Morphopathologic observations on high-velocity steel bullet wounds at various intervals after wounding

Soft-tissue wounds of both hind legs in 15 dogs were inflicted by spherical steel bullets. Histologic and ultrastructural changes were observed in the contusion zone and the concussion zone at 6, 12, and 24 hr after wounding. Histologically, it was shown that at 6 hr after wounding, there were degeneration and necrosis of myofibers and interstitial hemorrhage and edema in the contusion zone, while some fibers still appeared to have normal structure in the outer layers. In the inner layers of the concussion zone close to the entrance, there was focal necrosis of myofibers. Histologic changes at 12 and 24 hr after wounding were similar to those at 6 hr but there were more inflammatory reactions. A considerable number of ultrastructural changes were seen in the contusion zone at 6 hr after wounding, such as loss of sarcomeres, vacuolization and pyknosis of mitochondria, swelling of sarcoplasmic reticulum, irregular arrangement of Z-lines, breaking of some capillary endothelial cells, etc. However, in the concussion zone, the changes were much less than those above mentioned, although karyons and karyomeres of some monocytes appeared to be gathering to the side of cytoblast. On the whole, the ultrastructural changes were not so severe at 12 and 24 hr as those at 6 hr after wounding. Also, the characteristic features of the wound caused by high-velocity steel bullets were not similar to those caused by 5.56-mm high-velocity missiles. The severity of damage at the entrance of wound track caused by steel bullet was more marked than that at the exit.