Table 3.

The European Bone and Joint Infection Society (EBJIS) definition for diagnosing periprosthetic joint infection (knee and hips).

Infection	Unlikely	Likely	Confirmed
Clinical/blood
Clinical features	Implant dysfunction due to alternative cause (fracture, implant breakage, malposition, tumor).	Loosening on radiological analysis (≤5 years after implantation). History of wound healing issues. Recent fever or bacteremia. Periprosthetic purulence.	Sinus tract communicating to the joint or when prosthesis can be visualized.
CRP		More than 10 mg/L
Synovial fluid
Leukocyte count (cells/μL)	≤1500	>1500	>3000
PMN%	≤65%	>65%	>80%
Alpha-defensin			Positive
Microbiology
Culture – aspirated fluid		Positive
Culture – intraoperative	Negative	One positive	≥Two positives (same organism)
Sonication (CFU/mL)	No growth	>1 CFU/mL (any organism)	>50 CFU/mL (any organism)
Histology – High-power field (400×)	Negative	≥5 neutrophils/HPF	≥5 in ≥HPFs
			Visible organisms
Nuclear imaging	Negative 3-phase isotope bone scan	Positive white blood cell scintigraphy

C-reactive protein (CRP); erythrocyte sedimentation rate (ESR); CFU: colony forming unit; polymorphonuclear neutrophils (PMN).