What is the treatment and diagnosis for osteomyelitis (bone infection)?

Diagnosis and Treatment of Osteomyelitis (Bone Infection)

Diagnosis

The gold standard for diagnosing osteomyelitis is isolation of bacteria from a reliably obtained bone sample with histological findings of inflammatory cells and osteonecrosis. 1

Diagnostic Approach

• Begin with plain radiographs when osteomyelitis is suspected, though sensitivity is low in early stages 1
• If initial radiographs are negative but suspicion remains, repeat radiographs after 2-4 weeks 1
• MRI is the most accurate imaging study for defining bone infection and should be used when radiographic findings are equivocal 1, 2
• Nuclear medicine scans (preferably newer generation leukocyte or immunoglobulin techniques) can be used as a second choice if MRI is unavailable 1
• Bone biopsy is recommended when:
  • Diagnosis remains in doubt after imaging 1
  • Osteomyelitis is likely but the causative organism or antibiotic susceptibilities are not predictable 1
  • Mid or hind-foot lesions are involved (due to higher risk of amputation) 1

Bone Biopsy Procedure

• Can be performed percutaneously (preferably under fluoroscopic or CT guidance) or operatively 1
• Obtain 2-3 specimens if possible, with at least one for culture and another for histological analysis 1
• Should be performed after antibiotics have been stopped for 1-2 weeks if safe to do so 1

Treatment

Antibiotic Therapy

Initial Empiric Regimens

• Empiric therapy should cover Staphylococcus aureus (including MRSA) and gram-negative bacilli 3
• Recommended combinations include:
  • Vancomycin plus cefepime 3
  • Vancomycin plus ciprofloxacin 3
  • Vancomycin plus a carbapenem 3

Pathogen-Specific Therapy

• For MRSA: Vancomycin is the first-line agent 3, 4
• For methicillin-susceptible S. aureus: Nafcillin/oxacillin or cefazolin 3
• Adjust therapy based on culture results and antibiotic susceptibilities 3, 4

Route and Duration

• Initial parenteral therapy for 1-2 weeks before considering transition to oral antibiotics with good bioavailability (fluoroquinolones, rifampin, clindamycin, linezolid, fusidic acid, trimethoprim-sulfamethoxazole) 1, 3
• Total antibiotic duration typically 4-6 weeks 3, 5
• If all infected bone is surgically removed, shorter course (2-14 days) may be sufficient 1, 3

Surgical Management

• Consider surgical intervention when:
  • Infection is associated with substantial bone necrosis or exposed joint 1
  • Foot appears functionally nonsalvageable 1
  • Infecting pathogen is resistant to available antibiotics 1
  • Patient has a strong preference for surgical treatment 1

Medical vs. Surgical Management

• Nonsurgical management may be considered when:
  • There is no acceptable surgical target (radical cure would cause unacceptable functional loss) 1
  • Patient has limb ischemia due to unreconstructable vascular disease but wishes to avoid amputation 1
  • Infection is confined to the forefoot with minimal soft tissue loss 1
  • Patient and healthcare professional agree surgery carries excessive risk 1

Treatment Failure Considerations

• Assess for residual necrotic or infected bone that should be resected 1
• Evaluate if the antibiotic regimen covered the causative organism(s) and achieved adequate bone levels 1
• Consider noninfectious complications (inadequate off-loading, insufficient blood supply) 1

Special Considerations

• For chronic osteomyelitis, a combined medical and surgical approach is typically required 6, 7
• Local antibiotic delivery systems (beads, spacers, coated implants) may be used as adjunctive therapy 6, 8
• Monitor treatment response through clinical assessment and inflammatory markers 3
• If infection fails to respond to initial therapy, consider discontinuing antibiotics and obtaining new cultures 3

Common Pitfalls

• Relying solely on soft tissue cultures, which may not reflect the true bone pathogens 1
• Inadequate duration of antibiotic therapy, particularly for chronic osteomyelitis 1, 5
• Failure to obtain appropriate specimens for culture before starting antibiotics 3
• Delayed surgical intervention when indicated, leading to progressive bone destruction 1