Shock — caused by severe crushing, soft tissue injuries, and/or compound fracture.
Hemorrhage — occurs from traumatic amputation, compound fracture with severing of a large vessel, multiple lacerations, or severe avulsive wounds
of the skin and subcutaneous and underlying tissues, with tearing of numerous small vessels.
Venous thrombosis with fatal pulmonary embolism — Veins may be injured directly by fracture of the lower extremity, with resultant thrombosis. Thrombosis may also be secondary to venous stasis following prolonged immobilization of the lower extremity when the patient is confined to bed with a fractured extremity. There may be crushing injuries rather than fractures of the lower extremity with either direct injury to the veins or stasis bv compressing hemorrhage and edema resulting from the leg injury.
Fat embolism — Fat embolism follows mechanical trauma that mobilizes the fat from an injured fat deposit in the body. This happens rapidly, usually within a few seconds after injury. A few heartbeats are sufficient to bring fat to the lungs and even to the systemic circulation. For this reason, fat may be found even when death seems to be instantaneous —although, with sudden death, the amount of fat is usually small. The amount of fat in those surviving injury is proportional to the degree of injury and to the time of survival up to 24 h. Older persons are prone to have more massive fat embolization. Microscopic sections of the lungs show massive amounts of intravascular fat droplets, as well as free fat in the alveoli. Outside the lungs, fat emboli are more frequently seen in the kidney than in the brain. Microscopic sections of the brain show petechiae (small hemorrhages) throughout, with fat droplets within the capillaries.
Infection — Compound fractures are frequently contaminated with bacteria carried into the wound and lodged in the devitalized traumatized tissues. Depending on the virulence of the bacteria and immediateness and extent of surgical attention and cleansing of the wound, the infection may be limited to the skin or soft tissue or extend to the bone (osteomyelitis). A combination of aerobic and anaerobic organisms may cause gangrene of the lower extremity, a terminal hemolytic anemia, hemoglobinuric neph-rosis, uremia, and septicemia. Wounds contaminated with soil are occasionally infected with tetanus.
Crush syndrome: crushing injuries of the extremities — In this entity, there is traumatic or ischemic muscle necrosis in persons pinned by beams and falling debris. This causes myoglobin release with resultant acute tubular necrosis.
Effects of injury on preexisting natural disease — There may be delirium tremens in alcoholics, uremia in patients with chronic renal disease, cardiac decompensation in patients with heart disease, cerebral damage during shock, etc.
Injury to upper extremities occurs in association with motor vehicle accidents, falls, and assaults. In the case of homicide, the upper extremities should be closely scrutinized for defensive and offensive injuries. The fingernails, fingers, hands, and forearms should be carefully examined for abrasions, contusions, and lacerations. Broken or avulsed fingernails in a rape victim may indicate that the victim tried to protect herself. Fractured fingers and forearms are sustained by victims when they attempt to ward off a blunt instrument. Contusions, abrasions, and superficial lacerations over the knuckles may corroborate a perpetrator's contention of self-defense. Absence of injuries to the hand, however, does not exclude the possibility that blows were struck with the fists. Injuries to the back of the arms may indicate the victim was attempting to ward off blows.
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