The purposes of this study were to (1) test the accuracy of α-defensin and combined α-defensin-aspiration cultures in diagnosing periprosthetic joint infection (PJI) before revision total knee and hip arthroplasty and (2) evaluate Musculoskeletal Infection Society (MSIS) criteria and α-defensin as predictors of successful reimplantation (second-stage) at 1 year after surgery.
We retrospectively evaluated a total of 97 synovial fluid aspirations performed between August 2014 and September 2016 before revision due to septic or aseptic failures (n = 70) or before second-stage (n = 27) joint arthroplasty. Revisions were categorized as either septic or aseptic according to the MSIS criteria. Synovial fluid was tested for α-defensin, cell count with differential, and cultures. Reimplantations were assessed for success or failure (defined as the need for reoperation due to infection) within 1 year after surgery.
For septic and aseptic revision arthroplasty, the sensitivity, specificity, positive predictive value, and negative predicted value of α-defensin was 97% while for the combined α-defensin and aspiration culture, it was 96%, 100%, 100%, and 97%. Despite being performed with negative MSIS criteria and α-defensin test results, 11% (3/27) of reimplantations (second-stage) failed within 1 year postoperatively because of infection.
Alpha-defensin is an accurate diagnostic test for the diagnosis of PJI before revision arthroplasty. The combination of α-defensin and aspiration cultures has higher specificity and positive predictive value. MSIS criteria and α-defensin may help predict the success of reimplantations within 1 year after surgery.