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Flashcards in Bone and joint infections Deck (23):
1

Describe the classification of osteomyeltitis?

Haematogenous: could have come from anywhere in body and entered blood > bone

Non haematogenous - direct inoculation: bacteria from outside world get direct entry (trauma, surgery)

Non haematogenous - local invasion: e.g. pressure ulcer

2

From where in the blood do bacteria usually enter the bone?

Looped capillaries and venous sinusoids

Slow flow through here > lodge 

3

Describe the pathogenesis of osteomyelitis?

1) Slow flow through looped capillaries and venous sinusoids 

2) Bacteria seed metaphyseal-epiphyseal junction

3) Abscess forms > protected from immune response

4) pressure from pus further limits blood supply

5) Infection spreads to subperiosteal space > lifts periosteum, invades shaft

4

How can infection invade the epiphysis and joint in children?

Vessels that cross growth plate are still present in children, not in adults 

5

Describe the situations in which septic arthritis may develop?

Direct contamination (surgery, trauma)

Haematogenous contamination

Contiguous contamination (bone > joint) in children 

6

How are the pathogenic agents of osteomyelitis categorised?

Gram positive

Gram negative

Other (TB, fungi, parasites)

7

What are the most common Gram positive agents of osteomyelitis?

Staph aureus

Strep pyogenes/Group A strep

(Strep pneumoniae, Group B strep, coagulase negative staph)

8

What are the most common Gram negative agents of osteomyelitis?

Kingella kingae

Salmonella

(Haemophilus influenzae type B)

9

What is the single most common agent of bone and joint infection?

Why?

Staph aureus

Possesses virulence factors 

Colonises our skin commonly 

10

What are the most common agents of bone and joint infection after surgery?

Gram negative staph

11

What are the most common agents of bone and joint infection in newborns/infants?

Group B strep

Hib

Other Gram negative organisms (Enterobacter, Pseudomonas, E.coli)

12

What are the most common agents of bone and joint infection in people with chicken pox?

Strep pyogenes/Group A strep

13

What are the most common agents of bone and joint infection in sneaker penetration injuries?

Pseudomonas

14

What are the most common agents of bone and joint infection in developing countries?

Hib

TB

15

Which populations are most at risk of developing osteomyelitis?

Under 5 yo (50% of infections)

Boys (2:1)

Aboriginal and Maori children

Sickle cell disease

Immunocompromised 

Neonates 

 

16

Describe the clinical features of bone and joint infection?

Pain

Pseudoparalysis

Fever

Malaise

Tenderness

Swelling 

Heat

17

In which bones does osteomyelitis most commonly occur?

Long bones

Femur > tibia > humerus 

18

What are the important differential diagnoses for osteomyelitis?

Septic arthritis (often coexistent in children)

Malignancy

Cellulitis 

19

Describe the diagnosis of osteomyelitis?

Clinical signs 

X-ray, bone scan or MRI evidence

Positive blood or bone culture

Pus aspirated from bone

 

20

Describe the CRP and ESR levels in osteomyelitis?

Elevated >90%

CRP rises very quickly in first 24 hours 

ESR rises and falls more slowly

21

Describe the use of imaging to diagnose osteomyelitis?

PLAIN FILM

Not very good early on

Helpful for excluding fractures and malignancy

After 3 days, may see some swelling

After 2 weeks, will see periosteal lift 

BONE SCAN

More sensitive and accurate early on 

MRI

Very accurate, very high sensitivity

22

Describe the treatment of osteomyelitis?

Flucloxacillin: for all Gram positive causes except coagulase negative staph

If neonatal (Gram negatives) or unimmunised (Hib): flucloxacillin and cefotaxime 

Difficult cases: rifampicin 

 

3-5 days IV treatment, followed by 3 weeks oral treatment for uncomplicated patient 

23

In which situtation does osteomyelitis develop?

Suboptimal treatment of initial osteomyelitis