Epidemiology

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• Hematogenous osteomyelitis
  • More common in children and adolescents
  • Incidence is increasing in adults, driven by a rise in vertebral osteomyelitis
• Exogenous osteomyelitis: more common in adults

Etiology

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Routes of infection

• Hematogenous osteomyelitis (endogenous osteomyelitis): caused by hematogenous dissemination of a pathogen
• Exogenous osteomyelitis: caused by a spread of bacteria (typically multiple pathogens) from the surrounding environment
  • Posttraumatic: infection following deep injury (penetrating injury, open fractures, severe soft tissue injury)
  • Contiguous: spread of infection from adjacent tissue
    • Secondary to infected foot ulcer in patients with diabetes
    • Iatrogenic (e.g., postoperative infection of a prosthetic joint implant)

Pathogen

Staphylococcus aureus (most common cause)

• Children and adults
• Individuals that recreationally use IV drugs
• Patients with vertebral lesions
• Patients with prosthetics
• Diabetic patients with foot ulcers and pressure ulcers

Staphylococcus epidermidis

• Patients with prosthetics

Streptococci

• Diabetic patients with foot ulcers and pressure ulcers
• Neonates and infants

Pseudomonas aeruginosa

• Persons who inject drugs
• Plantar puncture wounds (especially if wearing rubber-soled footwear)

Enterobacteriaceae

• Salmonella
  • Patients with sickle cell anemia
• Klebsiella
  • Patients with UTIs

Mycobacterium tuberculosis

• See “Tuberculous spondylitis” (Pott disease)

Pasteurella multocida

• Bites from dogs and cats

Fungi (e.g., Candida)

• Immunocompromised patients
• Individuals that recreationally use IV drugs

Pathophysiology

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Clinical features

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Diagnostics

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Imaging

• X-ray: low sensitivity and specificity for osteomyelitis
  • Indication: initial evaluation as can also exclude differential diagnoses of osteomyelitis
  • Characteristic findings
    • Acute osteomyelitis: typically no pathological findings
    • Subacute/chronic osteomyelitis: bone destruction, sequestrum formation, periosteal reactions
• MRI with and without IV gadolinium: most sensitive study
  • Indications
    • Suspected acute osteomyelitis (evidence of inflammation can be seen ≤ 5 days after onset of infection)
  • Characteristic findings
    • Acute/subacute osteomyelitis: cortical destruction, bone marrow inflammation, soft-tissue involvement
      • Focal hyperperfusion and increased radiotracer uptake within the affected region.
    • Chronic osteomyelitis: fibrotic scarring of the marrow

Treatment

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