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Infection of bone, most often due to haematogenous spread or direct inoculation, leading to inflammation and necrosis.
Infection of bone, most often due to haematogenous spread or direct inoculation, leading to inflammation and necrosis.
Risk Factors
Recent infection (e.g. skin, respiratory, UTI)
Open fractures or orthopaedic surgery
Prosthetic joints or implants
Diabetes mellitus (especially in foot ulcers)
Peripheral vascular disease
Immunosuppression
IVDU
Children – metaphyseal bone involvement due to rich blood supply
Aetiology
Staphylococcus aureus (most common overall)
Methicillin-resistant S. aureus (MRSA)
Streptococcus species
Gram-negative bacilli – in immunocompromised or neonates
Salmonella – associated with sickle cell disease
Pseudomonas – in puncture wounds through sneakers or IVDU
Mycobacterium tuberculosis – in spinal TB (Pott’s disease)
Pathophysiology
Infection spreads to bone via haematogenous route, direct inoculation, or contiguous spread
Inflammation and exudate increase pressure within bone → vascular compromise and bone necrosis
Sequestrum (necrotic bone) forms, surrounded by new bone (involucrum)
Chronic osteomyelitis occurs if infection persists
Diagnosis
Localised bone pain, swelling, erythema
Reduced movement or refusal to weight bear (children)
Fever and systemic signs variable – more common in acute
In vertebral osteomyelitis – back pain ± neurological signs
Chronic – sinus tract formation, chronic discharge
Differential Diagnosis
Bone malignancy (e.g. Ewing’s sarcoma)
Bone infarct
Fracture
Septic arthritis
Cellulitis
TB or fungal bone infection
Investigations
FBC – elevated WCC
CRP, ESR – elevated
Blood cultures (positive in ~50%)
X-ray – may be normal early; later shows periosteal reaction, bone lysis
MRI – most sensitive and specific for early detection
CT – useful for surgical planning
Bone scan – if MRI contraindicated
Bone biopsy – for definitive diagnosis and culture
Management
Empiric IV antibiotics – flucloxacillin, cefazolin; vancomycin if MRSA suspected
Adjust based on culture results
Duration: usually 4–6 weeks (IV then oral)
Surgical debridement – remove necrotic bone/sequestrum
Drain abscess or sinus tracts if present
Immobilisation and pain relief
Optimise underlying conditions (e.g. diabetes control)
Complications & Prognosis
Chronic osteomyelitis
Pathological fractures
Growth arrest in children
Sepsis
Amputation in severe cases
Better prognosis with early treatment and no comorbidities
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