Pressure ulcer tissue histology: an appraisal of current knowledge.

Although it is well accepted that pressure ulcers occur as a result of mechanical loading of tissue, their specific etiology of development remains unknown. Knowledge of tissue response to pressure is critical to understanding and elucidating the specific mechanism of pressure ulcer development. A literature review to appraise the histology of pressure ulcer tissue shows that numerous in vitro and in vivo studies examining tissue changes in response to pressure have been conducted. In vitro findings indicate that relatively small loads cause structural changes to the dermal component of tissue. Studies examining tissue from humans with pressure ulcers have shown that changes visible at the surface are often minor compared to the damage seen in deeper tissue layers. In vivo animal studies evaluating the changes in tissue histology following application of various loads support findings related to human pressure ulcer tissue and further elucidate the tissue changes seen in response to load. Studies to evaluate whether the visible changes in human and animal tissue are precursors to ulcer development or remodeling responses to loading are needed to increase understanding of pressure ulcer formation.