In vivo model of the mechanical properties of the human skin under suction

Background/aims: A new method for the in vivo characterization of the mecha nical properties of skin has been developed. This comprises a suction chamb er and an ultrasound device to measure both the vertical displacement of th e skin's surface, and the skin's thickness. Methods: A mathematical model of the mechanical behaviour of a taught elast ic membrane is used to obtain a set of parameters intrinsic to the skin, su ch as Young's modulus (E) and the initial stress too), which reflect the st iffness and the natural tension of the skin, respectively. We also calculat ed an index of non-elasticity of the skin (unrestored energy ratio, UER), w hich takes into account the volume of tissue mobilized. It determines a rat io between the energy input to the skin and the energy it dissipates. These parameters were evaluated from the volar forearm of 10 normal male volunte ers. Results: The results were: 129+/-88 kPa for E, 13.5+/-5 kPa for a,, and 0.4 2+/-0.04 for UER; with reproducibilities of 9.5%, 12.4% and 6.4%, respectiv ely. Conclusions: This new suction device was found useful for the study of the behaviour of the skin, and the device may be used for the evaluation of cer tain skin diseases and their therapy.