Sampling
STERILE
Synovial fluid and deep tissue were obtained at the time of surgery. Synovial fluid was collected in a sterile manner using an 18-gauge needle prior to arthrotomy, and samples were immediately divided into aerobic and anaerobic blood culture bottles (BACTEC 9240 system; BD Diagnostic Systems) for microbiology, a sterile container free of nucleases or other amplification inhibitors for mNGS, and an ethylenediaminetetraacetic acid (EDTA) vial for white blood cell count and differential. At least three different deep tissue samples were taken from periprosthetic tissue with the most obvious inflammatory changes and from medullary canals. Deep tissue samples were immediately divided into separate sterile vials for culture and histological analysis (more than 5 neutrophils per high-power field in 5 high-power fields observed was positive). All samples for microbiological testing were processed within 4 hours. All cases with at least 1 positive culture were considered positive.