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LOCO2 > Bone and joint infections > Flashcards

Bone and joint infections Flashcards

1
Q

Septic arthritis is commonly [mono-articular / poly-articular]

The most common joint affected by septic arthritis is which joint? [1]

A

Septic arthritis is commonly mono-articular

Knee most common

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2
Q

When does non-pyogenic (cold) septic arthritis occur? [1]

Which pathogen causes this? [1]

A

Chronic infection; TB infection

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3
Q

Name an organism that cause septic arthritis for each organism type of bacteria

Gram positive cocci [1]

Gram positive bacilli [1]

Gram negative cocci: [1]

Gram negative bacilli [1]

A

Gram positive cocci: staphylococcus aureus

Gram positive bacilli: clostridium sp

Gram negative cocci: Neisseria gonorrhoea

Gram negative bacilli: Escherichia coli, pseudomonas aeruginosa, haemophilus influenza

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4
Q

Which populations suffer from septic arthritis the most? [2]

Explain why [1]

A

Young
Majority older population; undergoing more therapy for alternative diseases (RA; OA)

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5
Q

Describe pathogenesis of septic arthritis in children [1]

Describe pathogenesis of septic arthritis in adults [4]]

A

Children:
* hematogenous spread: infection elsewhere in the body goes into joint

Adult:
* hematogenous spread most common
* local soft tissue infection
* penetrating trauma
* diagnoistic or therapeutic procedures

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6
Q

What is the most common cause of septic athritis? [1]

A

Staphylococcus aureus : 90% of all cases

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7
Q

Biggest cause of mortality in septic arthritis is

Staphylococcus aureus
Streptococci spp.
Clostridium sp
Neisseria gonorrhoea
Escherichia coli

A

Biggest cause of mortality in septic arthritis is

Staphylococcus aureus

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8
Q

Biggest cause of mortality in septic arthritis is

Staphylococcus aureus
Streptococci spp.
Clostridium sp
Neisseria gonorrhoea
Escherichia coli

A

Biggest cause of mortality in septic arthritis is

Staphylococcus aureus

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9
Q

Septic arthritis

Which pathogen has reduced impact due to vaccination schemes [2]

A

Haemophilus influenza (paediatric before immunization)
Streptococcus

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10
Q

What are the age related differences in causative organism of septic arthritis?

A
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11
Q

What is the difference between children and adults regarding which joints are affected by septic arthritis?

A

Children: more spread out
* Knee most common
* Hip common
* Ankle
* Elbow

Adults:
* Mostly knee joint
* Other joints also affected though

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12
Q

Septic arthritis

What investigations would you conduct to diagnose? [5]

A
  • Elevated ESR
  • Children: neutrophilia
  • Synovial fluid analysis: yellow & cloudy; lumpy & purelent
  • Gram stain positive: due to Staphylococcus aureus being the most common
  • Blood culture positive
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13
Q

How would a S. aureus infection appear in culture? [1]

A

Appears as grape like clusters, on trypticase soy agar plate produces yellow pigment: staphlyoxanthin

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14
Q

Describe how septic arthritis joint (synovial) fluid examination would present [4]

A

Turbid or purulent
Leukocytes >50,000/mm3, pred. neutrophils
Gram stain positive in one-third
< 25mg/dL glucose (much lower than serum)

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15
Q

How does mycobacterial infection cause radiological changes? [4]

A

Joint space narrowing
Effusion
Erosions
Cyst formation

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16
Q

Describe pathophysiology of reactive athritis [1]

What are the triad of symptoms? [3]

A

Post infection (e.g. STDs / salmonella) arthritis can occur couple of weeks later in one joint

Triad of symptoms: urethritis/cervicitis, conjunctivitis and arthritis

17
Q

In which joints is reactive arthritis most common in? [2]

How does it differ from septic arhritis? [1]

A

knees, ankles and feet

completely sterile: no bacteria or virus, and normally clears up in a couple days.

18
Q

Which type of MRI imaging would be best for septic arthritis? [1]

Why? [1]

A

MRI T2: fluid appears white - easier to see inflammation

19
Q

Describe radiological changes seen in septic athritis patients? [4]

A

May see soft tissue swelling
Joint capsule distension
Destructive changes seen after at least 2 weeks
* Erosion of articular surface
* Associated soft tissue swelling

20
Q

Where does TB primarily spread to? [1]

A

Most commonly goes to thoracic top lumbar regions

21
Q
A
22
Q

Describe how TB can spread from spine to elsewhere in the body [4]

A

Can spread into surrounding tissues like psoas major –> iliacus -> sacrioilac joint / & or hip joint –> femoral side of knee

23
Q

Why does acute blood born osteomyelitis affect children? [2]

A

Have a very rich blood supply to the bones, especially the metaphyseal ends of the long bones as this is where the growth plate is

The capillary loops near the metaphysis have slow flow/sluggish flow due to a rich blood supply here, meaning they are more at risk for bacterial invasion of the bone from the blood here

24
Q

Describe how osteomyelitis causes abscesses to grow

A
  • Bacteria enters the bone, it commonly lodges just below the epiphyseal growth plate
  • Bone produces new bone around the bacterial infection to try and wall off and contain the bacteria in one location, however it walls it off yet this cannot be accessed by antibiotics as it is walled off.
  • Can cause bone to die
25
Q

Common consequences of osetomeylitis? [2]
Rare consequences of osetomeylitis? [2]

A

Common:
* Local bone loss
* Persistent drainage through sinuses

Rare
* Squamous cell carcinoma
* Amyloidosis

26
Q

Risk factors for osteomyelitis? [6]

A

Age
Malnutrition
Impairment of local vascular blood supply:
* Diabetes mellitus
* Venous stasis
* Radiation fibrosis (radiation therapy damaging blood vessels)
* Sickle cell disease (due to crisis)

27
Q

Describe how you diagnose osteomyelitis [4]

How does it appear on ultrasound? [2]

A

(same as SA)
Local non-specific pain
Elevated neutrophil count (< 50% of cases)
Elevated ESR

Ultrasound:
* Cortical thinning
* Inflamation
* Periosteal lifiting: abscess lifting it off

28
Q

What is this sign of osteomyelitis called? [1]

A

Brodie’s abscess

Lytic lesion oval in shape, surrounded by thick dense reactive sclerosis that fades into surrounding bone.
Lucent tortuous channel extending from growth plate prior to physeal closure

29
Q

How do you treat chronic osteomyelitis? [5]

A

Puncture drainage if abscessed

Surgical debridement

Reconstruct bone (allograft/ autograft)

Antibiotics (4-6wks, at least 2 IV):
* Vancomyocin cement beads
* Flucoxallin (gram +ve)
* Clindamycin
* Piperacillin
* Ciprofloxacilin

30
Q

Describe this radiological sign of chronic osteomyelitis? [1]

A

Abscess

31
Q

How do you investigate for chronic osteomyelitis? [3]

A

MRI:
* Bone scintigraphy if MRI not available or suspicion of multifocal osteomyelitis - radiation that shows reactive bone

  • Bone biopsy
  • Blood samples
  • Radiography
32
Q

Describe treatment of chronic osteomyeltis [5]

A

Puncture drainage if abscess identified

Reconstruct bone (allograft or autograft)

Surgical debridement to remove dead bone

Antibiotics for 4-6 weeks (at least 2wks IV):
* vancomycin cement beads: dissolve and give steady supply of vancomycin

Bone graft (& muscle graft)

33
Q

Which antibiotics would you give for chronic osteomyelitis [1]

A

Vancomycin cement beads

34
Q

How does prosthetic bone and joint infection present? [2]

A

Hot, swollen, down the line of the knee replacement.

It is usually gradual onset with progressive joint pain and occasionally sinus development (in which pus can drain out via scars from surgery, etc).

The gradual onset is usually due to the antibiotic in bone cement can hinder growth but not completely destroy them

35
Q

Why does joint infection occur when giving prosthetic bone / joint replacements occur? [2]

Where does it occur? [2]

A

Occurs in osseous tissue adjacent to prosthesis:
* bone cement interface
* bone contiguous with prosthesis (cementless devices)

Results from:
* local inoculation at surgery or post-op spread from wound sepsis
* haematogenous spread

36
Q

Management of infections that have occurred from joint replacement infections? [2]

A

Removal of prosthesis, antibiotics for 6wks, re-implantation of new prosthesis 4 weeks after removal - 90%+ success

Long term suppressive antibiotics

37
Q

What is sequestrum in chronic osteomyelitis? [1]

What is Involucrum in chronic osteomyelitis? [1]

A

Sequestrum: fragment of necrosed bone that has become separated from surrounding tissue

Involucrum: covering or sheath that contains a sequestrum of bone

LOCO2 (58 decks)

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