Background. Sinus tract appears up to 20% of patients with periprosthetic joint infection (PJI) after primary total joint arthroplasty (TJA). The adverse effect of different patient related risk factors is well known, but the role of the sinus tract in PJI recurrence wasn’t properly investigated. The purpose of the study was to analyze the influence of a sinus tract on the effectiveness of two-stage reimplantation in PJI. Material and Methods. In order to reduce the influence of known risk factors on effectiveness of infection eradication several including criteria were introduced: patients with PJI after primary total knee arthroplasty (TKA), without surgeries before TKA and after infection manifestation and without attempts of antibiotic suppression. Finally, 119 of 475 patients with PJI after primary TKA, treated with two-stage protocol, were retrospectively analyzed: 33 patients with presence of the sinus tract, 86 — without sinus tract. Pathogen type, comorbidities, PJI type, bone defects, duration of surgery, intraoperative blood loss and the effectiveness of twostage reimplantation were analyzed. Results. Pathogen structure in analyzed groups was comparable. Staphylococci were the leading cause of PJI in compared groups: 64.4% of patients without sinus tract and 59.1% of patients with sinus tract. Wherein S. aureus was more frequently isolated in case of active sinus tract while S. epidermidis played the leading role in compared group. Polymicrobial PJI was more likely to develop in patients with sinus tract (p = 0.09). Massive bone defects of femur and tibia (type 3 according AORI classification) were identified only in patients with sinus tract PJI, as well as significantly longer duration of the spacer implantation and higher intraoperative blood loss at this stage (p0.05). Infection eradication after spacer implantation stage was achieved in 98.8% (n = 79) of patients without sinus tract while only 81% (n = 17) of patients with sinus tract PJI successfully passed this stage of surgical treatment (p0.05), effectiveness of revision knee arthroplasty was 98.7% (n = 78) and 76.5% (n = 13) respectively (p0.05). Finally, complex effectiveness of twostage reimplantation in patients with sinus tract was significantly lower (61.9%) than in patients of compared group (97.5%), p0.05. Conclusion. Presence of the sinus tract in patients with PJI after primary TKA adversely effects on the effectiveness of two-stage reimplantation, this fact could be explained by aggressive development of infection, caused by more virulent pathogens and higher frequency of polymicrobial cases among this cohort of patients. The established patterns require further research to develop tactics for managing this category of patients in order to increase the effectiveness of two-stage reimplantation.

Abstract. Introduction The paper presents a comparative analysis of routine screening methods and the EBJIS 2021 algorithm in detection of latent periprosthetic joint infection in patients admitted for revision knee arthroplasty due to aseptic loosening and after spacer implantation. Materials and methods Group 1 included 49 patients who underwent revision knee arthroplasty due to aseptic loosening, group 2 were 47 patients with PJI after spacer implantation. Results and discussion There were no significant differences between patient groups in terms of age, gender, and preoperative ESR and CRP levels. In 62.2 % of all cases, the aspirate was inappropriate for cytological examination; this fact limited its diagnostic value. The most frequently intraoperatively isolated pathogen in both groups was coagulase-negative staphylococci. However, in 70 % of cases these results were not diagnostically significant, and infection was diagnosed only in 8.2 % of cases in group 1 and 12.8 % in group 2. Moreover, the chances of isolating the pathogen from tissue biopsies were 5.6 times higher than from intraoperative aspirate (OR = 5.6, 95 % CI = 1.2-26.4). In case of negative preoperative aspirate, in almost 25 % of cases, pathogens were isolated from intraoperative tissues, 40.9 % of them were diagnostically significant. The chances of its detection increased 4.7 times in combined increase in ESR and CRP blood level (OR = 4.686, 95 % CI = 0.765-28.700). Using EBJIS 2021 criteria, infection was confirmed in more than 10 % of cases in each group, and the diagnostic significance of the criteria exceeded the significance of using routine screening methods. At a follow-up period of more than 2 years, the effectiveness of treatment was 95.3 %, while signs of infection were detected in 4.7 % of cases, regardless of the group. Conclusion EBJIS 2021 criteria are characterized by high diagnostic sensitivity and specificity and enable to identify periprosthetic joint infection in knee revision cases even in its latent form and to correct treatment tactics in patients without a history of PJI.