Sex- and site-dependent variations in the thickness and mechanical properties of human skin in vivo

Abstract

A new method for the in vivo characterization of the physical properties of skin is presented. This comprises an ultrasound device to measure the vertical displacement of the surface of the skin, as well as its thickness and that of the hypodermis under suction. In combination with this, a mathematical model is used to calculate the following skin parameters: Young's modulus, the initial stress and an index of non-elasticity. These parameters were evaluated from the volar forearm and the forehead of 30 male and 30 females, of similar ages (28 +/- 6-years-old). The sensitivity of the testing procedure, allowing the characterization of the mechanical parameters of the skin, easily differentiated these two sites, and in some cases, differences between women and men were demonstrated. The main results showed for both sexes that the thickness (P = 0.0001), Young's modulus (P = 0.0001), and the index of non-elasticity (P = 0.0001) were greater for the forehead than for the ventral forearm, but that the initial stress was lower (P = 0.0001). The results show that the skin is thicker, stiffer and less tense and elastic on the forehead than on the ventral forearm, suggesting structural differences between these two sites (collagen fibre network, elastic fibres, epidermis, stratum corneum, microvascularization, actinic damage, presence of sebaceous glands, etc.). It is hoped that this device will be useful for the evaluation of certain skin disorders (scleroderma, Ehlers-Danlos syndrome, cutis laxa, oedema, etc.) and their therapy, as well as being a useful tool in skin ageing and cosmetic product assessment.

Skin Tensile Properties in Patients Treated for Acromegaly

“…This limitation permits indeed a comparison between the intrinsic properties of normal skin and those of a presumably thicker dermis in acromegaly. Hence, the well-recognized effect of tissue thickness upon the biomechanical properties of skin [1,25,34] is minimized. Our study indicates that the skin tensile properties are markedly altered in patients treated for acromegaly.…”

Influence of Array Interspacing on the Force Required for Successful Microneedle Skin Penetration: Theoretical and Practical Approaches

“…The group applied a multistage buckling model to analyse the mechanism of wrinkle formation as a result of buckling of different layers of the skin, relative to age related changes in skin structure. The skin will deform linearly under relatively low stress (Diridollou et al, 2000, Fung, 1993, and in this study as we aim to quantify the effect of spacing on insertion force, the equations based on assumption of linear behaviour for a beam on an elastic foundation are adaptable for this purpose.…”

Estimating material parameters of human skin in vivo

“…Some of the most common include suction tests (Alexander and Cook 1977;Elsner et al 1990;Diridollou et al 1998;Hendriks et al 2003), torsion tests (Escoffier et al 1989), indentation tests (Highley 1977), uniaxial tests (Snyder and Lee 1975), biaxial tests (Lanir and Fung 1974a;Schneider et al 1984) and multiaxial tests (Reihsner et al 1995). Recent work has tended to focus toward applying suction devices in combination with either an ultrasound (Diridollou et al 2000(Diridollou et al , 2001Hendriks et al 2003;Dahan et al 2004) or an OCT imaging device (Hendriks et al 2004) to measure the stress distribution in deformed skin. These devices are, however, inadequate for modelling purposes as they do not account for the anisotropic nature of skin.…”

“…These devices are, however, inadequate for modelling purposes as they do not account for the anisotropic nature of skin. Another trend has been to express the stress-strain relationship in terms of the Young's modulus (Escoffier et al 1989;Diridollou et al 2000Diridollou et al , 2001. This too constitutes an oversimplification, ignoring the non-linear properties.…”