Equis ISSN 2398-2977

Bone: osteitis - septic

Synonym(s): Osteomyelitis

Contributor(s): Steve Adair, Graham Munroe, Chris Whitton

Introduction

  • Cause: open fracture, open reduction of fracture, extension from septic arthritis   Joint: septic arthritis - adult  , laceration, puncture wounds that damage bone.
  • Signs: heat, pain, reduced weightbearing, pyrexia, poor wound healing, sinus tract.
  • Diagnosis: radiography, microbiology.
  • Treatment: surgical debridement, implant removal, bone graft, antibiotics.
  • Prognosis: guarded - osteomyelitis secondary to fractures and septic arthritis; fair - sequestration secondary to wounds.
  • See also:

Pathogenesis

Etiology

  • Trauma.
  • Iatrogenic.
  • Extension from joint infection/fracture.

Specific

  • Open and/or comminuted fractures.
  • Open reduction of fracture.
  • Surgical implants.
  • Wounds.
  • Joint infection.
  • Incomplete fractures

Pathophysiology

  • Loss of blood supply plus introduction of bacteria (traumatic or hematogenous)   →   death of bone   →   bacteria proliferate   →   inflammation and formation of a sequestrum.
  • Joint infection   →   bacteria spread via epiphyseal vascular channels or through defects in articular cartilage to bone.
  • Definitions:
    • Osteitis: inflammation of bone.
    • Osteomyelitis: inflammation of bone involving the medullary cavity.
Loss of blood supply
  • Blood is circulated in the bone from the medulla out toward the cortex.
  • Periosteal blood supply is best at the attachments of ligaments and tendons and at the extremities of the bone.
  • There is some continuity of the periosteal vessels with the medullary circulation.
  • Loss of periosteum   →   ischemic death of the outer third of the cortex.
  • Loss of blood supply   →   osteocytic death   →   necrotic bone.

Infection

  • Bacteria introduced during trauma or surgery, by hematogenous spread to an area of minor but chronic bone pathology, or by extension from joint infection.
  • Bacteria adhere to damaged endothelium   →   proliferate   →   inflammatory response   →   osteitis (inflammation in the periosteum and superficial cortex).
  • Inflammation   →   interstitial edema and capillary rupture   →   increased pressure in the osteonal system and trabecular space   →   pain and further disruption of blood supply.
  • Bacteria produce a protective layer of extra polysaccharide polymers suitable for adhesion of more bacteria and reducing susceptibility to antibiotics   →   loss of tissue viability.
  • Pieces of dead bone   →   good substrate for further colonization   →   infection penetrates deeper cortex and medulla   →   osteomyelitis.

Bone response

  • Granulation tissue proliferates   →   osteonal, trabecular and periosteal mesenchymal cells produce new bone   →   isolates infected bone.
  • Isolated abscess and necrotic bone = sequestrum.
  • New bone surrounding sequestrum = involucrum.
  • Formation of a sinus tract which drains exudate and sequestrum fragments   →   potentially spreads to joint(s) and/or overlying soft tissues   →   prevents healing.

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 fromPubMed andVetMedResource.
  • Kilcoyne I, Nieto J & Vaughan B (2014)Tibial osteomyelitis caused byRhodococcus equiin a mature horse.Equine Vet Educ26(6), 283-286VetMedResource.
  • Werpy N (2014)The use of magnetic resonance imaging for the diagnosis of osteomyelitis.Equine Vet Educ26(1), 15-17.
  • Garcia E Bet al(2014)Navicular bone osteomyelitis and navicular bursitis with associated fistula diagnosed with magnetic resonance fistulography in the horse.Equine Vet Educ26(1), 10-14VetMedResource.
  • Koch C & White S (2013)Septic osteitis and osteomyelitis in foals - are antimicrobials alone enough?Equine Vet Educ 25(2), 60-62VetMedResource.
  • Lawrence C P & Fraser B S L (2013)Septic osteitis of the axial border of the proximal sesamoid bones in two foals.Equine Vet Educ25(2), 63-66VetMedResource.
  • Close K, Gerard M, Davidson G & Schramme M (2011) Successful treatment of infectious (Salmonellatype III:44) polyarthritis and osteomyelitis in a 4-week old foal.Equine Vet J23 (3), 121-126VetMedResource
  • Dabareiner R M, Watkins J P, Carter G K, Honnas C M & Eastman T (2001)Osteitis of the axial border of the proximal sesamoid bones in horses - eight cases (1993-1999).JAVMA219(1), 82PubMed.
  • Booth LC (1998)Superficial septic osteitis and sequestrum formation in the horse.Equine Vet Educ10, 233-237VetMedResource.
  • Fitch G L and Martinelli M J (1998)Conservative and surgical management of a sequestrum involving the radial cortex in two horses.Equine Vet Educ10, 228-232VetMedResource.
  • Moore R Met al(1992)Antimicrobial susceptibility of bacterial isolates from 233 horses with musculoskeletal infection during 1979-1989.Equine Vet J24, 450-456PubMed.
  • Tulamo R-M and Alitalo I (1986)An unusual case of osteomyelitis in a horse.Equine Vet J18, 404-407PubMed.

Other sources of information

  • Ross M W & Dyson S J (2003)Antimicrobial Therapy.In:Diagnosis and Management of Lameness in the Horse. W BSaunders, Missouri. pp 601-602.


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