Osteomyelitis in Children
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Direct answer
Osteomyelitis in children is bone infection, most often acute haematogenous, with a predilection for the metaphysis of long bones such as the distal femur and proximal tibia. Staphylococcus aureus is the commonest organism overall, while Kingella kingae matters in young children and Salmonella in children with sickle cell disease. Early MRI is the most sensitive investigation, and treatment combines prolonged antibiotics with surgical drainage where an abscess is present.
What you must remember
- Metaphyseal predilection: sluggish, looping metaphyseal vessels slow bacterial clearance and allow organisms to lodge, with the distal femur and proximal tibia the commonest sites.
- Organisms by setting: Staphylococcus aureus overall; Kingella kingae in toddlers; group B streptococcus and Escherichia coli in neonates; Salmonella in sickle cell disease.
- Early radiograph: often normal for the first week or so, with periosteal reaction and lysis appearing later.
- MRI: the most sensitive investigation in early osteomyelitis, showing marrow oedema, periosteal reaction and abscess, ideally with contrast.
- Blood tests: raised ESR, CRP and white cell count support the diagnosis, and blood cultures should be taken before antibiotics.
- Antibiotics: IV anti-staphylococcal therapy first, with vancomycin or clindamycin where MRSA is prevalent, and oral switch once the child improves.
- Duration and surgery: several weeks of treatment, commonly about four to six, adjusted to response, with surgical drainage for subperiosteal abscess or sequestrum.
A stepwise approach to a child who will not bear weight
A 6-year-old refuses to stand on one leg, has fever and has a tender, warm shaft of the femur. The sequence below avoids the trap of calling it a sprain.
- Think of bone when a limb is tender. Refusal to bear weight with fever should prompt bone and joint assessment rather than a diagnosis of strain.
- Check blood tests. ESR, CRP and white cell count are usually raised, and blood cultures are drawn before antibiotics.
- Image early with MRI. Plain films are often normal early, so contrast MRI is used to show marrow oedema and any abscess.
- Aspirate or biopsy when needed. Aspirate a collection, or the bone, when there is no response or the organism is unclear, guided by imaging.
- Start IV antibiotics. Cover Staphylococcus aureus, with MRSA cover where prevalent, and switch to oral therapy once improving.
- Plan duration and follow-up. Continue for several weeks, adjusted to response and inflammatory markers, with surgery for collections.
Where the exam tries to catch you
Three traps recur on this topic.
- Trap: dismissing a child with bone pain and fever as a sprain Correct: fever with a tender, warm metaphysis and refusal to bear weight means osteomyelitis until proven otherwise.
- Trap: relying on a normal X-ray to exclude osteomyelitis Correct: radiographs lag behind infection, and MRI is the sensitive test in early disease.
- Trap: assuming Staphylococcus aureus is the only organism at every age Correct: Kingella kingae in toddlers, Salmonella in sickle cell disease and group B streptococcus in neonates change the empirical plan.
Frequently asked questions
Why does osteomyelitis in children favour the metaphysis?
Osteomyelitis in children favours the metaphysis because the sluggish, looping vessels of the growing metaphysis slow bacterial clearance and let organisms lodge. The distal femur and proximal tibia are the commonest sites.
Which organism is linked to osteomyelitis in children with sickle cell disease?
Salmonella is the organism classically linked to osteomyelitis in children with sickle cell disease, so it should be covered in the empirical regimen for this group. Staphylococcus aureus remains the commonest organism in the general paediatric population.
Why is MRI preferred over X-ray in early osteomyelitis?
MRI is preferred over X-ray in early osteomyelitis because radiographs are often normal in the first week or so. MRI detects marrow oedema, periosteal reaction and abscess earlier and more sensitively.
How long should antibiotics be continued in osteomyelitis?
Antibiotics in osteomyelitis are usually continued for several weeks, commonly about four to six, with oral therapy often replacing IV once the child improves. Duration depends on clinical response, inflammatory markers and whether surgical drainage was needed, and books differ on exact periods.