Inclusion Criteria:  THA/TKA patients that underwent revision surgery regardless of final aseptic vs. infected diagnosis between 01.01.2013 until 31.12.2018  Exclusion Criteria:  less than two years follow up less than four intraoperative microbiology samples (synovial fluid, tissue samples, implant sonication) no preoperative/intraoperative synovial fluid differential leukocyte count