Acute osteomyelitis

Pathogenesis

Acute osteomyelitis now commonly occurs in three different groups.

1.       It can occur in the premature baby, possibly as a result of blood-borne spread of infection from intravenous cannulae or other portals.

2.       Secondary to open fractures where there has been inadequate cleaning of a wound or it has been closed before it is clean.

3.       Following joint replacement or open reduction in internal fixation of fractures where contamination of the hone has occurred.

Osteomyelitis of the neonate

An infant with acute osteomyelitis will be fretful and pyrexial and will not feed. The only clue to the underlying diagnosis may be the child failing to move one limb. Premature babies on intensive care are particularly susceptible, especially as they will have drips and arterial lines, all of which can act as a source for septicaemia. The infection may be remote from the source as the infection spreads through the bloodstream. Unlike osteomyelitis in older patients, the pathogen need not be Staphylococcus aureus. It may be Streptococcus, Pneumo­coccus, Haemophilus influenzae or even Escherichia coli. The key to successful treatment is a high index of suspicion lead­ing to early diagnosis by blood culture. High-dose intra­venous antibiotics should be started as soon as possible but not before blood cultures have been taken. If the diagnosis and treatment are delayed, pus may collect either under the periosteum or within the medulla of the bone. The epiphyseal plate may be damaged and it will not be possible to bring the infection under control until the abscess has been drained.

Osteomyelitis in the neonate

Premature are babies susceptible

The baby may not move the limb

Organism may not be Staphylococcus

Antibiotics should be started as soon as cultures have been taken

 

Antibiotics must be starred blind after blood cultures have been taken because if the disease can be sterilised within the first 48 hours of onset, complete resolution can be guaran­teed. If, however, the diagnosis is reached more than 48 hours after the onset of symptoms, it should be assumed that there is a collection of pus and therefore surgery to drain this pus should be considered. Flucloxacillin should be given at a daily dose of 250 mg/kg in the very young child. Ampicillin 150 mg/kg should also be considered because it has a better spectrum against H. influenzae. If the child fails to settle rapidly, it must be assumed either that the organism is not sensitive to the antibiotic being used or that there is a collection of pus present which requires drainage.

Operation

Drainage of pus

Under general anaesthetic, the skin is opened over the most tender red area. The incision is carried down to the periosteum and when this is opened it is usual to find pus expressed at high pressure. This pus should be sent for culture. If no pus is found it is probably worth drilling through the cortex to make sure that there is no pus in the medullary cavity (Fig. 24.1).