Crush injuries occur when a part of the body is subjected to a high degree of energy or pressure. It happens usually after being hit by a heavy object or being squeezed between two objects. The greater the energy involved the more severe the tissue damage.
Definition of Crush Injury:
• Two or more tissues (muscle, bone, skin, nerve) involved
• Injury severe enough that tissue survival is questionable
• If tissue recovers, functional deficits are likely
• Gradient of injury from minimal to irreversible with a partial viable grey zone between the two
Crush injury involves severe trauma to two or more tissues as bone, soft tissue, nerve, and vascular structures. Damage includes: laceration (open wound), fracture, bleeding, bruising, compartment syndrome, and others.
There is a gradient of injury from minimal to irreversible with a grey zone of partial viable tissue between the two. When crush injuries are severe, the rate of complications including infection, non-healing of fractures and tissue range up to 50 to 60 percent with a high amputation-rate. The main target of the therapy is to take measures to help the partial viable tissue to recover and to prevent further generalized tissue damage.
The immediate threat to the tissue after crush injury is whether perfusion is sufficient to maintain oxygenation and viability of tissues. Blood flow is most important to tissue viability. A decreased blood flow and thrombosis of micro vessels compromise tissue perfusion and cause tissue hypoxia. Cellular hypoxia disturbs the cellular metabolism. Hypoxic cells are unable to resist bacteria and loose their water content because of insufficient energy production needed for active transport mechanisms in the cell membrane. Leakage of intracellular fluid to the extracellular space and extravasation of plasma from ruptured blood and lymph vessels promote oedema formation. Posttraumatic oedema contributes to reduced microcirculation and ischemia of the partially viable tissue. Oxygen availability to tissues is further reduced.
Massive posttraumatic oedema has detrimental effects on wound healing and infection control in the traumatised tissue. The diffusion distance from the capillary to the cell is increased, reducing furthermore the oxygen availability to cells that already have increased oxygen needs. Oxygen diffusion decreases by an approximately three-fold factor as the diffusion distance is increased. Furthermore oedema leads to collapse of capillaries because of increasing interstitial pressure around the capillaries from the oedema fluid (see compartment syndrome).
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