The incidence of periprosthetic joint infections (PJIs) is ~2% of total procedures and it is expected to rise due to an ageing population. Despite the large burden PJI has on both the individual and society, the immune response to the most commonly isolated pathogens, i.e., Staphylococcus aureus and Staphylococcus epidermidis, remains incompletely understood. In this work, we integrate the analysis of synovial fluids from patients undergoing hip and knee replacement surgery with in-vitro experimental data obtained using a newly developed platform, mimicking the environment of periprosthetic implants. We found that the presence of an implant, even in patients undergoing aseptic revisions, is sufficient to induce an immune response, which is significantly different between septic and aseptic revisions. This difference is confirmed by the presence of pro- and anti-inflammatory cytokines in synovial fluids. Moreover, we discovered that the immune response is also dependent on the type of bacteria and the topography of the implant surface. While S. epidermidis seems to be able to hide better from the attack of the immune system when cultured on rough surfaces (indicative of uncemented prostheses), S. aureus reacts differently depending on the contact surface it is exposed to. The experiments we performed in-vitro also showed a higher biofilm formation on rough surfaces compared to flat ones for both species, suggesting that the topography of the implant could influence both biofilm formation and the consequent immune response.

Background/Objectives: A missed periprosthetic joint infection (PJI) diagnosis can lead to implant failure. However, to date, no gold standard for PJI diagnosis exists, although several classification scores have been developed in the past years. The primary objective of the study was the evaluation of inter-rater reliability between five PJI classification systems when defining a patient who is infected. Two secondary outcomes were further examined: the inter-rater reliability assessed by comparing the classifications in pairs, and the evaluation of each classification system within the subcategories defined by the World Association against Infection in Orthopaedics and Trauma (WAIOT) definition. Methods: Retrospectively collected data on patients with knee and hip PJIs were used to assess the agreement among five PJI scoring systems: the Musculoskeletal Infection Society (MSIS) 2013 definition, the Infection Consensus Group (ICG) 2018 definition, the European Bones and Joints Infection Society (EBJIS) 2018 definition, the WAIOT definition, and the EBJIS 2021 definition. Results: In total, 203 patients with PJI were included in the study, and the agreement among the examined scores was 0.90 (Krippendorff’s alpha = 0.81; p-value < 0.001), with the MSIS 2013 and ICG 2018 classification systems showing the highest agreement (Cohen’s Kappa = 0.91; p-value < 0.001). Conclusions: There is a strong agreement between the major PJI classification systems. However, a subset of patients (n = 11, 5.42%) still falls into a diagnostic grey zone, especially in cases of low-grade infections. This highlights the need for enhanced diagnostic criteria that incorporate tools that are available even with limited resources, and the potential of artificial intelligence-based techniques in improving early detection and management of PJIs.

Periprosthetic joint infection (PJI) is a serious complication of prosthetic joint implantation, which poses a significant burden on both individuals and s

Purpose: Despite advances in surgical techniques and rehabilitation protocols, arthrofibrosis following total knee arthroplasty (TKA) still has poor outcomes. In the last decade, attention has been focused on the pathogenesis and cascade of events leading to the development of fibrosis. Currently, one of the most promising approaches consists in the indirect antagonisation of transforming growth factor beta 1 (TGF‐beta 1) through the downregulation of the renin–angiotensin–aldosterone system (RAAS). This systematic review aims to analyse the available evidence regarding the use of angiotensin receptor blockers (ARBs)/angiotensin‐converting‐enzyme inhibitors (ACEi) in order to prevent post‐operative knee arthrofibrosis following TKA.Methods: Extensive research on the PubMed, Cochrane, and Google Scholar databases was performed on 8 July 2024, using keywords related to ARBs, ACE inhibitors and arthrofibrosis. Inclusion criteria included: (1) clinical trials of any level of evidence; (2) written in English; (3) studies conducted on humans; and (4) evaluating the antifibrotic effects of ACE inhibitors or ARBs administered for TKA surgeries. Exclusion criteria were articles written in other languages; preclinical studies; expert opinions; reviews and trials evaluating the effects of ACEi/ARBs not related to their antifibrotic effect after TKA.Results: A total of six studies met the inclusion criteria and were analysed. All studies were retrospective and involved a total of 158,310 patients. Time of administration varied among the studies as well as the dosage, which fell within the range for cardiological use. Four out of six studies focused exclusively on losartan. Three studies reported a clear, significant correlation between the use of ARBs and/or ACEi and a reduced likelihood of developing arthrofibrosis.Conclusions: The RAAS antagonism could have potential for stiffness prevention after TKA. However, given the side effects and the limited evidence available, the use of ACEi/sartans for the sole purpose of avoiding arthrofibrosis after TKA is not currently recommended.Level of Evidence: Level III.

Introduction Periprosthetic joint infections (PJIs) complicate 1–2% of primary and up to 4% of revision arthroplasties, and their diagnosis remains challenging due to the lack of a diagnostic gold standard. Differentiating PJI from aseptic failure is particularly difficult in low-grade or biofilm-related infections. Routine intraoperative microbiological screening is not recommended in presumed aseptic revisions. This study aimed to evaluate the association between routine intraoperative microbiological screening and implant survival in presumed aseptic revision arthroplasty. A secondary objective was to identify preoperative predictors of unexpected PJIs. Methods Retrospectively collected data of patients undergoing presumed aseptic THA and TKA revisions between 2013 and 2019 were included. Two matched cohorts were compared: a screened group (2016–2019) undergoing routine intraoperative microbiological sampling, and an unscreened one (2013–2015) without systematic screening. Kaplan-Meier survival analysis with log-rank testing assessed overall and infection-free survival. Univariate conditional logistic regression and receiver operating characteristic (ROC) analyses evaluated potential associations between preoperative serum markers and unexpected PJI. Results A total of 559 patients were included, of whom 295 underwent screening and 264 did not. Unexpected infections occurred in 20.3% (n = 60) of screened patients. No significant differences in implant survival were observed between groups. Although overall and infection-free survival were numerically higher in the screened cohort, these differences were not statistically significant (p = 0.168 and p = 0.118, respectively). Stratified analyses by joint and failure mechanism showed comparable findings. C-reactive protein and erythrocyte sedimentation rate were associated with unexpected PJI (p = 0.004 and p = 0.046), but ROC analysis suggested limited discrimination of individual markers, whereas a combined serum model improved diagnostic performance (AUC = 0.833). Conclusions Routine intraoperative microbiological screening in presumed aseptic revision arthroplasty was not associated with a significant improvement in implant survival. Future studies should investigate whether selective screening improves outcomes. Level III retrospective cohort study.