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Osteomyelitis

Osteomyelitis is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • An acute or chronic bone infection with associated inflammation; can occur as a result of hematogenous seeding, contiguous spread of infection, or direct inoculation into intact bone (trauma or surgery)
  • Two major classification systems:
    • Lew and Waldvogel
      • Classified according to duration (acute or chronic) and mechanism of infection (hematogenous, contiguous)
    • Cierny-Mader classification
      • Based on the portion of bone affected, physiologic status of the host, and risk factors
      • Stage 1: medullary bone (often monomicrobial)
      • Stage 2: bony surface, involving only cortical bone (deep soft-tissue infection or ulcer)
      • Stage 3: advance local infection, often involves both cortical and medullary (polymicrobial); often associated with open fracture or infected orthopedic hardware
      • Stage 4: Extensive disease (multiple tissue layers) requires combination medical and surgical therapy.
      • Class A host: otherwise normal
      • Class B host: immunocompromised
      • Class C host: treatment risk benefit
  • Special situations
    • Vertebral osteomyelitis
      • Acute, subacute, or chronic
      • May result from hematogenous seeding, direct inoculation, or contiguous spread
      • Back pain is most common initial symptom.
      • Lumbar spine is most commonly involved, followed by thoracic spine.
    • Infections of prosthetic joints
      • Easier to obtain specific diagnosis and targeted therapy (better access)
      • X-ray, and then three-phase bone scan, as MRI/CT is limited use with prostheses
      • Treat with combination of antibiotics. Include rifampin (4 to 6 weeks) for higher success rate—penetrates biofilm.
    • Posttraumatic infections depend on type and severity of fracture; level of contamination
      • Tibia is the most commonly involved.
  • System(s) affected: musculoskeletal

Epidemiology

  • Predominant age: more common in older adults
  • Predominant sex: male > female
  • Hematogenous osteomyelitis
    • Adults (most >50 years of age): vertebral
    • Children: long bones
  • Contiguous osteomyelitis: related to trauma and surgery in younger adults and decubitus ulcers and infected total joint arthroplasties in older adults

Incidence
Generally low; normal bone is resistant to infection.

Prevalence
Up to 66% of diabetics with foot ulcers

Etiology and Pathophysiology

  • Infection is caused by biofilm bacteria (protects from antimicrobial agents and host immune responses).
  • Acute: suppurative infection of bone with edema and vascular compromise leading to sequestra
  • Chronic: presence of necrotic bone or sequestra or recurrence of previous infection
  • Hematogenous osteomyelitis (typically monomicrobial)
    • Staphylococcus aureus (most common)
    • Coagulase-negative staphylococci and aerobic gram-negative bacteria
    • Pseudomonas aeruginosa (intravenous drug user)
    • Salmonella sp. (sickle cell disease)
    • Mycobacterium tuberculosis and fungi (rare) in endemic areas or in immunocompromised hosts
  • Contiguous focus osteomyelitis (polymicrobial)
    • Diabetes or vascular insufficiency
      • Coagulase-positive and coagulase-negative staphylococci
      • Streptococci, gram-negative bacilli, anaerobes (Peptostreptococcus sp.)
    • Prosthetic device
      • Coagulase-negative staph and S. aureus

Risk Factors

  • Diabetes mellitus
  • Recent trauma/surgery
  • Foreign body (e.g., prosthetic implant)
  • Neuropathy and vascular insufficiency
  • Immunosuppression
  • Sickle cell disease
  • Injection drug use
  • Previous osteomyelitis

General Prevention

  • Antibiotic prophylaxis
    • Clean bone surgery
      • Administer IV antibiotics within an hour of skin incision; continue ≤24 hours postprocedure.
    • Closed fractures
      • Cefazolin, cefuroxime, clindamycin (β-lactam allergy), or vancomycin (β-lactam allergy or MRSA infection)
    • Open fractures
      • In patients who can receive antibiotics within 3 hours of injury with prompt operative treatment, 1st-generation cephalosporins are preferred (clindamycin or vancomycin if allergy exists). Add aminoglycoside if type III fracture and penicillin for anaerobic coverage if farm injury or possible bowel contamination.
  • Annual foot examination for diabetic patients.

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Citation

Stephens, Mark B., et al., editors. "Osteomyelitis." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116421/all/Osteomyelitis.
Osteomyelitis. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116421/all/Osteomyelitis. Accessed April 24, 2019.
Osteomyelitis. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116421/all/Osteomyelitis
Osteomyelitis [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 April 24]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116421/all/Osteomyelitis.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Osteomyelitis ID - 116421 ED - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116421/all/Osteomyelitis PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -