Difference between revisions of "Osteomyelitis"

Revision as of 16:36, 3 March 2011

Localised osteomyelitis plus sequestrum (Image sourced from Bristol Biomed Image Archive with permission)

Mainly due to haematogenous spread in young animals
Often as an extension from suppurative arthritis
Usually isolated: Actinomyces pyogenes, Salmonella, E.coli, Klebsiella, Streptococci
Metaphyses and epiphyses mostly affected
Most infections are exacerbated by host response
Pathogenesis:
- Prostaglandin and cytokines stimulate osteoclastic bone resorption
- Blood vessel occlusion and tissue necrosis -> lack of removal of agent and cartilage -> cartilage thickening + persistance of infection
Affected area may be surrounded by fibrous inflammatory tissue
Metaphyseal abscesses may develop
Sequestra may also develop -> surrounded by granulation tissue
- Isolated from osteoclastic resorption
- May persist for long time
- Obstruct repair

Vertebral osteomyelitis
- Lesions may affect the spinal cord
- Usually due to Actinomyces pyogenes
- Suppurative inflammation may cause fracture of vertebral body -> dorsal displacement -> damage to spinal cord
- May form encapsulated abscess protruding into spinal canal -> spinal cord compression

Actinomycosis
- = Lumpy jaw in cattle
- Caused by Actinomyces bovis
  - Gram positive, branching, filamentous
  - Obligatory parasite of mucous membranes of oropharynx
  - Surface tissue is usually injured for infection to occur
  - Osteomyelitis of mandible -> destruction of bone -> replacement by fibrous tissue with pyogranulomatous nodules cotaining 'club colonies' of bacteria
  - Suppurative osteomyelitis
  - Fistulous tracts may discharge onto skin and into oral cavity
  - Excessive periosteal bone formation
  - Greatly enlarged mandible

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-{{OpenPagesTop}}
+[[Image:Cattle localised osteomyelitis with sequestrum.jpg|right|thumb|100px|<small><center>Localised osteomyelitis plus sequestrum (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
-==Introduction==
-[[Image:Cattle localised osteomyelitis with sequestrum.jpg|right|thumb|200px|<small><center>Localised osteomyelitis plus sequestrum (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
-Osteomyelitis describes '''inflammation and infection of the medullary cavity, cortex and periosteum of bone'''. This occurs most commonly at the '''metaphyses and epiphyses'''.
-It can arise from '''direct penetration of bone''' by microorganisms or by '''haematogenous spread'''. The latter is the most common cause of osteomyelitis in young animals. It can also accompany '''[[Arthritis|septic arthritis]]''', more commonly in foals. Other causes include: '''open [[fractures]] and traumatic injuries''', foreign bodies, extension of soft tissue infection etc.
+*Mainly due to haematogenous spread in young animals
+*Often as an extension from [[Arthritis|suppurative arthritis]]
+*Usually isolated: ''[[Actinomyces pyogenes]]'', [[Salmonella|''Salmonella'']], [[Escherichia coli|''E.coli'']], [[Klebsiella|''Klebsiella'']], [[:Category:Streptococcus species|''Streptococci'']]
+*Metaphyses and epiphyses mostly affected
+*Most infections are exacerbated by host response
+*Pathogenesis:
+**Prostaglandin and cytokines stimulate [[Bones - Anatomy & Physiology|osteoclastic]] bone resorption
+**Blood vessel occlusion and tissue necrosis -> lack of removal of agent and cartilage -> cartilage thickening + persistance of infection
+*Affected area may be surrounded by fibrous inflammatory tissue
+*Metaphyseal abscesses may develop
+*Sequestra may also develop -> surrounded by [[Granulation Tissue|granulation tissue]]
+**Isolated from osteoclastic resorption
+**May persist for long time
+**Obstruct repair
-Organisms commonly isolated include: ''[[Actinomyces pyogenes]]'', [[Salmonella|''Salmonella'']], [[Escherichia coli|''E.coli'']], [[Klebsiella|''Klebsiella'']], [[:Category:Streptococcus species|''Streptococci'']].
-'''Fungal organisms''' have also been implicated, and diseases, based on geographic distributions, include ''Coccidoides immitis'' (southwestern USA), [[Blastomycosis|''Blastomyces dermatitidis'']] (southeastern USA), [[Histoplasma capsulatum var. farciminosum|''Histoplasma capsulatum'']] (central USA), ''[[Cryptococcus neoformans]]'' and ''[[Aspergillus spp.|Aspergillus]]'' (worldwide).
+*'''Vertebral osteomyelitis'''
+**Lesions may affect the spinal cord
+**Usually due to ''[[Actinomyces pyogenes]]''
+**Suppurative inflammation may cause fracture of vertebral body -> dorsal displacement -> damage to spinal cord
+**May form encapsulated abscess protruding into spinal canal -> spinal cord compression
-'''Pathogenesis''' involves: [[Bones - Anatomy & Physiology|osteoclastic]] bone resorption stimulated by prostaglandin and cytokines. Blood vessels become occluded and there is tissue necrosis with thickening of cartilage and persistence of infection. The affected area my be surround by fibrous inflammatory tissue.
+*'''''Actinomycosis'''''
+**= '''[[Lumpy jaw]]''' in cattle
+**Caused by ''[[Actinomyces bovis]]''
+***Gram positive, branching, filamentous
+***Obligatory parasite of mucous membranes of [[Oropharynx - Anatomy & Physiology|oropharynx]]
+***Surface tissue is usually injured for infection to occur
+***[[Mandibular Osteomyelitis|Osteomyelitis of mandible]] -> destruction of bone -> replacement by fibrous tissue with pyogranulomatous nodules cotaining 'club colonies' of bacteria
+***Suppurative osteomyelitis
+***Fistulous tracts may discharge onto skin and into [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]]
+***Excessive periosteal bone formation
+***Greatly enlarged mandible
-Metaphyseal abscesses may develop.
-'''Sequestra''' may also develop, and are surrounded by [[Granulation Tissue|granulation tissue]]. These are isolated from osteoclastic resorption and may persist for a long time and obstruct repair.
-'''Risk factors''' include: open fracture and bone contamination, soft tissue trauma, bite and claw wounds, migrating foreign body, orthopaedic surgery and orthopaedic implants, cortical bone allograft and immunodeficiency.
-==Clinical Signs==
-Clinical signs may be acute or chronic and can vary widely.
-'''Acute disease''' in small animals presents as a sudden onset ''''systemic illness''' with pyrexia, lethargy, '''limb pain''', and local signs of acute inflammation (heat, swelling, pain, redness, loss of function).
-'''Chronic cases''' are usually associated with chronic '''draining tracts, non-healing ulcers, pain, secondary muscle atrophy and joint stiffness'''.
-'''Unhealed fractures''' with a concurrent infection may show instability, crepitus and limb deformity.
-'''Vertebral osteomyelitis''' which affects the spinal cord leads to spinal pain. Neurological deficits, such as paresis or paralysis, can develop if there is damage to the spinal cord due to vertebral body fracture, or compression of the cord due to an abscess.
-'''Large animal cases''' often present with a non-healing wound and draining tract with soft tissue swelling.
-'''Cattle''' with [[Mandibular Osteomyelitis|lumpy jaw]] present with a distorted face and draining fistulous tracts around the mandibular area.
-==Diagnosis==
-'''Radiography''' is a very helpful tool, especially in chronic cases. It may reveal '''bone lysis''' (widening of fracture gaps), '''sequestration''' (avascular segment of cortical bone), '''reactive periosteal new bone'''.
-If orthopaedic surgery has been performed, radiography might reveal a '''loosening of any implants'''.
-Deep '''fine-needle aspiration or biopsies''' can be cultured to identify the causative organism.
-'''Histopathology''' can help diagnose fungal infections and rule out neoplasia.
-Culture of the purulent fluid from the draining tracts might be misleading due to skin contaminants.
-'''Blood cultures''' may be useful in cases with systemic bacteraemia or septicaemia.
-==Treatment==
-Both medical and surgical therapies can be used.
-'''Long-term oral or injectable antimicrobials''' such as cephalexin, clindamycin, enrofloxacin or combinations should be administered. Results of the '''culture and sensitivity tests''' should be taken into account when choosing an antimicrobial.
-Acute infections may resolve with antimicrobial therapy alone provided there is limited bone necrosis and no fracture.
-'''Surgical debridement and lavage of the wound''' along with removal of any loose implants should generally also be carried out, especially in chronic cases. Open or closed wound drainage can be used.
-In chronic, refractory small animal cases, '''limb amputation''' may be necessary.
-In '''vertebral osteomyelitis cases''', antibiotic therapy might be sufficient, or surgery to decompress the spinal cord may be necessary.
-Patient progress should be monitored with '''repeat radiographs every 4-6 weeks''', and repeat bone culturing might be necessary if a persistent infection is suspected.
-'''Prognosis is variable''' and based on the severity and chronicity of the infection and the organism involved.
-{{Learning
-|flashcards = [[Equine Orthopaedics and Rheumatology Q&A 12]]
-}}
-==References==
-Shires, P. (2005) '''The 5-minute veterinary consult: musculoskeletal disorders''' ''Wiley-Blackwell''
-Kahn, C. (2005) '''Merck Veterinary Manual''' ''Merck and Co''
-Fenner, W. (2000) '''Quick Reference to Veterinary Medicine''' ''Wiley-Blackwell''
-{{review}}
-{{OpenPages}}
-[[Category:Musculoskeletal Diseases - Dog]]
-[[Category:Expert Review]]
-[[Category:Musculoskeletal Diseases - Horse]]
 [[Category:Bones - Inflammatory Pathology]]
-[[Category:Musculoskeletal Diseases - Cat]]

Difference between revisions of "Osteomyelitis"

Revision as of 16:36, 3 March 2011

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