Wounds produced by dynamite explosions and the bursting of boilers have the same general characters as shell wounds.  Fragments of stone, coal, or metal may lodge in the tissues, and favour the occurrence of infective complications.

All such injuries are to be treated on the general principles governing contused and lacerated wounds.

EMBEDDED FOREIGN BODIES

In the course of many operations foreign substances are introduced into the tissues and intentionally left there, for example, suture and ligature materials, steel or aluminium plates, silver wire or ivory pegs used to secure the fixation of bones, or solid paraffin employed to correct deformities.  Other substances, such as gauze, drainage tubes, or metal instruments, may be unintentionally left in a wound.

Foreign bodies may also lodge in accidentally inflicted wounds, for example, bullets, needles, splinters of wood, or fragments of clothing.  The needles of hypodermic syringes sometimes break and a portion remains embedded in the tissues.  As a result of explosions, particles of carbon, in the form of coal-dust or gunpowder, or portions of shale, may lodge in a wound.

The embedded foreign body at first acts as an irritant, and induces a reaction in the tissues in which it lodges, in the form of hyperaemia, local leucocytosis, proliferation of fibroblasts, and the formation of granulation tissue.  The subsequent changes depend upon whether or not the wound is infected with pyogenic bacteria.  If it is so infected, suppuration ensues, a sinus forms, and persists until the foreign body is either cast out or removed.

If the wound is aseptic, the fate of the foreign body varies with its character.  A substance that is absorbable, such as catgut or fine silk, is surrounded and permeated by the phagocytes, which soften and disintegrate it, the debris being gradually absorbed in much the same manner as a fibrinous exudate.  Minute bodies that are not capable of being absorbed, such as particles of carbon, or of pigment used in tattooing, are taken up by the phagocytes, and in course of time removed.  Larger bodies, such as needles or bullets, which are not capable of being destroyed by the phagocytes, become encapsulated.  In the granulation tissue by which they are surrounded large multinuclear giant-cells appear ("foreign-body giant-cells”) and attach themselves to the foreign body, the fibroblasts proliferate and a capsule of scar tissue is eventually formed around the body.  The tissues of the capsule may show evidence of iron pigmentation.  Sometimes fluid accumulates around a foreign body within its capsule, constituting a cyst.

Substances like paraffin, strands of silk used to bridge a gap in a tendon, or portions of calcined bone, instead of being encapsulated, are gradually permeated and eventually replaced by new connective tissue.