Osteomyelitis

1. Classification: Waldvogel System
   1. Acute Osteomyelitis: Hematogenous Seeding
      1. Child with long bone metaphysis infection
   2. Chronic Osteomyelitis: Wound associated
      1. Adult with open injury to bone and soft tissue
   3. Contiguous spread of infection
      1. No generalized vascular disease
      2. Generalized vascular disease
2. Causes
   1. See Osteomyelitis Causes
3. Types
   1. Acute Osteomyelitis
      1. Typical case is a 1-2 week history of fever, Joint Pain in the long bone of a child (hematogenous spread)
   2. Chronic Osteomyelitis
      1. Typical case is a 4-6 week history of malaise, regional pain at an open wound in an adult (contiguous spread)
4. Labs
   1. Inflammation markers
      1. General
         1. More useful in children, especially in ruling out Osteomyelitis (serial negative markers)
         2. Sensitive, but not specific
      2. Complete Blood Count (CBC)
         1. Leukocytosis
      3. Erythrocyte Sedimentation Rate (ESR) exceeds 70
         1. Test Sensitivity: 28%
      4. C-Reactive Protein (CRP)
   2. Bone Biopsy (Gold Standard)
      1. Test Sensitivity: 95%
      2. Specificity: 99%
      3. Polymicrobial infections are more common in Chronic Osteomyelitis
      4. Consider specific testing in atypical cases (e.g. Mycobacterium tuberculosis)
   3. Blood Culture
      1. Test Sensitivity: <50%
      2. Positive Blood Culture with clinical findings suggestive of Osteomyelitis may obviate the need for bone culture
   4. Superficial wound culture
      1. Not recommended due to contamination
5. Imaging
   1. Osteomyelitis XRay
      1. Typical appearance is the "rat bite" of destroyed bony cortex
      2. First line study due to low cost and high availability
      3. Narrows differential diagnosis by ruling out other causes
      4. Typically normal in first 2-3 weeks (esp. acute Osteomyelitis in Children)
   2. Osteomyelitis Bone Scan
      1. Low Test Specificity (can not distinguish Osteomyelitis from Trauma or recent post-surgical changes)
      2. Distinguishes Cellulitis from Osteomyelitis
      3. In combination with Leokocyte Scintigraphy, efficacy approaches that of MRI
         1. Consider in patients for whom MRI is contraindicated (e.g. due to Pacemaker)
   3. Osteomyelitis MRI
      1. Best Test Sensitivity and Specificity (except in region of surgical hardware)
      2. Best distinguishes soft tissue infection from bone infection and defines infection margins
   4. Osteomyelitis PET
      1. Very high Test Sensitivity and Test Specificity, but cost prohibitive
   5. Osteomyelitis CT
      1. Avoid for Osteomyelitis evaluation unless MRI contraindicated
      2. May also identify soft tissue abscess, gas formation, foreign bodies and bony destruction
   6. Bone Ultrasound Findings (may have niche applicability, such as in Sickle Cell Disease related Osteomyelitis)
      1. Bone abscess
      2. Periostitis
6. Management
   1. See Osteomyelitis Management
   2. See Suspected Osteomyelitis in Diabetes Mellitus
7. References
   1. Jhun and Raam in Herbert (2016) EM:Rap 16(2):15-6
   2. Boutin (1998) Orthop Clin North Am 29:41-66 [PubMed]
   3. Carek (2001) Am Fam Physician 63(12):2413-20 [PubMed]
   4. Dirschl (1993) Drugs 45:29-43 [PubMed]
   5. Eckman (1995) JAMA 273:712-20 [PubMed]
   6. Haas (1996) Am J Med 101:550-61 [PubMed]
   7. Lew (1997) N Engl J Med 336:999-1007 [PubMed]
   8. Lipsky (1997) Clin Infect Dis 25:1318-26 [PubMed]