Osteomyelitis

Snapshot

• A 53-year-old man presents to the emergency department for fever, chills, and pain in the left foot. His symptoms began several weeks ago and have progressively worsened since. The pain is present with and without movement; he denies any recent trauma to the area. He feels feverish and experiences rigors at night. Medical history is significant for poorly controlled type II diabetes mellitus and peripheral vascular disease. On physical exam, there is a tender and erythematous ulcer on the pedal surface of the left foot. A probe-to-bone test is performed and demonstrates a hard and gritty surface. Laboratory testing is significant for an elevated erythrocyte sedimentation rate and C-reactive protein and leukocytosis. A plain radiograph demonstrates periosteal thickening and soft tissue swelling. Microbial cultures are obtained and he is started on empiric antibiotics.

Introduction

• Clinical definition
  • inflammation of the bone and bone marrow most commonly due secondarily to infection that can be categorized as
    • acute osteomyelitis
      • more common in children
      • typically symptom onset is within 2 weeks postinfection
    • chronic osteomyelitis
      • more common in adults
      • typically symptoms persists months or years postinfection
• Epidemiology
  • risk factors
    • diabetes
    • peripheral vascular disease
    • open fracture
    • intravenous drug use
    • catheter use
    • surgery
• Etiology
  • note that infection can be due to bacteria, fungi, and mycobacteria
  • microbiology
    • Staphylococcus auerus 
      • most common cause overall 
        • may be seen in
          • sickle cell disease
          • prosthetic joint replacement
          • vertebral involvement
          • intravenous drug use
    • Neisseria gonorrhoeae
      • rare
    • Staphylococcus epidermidis
      • can also be seen in prosthetic joint involvement
    • Salmonella species
      • may be seen in hemoglobinathies such as sickle cell disease or thalassemia
    • Mycobacterium tuberculosis
      • can also be seen in cases of vertebral involvement (Pott disease)
    • Pasteurella multocida
      • seen in cases caused by cat and dog bites
    • Pseudomonas and Candida
      • can also be seen in cases caused by intravenous drug abuse
• Pathogenesis
  • hematogenous seeding of bone
  • contiguous spread of infection from adjacent structures (e.g., soft tissues and joints)
  • direct inoculation
    • e.g., penetrating trauma and contaminated surgical tools
• Prognosis
• mortality has significantly decreased since the use of antibiotics

Presentation

• Symptoms
  • acute osteomyelitis
    • lethargy
    • acute pain in affected site
    • erythema and
  • chronic osteomyelitis
    • chronic pain
• Physical exam 
  • swelling
  • erythema
  • tenderness
  • reduced range of motion
  • bone tenderness
  • ulcers
  • exposed bone may be seen
  • sinus tract
    • pathognomonic for chronic osteomyelitis
• must perform a neurovascular exam

Imaging

• Radiographs
  • indication
    • preferred initial test in evaluating for osteomyelitis
      • note that it takes 10-14 days postinfection for findings to appear
  • findings
    • periosteal thickening and elevation “Codman triangle”
• Magnetic resonance imaging
  • indication
    • considered when radiography is unrevealing
  • findigs
• may reveal bone necrosis, abscess, and sinus tracts

Studies

• Labs
  • ↑ C-reactive protein 
  • ↑ erythrocyte sedimentation rate
  • leukocytosis
    • present in acute osteomyelitis
    • unlikely to be found in chronic osteomyelitis
• Biopsy and culture
• confirms the diagnosis

Differential

• Septic arthritis
• Gout
• Cellulitis
• Osteosarcoma

Treatment

• Medical
  • empiric antibiotics
    • indication
      • considered the mainstay of treatment
        • eventually tailored to organism after culture sensitivities return
• Operative
  • debridement
    • indication
• to remove necrotic tissue

Complications

• Bone necrosis
• Sepsis
• Squamous cell carcinoma
  • most common tumor associated with osteomyelitis