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MD1 Locomotor > Bone and Joint Infections > Flashcards

Bone and Joint Infections Flashcards

1
Q

How can an asymptomatic bacteraemia happen?

A

Pull out tooth
Pass stool
Usually happens when you do nothing - immune system clears it

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2
Q

What is the most common source of bone and joint infection in children?

A

Haematogenous

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3
Q

What can cause bone and joint infections through direct inoculation?

A 
Trauma
- Fractures
- Puncture wounds
Surgery
- Pins
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4
Q

What can cause bone and joint infects through local invasion?

A

Pressure ulcer
Periodontal disease
Sinus disease

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5
Q

How does haematogenous osteomyelitis occur?

A

In metaphysis have looped capillaries and venous sinusoids
Blood goes very slowly through these
Bacteria seed metaphyseal-epiphyseal junction
Protected from immune response
Bacteria can establish and infect bone
Pressure from pus further limits blood supply
Established infection enlarges
Limited by growth plate
Infection therefore spreads into periosteum and supperiosteal space

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6
Q

Why is bacteria seeded in the metaphyseal-epiphyseal junction protected from the immune response?

A

Poorly developed reticular endothelium system
Poor penetration of WBCs
Diminished immune mediators

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7
Q

What happens once infection spreads into the periosteum and subperiosteal space?

A

Lifts periosteum

Invades shaft

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8
Q

What is the most likely source of osteomyelitis in adults?

A

Direct inoculation

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9
Q

What is the definition of an infant?

A

Less than 1 year old

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10
Q

Why are infants’ joints particularly at risk of infection?

A

Growth plate not as good a barrier between bone and joint
Vessels cross growth plate
Infection can easily spread from bone to joint

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11
Q

How can septic arthritis occur?

A 
Haematogenous contamination: blood > joint space
Direct contamination
- Trauma
- Surgery
Contiguous contamination from bone
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12
Q

What is the most common cause of bone and joint infections?

A

Staphylococcus aureus

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13
Q

What is the second most common cause of bone and joint infections?

A

Streptococcus pyogenes

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14
Q

To which bacteria are you more susceptible to after a chicken pox infection, in terms of bone and joint infections?

A

Streptococcus pyogenes

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15
Q

Which bacteria are newborns and infants susceptible to from the birth canal, which can cause bone and joint infections?

A 
Group B Streptococcus
Haemophilus influenzae type b
Other Gram negative bacteria
- Enterobacter
- Pseudomonas
- E coli
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16
Q

Which bacteria are people after surgery susceptible to, that can cause bone and joint infections?

A

Coagulase negative staphylococci

  • Often from skin
  • Eg: Staphylococcus epidermidis
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17
Q

Which bacteria are people susceptible to if they’re in developing countries, in terms of bone and joint infections?

A

Haemophilus influenzae type b

Mycobacterium tuberculosis

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18
Q

Which Gram negative bacteria are slightly more common causes of bone and joint infections in children?

A

Kingella kingae

Salmonella

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19
Q

Which bacteria can cause bone and joint infections via a sneaker penetration injury?

A

Pseudomonas

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20
Q

What host factors make you more susceptible to a bone and joint infection?

A 
Genetic
Young age
Recent respiratory infection
Neuroanatomical defects
Immunodeficiency
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21
Q

What proportion of people carry S aureus as part of their normal skin flora?

A

30%

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22
Q

What S aureus strain is most likely to cause bacteraemia?

A

Those colonised in their nasopharynx

23
Q

What proportion of bone and joint infections occur in those under the age of 5?

A

50%

24
Q

What is the ratio of bone and joint infections in boys:girls?

A

2:1

25
Q

What increases your risk of contracting a bone and joint infection?

A

Aboriginal and Maori
Sickle cell disease
Immunocompromise
Neonates

26
Q

What are the clinical features of bone and joint infections?

A 
Fever
Pain and localised tenderness
Joint/bone may feel warm
Erythema
Oedema
History of preceding trauma in 1/3 of cases
27
Q

What can cause delayed presentation of bone and joint infections?

A 
Subperiosteal collection
Signs include
- Local erythema
- Tenderness
- Swelling
28
Q

What are the most common bones in which infections occur?

A

Long bones

  • Humerus
  • Femur
  • Tibia
29
Q

Why are infections more common in tubular rather than flat bones?

A

Grow faster

30
Q

What are the most common bones in which infections occur in babies?

A

Humerus
Femur
Tibia
Hands and feet

31
Q

How can vertebral osteomyelitis present?

A

Delayed presentation
Occurs in older children
Dull, constant back pain for long time

32
Q

How does a delayed diagnosis of pelvic osteomyelitis present?

A

Vague pain in buttocks and groin

33
Q

Why are infections difficult to diagnose in neonates?

A

Hard to work out where they are

34
Q

What are the differential diagnoses for osteomyelitis?

A

Septic arthritis
- Often co-existent
Malignancy
Cellulitis

35
Q

What can indicate a malignancy rather than osteomyelitis?

A

FBE
X-ray
Absence of fever and inflammatory markers
Delayed response to drugs

36
Q

What do blood tests show in osteomyelitis?

A

White cell count can be normal > FBE and film essential

CRP/ESR increased >90%

37
Q

What is the CRP and ESR profile in osteomyelitis?

A

CRP rises rapidly over 1st 24 hours
If infection treated, decreases over 1-2 weeks
ESR goes up much slower over 48 hours
Comes down over prolonged period of weeks

38
Q

How are x-rays used in the diagnosis of bone and joint infections?

A

Only useful in osteomyelitis
Often normal
May see swelling in 1st few days
Sometimes done in children to exclude non-accidental injury

39
Q

How are bone scans used in the diagnosis of bone and joint infections?

A

Increased uptake of isotope in area of infection

Highly sensitive and specific

40
Q

What cultures are done in bone and joint infections?

A

Blood
- Often bacteraemia cleared but bone and joint infection established
Bone
Pus aspirated from bone

41
Q

When is a biopsy done in bone and joint infections?

A 
Delayed presentation
Predisposing condition
Unusual radiographic findings
High likelihood of MRSA
Suspected complication; eg: abscess
Suspected alternative diagnosis; eg: malignancy
Delayed response to antibiotics
42
Q

When is flucloxacillin used to treat bone and joint infections?

A

Majority of S aureus susceptible to it

Kills all Gram positive causes

43
Q

How is flucloxacillin administered?

A

High doses

IV

44
Q

Which antibiotic is more commonly used in adults instead of flucloxacillin, and why?

A

Dicloxacillin, because less likely to cause liver toxicity

45
Q

What are the treatment options if MRSA is present?

A

Vancomycin

Combination of rifampicin and fusidic acid

46
Q

What is the treatment if

  • Neonatal?
  • Gram negative bacteria
  • Unimmunised for H influenzae?
A

Flucloxacillin and cefotaxime

47
Q

What antibiotic is added to create synergy for difficult cases of bone and joint infections?

A

Fusidic acid

Rifampicin

48
Q

What antibiotics are used to treat Pseudomonas bone and joint infections?

A

Timentin and gentamicin

49
Q

For how long are bone and joint infections treated for?

A

3-5 days IV

Complete 3 week course with oral high dose antibiotics

50
Q

What route of administration is used in neonatal cases of bone and joint infections?

A

IV for full duration

51
Q

When might longer treatment for bone and joint infections be needed?

A

Unusual sites

52
Q

What is chronic osteomyelitis often associated with?

A

Suboptimal initial treatment

53
Q

What are the treatment options for chronic osteomyelitis?

A

Surgical debridement and long-term antibiotics

  • IV 2 weeks
  • Oral 3-6 months or more

MD1 Locomotor (17 decks)

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