TAPPING OUR RESOURCES: DO PREOPERATIVE ASPIRATIONS ADD DIAGNOSTIC VALUE?

Aim Discrepancies between preoperative synovial aspiration and intraoperative cultures may occur, even in the absence of antibiotic therapy. This study evaluated the concordance between preoperative synovial aspiration and intraoperative culture results in patients undergoing surgery for hip and knee prosthetic joint infection (PJI). Methods Retrospective review of patients >18 years diagnosed with their first episode of hip or knee PJI between September 2017 and December 2020 who underwent surgical management. Demographics, microbiology (synovial aspiration and intraoperative cultures), and use of antibiotics relative to preoperative arthrocentesis and surgery were assessed. Concordance was defined as either matching organisms or negative results in both settings. Results Among 75 patients (mean age 70.0 +/- 13.3 years, 50.7% male, 71% white/Caucasian and 95% non-Hispanic), 54 (72%) had concordant results and 21 patients (28%) were discordant. Among the concordant group, 45/54 (83%) had identical organisms isolated, most commonly methicillin-sensitive Staphylococcus aureus (MSSA). Nine (17%) had negative cultures in both settings. Only 2/9 (22%) received antibiotics before preoperative synovial aspiration, and 4/9 (44%) received preoperative antibiotics. Among discordant patients, 14/21 (67%) had positive preoperative synovial aspiration culture. 11/14 (78%) with a positive preoperative synovial had negative intraoperative culture and 9/11 (82%) had received preoperative antibiotics. 3/14 (22%) had differing organisms across samples. 7/21 (33%) had negative preoperative synovial aspiration culture and positive intraoperative cultures; none received antibiotics prior to preoperative synovial aspiration. (Table 1) Conclusions Almost 75% of patients had concordance between synovial preoperative aspiration and intraoperative culture. Negative preoperative cultures do not exclude infection and isolation of a pathogen does not preclude polymicrobial infection. Our results support the recommendation to obtain multiple intraoperative specimens at the time of surgery. For any figures or tables, please contact the authors directly.