The Musculoskeletal Infection Society defined a periprosthetic joint infection (PJI) based on a number of criteria.
Criteria for a definite diagnosis of PJI - one or or more of the following:
(1) presence of a sinus tract communicating with the prosthesis
(2) isolation of the same pathogen by culture from the affected joint from 2 or more separate tissue or fluid samples
(3) >= 4 of the following:
(3a) elevated erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) concentration
(3b) elevated synovial white blood cell count
(3c) elevated synovial polymorphonuclear (neutrophil) percentage (PMN %)
(3d) presence of purulence in the affected joint
(3e) isolation of a micro-organism in one culture of periprosthetic tissue or fluid
(3f) > 5 neutrophils per high-power field in 5 high- power fields observed from histologic analysis of periprosthetic tissue at × 400 magnification
where:
• An ESR > 30 mm/h and CRP > 10 mg/L may be used as cutoffs.
• The number and percent of neutrophils depend on a number of factors such as duration and the presence of an inflammatory arthropathy.
