forensic science, as it can affect significantly the extent of gaping following a cut, and then the resulting healing time. The so-called Langer Lines are often considered to be the lines of maximum in vivo tension in the skin. They form an involved map over the body. To minimise the likelihood of excessive wound tension, wound rupture and subsequent unsightly scars, surgical incisions should be made parallel to Langer lines, which lie along the path of maximum skin tension [6]. The discovery of tension lines in skin is widely attributed to a nineteenth Century Austrian surgeon, Karl Langer, after whom the lines are named. The conventional wisdom is that Langer identified the existence of skin tension lines in 1861. In
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