Definitions of the physical properties of pressure ulcers and characterisation of their regional variance.

A pressure ulcer is a localised injury of the skin and underlying tissue that usually develops over a bony prominence. A decrease in the pressure over the bony prominence effectively prevents pressure ulcers; however, no studies have systematically assessed the physical properties of existing pressure ulcers. To characterise pressure ulcers, we established new terminology that clarifies the physical properties of pressure ulcers: wound mobility was defined as movement using the bony prominence as a predefined specific marker, and wound deformity was defined as a change in the three-dimensional shape of the wound. Observational studies using this terminology showed that the distinct physical properties of pressure ulcers depend on the site of development and the wound depth according to the National Pressure Ulcer Advisory Panel criteria. Most grade IV sacrum pressure ulcers exhibited mobility and deformity. Superficial sacrum pressure ulcers below grade II showed only mobility. In contrast, foot pressure ulcers did not exhibit mobility or deformity. We propose a new concept, 'wound physical property', for understanding the unique pathogenesis of pressure ulcers.