Elasticity of human skin in vivo. A study of the physical properties of the skin in rheumatoid arthritis and the effect of corticosteroids.

M E T H O D The method is essentially a clinical adaptation of a well-authenticated method for measuring skin elasticity in vitro—namely, the method of Dick (1951). In this system a circle or diaphragm of skin, clamped at its periphery, is subjected to uniform pressure from below, and the resultant distortion is recorded (Fig. 1). Using the standard formulae that express pressure changes across spherical membranes, Tregear (1966) evolved the following formulae to express stressf and strain§ in mathematical terms.