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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
  • Special situations
    • Vertebral osteomyelitis
      • Also results from hematogenous seeding (most common), direct inoculation, or contiguous spread
      • Back pain is most common initial symptom.
      • Lumbar spine is most commonly involved, followed by thoracic spine.
      • Neurologic symptoms in 1/3 of patients (1)[C]
      • Surgery is required if neurologic symptoms or infected spinal implant. Uncomplicated acute hematogenous vertebral osteomyelitis can be treated with 6 weeks of antibiotics alone (1)[C].
    • Infections of prosthetic joints
      • X-ray and three-phase bone scan. MRI/CT is of limited use with prostheses.
      • Treat with pathogen-directed antibiotic therapy; may 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.

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 diabetic foot infections (DFIs), decubitus ulcers, and infected total joint arthroplasties in older adults; trauma and surgery in younger adults
  • Mycobacterium tuberculosis (MTB) is the most common cause of vertebral osteomyelitis worldwide. It is more likely to involve multiple vertebral bodies—especially of the thoracic spine—and is associated with paraspinal abscess formation.

Incidence
Generally low; normal bone is resistant to infection.

Prevalence
Up to 66% of diabetics with foot ulcerations

Etiology and Pathophysiology

  • Acute: suppurative infection of bone with edema and vascular compromise leading to sequestrum (segments of necrotic bone, may contain pus)
  • Chronic: presence of necrotic bone or sequestrum or recurrence of previous infection
  • Hematogenous osteomyelitis (typically monomicrobial)
    • Staphylococcus aureus (most common)
    • Coagulase-negative staphylococci and aerobic gram-negative bacteria
    • Pseudomonas aeruginosa (intravenous [IV] drug user)
    • Salmonella sp. (sickle cell disease)
    • MTB 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.)
    • Sacral decubitus ulcer
      • Pressure-related skin ulceration and necrosis
      • May require débridement to healthy bone and/or soft tissue coverage/surgical flap procedure (2)[C]
    • Nail puncture through a shoe
      • P. aeruginosa
  • Prosthetic device
    • Coagulase-negative staph and S. aureus

Risk Factors

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

General Prevention

  • Comprehensive annual foot exam for diabetic patients
  • Screen for peripheral artery disease.
  • Optimize glycemic control in diabetes.
  • Antibiotic prophylaxis for posttraumatic infection
    • 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 allergic). Ceftriaxone for type III fractures. Add metronidazole if associated with soil or fecal matter contamination.

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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/116421/0.4/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/116421/0.4/Osteomyelitis. Accessed June 27, 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/116421/0.4/Osteomyelitis
Osteomyelitis [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 June 27]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116421/0.4/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/116421/0.4/Osteomyelitis PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -