Explosive wounds in connection with fractures.—The aperture of entry in these injuries presented little or no deviation from the normal, unless it was due to the passage of ricochet bullets, when it might be very irregular, but usually not of great size.
Fig. 47
(21) 'Explosive' Exit Wound of Forearm over margin of ulna. Note creased tongue of skin originally covering whole wound. The entry wound was a small typical circular one
The aperture of exit offered special features beyond simple increase in size. First of all, as in the small type wounds, the actual extent of destruction of the skin was small, this having been projected outwards by the passing bullet and then either burst or torn by the bullet and accompanying bony fragments. Fig. 47 well illustrates this feature. A triangular tongue of skin was lifted by the passing bullet and probably by the lower end of the upper fragment of the fractured ulna; through the resulting opening a mass of soft tissues and bone fragments, bound together by an infiltration of coagulated blood, was extruded, separating the lateral lips of the aperture, while the original tongue has shortened and retracted up to the top of the wound.
The small extent of skin actually destroyed is an important element in the rapid contraction often seen in these wounds when they progress favourably. Thus the large wound portrayed in fig. 48 contracted to one-fourth its original size ten days after the diagram and measurements were made. The large mass of protruded tissue was often most striking when a muscle such as the biceps in fig. 48 had been divided; but the herniæ were more persistent when the mass projected in regions where tendons formed a large integral constituent, as at the wrist or lower third of the forearm. The protruding tissues naturally consisted of many varieties, according to what lay in the track of any particular wound.
It should be added that for 'explosive' features to reach their strongest development, it is necessary that the bone affected should lie near the surface of the body; hence the most characteristic explosive wounds were met with in the forearm or leg, over the metacarpus or metatarsus, or in the arm. In the thigh, on the other hand, where the femur in a great part of its course not only lies deeply, but is also protected by particularly strong and resistent skin and fascia, another type of wound was met with. The explosive exit aperture, although large, was still only moderate in extent, sometimes, as in the front of the lower third, exposing a somewhat angular large track walled by the divided quadriceps extensor cruris. In other cases, on introducing the finger through a moderate exit opening on the inner aspect of the thigh, a large cavity, sometimes 4 or 5 inches in diameter, was discovered, full of clot and shreds of destroyed tissue and lined by a layer of similar material. In either of these latter cases the fractured bone ends were situated too deeply to take part in the actual laceration of the skin, while the force transmitted to the bone fragments, although sufficient to cause them to widely destroy the first soft tissues met with, did not suffice to cause them to burst or lacerate the skin widely.
Fig. 48.