Osteomyelitis
Osteomyelitis is an
infection of
bone, usually caused by
pyogenic bacteria or
mycobacteria. It can be usefully subclassifed on the basis of the causative organism, the route, duration and anatomic location of the infection.
Generally microorganisms may be disseminated to bone hematogenously (
i.e., via the blood stream), spread contiguously to bone from local areas of infection, such as
cellulitis, or be introduced by penetrating
trauma including
iatrogenic causes such as joint replacements or internal fixation of fractures.
Leukocytes then enter the infected area, and in their attempt to
engulf the infectious organisms, release enzymes that lyse bone.
Pus spreads into the bone's blood vessels, impairing the flow, and areas of devitalized infected bone, known as
sequestra, form the basis of a chronic infection. On
histologic examination, these areas of necrotic bone are the basis for distinguishing between
acute osteomyelitis and
chronic osteomyelitis. Osteomyelitis is an infective process which encompasses all of the bone (osseous) components, including the bone marrow. When it is chronic it can lead to bone sclerosis and deformity.
Because of the particulars of their blood supply, the
tibia, the
femur, the
humerus, and the
vertebral bodies are especially prone to osteomyelitis.
Acute osteomyelitis almost invariably occurs in children. when adults are affected it may be because of compromised host resistance due to debilitation, intravenous drug abuse, disease or drugs (e.g.
immunosuppressive therapy).
Osteomyelitis often requires prolonged
antibiotic therapy, lasting a matter of weeks or months, and may require surgical
debridement. Severe cases may lead to the loss of a limb. Initial first line antibiotics is determined by the patient's history and regional differences of common infective organisms. For example, in a 1 year old child, it would be appropriate to start a combination of Flucloxacillin and Fusidic Acid.
The vast predominance of hematogenously seeded osteomyelitis is caused by
Staphylococcus aureus.
Escherichia coli, and
streptococci are other common
pathogens. In some subpopulations, including intravenous drug users and
splenectomized patients,
Gram negative bacteria, including enteric bacilli, are significant pathogens.
Staphylococcus aureus is also the most common organism seen in osteomyelitis seeded from areas of contiguous infection, but here Gram negative organisms and
anaerobes are somewhat more common, and mixed infections may be seen.
In osteomyelitis involving the vertebral bodies, about half the cases are due to
Staphylococcus aureus, and the other half are due to
tuberculosis (spread hematogenously from the
lungs). Tubercular osteomyelitis of the spine was so common before the initiation of effective antitubercular therapy that it acquired a special name,
Pott's disease, by which it is sometimes still known.
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Wrong Diagnosis Osteomyelitis - ''Statistics on Osteomyelitis in England
