<p>A pressure ulcer (PU) is defined as ‘localized injury to the skin and/or underlying tissue usually over a bony prominence, as a result of pressure, or pressure in combination with shear. A number of contributing or confounding factors are also associated with pressure ulcers; the significance of these factors is yet to be elucidated’ [1]. Pressure is the amount of force acting on a unit of area[2], whereas shear forces occur in soft tissue when these tissues are stretched, as happens when the bony structures move, but the skin does not move correspondingly[3].</p>
