Pathogens infect bone in posttraumatic osteomyelitis after a recent
fracture. Bacteria, fungus and other microorganisms are typically the
causative agents. The more susceptible a bone is to fracturing, the
greater the chances of becoming infected and developing disease. Trauma
from recent injuries and diabetes are major risk factors for osteomyelitis.The
bone can be directly infected from the wound or indirectly via the blood
from another site of infection, called hematogenous osteomyelitis.
The vertebrae and pelvis are often affected in adults in this blood-borne
variety, while children are usually affected in long bones.
The classification of osteomyelitis can be broken down into the following categories: exogenous ostemyelitis (47%), secondary to vascular insufficiency (34%) and hematogenous osteomyeltis (19%). The implantation of an orthopedic device (pins, plate, screws, artificial joint) can also seed infection as a nidus for pathogens, and therefore create post-operative osteomyelitis.
The presence of bacteria alone in an open fracture
is not sufficient to cause osteomyelitis. In most cases, the body's
immune system is capable of preventing the colonization of pathogens.
The micro-environment determines whether infection occurs. The timing
and extent of treatment are critical in determining whether infection
develops. The likelihood of developing ostemyelitis increases with impaired
immune function, extensive tissue damage, or reduced blood supply to
the affected area. Patients with diabetes, poor circulation or low white
blood cell count are at greater risk.
CLINICAL DIAGNOSIS AND MANIFESTATIONS
The diagnosis of osteomyelitis
is made from clinical, laboratory and imaging studies.
When the skeletal system is involved, pain, fever and leukocytosis (an
increase in white blood cell count due to infection or inflammation)
occur. The affected area is painful. Initial x-rays are typically normal.
As early as 4 days, an area of lucency may be seen on x-ray.
Osteomyelitis is an infection involving the
bone. The bones usually affected are the weight-bearing bones, particularly
before the physis has closed. Exogenous osteomyelitis occurs from open
trauma, sometimes relatively minor in nature. Hematogenous osteomyelitis
occurs from bacteria circulating in the bloodstream. Acute and chronic
subtypes are classified according to the timing and duration of the
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5. Widmer AF. New developments in diagnosis and treatment of infection in orthopedic implants. Clin Infect Dis. 2001; 33: S94-S106.
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