PROSTHETIC JOINT INFECTIONS

Question 1

what percent of primary TKRs and THRs become infected?

• Knees
• hips
• shoulders

Answer 1

1.5-2.5%

Question 2

what percent of revision TKRs and THRs become infected?

Answer 2

3-5%

Question 3

risk factors for PJI?

Answer 3

immunosuppression:prednisone, TNF inhibitors

revision surgery

prior joint infection

American society of anesthesiologists

prolonged surgery

Question 4

most common organisms?

Answer 4

Coagulase-negative staphylococci (30-40%)

Staphylococcus aureus (both methicillin-resistant and
methicillin-susceptible) (12-20%)

Gram-negative bacilli (~ 5%)

Enterococci (~ 5-7%)

Anaerobes (~ 2-5%)

Question 5

major source of pathogenesis?

Answer 5

biofilm

Question 6

when are bacteria in biofilms more resistant to antibiotics?

Answer 6

bacteria growing in planktonic state

Question 7

affect of no local blood supply around the device?

Answer 7

local immune system limited

Question 8

amount of S. aureus needed to infect a foreign body is decreased by at least?

Answer 8

100,000x

Question 9

very tiny inocula of bacteria can cause?

Answer 9

infection

Question 10

early or late PJI?

< 3 mos

acute joint pain

+/- sinus tracts, often cellulitis

virulent org: staph aureus, gran negative bacilli, anaerobes

Answer 10

early

Question 11

early or late PJI?

> 24 mos

acute or subacute

mild mod joint pain

Hematogenous
Often from another
focus, e.g., UTIs,
pneumonia. S. aureus,
beta-hemolytic
streptococci, +/- GNB

Answer 11

late

Question 12

cultures of tissue around joint taken where?

Answer 12

in the OR, >90% sensitive

2 or more positive cultures essentially diagnostic