Effects of skin wrinkles, age and wetness on mechanical loads in the stratum corneum as related to skin lesions.

Finite element models of skin were developed to determine the effects of wetness, age, and wrinkles on mechanical strains and stresses in the stratum corneum (SC) as related to skin lesions. We modeled two geometries, young (0.12-mm-deep wrinkles) and aged (0.18-mm-deep wrinkles), and for each geometry, three loading conditions were applied (compression in a dry environment, compression and shear in dryness, and compression with shear in wetness). Effects of skin wrinkling were studied independently or while coupled with age-related mechanical property changes. For each simulation, we calculated the peak maximal shear strain and stress in the SC, peak shear stress on the skin surface, and volumetric exposure of the SC to potentially injurious shear stresses (<70 kPa). Compression and shear with wetness produced the highest skin surface loads. Volumetric exposure of aged skin to potentially injurious shear stresses was six times greater than in the young skin for these conditions. Deeper wrinkles caused elevated loads in the SC consistently for all outcome measures and independently of the age factor. Thinning and/or stiffening the SC increased both the surface and internal SC stresses. Our findings indicate that theoretically, wetness, skin aging, and/or skin wrinkling are all risk factors for skin lesions such as superficial pressure ulcers.