Reproduction and analysis of an animal model for assessing the efficacy of debridement agent for firearm injuries

Objective To reproduce an animal model for assessing the efficacy of a debridement agent for firearm injuries.Methods Rabbits and goats(4 each) were assigned to group A and group B,and 8 pigs were randomly divided into group C and group D(4 each).Spherical projectiles(initial velocity 850m/s,weight 0.375g) fired by a 53-type musket were used to produce soft tissue injuries of hind limbs in group A,B and C,and cylindrical projectiles(initial velocity 950m/s,weight 0.87g) fired by a 53-type musket were used in group D.The local traumatic condition,pathological zones,bacterial counts and cytokine levels of tissues around the wound tracks were measured,and the constancy of the model was evaluated using coefficient of variation(CV).Results Penetrating wounds of soft tissues were made in hind limbs in all animal.The consistency degree of wound track entrance size,exit size and volume of wound track was higher in group B and D than in group A and D.Typical pathological zones of firearm wounds were observed under light microscope,and it was found that the local traumatic condition was more constant in group C than in other three groups.Determination of bacterial counts showed a heavy bacterial contamination of tissues in wound tracks,but significant difference was found among these groups.TNF-α and IL-6 levels in wound tissues increased gradually within 24 hours after the injury,and the changes in TNF-α and IL-6 levels in plasma showed a similar trend,but all the cytokine levels were low.Conclusions Simple soft tissue penetrating wounds in posterior limbs of pigs produced by spherical projectiles(velocity 850m/s,weight 0.375g) possess typical histopathological and bacterial characteristics of firearm injuries.This model is simple to reproduce,the traumatic condition is constant,and has a good reproducibility.