Osteomyelitis
Osteomyelitis is an infection of bone and bone marrow, usually caused by bacteria.
Causes and Risk Factors
Mechanisms of Infection
Osteomyelitis usually results from 3 main mechanisms:
| Mechanism | Associated risk factors |
|---|---|
| Haematogenous spread from systemic infection – common in children |
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| Direct inoculation (direct introduction of organisms into the joint) – common in adults |
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| Contiguous spread from adjacent infection – common in adults |
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Shared systemic risk factors:
- Immunosuppression (e.g. diabetes)
- IVDU
- Vascular insufficiency
Causative Organisms
- Staphylococcus aureus – most common organism overall
- Salmonella species – increased risk in those with sickle cell disease and other haemoglobinopathies
- Kingella kingae – in younger pre-school-aged children (esp. when epiphyseal osteomyelitis is suspected)
- Haemophilus influenzae type b – increased risk in those with incomplete childhood immunisation
Clinical Features
| Acute osteomyelitis | Acute osteomyelitis is the hallmark of paediatric osteomyelitis, also common in older adults and immunocompromised patients who develop bacteraemia
Develops rapidly over days to weeks following the initial infection
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| Chronic osteomyelitis | Chronic osteomyelitis is common in adults with systemic comorbidities (e.g. diabetic, vascular insufficiency)
Develops gradually over months to years of persistent infection:
The probe-to-bone test is a clinical test for diabetic foot osteomyelitis
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Vertebral osteomyelitis has a slightly different presentation:
- Gradual onset of back pain – worsened by activity
- Fever is not always present
- Most commonly affects the lumbar spine
- May cause / co-exist with epidural abscess (triad of back pain + fever + neurological deficits)
Clinical presentation also varies depending on the mechanism of infection: [Ref]
| Haematogenous spread | Haematogenous spread osteomyelitis is more common in children:
Haematogenous osteomyelitis more commonly presents acutely |
| Non-haematogenous spread (direct inoculation / contiguous spread) | Non-haematogenous spread osteomyelitis is more common in adults, and there are often adjacent sources of infection, such as:
Non-haematogenous osteomyelitis more commonly presents chronically |
Investigation and Diagnosis
| Blood tests |
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| Imaging |
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| Biopsy | A definitive diagnosis can be established through bone biopsy and bacterial culture
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Management
Approach:
- Initial management: empirical antibiotics (after blood cultures)
- Definitive management: orthopaedic assessment to determine the need for surgical debridement
Antibiotic Therapy
1st line:
- Flucloxacillin for 6 weeks
- Consider adding fusidic acid or rifampicin for the initial 2 weeks
Alternative:
- If penicillin allergic: clindamycin
- If MRSA suspected: vancomycin or teicoplanin +/- fusidic acid or rifampicin
Surgical Debridement
| Indications for urgent surgical debridement |
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| Indications for planned surgical debridement |
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