Age-Related Mechanical Properties of Human Skin: An In Vivo Study.

Abstract

We have investigated in vivo how various viscoelastic parameters that describe the mechanical properties of the human skin may vary with age. Accordingly, we have used a mechanical device that records the torsional extensibility of the skin. When submitted to a low torque, the time-response curve of the skin affords the determination of the immediate extensibility (UE), the immediate recovery (UR), the viscoelastic part of the deformation (UV), the elastic recovery (UR/UE), and the creep relaxation time (tau). Because the skin thickness varies with age and primarily governs the mechanical properties, it was measured through an ultrasound technique at the same sites (forearm) where the torque was applied. The results show that the skin maintains its thickness and extensibility up to the seventh decade as opposed to its elasticity or recovery capacities, which decrease from an early age. The viscous part of the deformation is constant through life, whereas the creep relaxation time decreases linearily with age. Except for skin thickness, no differences in these parameters between men and women were detected. The significance of these results are discussed in terms of structure alterations. The determination of the elastic recovery (UR/UE) appears to be a parameter of choice for illustrating skin aging.

Tissue elasticity and the ageing elastic fibre

“…In contrast, mildly photoaged skin appears roughened and deeply wrinkled and is characterised histologically by the loss of fibrillin microfibrils (Watson et al 1999) and fibulin (Kadoya et al 2005) from the papillary dermis. In severely photoaged skin, however, abundant deposits of highly disorganised, elastic fibre material are distributed throughout the dermis (Warren et al 1991;Watson et al 2001;Werth et al 1996;Yaar and Gilchrest 2007) Early attempts to quantify the effects of ageing on the mechanical properties of skin were hampered by: the use of terminology which was open to misinterpretation (Doubal and Klemera 2002), the diversity of both mechanical tests (Diridollou et al 1998;Rodrigues 2001) and anatomical sites (Escoffier et al 1989), and most importantly by the heterogeneity and anisotropy of the skin layers themselves (Diridollou et al 1998;Pierard 1999). The mechanical response of skin to the application of tensile and torsional forces and to deformations induced by indentation and suction have all been reported in the literature (see Rodrigues 2001 for an excellent review).…”

“…The mechanical response of skin to the application of tensile and torsional forces and to deformations induced by indentation and suction have all been reported in the literature (see Rodrigues 2001 for an excellent review). Of these techniques, torsional approaches, which may be used in vivo, have the advantage of applying mechanical stresses parallel to the plane of the skin, thereby minimising the influence of tissue anisotropy and underlying tissue structures on the measured mechanical parameters (Escoffier et al 1989). The device rotates a disk which has been adhered to the skin and records the torque (rotational force) and degree of rotation (Fig.…”

“…By introducing guard rings of variable diameter, it has been proposed that the depth of mechanical deformation can be controlled (Batisse et al 2002). Since their introduction in the 1970s (Finlay 1970) torsional approaches have been applied to the study of both intrinsic (Escoffier et al 1989) and extrinsic ageing Batisse et al 2002;Sanders 1973) and a commercial device, the Dermal Torque Meter is now in use (Batisse et al 2002). Suction methods which use a negative pressure to deform the skin (Fig.…”

“…Commercially developed devices include the Cutometer, which measures skin deformations optically, and the Dermaflex A, which measures vertical skin displacements by changes in capacitance (Diridollou et al 1998;Smalls et al 2006 biomechanical properties measured by these techniques requires quantitation of skin thickness. Early attempts to measure skin thickness using callipers ) have largely been superseded by the use of ultrasound (Diridollou et al 1999;Escoffier et al 1989;Takema et al 1994). Applying either suction or torsional forces to skin induces a rapid elastic deformation (U E ), followed by a slower viscoelastic deformation (U V ) until finally the total skin deformation (U F ) is reached (Fig.…”

“…Applying either suction or torsional forces to skin induces a rapid elastic deformation (U E ), followed by a slower viscoelastic deformation (U V ) until finally the total skin deformation (U F ) is reached (Fig. 4d, e) (Escoffier et al 1989;Leveque et al 1980;Rodrigues 2001;Takema et al 1994). Removing the force allows the skin to recover and the ratio of the recovery to initial deformation quantifies the ability of the skin to elastically recoil.…”