Abstract: Objective To observe the effect of early NPWT application on infection control and granulation formation in explosive soft tissue defects by comparing the bacteria colony-forming unit and pathological changing.Methods Explosive soft tissue defects were created in pig model.Twelve defects were created on 3 pigs and divided into 2 groups randomly.NPWT group was on one side and Gauze group on opposed side.Each group had 6 wounds.Exposure group was composed of another 2 pigs with 6 wounds.At 6 hours,Day 3,Day 5 and Day 7,specimens were harvested in the center of the wound for counting of bacteria and HE staining.Microscopy was used for observation Granulation formation was observed by microscope.Results The numbers of bacteria colony on NPWT group were smaller than that of Gauze group and Exposure group at Day 3,5 and 7.The counting of NPWT group peaked at Day 3 and declined below the critical value of infection at Day 5.After the NPWT application,the wound area shrank and became superficial.Compared with Gauze group,more granulation formation,and obvious staining with fibroblast and endothelium cell,as well as edema fading of the cells were observed in NPWT group.Conclusion Compared with the Gauze group,early application of NPWT can effectively control the bacteria multiplication and promote granulation formation on soft tissue explosive defects.

Key words: Explosive injury, Negative pressure wound therapy, Infection, Granulation