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Week 7 - Clinical Microbiology & Infections 2 > Bone & Joint Infection > Flashcards

Bone & Joint Infection Flashcards

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1
Q

Label the following diagram of a normal joint [11]

A
  1. muscle
  2. synovial cavity
  3. bursa
  4. joint capsule and synovial lining
  5. tendon
  6. enthesis
  7. enthesis
  8. ligament
  9. articular cartilage
  10. epiphysis of bone
  11. enthesis
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2
Q

Define septic arthritis [1]

A

infection in a joint

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3
Q

Why should septic arthritis be treated as a medical emergency? [2]

A
  • Treat as a medical emergency as an untreated joint infection can lead to:
    1. Loss of cartilage → osteoarthritis in later life
    2. Severe sepsis → septic shock
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4
Q

What are the typical presenting signs & symptoms of septic arthritis? [5]

A
  1. Fever (60-80% of cases)
  2. Single hot joint
    • Knee (50%)
    • Hip (20%)
  3. Polyarticular involvement (10-20%)
  4. Loss of movement
  5. Pain
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5
Q

What are the key investigations that should be carried when diagnosing suspected septic arthritis? [5]

A
  1. Blood cultures
  2. Joint aspirate (gram, microscopy for crystals and culture)
  3. FBC
  4. CRP
  5. Imaging
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6
Q

What are the common pathogens that cause septic arthritis? [10]

A
  • Gram +ve
    1. MSSA
    2. MRSA
    3. Streptococci
      • S. pyogenes
      • Group G strep
      • Pneumococcus (commoner in children)
  • Gram -ve
    1. H. influenzae (commoner in children)
    2. Kingella
    3. N. meningitidis
    4. N. gonorrhoeae
    5. E. coli
    6. P. aeruginosa
    7. Salmonella species
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7
Q

How should septic arthritis be treated and monitored? [3]

A
  1. Often 3 weeks IV antibiotics followed by 3 weeks oral
  2. Monitor response by CRP and clinical
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8
Q

Define arthroplasty [1]

A

putting in an artificial joint

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9
Q

What is resection arthroplasty? [1]

A

taking the diseased joint out and putting in an artificial one

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10
Q

What is revision arthroplasty? [1]

A

re-operating on an artificial joint

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11
Q

Define arthrodesis [1]

A

fusing 2 bones together

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12
Q

Define arthrosis [1]

A

a joint

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13
Q

Define pseudo-arthrosis [1]

A

allowing 2 bones to articulate against one another but without a joint, e.g. Girdlestone

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14
Q

What are the risk factors for prosthetic joint infections associated with primary arthroplasty? [7]

A
  1. Rheumatoid arthritis
  2. Diabetes mellitus
  3. Poor nutritional status
  4. Obesity
  5. Concurrent UTI
  6. Steroids
  7. Malignancy
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15
Q

What are the risk factors for prosthetic joint infections associated with a revision arthroplasty? [3]

A
  1. Prior joint surgery
  2. Prolonged operating room time
  3. Pre-op infection (teeth, skin, UTI)
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16
Q

What are the microbial causes of prosthetic joint infections? [8]

A
  1. Staphylococcus aureus
  2. Coagulase-negative staphylococci (CoNS)
  3. Streptococcus
  4. Gram-negative bacilli
  5. Anaerobic organisms
  6. Enterococcus
  7. Culture negative
  8. Polymicrobial (mixed)
17
Q

Describe the pathogenesis of the development of prosthetic joint infections [3]

A
  1. Prosthesis requires fewer bacteria to establish sepsis than soft tissue
  2. Avascular surface allow survival of bacteria as protects from circulating immunological defences and most antibiotics
  3. Cement can inhibit phagocytosis and lymphocyte/complement function
18
Q

How can prosthetic joint infections spread and how long does it take for each type to present? [4]

A
  1. Local Spread
    • Usually manifests in immediate post-op period
      • Acute <4 weeks
      • Delayed/late >4 weeks (up to 50% PJIs present two or more years after surgery)
  2. Haematogenous spread
    • Presents later
19
Q

The virulence (ability to infect) of the organism will dictate its presentation. What do low virulence organsims result in and give examples? [2]

A
  1. Low virulence organisms result in low grade indolent infections which are tenacious
  2. e.g. coagulase negative staphylococci
20
Q

The virulence (ability to infect) of the organism will dictate its presentation. What do high virulence organsims result in and give examples? [4]

A
  1. Highly virulent organisms result in fulminant infection or septic shock
  • e.g.
    1. MSSA
    2. MRSA
    3. Group A or G Beta Haemolytic Streptococcus
21
Q

How does prosthetic joint infections typically present (signs & symptoms)? [7]

A
  1. Pain
  2. Effusion
  3. Warm joint
  4. Fever and systemic symptoms
  5. Loosening on X-ray
  6. Discharging sinus
  7. Mechanical dysfunction
22
Q

Describe the antibiotic prophylaxis used for prosthetic joint infections [2]

A
  1. Cephalosporin should be given 30-60mins before skin incision
  2. Evidence supports the use of cephalosporin (+ vancomycin or teicoplanin if MRSA colonised) in prevention of PJI
23
Q

State the 2 surgical options for treatment of prosthetic joint infections [2]

A
  1. DAIR (Debride, Antibiotics, Implant Retained) to Leave the Infected Joint In
  2. Take the Infected Joint Out
24
Q

Describe when DAIR is indicated and how the process works [3]

A
  1. If prosthesis infection is acute (<30 days since insertion), then it is still mechanically functional and can be kept in
  2. but infected tissues should be debrided and the joint washed out to reduce the burden of infection
  3. then IV antibiotics started for 4-6 weeks
25
Q

Describe when surgical removal of joint is indicated and how the process works [5]

A
  1. If the infection occurs over 30 days since surgery then it may no longer be fully functional and may need removed.
  2. Removal involves taking out the prosthesis and all cement (can’t heal if foreign body retained)
  3. Options:
    • Girdlestone procedure
    • One stage revision (put a new one in during the same operation as removing the infected one)
    • Two stage revision (delay putting in a new one until treated the existing infection for 4-6 weeks)
26
Q

Name the antibiotics that are able to penetrate bone [10]

A
  1. Cephalosporins
  2. Tazocin
  3. Carbapenems
  4. Fusidic acid
  5. Doxycycline
  6. Rifampicin
  7. Linezolid
  8. Trimethoprim
  9. Ciprofloxacin
  10. Clindamycin
27
Q

Define osteomyelitis [1]

A

progressive infection of bone characterised by death of bone and the formation of sequestra

28
Q

How can osteomyelitis spread? [2]

A
  1. Haematogenous spread
  2. Contiguous spread
    • Overlying infection (e.g. cellulitic ulcer)
    • Trauma (compound fracture)
    • Surgical inoculation
29
Q

Who most commonly gets affected by acute osteomyelitis? [1]

A

children

30
Q

What kinds of bacteria cause osteomyelitis? [2]

A

similar to septic arthritis but also include anaerobes

31
Q

How do you treat osteomyelitis? [3]

A
  1. surgery to debulk infection back to healthy bone and manage dead space that remains
    • (e.g. with muscle flaps)
  2. stabilise infected fractures (external fixation often used) and to debride sinuses and close wounds
  3. Antibiotic choice is determined by what grows from debrided bone
    • May require long term antibiotic treatment
    • 4- 6 weeks IV
32
Q

How is diabetic food infection more complex than septic arthritis? [1]

A

usually involves bone (osteomyelitis) but can also involve joints

33
Q

Define vertebral discitis [1]

A

Infection of a disc space and adjacent vertebral end plates

34
Q

What is a possible cause of vertebral discitis that mustn’t be forgotten? [1]

A

Tuberculosis (TB)

Week 7 - Clinical Microbiology & Infections 2 (16 decks)

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