Development of a simple, noninvasive, clinically relevant model of pressure ulcers in the mouse

The formation of pressure ulcers and other skin wounds is considered to be a multifactorial process. Cycles of ischemia-reperfusion have been considered to be significant contributing factors in the pathogenesis of pressure ulcers. This study reports the development of a reproducible murine model of ischemia-reperfusion injury by the external application of magnets. Mice were sedated with 50% CO2:50% O2 for 50-60 s. Dorsal hair was shaved and the area cleaned. The skin was gently pulled and placed between two round ceramic magnetic plates (5 x 12 mm diameter, 2.4 g weight, 1000 G magnetic force). The resultant "pinch" procedure was designed to leave a 5-mm skin bridge between the magnets, creating 50 mm Hg pressure between the plates. Three 12-h ischemia-reperfusion cycles were employed to cause pressure ulcer formation. Animals tolerated the procedure well. They returned to normal activity a few minutes after magnet placement. The lesions reached their maximum at 10 days postinjury. Full-thickness skin loss with damage and necrosis of subcutaneous tissue (ulcer stage 3) was observed in all cases, reaching a mean stage score of 3.6 +/- 0.6 of based on a 0-5 scale for extent of injury by visual assessment. Thus, an inexpensive, reproducible murine pressure ulcer model was developed, which results in graded injury without long-term immobilization of the animals. This method will facilitate the development of new prevention and management strategies.