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

当皮肤保持静止而底层组织发生移位时，发生剪切力损伤。这种转变减少了皮肤的血液供应，很快导致缺血和组织损伤。然而，目前尚未建立令人满意的剪切力缺血性创面动物模型，剪切力对缺血性创面愈合过程的影响尚不清楚。因此，本研究旨在制备剪切力诱导的缺血性创面模型，并从组织学上阐明剪切力对创面愈合的影响。在16只大鼠的腹膜侧区做两个切口至腹膜腔，金属板从腹膜下的一个切口穿过，从另一个切口取出。从外表面施加8 kg压力于侧翼皮肤和腹肌6小时，准备缺血创面。观察创面2周，第7、14天分别制作组织切片。比较两组创面愈合情况：剪切力组（加载1.0 kg剪切力）和对照组（仅施加压力制备缺血创面）。剪切力诱导的缺血性创面愈合时间比压力诱导的缺血性创面愈合时间长一周。剪切力致缺血性损伤的组织病理学表现为尾肌层变性和颅真皮层充血出血。对照组第7天组织病理表现为肌肉层变性，第14天组织再生。

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.