Fine-structure studies of experimental skeletal muscle trauma.

A study was made of damage to skeletal muscle caused by a high-velocity rifle bullet. Such damage extends peripherally from the permanent wound cavity and is focal in nature. A fine-structure investigation of this region suggests that some components of the muscle are more susceptible to the wounding process than others. The sarcoplasmic reticulum appeared most sensitive and areas as far as 3 cm from the wound cavity frequently showed gross vacuolization. Mitochrondrial damage was seen, but only in areas where there was also damage to myofibrils and the microvasculature. Focal capillary leakage up to 3 cm from the wound cavity was demonstrated in an earlier study by the use of a fluorescein-labelled dextran (Paddle and Freeman, 1979). This finding was confirmed. A possible correlate at the fine structural level was swelling of te capillary endothelial cells, which occurred in the absence of other signs of microvascular damage. Damage to the endothelial junctions was not observed, even in severely damaged tissue. Intravascular colloidal carbon escaped into the extravascular space only when the microvasculature was fractured. The relationship of these findings to macroscopic damage is discussed.