Histopathological analysis for the effects of shear force caused by position change on pressure ulcer healing

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Shear force injury occurs when the skin remains stationary and the underlying tissue shifts. This shift diminishes blood supply to the skin and soon results in ischemia and tissue damage. However, no satisfactory animal models of a shear force induced ischemic wound have been constructed, and the effects of shear force on the healing process of such wounds have yet to be clarified. The present study therefore aimed to prepare a shear force induced ischemic wound model and histologically clarify the effects of shear force on wound healing.Two incisions were made down to the peritoneal cavity in the flank region of 16 rats, and a metal plate was passed through one incision under the peritoneum and then exited from the other. From the exterior surface, 8 kg of pressure was applied for 6 hours to the flank skin and abdominal muscle to prepare an ischemic wound. The wound was observed for two weeks, and histological tissue sections were prepared on days 7 and 14. Wound healing was compared between two groups : a shear force group (1.0 kg shear force loading) and a control group (only pressure was applied to prepare an'ischemic wound).It took one week longer for a shear force induced ischemic wound to heal than a pressure induced ischemic wound. Histopathlogical findings of the shear force induced ischemic wound were the caudal muscle layer's degeneration and the cranial dermis layer's congestion and hemorrhage. Control group's histopathlogical findings were muscle layer's degeneration on Day 7, and tissue regeneration on Day 14.