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
  • Most useful for Bartonella henselae and Kingella kingae

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

• Arthritis 
  • Septic
  • Degenerative
  • Crystalline
  • Reactive
• Juvenile rheumatoid arthritis
• Neuropathic disease
• Metastatic bone disease
• Paget disease

Monitoring

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

• Most common organism – Staphylococcus aureus
• Diabetes mellitus, peripheral vascular disease – Streptococcus spp, coagulase-positive and -negative Staphylococcus spp, Enterococcus spp, anaerobic spp, often polymicrobial
• Intravenous drug use – Pseudomonas aeruginosa
• Infants and children – Staphylococcus spp, S. pneumoniae, Group A Streptococcus (especially post-chickenpox), Kingella kingae
• Neonates – Group B Streptococcus, gram-negative species
• Hemoglobinopathies – Salmonella spp

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

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Bartonella Species by PCR 0093057 Method: Qualitative Polymerase Chain Reaction	Consider if cultures are negative and strong suspicion exists