Periprosthetic joint infection

Question 1

periprosthetic joint infection overview

Answer 1

Implanted material :
highly susceptible to local infection
exogenous or hematogenous insult
covered with host proteins
favors staphylococci adherence
- forms a biofilm

common organisms
- staphylococcus aureus and coagulase-negative
- staphylococci ( 50-70%)

streptococci ( 6-10%)

Gram negative bacilli ( 4-10%)

culibacterium acnes:
- causes 1/3 of PJ shoulder infection
associatited with chronic PJI

Question 2

PJI classifications

Answer 2

early < 3 months
delayed 3-24 months
late > 2 years after implant

Question 3

clinical findings PJI

Answer 3

Acute exogenous PJI
- local signs of infection

hematogenous PJI
S. aureus
new onset of pain
- no initial local-inflammatory signs
- sepsis syndrome dominates the clinical picture

Chronic PJI
joint effusion
local and chronic pain
implant loosening
sinus tract

Question 4

PJI diagnosis

Answer 4

labs;
CBC, CRP, and ESR

Arthrocentesis:
- synovial fluid analysis
- early onset of PJI
- > 10,000 cells

late onset:
> 3000 cells

obtain culture:
radiology:
X-ray
- identify effusion
- abnormal findings

CT and MRI
Sinus tract
detect soft tissue infection
prosthetic loosening
bone erosion
effusion

three phase bone scan:
highly sensitive non specpic

Question 5

Diagnosis of PJI criteria : 1 major criteria exist or 4 our of 6 minor criteria exist

Answer 5

major = 2 + periosthetic cultures w phenotypically identkical
sinus tract communication

minor= elevated ESR & CRP

Elevated synovial fluid WBC count or ++ change on leukocyte esterase test strip

elevated synovial fluid PMN

presence of purulence in the affected joint

positive histologic analysis of periprosthetic tissue

a single positive culture

Question 6

PJI therapy

Answer 6

pain-free functional joint
eradication of pathogen

Antibiotics regimen:
directed at common organisms
empiric therapy
- rifampin plus nafcillin plus vancomycin
- rifampin with biofilm activity

gram-negative infections
fluoroquinolones
- activity against biofilms

Surgical options:
debride the area and retain the implant
one-stage implant exchange
two-stage implant exchange
remove implant without replacement
need 3-6 samples for culture and histopathology