Prosthetic Joint Infection (PJI) Critera

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The 2013 ICM criteria for defining Periprosthetic joint infection (PJI) can be remembered using the mnemonic below:

Mnemonic: 1 tract or 2 bact. and 3 of ABCDEF

1 sinus tract communication with the joint OR

2 positive periprosthetic cultures with phenotypically identical bacteria


3 of the following six minor criteria:

a. Acute phase reactants: CRP >10 mg/L and ESR >30 mm/hr

b. Biopsy of periprosthetic tissue: >5 neutrophils/hpf in 5 high power fields

c. Culture positive: Single

d. Differential count in synovial fluid: >80% PMN

e. Esterase: Leukocyte esterase ++

(2011 MSIS criteria uses purulence in the affected joint as a minor criterion insted of leukocyte esterase and would require 4 out of six insted of 3 out of six minor criteria for diagnosis)

f. Full count in synovial fluid: >3000 WBC/microlitre

The 2018 PJI definition is based on scoring system and is diagnosed with score of 6 or more preoperatively or intraoperatively. The new 2018 definition of PJI is available here:

Reference: Guan, H., Fu, J., Li, X. et al. The 2018 new definition of periprosthetic joint infection improves the diagnostic efficiency in the Chinese population. J Orthop Surg Res 14, 151 (2019).

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