Skin elasticity measured by dynamic admittance. A new technique for mechanical measurements in patients with scleroderma.

A new method is presented for determining overall mechanical properties of the skin. The technique is called dynamic admittance measurement. By computerized calculations of mechanical resonance measurements, information is obtained on the elastic modulus representing the type and amount of collagen in the skin, the quality factor describing the mechanical quality (effectiveness) of the collagen, and the mechanical resistance of the viscous, non-elastic component of the skin. The method is suitable for measuring mechanical properties of small skin areas, e.g. distally on the fingers in acrosclerotic lesions of scleroderma. Highly reproducible, standardized results are obtained. In generalized scleroderma, the elastic modulus of the cutaneous network of collagen and elastin is increased, not only in clinically affected skin, but also in clinically unaffected areas, whereas the mechanical quality factor and the viscous resistance (mechanical impedance) was unaltered in scleroderma compared with normal controls. The dynamic admittance method for determining the mechanical properties of the skin in vivo may be of importance for accurate monitoring of disease status and for assessing the effect of therapy in diseases, where alterations in the mechanical properties of the skin are of significance.