Osteomyelitis

Diagnosis

Indications for Testing

  • History and physical examination suggestive of osteomyelitis
  • Chronic, nonhealing ulcer that can be probed to the bone (particularly in a diabetic patient)

Laboratory Testing

  • CBC – may help in differentiating bacterial etiology versus other cause
    • Frequently shows leukocytosis and left shift to immature forms
    • May be normal in chronic osteomyelitis
  • ESR/CRP – frequently elevated, but not diagnostic
  • Blood culture – detect bacterial infection
    • Requires 3-5 sets from separate venipuncture sites
    • Positive in 50% of children
  • Bone culture – diagnostic if positive
  • PCR – not widely available; may be useful if all cultures are negative

Imaging Studies

  • Plain x-ray films – may not demonstrate presence of osteomyelitis until 10-14 days after infection is established
    • Negative film does not rule out diagnosis
    • Evidence for osteomyelitis on film – periosteal lifting or lytic lesions
  • Bone scan with technetium-99 pyrophosphate – most useful if 3-phase scintigraphy is used
    • 90% sensitive in long bone osteomyelitis
  • MRI – probably most sensitive imaging tool but may not distinguish infections from other bone disorders
    • Evidence for osteomyelitis – bone marrow edema, abscesses
    • May need to use 18FDG-PET for vertebral osteomyelitis
  • CT – not as sensitive as MRI; not useful if metal is near the infection
    • In acute osteomyelitis, CT can depict changes earlier in disease process than plain imaging

Differential Diagnosis

Monitoring

  • CRP/ESR – may be helpful in gauging success of therapy
    • Values should decrease into the normal range

Clinical Background

Osteomyelitis is an infection of the bone acquired hematogenously or by contiguous site infection.

Epidemiology

  • Incidence – 2/10,000
  • Sex – M>F (slight risk increases through childhood, peaks in adolescence, and falls to a low ratio in adults)
  • Age – bimodal age distribution
    • Children – acute hematogenous osteomyelitis
    • Adults – direct trauma/contiguous focus osteomyelitis; vertebral osteomyelitis

Risk Factors

  • Children
    • Blunt trauma
    • Postoperative
  • Adults
    • Peripheral vascular disease
    • Diabetes mellitus
    • Renal or hepatic failure
    • Immunosuppression
    • Malignancy
    • Neuropathy
    • Intravenous drug use
    • Trauma
    • Surgery – particularly prosthetic implants

Organisms

Clinical Presentation

  • Constitutional – fever, nonspecific pain
  • Soft tissue inflammation overlying area of osteomyelitis
  • Open and nonhealing wound over area of bone
  • Vertebral disease – may present with severe back pain

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Initial test for differentiating bacterial from viral infection

   
Blood Culture 0060102
Method: Continuous Monitoring Blood Culture/Identification

Evaluate presence of bacterial infection

Limited to the University of Utah Health Sciences Center only

 
Sedimentation Rate, Westergren (ESR) 0040325
Method: Visual Identification

Evaluate presence of inflammation

   
C-Reactive Protein 0050180
Method: Quantitative Immunoturbidimetry

Evaluate presence of inflammation

   
Bone Culture and Gram Stain 0060103
Method: Culture/Identification

Use to diagnose osteomyelitis

   
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Bartonella Species by PCR 0093057
Method: Qualitative Polymerase Chain Reaction

Consider if cultures are negative and strong suspicion exists