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Block G -- Infection > Dr. Loo -- Bone and Joint Infections > Flashcards

Dr. Loo -- Bone and Joint Infections Flashcards

1
Q

Describe the Lew and Waldwogel classification for osteomyelitis

A
  • Acute vs. chronic
    • Acute <2 weeks
    • Subacute 2 weeks - 3 months
    • Chronic > 3 months
  • Mechanism of infection
    • Hematogenous
    • Contiguous
  • Presence of vascular insufficiency
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2
Q

3 pathophysiologies of osteomyelitis

A
  • Hematogenous
  • Contiguous spread
  • Direct inoculation of infection to bone from trauma or surgery
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3
Q

3 risk factors for hematogenous osteomyelitis in children

A
  • Immunodeficiency – chronic granulomatous disorders
  • Bacteremia
  • Sickle cell disease
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4
Q

Most common site of hematogenous osteomyelitis in children

A

Long bones = metaphysis

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5
Q

Most common locations of hematogenous osteomyelitis in adults

A

Vertebrae – neighboring endplates involved

  1. Lumbar
  2. Thoracic
  3. Cervical
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6
Q

Why are neighboring endplates of vertebrae in adults commonly affected by hematogenous osteomyelitis?

A

They have an artery bifurcating to supply the endplates

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7
Q

Most common pathogen in children and adults for hematogenous osteomyelitis

A

*S. aureus *(50 - 60%)

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8
Q

Virulence factors of *S. aureus *explaining why it is a common pathogen in hematogenous osteomyelitis

A

Adhere to bone via adhesins

Can survive within osteoblasts

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9
Q

3 pathogens causing hematogenous osteomyelitis in children (besides S. aureus)

A
  • Streptococcus pneumoniae
  • *Streptococcus pyogenes *(GAS)
  • *Kingella kingae *(<4 years old)
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10
Q

2 pathogens for hematogenous osteomyelitis in neonates

A
  • *Streptococcus agalactiae *(GBS)
  • E. coli
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11
Q

Pathogen for hematogenous osteomyelitis in the setting of sickle cell anemia

A

Salmonella

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12
Q

Define the pathophysiology of contiguous osteomyelitis

A

Infection of bone usually from a skin and soft tissue infection that extends into the adjacent bone (i.e. diabetic patients with longstanding cutaneous ulcers)

Can also occur with prosthetic hardware

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13
Q

5 pathogens involved in contiguous osteomyelitis

A

Polymicrobial

  • Staphylococcus aureus
  • *Streptococcus *(B-hemolytic)
  • Enterococcus
  • Aerobic gram negative bacilli – Enterobacteriaceae
  • Anaerobes
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14
Q

4 contributing factors to diabetic foot ulcers causing contiguous osteomyelitis

A
  • Neuropathy
  • Vascular insufficiency
  • Hyperglycemia
  • Poor vision

NOTE: Ulcers larger than 2 x 2 cm usually associated with underlying osteomyelitis

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15
Q

8 clinical manifestations of osteomyelitis

A
  • Pain at involved site, with or without movement
  • Warmth
  • Erythema
  • Swelling
  • Fever (20 - 50%)
  • Long bone = may spread to involve joint
  • Vertebral = may have associated epidural abscess
  • Presence of sinus tract = suggestive of chronic osteomyelitis
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16
Q

5 things to check on examination of patient with suspected osteomyelitis

A
  • Vital signs (temp, fever)
  • Anatomic area of pain
  • Signs of inflammation
  • Wounds as portal of entry
  • Signs of endocarditis (i.e. heart murmur, emboli)
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17
Q

Initial assessment of diabetic patients with foot ulcers

A

Probe to bone

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18
Q

4 diagnostic tests for osteomyelitis and their usual results

A
  • CBC (increased)
  • CRP (increased in 80%)
  • Blood cultures (50% + in hematogenous)
  • Bone biopsy (+ in up to 87% and also send for pathology)

NOTE: Swabs of skin ulcers should not be used (correlatoin with bone biopsy results is poor)

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19
Q

How long does it take to see changes due to osteomyelitis on plain X-ray

A

2 - 4 weeks

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20
Q

For what kind of osteomyelitis is plain X-ray useful?

A

Chronic

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21
Q

5 findings on X-ray for chronic osteomyelitis

A
  • Cortical erosion
  • Periosteal reaction
  • Mixed lucency
  • Sclerosis
  • Sequestra

NOTE: May be difficult to distinguish from Charcot arthropathy

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22
Q

Pros and cons of using nuclear scans to diagnose osteomyelitis

A
  • Pro = sensitive
  • Cons = can be nonspecific; degenerative disease can give false +
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23
Q

Imaging of choice for osteomyelitis diagnosis and why

A

MRI because of excellent resolution and early signs present:

  • Diabetic patients with possible osteomyelitis of foot
  • Vertebral osteomyelitis
  • High NPV
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24
Q

When is CT scan performed in diagnosis of osteomyelitis

A

If MRI cannot be obtained

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25
Q

One area of body where CT scan is especially good for diagnosis of osteomyelitis

A

Pelvic area

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26
Q

6 things that CT scan can detect in the diagnosis of osteomyelitis

A
  • Cortical integrity
  • Periosteal reaction
  • Intraosseous gas
  • Sinus tracts
  • Associated abscesses
  • Sequestra
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27
Q

3 points of management in terms of surgery to treat osteomyelitis

A
  • Debridement should be considered for chronic to remove devitalized bone
  • Revascularization may be necessary
  • Surgery usually not required for children unless abscess or devitalized bone
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28
Q

First choice antibiotics to treat against MSSA in osteomyelitis

A
  • Cloxacillin
  • Cefazolin
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29
Q

Second choice antibiotic to treat against MSSA in osteomyelitis

A

Vancomycin

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30
Q

First choice antibiotics to treat against MRSA in osteomyelitis

A
  • Vancomycin
  • Daptomycin
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31
Q

Second choice antibiotic to treat against MSSA in osteomyelitis

A

Linezolid with rifampin

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32
Q

First choice antibiotics to treat against penicillin susceptible Streptoccocus in osteomyelitis

A
  • Penicillin
  • Ceftriaxone
  • Cefazolin
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33
Q

Second choice antibiotic to treat against penicillin susceptible streptococcus in osteomyelitis

A

Vancomycin

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34
Q

First choice antibiotic to treat against Enterococcus in osteomyelitis

A

Ampicillin +/- aminoglycoside

35
Q

Second choice antibiotic to treat against enterococcus in osteomyelitis

A

Vancomycin +/- aminoglycoside

36
Q

First choice antibiotic to treat against enterobacteriaceae in osteomyelitis

A

Ceftriaxone

37
Q

Second choice antibiotic to treat against enterobacteriaceae in osteomyelitis

A

Ciprofloxacin (not if <15 years old)

38
Q

First choice antibiotic to treat against polymicrobial osteomyelitis

A
  • Ertapenem
  • Pip/tazo
39
Q

Antibiotic duration against osteomyelitis in children

A

7 - 10 days of IV and then step down to oral if:

  • Afebrile
  • Clinically improving
  • CRP decreased by at least 50%
  • Duration usually 4 weeks but longer may be required in some patients
40
Q

Antibiotic duration against osteomyelitis in adults

A

6 weeks IV

41
Q

Antibiotic duration for chronic osteomyelitis

A

Usually requires months of therapy guided by clinical response and imaging

42
Q

3 laboratory parameters to asses during and post treatment of osteomyelitis

A
  • WBC (usually normalizes within 7 days of therapy)
  • CRP (better than ESR) = more indivative of response to therapy
  • Note side effects of medications

NOTE: Repeat imaging generally not required

43
Q

2 methods of acquisition of joint infection

A

Hematogenous

Contiguous

44
Q

4 ways contiguous joint infection can be acquired

A
  • Surgery
  • Trauma
  • Percutaneous puncture
  • Infected skin or bone
45
Q

4 risk factors for native joint infection

A
  • Pre-existing joint architecture
  • Age > 80 years
  • Diabetes
  • Rheumatoid arthritis
46
Q

Most common pathogen of native joint infection

A

S. aureus

47
Q

VIrulence factor of *S. aureus *explaining why it is a pathogen in native joint infection

A

Bacterial adherence

48
Q

VIrulence factors of N. gonorrhoeae explaining why it is a pathogen in native joint infection

A
  • Pili adherence
  • Inhibition of host phagocytosis
49
Q

Describe the pathophysiology of native joint infection

A
  1. Trauma or injury
  2. Increased amount or exposure of host proteins that promote bacterial attachment
  3. Host inflammatory response to bacteria results in joint damage
50
Q

9 clinical features of non-gonococcal native joint infection

A
  • Monoarticular in 80 - 90%
  • Knee involved in 50%
  • Small joints usually not involved unless contiguous spread
  • Pain
  • Redness
  • Swelling
  • Increased warmth
  • Decreased function
  • Fever in 50%
51
Q

3 clinical features of gonococcal native joint infection

A
  • Occult bacteremia
  • Complicates 0.5 - 5% of mucosal gonococcal infections
  • Monoarthritis in 40 - 85% in disseminated gonogoccal infection (DGI)
52
Q

3 clinical features of DGI

A
  • Dermatitis (60%)
  • Tenosynovitis
  • Migratory polyarthralgia or polyarthritis
53
Q

8 lab parameters of native joint infection

A
  • ↑ Blood WBC
  • ↑ C-reactive protein
  • Fluid analysis
    • WBC > 25,000/mm3
    • Low glucose
    • Nongonococcal
      • Gram stain positive 50%
      • Culture positive in 80-90%
    • Gonococcal
      • Gram stain positive in 25%
      • Culture positive in 20-30% DGI and 50% septic monoarthritis
54
Q

2 body locations where recovery of gonococcal culture for native joint infection is highest

A

Cervix and urethra

55
Q

4 findings on plain X-ray for native joint infection

A
  • Soft tissue swelling
  • Joint space loss
  • Periosteal rection
  • Subchondral bone destruction
56
Q

2 uses for ultrasound in diagnosis of native joint infection

A

Effusion confirmation and aspiration

57
Q

3 uses for CT scan in diagnosis of native joint infection

A
  • Erosive bone changes
  • Joint effusions
  • Good for deep articulations
58
Q

5 imaging techniques for diagnosis of native joint infection

A
  • Plain X-ray
  • Ultrasound
  • CT scan
  • MRI (Sensitive)
  • Bone and gallium scans
59
Q

Empiric treatment for native joint infection with a gram positive cocci stain

A

Vancomycin

60
Q

Empiric treatment for native joint infection with a gram negative cocci stain

A

Ceftriaxone

61
Q

4 Empiric treatments for native joint infection with a gram negative rods stain

A
  • Ceftriazone
  • Ceftazidime
  • Pip/tazo
  • Carbapenem
62
Q

2 empiric treatments for native joint infection with a gram negative stain

A
  • Vancomycin + Ceftriaxone
  • Vancomycin + Ciprofloxacin (not in kids)
63
Q

Duration of empiric treatment for native joint infection

A

4 - 6 weeks

64
Q

Surgical treatment for native joint infection

A

Drainage via

  • Daily closed needle aspiration
  • Arhtroscopy-irrigation of joint, lysis of adhesions and removal of purulent material
65
Q

3 lab parameters to look out for with monitoring during and post treatment in native joint infection (and their usual results)

A
  • WBC (usually normalizes within 7 days of therapy)
  • CRP = more indicative of response to therapy
  • Side effects of meds:
    • Exam CBC
    • Renal function
    • LFTs

NOTE: Repeat imaging generally not required

66
Q

7 risk factors for prosthetic joint infection

A
  • Prior surgery at the same site
  • Rheumatoid arthritis
  • Immunocompromised
  • Diabetes
  • Age
  • Prolonged operation > 2.5 hours
  • Delayed wound healing
67
Q

How is hematogenous prosthetic joint infection acquired?

A

Secondary infection

68
Q

How is contiguous prosthetic joint infection acqured

A

Wound infection

Impaired wound healing

69
Q

2 pathogens commonly associated with prosthetic joint infection

A
  • S. aureus
  • Coagulase negative Staphylococcus
70
Q

Pathophysiology of prosthetic joint infection

A
  1. Traum or injury
  2. Increased amount or exposure of host derived proteins that promote bacterial attachment
  3. Foreign Body and cement permit bacteria to persist on avascular surfaces
71
Q

4 clinical features of prosthetic joint infection

A
  • Joint pain
  • Fever
  • Periarticular swelling
  • Cutaneous sinus drainage
72
Q

3 diagnostic tests for prosthetic joint infection

A
  • ↑ Blood WBC
  • ↑ C-reactive protein
    • ​Sensitivity 70-90%
    • Specificity 80-85%
  • ​Fluid analysis
    • ​WBC > 1500/mm3 with neutrophil predominance
    • Gram stain and culture-sensitivity 50-75%

NOTE: May need 5-6 tissue specimens taken at OR

73
Q

Number of positive specimens to indicate prosthetic joint infection

A

3

74
Q

5 findings on plain X-ray for prosthetic joint infection

A
  • Lucencies
  • Migration of prosthesis
  • Cement fractures
  • Periosteal reaction
  • Motion of components on stress view
75
Q

Procedure with highest success rate for treating prosthetic joint infection and describe the procedure

A

2-step procedure (95% success)

  1. Removal of prosthesis
  2. Administration of antibiotics for 6 weeks
  3. Re-implantation of new prosthesis
76
Q

2 alternative treatments to the 2-step treatment for prosthetic jiont infection

A
  • Antibiotic impregnated cement
  • Debridement with retention of prosthesis + 3 - 6 months of antibiotics
77
Q

Duration of antibiotic treatment for prosthetic joint infection

A

6 weeks IV followed by oral

78
Q

When may rifampin be added to the regimen of treatment for prosthetic joint infection

A

If staphylococcus isolated to help with biofilm penetration

79
Q

Treatment for those with prosthetic joint infection who cannot have surgery

A

Lifelong suppressive therapy

80
Q

First choice antibiotic against Staphylococcus coagulase **negative

A
  • Depends on sensitivities
  • Check if oxacillin susceptible
  • Vancomycin
81
Q

Second choice antibiotic against Staphylococcus coagulase negative

A

Daptomycin

82
Q

3 preventive measures against prosthetic joint infection

A
  • Before surgery, evaluate for dental problems
  • Antibiotic prophylaxis – standard
  • OR rooms – laminar airflow HEPA filtered
83
Q

2 situations where antibiotic prophylaxis against prosthetic joint infection in dental and urological procedures may be routine

A
  • Previous prosthetic infections
  • Immunosuppression
84
Q
A

Block G -- Infection (23 decks)

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