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Bone can be infected by haematogenous spread, by direct
extension from an infected joint, or following trauma, surgery or
The formation of pus precipitates ischaemia and necrosis; the
central area of dead bone is known as the sequestrum.
New bone (the involucrum) may form around the infection site.
In children, the metaphysis of the long bones (femur, tibia and
humerus) are most often involved. Infection of the spine is common
Staphylococcus aureus accounts for 90% of infections; rarer
causes includeStreptococcus pyogenes (4%), Haemophilus influenzae
(4%), Escherichia coli, Salmonella spp., Mycobacterium tuberculosis
Patients with sickle cell disease are especially prone to Salmonella
- Presentation is with fever and pain. In the young, pain may be
poorly localized but they may stop moving the affected limb
- Later, soft-tissue swelling may occur and can be followed by
- Pathological fractures may develop.
- Delayed treatment increases the risk of development of chronic
- Infection may develop around foreign bodies (e.g. surgical nails
or debris from trauma).
- Diagnosis is clinical.
- Radiological changes develop late in the course of infection and
many not be seen.
- Isotope scans indicate sites of inflammation.
- Fluorodeoxyglucose positron emission tomography (FDGPET)
is more sensitive.
- Blood cultures and pus from bone obtained via needle or open
biopsy allow culture for pathogen identification and susceptibility
- Drainage and excision of the sequestrum is supplemented by
antibiotic therapy (e.g. flucloxacillin and fusidic acid pending
- If Salmonella is isolated or suspected, ciprofloxacin may be used.
- Treatment lasts for 6 weeks or until there is evidence that inflammation
has disappeared and the bone has healed.
- Follows inadequately treated acute infection, or may be secondary
to surgery or a fracture. Infection of prosthetic materials with
organisms with reduced virulence, such as coagulase-negative staphylococci
(CoNS) is increasingly common.
- S. aureus is implicated in 50% of cases; the remainder are associated
with Gram-negative pathogens (e.g. Pseudomonas, Proteus and E. coli).
- On-going pain, swelling, deformity and/or a chronically discharging
sinus may be found.
- Culture-based diagnosis is essential.
- A prolonged course of appropriate antibiotics should accompany
- Infected prosthetic devices are usually removed.
- Follows bacteraemia or injection of the joint.
- 95% of cases are caused by S. aureus and S. pyogenes. Other
causes include Enterobacteriaceae, Neisseria gonorrhoeae, H. influenzae,
Salmonella spp., Brucella spp., Borrelia burgdorferi, Pasteurella
and M. tuberculosis.
- Large joints (e.g. the knee) are most commonly affected.
- Prosthetic joints are at risk of early and late infections (see
- Pain, swelling and reduced movement.
- In adults, the onset may be insidious; a history of recent urinary
infection or salmonellosis may be reported.
- Cellulitis or specific signs, such as gonococcal rash may be
- Septic arthritis must be differentiated from acute rheumatoid
arthritis, osteoarthritis, gout, pseudogout or reactive arthritis.
- A diagnostic tap will yield cloudy fluid, and Gram stain and
white blood cell count may suggest infection that can be confirmed
by culture or nucleic acid amplification test (NAAT).
- Culture for brucellosis should be performed if the history is
Intravenous antibiotics that are appropriate to the infecting
organisms, either isolated or suspected, should be commenced,
and oral therapy is continued for up to 6 weeks. Aspiration and
irrigation of the joint may be helpful in severe cases as it reduces
Some viruses are associated with arthritis, for example parvovirus,
rubella, mumps and hepatitis B. Rubella-related arthritis is more
common in females and develops a few days after the rash. Several
of the alphaviruses cause severe bone and joint symptoms. Reactive
arthritis caused by an immune response to the pathogen can
follow recovery, for example after meningococcal disease, or Shigella
infection. The latter can be associated with
uveitis and is known as Reiter's syndrome.
Prosthetic joint infections
Prosthetic joints may become infected at the time of operation
(early presentation) or as a result of haematogenous spread (later
presentation). In early presentation the organisms are from the
skin (e.g. S. epidermidis
and S. aureus
Treatment is with intravenous antibiotics, depending on the
susceptibility of the infecting organisms. Infection usually results
in loss of the prosthesis. Prevention of infection by control measures
in both the ward and theatre and antibiotic prophylaxis with
an agent active against S. aureus
) is vital.