Canis ISSN: 2398-2942

Osteomyelitis

Synonym(s): Bacterial osteomyelitis, fungal osteomyelitis

Contributor(s): Joseph Harari

Introduction

  • Cause: (most common) bacterial infection introduced during orthopedic surgery or contamination from wounds.
  • Treatment:
    • Early antibiotics; culture and sensitivity is essential because expensive antibiotics needed for a protracted time.
    • Stabilization of fractures and excision of necrotic material/bone sequestrae.
    • Surgery; if chronic osteomyelitis.
  • Diagnosis:
    • Radiographic changes: these lag 10-14 days behind surgery or introduction of infection.
    • Clinical signs.
    • Discharging sinuses, swelling at surgery site, limb dysfunction.

Pathogenesis

Etiology

  • Neonatal primary osteomyelitis generally occurs near growth plates because the tortuous course of blood vessels allows pathogenic bacteria to settle and multiply → infection.
  • Usually the condition results from poor surgical techniques, prolonged operating time, excessive soft tissue (very important) damage and inadequate fracture stabilization.
  • Appropriate early treatment of open fractures, even if contaminated, will prevent infection.
  • Soft tissue management is of equal importance to implant selection since the special blood supply of healing bone originates in the soft tissues.
  • Spontaneous resolution of infection is unlikely as the dead bone → nidus of bacteria.

Predisposing factors

General

  • Inadequate fracture stabilization.
  • Unsterile surgery.
  • Prolonged operating time.
  • Poor technique → soft tissue damage.
  • Primarily immunocompromised patient.
  • Contaminated wound, inappropriate antibiotics.

Pathophysiology

  • Inflammation → edema and vascular congestion → depriving osteocytes of adequate oxygen → osteocytic death.
  • Compromised blood supply to bone and surrounding soft tissue following trauma and fracture repair allows establishment of bacteria before the body's defenses can mobilize to the site.
  • Inadequate blood → poor invasion of site by host defenses and poor antibiotic perfusion.
  • Unresorbed bone → sequestrum and may wall off → involucrum.
  • Chronic infections → granulation tissue production → fistulae.
  • Bacterial contamination of surgical field at time of fracture fixation.
  • Inadequate blood supply post-operatively prevents tissue fluids transporting adequate host defense mechanisms to site.
  • Soft tissue damage exacerbates effects of inadequate blood supply.
  • Bacterial contamination/multiplication - usually skin contaminants, eg Staphylococcus spp Staphylococcus sppStreptococcus spp Streptococcus spp.
  • Bacterial toxins → further tissue damage → further isolating of the body's defense mechanisms.
  • Inadequate MIC levels at the bacterial site because of poor blood supply to infected area reduces efficacy of systemic antibiotics.

Timecourse

  • Rapid if acute: systemic illness within days.
  • Control of low grade surgical contamination possible within a few days if host +/- antibiotics successfully eliminates organism. Mild pyrexia may occur.
  • Chronic osteomyelitis with draining fistulous tracts may take months to achieve resolution.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Lindsey M J (2000) Metaphyseal osteomyelitis. Vet Rec 146 (1), 28 PubMed.
  • Dernell W (1999) Treatment of severe orthopedic infections. Vet Clin North Am Small Anim Prac 29 (5), 1261-1274 PubMed.


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