Flashcards in Bone and Joint Infections Deck (40):
1
Osteomyelitis
Infection of the bone
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3 mechanisms of how bone infection may be brought about
Haematogenous- bacteria in the blood seed bone
Contiguous focus-spread from adjacent area of infection
Direct incoculation-trauma or surgery
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Stage 1 of osteomyelitis and likely cause
Medullary-necrosis of medullary contents- haematogenous
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Stage 2 of osteomyelitis
Superficial-necrosis limited to exposed surfaces
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Cause of stage 2 superficial osteomyelitis
Contiguous- Diabetic foot ulcer, pressure sores
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Complications of stage 3
Necrosis- no blood supply- can't treat with antibiotics. Surgery required to cure
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Stage 3 osteomyelitis
Localised- full thickness cortical sequestation, stable before and after debridement
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Stage 4 osteomyelitis
Diffuse- extensive, unstable bone
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describe the pain with osteomyelitis
localised pain, not relieved with resting and progressive
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Clinical presentation of osteomyelitis
Pain
Soft tissue swelling
Erythema
Warmth
Localised tenderness
Reduced movement of affected limb
Systemic upset uncommon (fever, chills, night sweats)
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Most common causative organism of osteomyelitis (60%)
Staph A
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6 main causative organisms of osteomyelitis
Staph A
Stretococci
Enterococci
Gram -ve bacilli
Anaerobes
M. TB
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Gold standard diagnostic procedure for osteomyelitis
Cultures and histology of bone biopsy/needle aspirate
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Name 4 diagnostic tests for osteomyelitis
Gold standard
Blood cultures
Superficial swabs
C-reactive protein
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When would you give empirical antimicrobial therapy in osteomyelitis?
When signs of sepsis
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Which 5 antibiotics have acceptable penetrance in bone?
Clindamycin
Ciprofloxacin
Vancomycin
Beta-Lactam
Gentamicin
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What is the treatment of choice for Staph A. osteomyelitis
Flucloxacillin IV
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How are antibiotics usually administered in osteomyelitis?
IV
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Septic arthritis
Inflammatory reaction in joint space (arthritis) caused by infection, resulting from direct invasion of the joint
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2 classifications of septic arthritis
Native (natural) joint infection
Prosthetic (artificial) joint infection
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2 ways in which organisms enter the joint in native joint infection
Haematogenous or trauma
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How does synovial tissue facilitate 'seeding'?
Highly vascular and lacks a basement membrane
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Predisposing factors for native joint infection
RA
Trauma
IVDU
Immunosuppressive disease
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Prognosis for native joint infection
Not fatal but severe lack of function if not treated
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How do organisms enter the joint in prosthetic joint infections?
Haematogenous
During surgery or following wound infection after surgery
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Why are prosthetic joints susceptible to infection?
Cement provides a surface for bacterial attachment
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How does infection affect the joint in prosthetic infection?
Polymorph infiltration results in tissue damage instability of the prosthesis
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How does infection affect the joint in native infection?
Cartilage erosion causes joint space narrowing/impaired function
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Predisposing factors to prosthetic joint infection
Prior surgery at site
RB
Corticosteroid therapy
DM
Poor nutritional status
Obestiy
Age
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Clincial presentation of septic arthritis
Pain
Swelling
Tenderness
Redness
Limitation of movement
Systemic upset
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Causative organisms of septic arthritis
Bacteria
Fungi e.g. candida
Viruses e.g. parovirus B19, rubella, mumps (usually self limiting part of systemic illness)
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Name for group A streptococcus
Strep. pyogenes
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Causative organisms for native joint infections
Staph A
Streptococci A, B, C, G
Gram -ve bacilli
Neisseria gonorrheoae
Neisseria meningitidis
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Causative organisms for prosthetic joint infection
Staph A
Coagulase -ve staphylocoi
Enterococci
Gram -ve bacilli
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What do you look for in an examination of joint aspirate?
High total WBCs
Lots of polymorphs
Gram stain- not particularly reliable
Crystal examination- gout can mimic infection
Culture
PCR e.g. M.TB
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Therapy for native joint infection
Removal of purulent material -joint drainage/washout
Empirical followed by directed antimicrobial therapy (after microbiological samples have been taken)
2-4 weeks treatment
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Difference in therapy for prosthetic joint infection, compared to native
Removal of implant/replacement of some elements if unstable
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2 stage revision procedure
Take out implant and replace with cement and antimicrobials before replacing
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Treatment for Staph A in prosthetic joint infection
Flucoxacillin with rifampicin (Staph A. easily becomes resistant to rifampicin, so must always be used in combination for Staph A)
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