This Musculoskeletal Infection Society workgroup consensus document proposes a standardized definition for periprosthetic joint infection of the hip and knee. It addresses the prior lack of any single accepted set of diagnostic criteria. The goal was a definition usable in both clinical practice and research.
When you suspect PJI, work the definition in order. First check the two major criteria, a sinus tract or two positive cultures, because either one is diagnostic by itself and ends the workup. If neither is present, count the six minor criteria and look for at least four. This is the structure that nearly every subsequent arthroplasty infection paper now uses for inclusion.
Know the numbers cold: ESR >30, CRP >10, histology >5 PMN/HPF in 5 fields. These are common OITE stems. Remember the acute versus chronic split at 3 months. Synovial thresholds and treatment differ, with acute infection showing far higher cell counts (around 20,000 cells/uL and 89% PMN) and being candidates for debridement and implant retention.
The key pitfall: ESR and CRP stay elevated for 30 to 60 days after surgery, so do not over-read them in the early postoperative window, and treat a single low-virulence culture as likely contamination rather than proof of infection.
This Musculoskeletal Infection Society workgroup consensus document proposes a standardized definition for periprosthetic joint infection of the hip and knee. It addresses the prior lack of any single accepted set of diagnostic criteria. The goal was a definition usable in both clinical practice and research.
When you suspect PJI, work the definition in order. First check the two major criteria, a sinus tract or two positive cultures, because either one is diagnostic by itself and ends the workup. If neither is present, count the six minor criteria and look for at least four. This is the structure that nearly every subsequent arthroplasty infection paper now uses for inclusion.
Know the numbers cold: ESR >30, CRP >10, histology >5 PMN/HPF in 5 fields. These are common OITE stems. Remember the acute versus chronic split at 3 months. Synovial thresholds and treatment differ, with acute infection showing far higher cell counts (around 20,000 cells/uL and 89% PMN) and being candidates for debridement and implant retention.
The key pitfall: ESR and CRP stay elevated for 30 to 60 days after surgery, so do not over-read them in the early postoperative window, and treat a single low-virulence culture as likely contamination rather than proof of infection.