Table 1.

Musculoskeletal Infection Society (MSIS) criteria for a definite diagnosis of PJI.

1. A sinus tract communicating with the prosthesis; or      2. A pathogen is isolated by culture from two separate tissue or fluid samples obtained from the affected prosthetic joint; or      3. Four of the following six criteria exist:                a. Elevated serum erythrocyte sedimentation rate (ESR) or serum C-reactive protein (CRP) concentration                b. Elevated synovial white blood cell (WBC) count                c. Elevated synovial neutrophil percentage (PMN%)                d. Presence of purulence in the affected joint                e. Isolation of a microorganism in one culture of periprosthetic tissue or fluid                f. Greater than five neutrophils per high-power field in five high-power fields observed from histologic analysis of periprosthetic tissue at 400 times magnification           However, it should be noted that PJI may be present even if fewer than four of these criteria are met.