Rosen & Barkin's 5-Minute Emergency Medicine Consult (496 page)

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Specific Orthopedic Injuries

CODES

756.51 Osteogenesis imperfecta

BASICS

• Osteomyelitis (OM): Infection of bone with ongoing inflammatory destruction
  
• Usually bacterial, but fungal OM does occur
  
• Could be acute or chronic
  

• Hematogenous OM:
  
  • Primarily in children, elderly, IV drug abuse (IVDA) patients
    
  • Seeding of bacteria to bone from remote site of infection via bloodstream
    
  • Children have acute OM and adults subacute or chronic.
    
  • Hematogenous OM of long bones rarely occurs in adults.
    
  • Most children with acute hematogenous OM have no preceding illness.
    
  • 1/3 have history of trauma to affected area.
    
  • Staphylococcus aureus
    is the most common cause of OM in all ages.
    
  • Neonates:
    S. aureus, Enterobacteriaceae
    , group A and B streptococci, and
    Escherichia coli
    
  • Children:
    S. aureus,
    group A streptococci,
    Haemophilus influenzae, Enterobacteriaceae
    
  • Salmonella:
    Common in sickle cell disease
    
  • Adults:
    S. aureus
    ,
    Enterobacteriaceae
    ,
    Pseudomonas
    , gram-negative rods,
    Staphylococcus epidermidis
    , gram-positive anaerobes, especially
    Peptostreptococcus
    
  • Illicit drug users:
    Candida, Pseudomonas
    ,
    Serratia marcescens
    
  • Prolonged neutropenia:
    Candida, Aspergillus, Rhizopus, Blastomyces
    , coccidioidomycosis
    
• Hematogenous vertebral OM:
  
  • Uncommon
    
  • Most prevalent in adults >45 yr
    
  • Involves the disk and vertebra above and below
    
  • Often in the setting of long-term urinary catheter placement, IVDA, cancer, hemodialysis, or diabetes
    
  • IVDA: OM of pubic symphysis, sternoclavicular, and sacroiliac (SI) joints
    
  • Lumbar vertebrae most common, followed by thoracic, then cervical
    
  • Posterior extension leads to epidural/subdural abscess or meningitis.
    
  • Anterior extension may lead to paravertebral, retropharyngeal, mediastinal, subphrenic, retroperitoneal, or psoas abscess.
    
• Direct or contiguous OM:
  
  • Organism(s) directly seeded in bone due to trauma, especially following open fractures:
    
    • Spread from adjacent site of infection or from surgery
      
  • More common in adults and adolescents
    
  • S. aureus, Enterobacteriaceae
    ,
    Pseudomonas
    
  • Normal vascularity:
    
    • S. aureus
      and
      S. epidermidis
      , gram-negative bacilli, and anaerobic organisms
      
  • Vascular insufficiency/diabetes:
    
    • Small bones of feet are common sites.
      
    • Infection resulting from minor trauma, infected nail beds, cellulitis, or skin ulceration
      
    • Polymicrobial, including anaerobes
      
  • Puncture wound through tennis shoe:
    S. aureus, Pseudomonas
    
  • Clavicular OM can occur as complication of subclavian vein catheterization.
    
• Chronic OM:
  
  • OM that persists or recurs
    
  • Distinguishing characteristic is necrotic bone (sequestrum) that must be débrided.
    
  • S. epidermidis, S. aureus, Pseudomonas aeruginosa, S. marcescens
    , and
    E. coli
    

DIAGNOSIS

Vary with duration of disease

• Mainly nonspecific symptoms
  
• Pain: Localized, deep, dull, and throbbing; occurs with and without movement
  
• Fever and chills; may be absent in chronic OM
  
• Malaise, nausea, vomiting
  
• Reluctance to use extremity
  
• Nonhealing ulcers despite proper therapy
  
• Consider OM as a cause of fracture nonunion
  
• Predisposing factors: DM, vasculopathy, IVDA, invasive procedures, trauma
  

• Tenderness to palpation, warmth, erythema, edema, decreased range of motion
  
• Drainage of sinus tract
  
• Deep ulcers and palpable bone (+ “probe to bone” test has very high positive predictive value)
  
• If ulcer size >2 cm
  ²
  and >3 mm in depth, bone involvement is likely.
  

• CBC
  
• ESR and C-reactive protein
  
• Radiographs
  
• Blood and wound cultures and sensitivities
  

• CBC; WBC may be elevated but often normal
  
• ESR; elevated in >90% of cases
  
• C-reactive protein (usually elevated)
  
• Blood cultures (positive in ∼50% of cases)
  

• Plays a central role in evaluation
  
• Start with plain films; other tests often required
  
• Radiographs:
  
  • May be normal for the 1st 2–3 wk of symptoms
    
  • Earliest finding is periosteal elevation, followed by cortical erosions, then new bone formation.
    
  • 40–50% of focal bone loss needed to detect lucency on radiograph; fewer than 1/3 of cases have diagnostic findings at 10 days
    
  • Obtain CXR if TB suspected
    
• MRI:
  
  • Best modality to obtain detailed anatomy and extension of soft tissue and bone marrow involvement
    
  • Sensitivity and specificity of ∼90%
    
  • Reveals bone edema, cortical destruction, periosteal reaction, joint surface damage, and soft tissue involvement before x-rays
    
  • Effective in early detection (3–5 days from onset of infection)
    
  • Test of choice to identify vertebral OM and OM in diabetic foot ulcers
    
  • Occasional false-positive results in trauma, previous surgical procedures, or neuropathic joint disease
    
  • Negative study after 1 wk of symptoms rules out acute OM
    
• CT:
  
  • Modality of choice when MRI cannot be done
    
  • Reveals bone edema, cortical destruction, periosteal reaction, small foci of gas or foreign bodies, joint surface damage, and soft tissue involvement when plain films not helpful
    
  • Useful in OM of vertebrae, sternum, calcaneus, pelvic bones
    
  • Useful to surgeons in guiding débridement and biopsy
    
• Bone scan:
  
  • Technetium 99m methylene diphosphonate (
    ^99m
    Tc-MDP)
    
  • Measures increase in bone metabolic activity
    
  • ∼95% sensitive but less specific than MRI
    
  • Bone scan abnormal after 2–3 days of symptoms
    
  • False-positive may occur in trauma, surgery, chronic soft tissue infection, tumor
    
  • High radiation burden, useful if suspect multifocal disease
    
• Leukocyte scintigraphy:
  
  • Indium
    ¹¹¹
    -labeled WBCs
    
  • More specific but less sensitive than bone scan
    
  • Difficult to distinguish bone inflammation from soft tissue inflammation (i.e., cellulitis, tumors, inflammatory arthritis)
    
• US:
  
  • An emerging modality for OM especially in children
    
  • Periosteal elevation or thickening, fluid collections adjacent to bone often seen
    
  • May show findings of OM days prior to plain films
    
  • Useful in guiding biopsy
    

• Gold standard for diagnosis is bone biopsy with histology and tissue Gram stains, including culture and sensitivities.
  
• Needle aspiration has lower sensitivity than open biopsy.
  
• Culture of sinus or drainage from wound can be misleading; correlates well with
  S. aureus
  , but not as reliable for other organisms.
  

• 70–85% of children have fever higher than 38.5°C.
  
• Neonates are commonly afebrile.
  
• Only ∼1 in 3 of children will have leukocytosis.
  
• Blood cultures positive in ∼50%
  
• US
  

• Cellulitis
  
• Paronychia/felon
  
• Bursitis, toxic synovitis, septic arthritis
  
• Extremity fracture
  
• Bone infarction in sickle cell patients
  
• Acute leukemia, malignant bone tumors
  
• Mechanical back pain
  
• Spinal epidural abscess
  
• Brucellosis, especially in SI joint
  
• TB, more common in thoracic spine (Pott disease)
  

TREATMENT