Aim. Accurate diagnosis is key in correctly managing prosthetic joint infection(PJI). Shoulder PJI definition and diagnosis is challenging. Current PJI definitions, based overwhelmingly in hip/knee research, may not accurately diagnose shoulder PJI. Our aim is to compare the preoperative performance of two PJI definitions comparing it to definitive postoperative classification. Method. This is a retrospective study of patients who have undergone total shoulder revision surgery for infection between 2005 and 2022. Cases were classified using two different PJI definitions: a)the European Bone and Joint Infection Society (EBJIS) and; 2)the 2018 International Consensus Meeting(ICM) PJI specific shoulder definition. Preoperative classification was based on clinical features, inflammatory markers and synovial fluid leukocyte count and definitive classification also considered microbiology and histology results. Results. Preoperative and definitive PJI classification status of the 21 patients included were evaluated and is summarized in table 1. The shoulder specific 2018 ICM definition showed the highest agreement between preoperative and definitive classification (76.2%, k=0.153, p=0.006) compared to EBJIS (52.4%, k=0.205, p=0.006). In all cases, the classification was changed because of positive intraoperative microbiology (at least two identical isolates). Microbiology findings showed coagulase negative staphylococci, Staphyloccocus aureus and Cutibacterium acnes to be the most frequent. Four patients had polymicrobial infections. Conclusions. Both the EBJIS 2021 and 2018 ICM definitions have low accuracy in predicting shoulder PJI preoperatively. Clearly further studies with larger cohorts are in dire need focusing specifically on shoulder revision arthroplasty to improve on existing definitions. Caution is advised while extrapolating of criteria/thresholds recommended for hip/knee joints. For any tables or figures, please contact the authors directly

Aim. Our goal is to assess diagnostic accuracy of synovial fluid testing in diagnosing prosthetic joint infection (PJI) as defined by the European Bone and Joint Infection Society (EBJIS). In addition to differential leukocyte count, simples and inexpensive biomarkers such as synovial fluid C-reactive protein (CRP), adenosine deaminase (ADA) and alpha-2-macrogloblulin(A2M) were also investigated and its possible role in increasing accuracy assessed. Method. Between January/2013 and December/2019 total hip or knee arthroplasty revision cases (regardless of preoperative diagnosis) were prospectively included provided enough synovial fluid for biomarker analysis was collected and at least four tissue samples, as well as the implant for sonication, were gathered for microbiological study. Definitive diagnosis was classified according to the new EBJIS PJI definition. Using receiver operating characteristic curves, we determined cutoff values as well as diagnostic accuracy for each marker. Results. Out of 364 revision arthroplasties performed, 102 fully respected inclusion criteria. There were 58 unlikely, 8 likely and 36 confirmed infections. Synovial fluid total leukocyte count, proportion of polymorphonuclear neutrophils (PMN), CRP, ADA and A2M were significantly different between groups. Area under the curve was 0.94 for total leucocyte count, 0.91 for proportion of PMN, 0.90 for CRP, 0.82 for ADA and 0.76 for A2M. Sensitivity, specificity, and predictive values for statistically optimal but also selected rule-in and rule-out cutoffs values are shown in Table 1. Interpreting a raised level of CRP(>2.7mg/L) or ADA(>60U/L) together with high leukocyte count (>1470 cells/μL) or proportion of PMN (>62.5%) significantly increases specificity and positive predictive value for affirming PJI. Conclusions. Differential leukocyte count cutoffs proposed by the EBJIS PJI definition are shown to perform well in ruling out (<1,500 cells/μL) and ruling in (>3,000 cells/μL) PJI. Adding simple and inexpensive biomarkers such synovial CRP or ADA is helpful in interpreting inconclusive results. For any tables or figures, please contact the authors directly

Aim

The aim of this systematic review was to assess the existing published data on tuberculous arthritis involving native joints in adults aged 18 years and older. The specific research questions focused on the diagnosis and management of the disease.

Aim. Periprosthetic joint infection (PJI) is one of the main reasons for revision surgery after primary unicompartmental knee arthroplasty (UKA), total knee arthroplasty (TKA) or total hip arthroplasty (THA). Currently the MSIS and EBJIS criteria sets are considered to be the gold standards in determining PJI. These criteria sets are complex and contain tests that are time-consuming and many are rather costly. Therefore, further research is indicated to find a simpler but equally reliable diagnostic test. In this study we evaluated the additional value of calprotectine measurement in synovial fluid in patients undergoing hip and knee (revision) arthroplasty following routine work-up. Method. In a retrospective cohort study, we analyzed 182 synovial fluid samples from 143 patients with suspected PJI after UKA, TKA, THA or revision arthroplasty. Twenty-six of those cases were classified as PJI according to the MSIS and EBJIS criteria. Subsequently, synovial calprotectin was determined, using a lateral flow assay and two cut-off thresholds of ≥14 mg/L and ≥50 mg/L. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of synovial calprotectin was determined. Results. When applying the MSIS and EBJIS criteria and a calprotectin level ≥14 mg/L, synovial calprotectin revealed an area under the curve of 0.96 (95% CI 0.90-1.00), with 92.3% sensitivity and 100% specificity. The PPV and NPV were 100% and 92.9% respectively. When applying the MSIS and EBJIS criteria and a calprotectin level ≥ 50 mg/L, synovial calprotectin revealed an area under the curve of 0.94 (95% CI 0.87-1.00), with 88.5% sensitivity and 100% specificity. The PPV and NPV were 100% and 89.7% respectively. Conclusions. The value of calprotectin in synovial fluid gives valuable information with a single test result, resulting in high predictive value in the diagnosis of PJI after hip or knee arthroplasty and should seriously be considered as part of PJI diagnostics in an outpatient clinical setting. The high specificity can help rule in patients that are suspected of PJI. Therefor this test can be helpful in a preop diagnostic work-up to avoid unnecessary revisions in patients with well-placed and well-fixed arthroplasties with a suspected PJI. These conclusions are independent of which criteria set was used as a gold standard

Aim. There have been many attempts to define the criteria by which prosthetic joint infection (PJI) is diagnosed. Our aim is to validate the 2021 European Bone and Joint Infection Society (EBJIS) definition of PJI. Method. This is a multicenter retrospective study of patients who have undergone total hip or knee revision surgery in four different European institutions between 2013–2018. Cases with less than four intraoperative microbiology samples; no preoperative/intraoperative synovial fluid differential leukocyte count or intraoperative histology were excluded. Minimum follow-up of at least two years after revision surgery if no subsequent infection and/or the need for implant removal was also required. All cases were classified using the 2021 EBJIS, the 2018 International Consensus Meeting (ICM) and the 2013 Musculoskeletal Infection Society (MSIS) PJI definitions. Results. Definitive PJI classification according to the different definitions of the 507 patients included are presented in table 1. The EBJIS definition classifies 40.4%(205/507) of the cases as confirmed infections compared to 33.9%(p=0.038) and 29.4%(p<0.001) in 2018 ICM and 2013 MSIS classifications respectively. Compared to 2018 ICM classification it also offers significantly less undetermined cases – 5.0% vs. 11.4%(p<0.001). Free from infection Kaplan-Meyer survival curve shows significantly better outcome for EBJIS unlikely compared to confirmed subgroup(p=0.031). EBJIS likely subgroup survival is not significantly different from unlikely(p=0.529) or confirmed(p=0.717) cohorts. Among the MSIS not infected cohort the newly classified EBJIS confirmed/likely cases present higher subsequent infection rate (albeit not statistically significant) when compared to EBJIS infection unlikely cases − 16.0%(13/81) vs. 10.1%(28/277). This subsequent PJI rate is similar to the MSIS infected cohort. A similar trend is not obvious within ICM 2018 not infected subgroup. Conclusions. The EBJIS 2021 definition is shown to be the most sensitive definition while also offering a smaller number of undetermined cases. Newly diagnosed infections seem to have a similar prognosis as “classically” infected cases. For any tables or figures, please contact the authors directly

Aim. We prospectively evaluated four different microbiological tools for diagnostics of prosthetic joint infections (PJI), and assessed their impact on the categorization of infection according to EBJIS guidelines. We compared culture, in-house real-time mPCR for S. aureus, S. lugdunensis, S. hominis, S. epidermidis, S. capitis, S. haemolyticus, C. acnes (mPCR), broad-spectrum PCR (Molzym) with 16S rRNA V3-V4 amplicon Sanger sequencing (16S PCR), and 16S rRNA V3-V4 amplicon next-generation sequencing (16S NGS) on MiSeq (Ilumina). Methods. A total of 341 samples (sonication fluid, tissue biopsy, synovial fluid) were collected from 32 patients with suspected PJI who underwent 56 revision surgeries at the Orthopaedic Centre University Hospital Ljubljana, between 2022 and 2024. Samples were processed using standard protocols for routine culture, followed by DNA isolation using the MagnaPure24 (Roche). All samples were tested with mPCR, and an additional ≥4 samples from each revision (244 in total) were subjected to further metagenomic analysis. Culture results were considered positive if the same microorganism was detected in ≥2 samples, ≥50 CFU/ml were present in the sonication fluid, or ≥1 sample was positive for a more virulent microorganism or if the patient had received antibiotic treatment. Results. Each tool demonstrated high sensitivity for correct EBJIS categorization (100% culture and 16S NGS, 96.88% mPCR and 16S PCR). The highest specificity was observed with mPCR and 16S PCR (87.5%), while culture (79.17%) and NGS (37.5%) showed lower specificity. In 27% (15/56) of revisions, all microbiological tests were negative, although infection was confirmed with histology in one case, and four cases were classified as infection-likely based on clinical signs. In 20% (11/56) of cases, all microbiological tests were positive; in three cases a combination of other EBJIS criteria (without microbiology) categorized the episodes as infection-likely and one as infection-unlikely, emphasizing the importance of microbiological tests in diagnostic criteria. In 43% (24/56) of revisions categorized as infection-unlikely using a combination of other EBJIS criteria, five had positive culture, and three had positive mPCR and 16S PCR. Fifteen (62%) had positive 16S NGS, 12 due to a low number of reads, which may indicate low-grade infection or possible contamination. Conclusion. To date, no test can be established as the ultimate gold standard. The lack of interpretation criteria can result in low specificity of some methods, as the threshold is difficult to determine. A multidisciplinary approach with combination of microbiological tools is still considered the most efficient

Aim. Accurate diagnosis is key in correctly managing prosthetic joint infection (PJI). Our aim is to compare the preoperative performance of three PJI definitions comparing it to definitive postoperative classification. Method. This is a multicenter retrospective study of patients who have undergone total hip or knee revision surgery in four different European institutions. For this specific study, cases with no preoperative synovial fluid differential leukocyte count and less than four intraoperative microbiology samples were excluded. Cases were classified using the 2021 EBJIS, the 2018 International Consensus Meeting (ICM) and the 2013 Musculoskeletal Infection Society (MSIS) PJI definitions. Preoperative classification was based on clinical features, inflammatory markers and synovial fluid leukocyte count and microbiology results. Results. Preoperative and definitive PJI classification status of the 384 patients included are presented in figure 1. EBJIS definition showed the highest agreement between preoperative and definitive classification (k=0.86, CI95% 0.81–0.90, p<0.001) compared to ICM 2018 (k=0.80, CI95% 0.75–0.84, p<0.001) or MSIS 2013 (k=0.70, CI95% 0.62–0.77, p<0.001). Compared to its respective definitive classification: EBJIS preoperative unlikely result shows 86.8% (95%CI 81.3%–91.2%) sensitivity and 87.7% (95%CI 83.3%–91.1%) negative predictive value (NPV); ICM 2018 preoperative not infected result shows 83.5% (95%CI 77.4%–88.5%) sensitivity and 86.2% (95%CI 81.9%–88.6%) NPV and; MSIS 2013 preoperative not infected result shows 63.9% (95%CI 55.0%–72.1%) sensitivity and 84.3% (95%CI 81.1%–87.1%) NPV. Around half of the preoperative EBJIS likely (45.8%) and ICM 2018 inconclusive (54.5%) turn out to be infected postoperatively. If we consider the more sensitive definition (EBJIS) as the gold standard: ICM 2018 preoperative not infected result shows 75.1% (95%CI 68.5%–81.0%) sensitivity and 78.3% (95%CI 73.9%–82.2%) NPV and; MSIS 2013 preoperative not infected result shows 42.1% (95% CI 35.2%–49.4%) sensitivity and 62.0% (59.2%–64.8) NPV. Conclusions. The EBJIS 2021 definition is not only the most sensitive definition as it was shown to be the most effective in preoperatively ruling out PJI when there is a negative result. For any tables or figures, please contact the authors directly

Aim. Diagnosing periprosthetic joint infections (PJI) can be very challenging, especially infections caused by low virulence microorganisms. No single test with a 100% accuracy is available yet. Hence, different infection definitions were introduced to improve the diagnostic confidence and quality of research articles. Due to constant developments in this field, infection definitions are adopted continuously. The aim of our study was to find the most sensitive currently available infection definition among three currently used criteria (International Consensus Meeting – criteria 2018 (ICM), Infectious Diseases Society of America - criteria 2013 (IDSA), and European Bone and Joint Infection Society – criteria 2021 (EBJIS)) for the diagnosis of PJI. Method. Between 2015 and 2020, patients with an indicated revision surgery due to septic or aseptic failure after a total hip or knee replacement were included in this retrospective analysis of prospectively collected data. A standardized diagnostic workup was done in all patients. The components of the IDSA-, ICM-, and EBJIS- criteria for the diagnosis of PJI were identified in each patient. Results. Overall, 206 patients (hip: n=104 (50%); knee: n=102 (50%)) with a median age of 74 years (IQR 65 – 80y) were included. 101 patients (49%) were diagnosed with PJI when using the EBJIS- criteria. Based on the IDSA- and ICM- criteria, 99 patients (48%, IDSA) and 86 patients (42%, ICM) were classified as septic. Based on all three criteria, 84 cases (41%) had an infection. 15 septic cases (n=15/206; 7%) were only identified by the IDSA- and EBJIS- criteria. In 2 patients (n=2/206, 1%), an infection was present based on only the ICM and EBJIS criteria. No case was classified as infected by one infection definition alone. A statistically significant higher number of inconclusive cases was observed when the ICM criteria (n=30/206; 15%) were used in comparison to the EBJIS criteria (likely infections: n=16/206; 8%) (Fisher's exact test, p=0.041). The EBJIS definition showed a better preoperative performance in comparison to the other two definitions (p<0.0001). Conclusions. The most sensitive infection definition seems to be the novel EBJIS– criteria covering all infections diagnosed by the IDSA- and ICM-criteria without detecting any further infection. In addition, less inconclusive (infection likely) cases were detected by the EBJIS-criteria in comparison with the ICM-criteria reducing the so called ‘grey zone’ significantly which is of utmost importance in clinical routine

Background. Two-stage revision arthroplasty is the standard treatment for chronic hip and knee periprosthetic joint infections (PJI). Accurate diagnosis of persistent infections at 2nd stage using established biomarkers and diagnostic criteria is of paramount importance. This study aimed to evaluate the diagnostic value of synovial calprotectin and alpha-defensin, and compare established diagnostic criteria from the International Consensus Meeting (ICM 2018) and the European Bone and Joint Infection Society (EBJIS 2021) to determine persistent PJI at the 2nd stage of a two-stage revision arthroplasty. Methods. We retrospectively analyzed 97 patients who underwent 100 two-stage revisions (hip: 39, knee: 61). Synovial fluid samples were assessed for calprotectin and alpha-defensin levels. ICM 2018 and EBJIS 2021 were applied to all patients undergoing 2nd stage revision. Receiver operating characteristic (ROC) curves and Youden Index were utilized to determine optimal cut-off values, and correlations between biomarkers were evaluated. The microbiological spectrum was analyzed at 2nd stage and re-revision surgery. Results. Calprotectin levels showed a sensitivity of 66.7%, specificity of 32.9%, and accuracy of 38.0% in predicting septic failure. Alpha-defensin showed sensitivity of 28.6%, specificity of 87.8%, and accuracy of 79.2%. Significant correlations included: calprotectin with PMN% (r = 0.471, p = 0.05) and alpha-defensin with WBC (r = 0.830, p < 0.01) in the successful cohort. For septic re-revisions, calprotectin and alpha-defensin were highly correlated (r = 0.969, p < 0.01). ICM correctly diagnosed persistent PJI in 26.7%, while EBJIS diagnosed 24.2%. The microbial spectrum shifted from gram-positive to gram-negative bacteria between reimplantation and re-revision surgeries. Conclusion. Synovial calprotectin and alpha-defensin demonstrated limited accuracy in ruling out persistent PJI at reimplantation. The low sensitivity of current diagnostic criteria, combined with the observed shift in microbial spectrum, underscores the challenges in diagnosing persistent PJI during 2nd stage of a two-stage revisions arthroplasty

Aim. Apart from other biomarkers isolated in the synovial fluid, alpha-defensin appears to be a promising diagnostic tool to confirm a periprosthetic joint infection (PJI) in the hip or knee. The purpose of this study was to evaluate the sensitivity and specificity of an alpha defensin lateral flow (ADLF) test compared to usual standard classifications in the diagnostic management of PJI. Method. This investigation was set up as a multicenter prospective cohort study. Synovial fluid was obtained by means of joint aspiration or intra-operative tissue biopsies. A presumptive PJI diagnosis was made according to criteria outlined by the Musculoskeletal Infection Society (MSIS), the Infectious Diseases Society of America (IDSA) and the European Bone and Joint Infection Society (EBJIS). The intention to treat by the surgeon was logged. Sensibility and specificity for the ADLF test was plotted for each aforementioned diagnostic algorithm. Spearman correlations between all scores were analyzed. Multiple logistic regression was used to determine the contribution of independent variables to the probability of PJI. Results. Hundred thirty-six patients with a painful arthroplasty were assessed for infection and rated by the treating surgeon as potentially infected or not on the basis of clinical and laboratory information. According to the EBJIS criteria sixty-eight patients were deemed infected, fifty according to the IDSA criteria, forty-one according to the MSIS criteria and forty according to the ADLF test. However, the sensitivity of ADLF test was 87.8% for MSIS, 70% for IDSA and 55.8% for EBJIS. The specificity of ADLF test was between 94% – 97%. Good correlation was observed between synovial fluid culture and ADLF test (r = 0.73). Low to excellent correlations between the ADLF test and the EBJIS (r = 0.58), IDSA (r = 0.68), and MSIS score (r = 0.84) were observed. The surgeon's intention to treat correlated well with the MSIS score (r = 0.86), and moderately with the EBJIS (r = 0.59). Conclusions. ADLF test sensibility was variable, but its specificity was excellent. Most of the cases, not retained by MSIS but classified by EBJIS as infected, got a negative microbiological result. Considering an accepted 20% negative microbiological result rate in PJI diagnostic, EBJIS is clearly overestimating the number of infected cases. MSIS score correlates with the surgeon intention to treat and ADLF test

Aim. It still remains unclear whether postoperative antibiotic treatment is advantageous in presumed aseptic revision-arthroplasties of the hip (rTHA) and knee (rTKA) with unexpected-positive-intraoperative-cultures (UPIC). The aim of this study was to evaluate if there is a difference in the septic and/or aseptic re-revision rate in patients with or without postoperative antibiotics. Method. In this retrospective propensity-score (PS) matched cohort-study we compared the re-revision rate and the microbiological spectrum in rTHA and rTKA treated with (AB-Group; n=70) and without (non-AB-Group; n=70) antibiotic treatment in patients with UPIC. Baseline covariates for PS-matching were type of revision, sex, Body-Mass-Index, age, Surgical-Site-Infection-Score, American-Society-of-Anesthesiologists-Classification, serum C-reactive-protein. All patients received routine antibiotic prophylaxis, but empiric AB treatment was started only in patients in the AB-Group. Post-operative treatment was decided on an individual basis according to the preference of the surgeon and the infectious disease specialist for a minimum duration of two weeks. In total, 90 rTHA (45 AB-Group, 45 in non-AB-Group) patients with UPICs and 50 rTKA (25 AB-Group, 25 in non-AB-Group) were included in the study. There was no significant variation in patient demographics. Results. After a median follow-up of 4.1 (IQR: 2.9-5.5) years after rTHA and rTKA, there was no higher re-revision rate (p=0.813) between the AB-group 10/70 (14.3%), and the non-AB-group 11/70 (15.7%). In the AB group, 4.3% (3/70) of patients underwent revision due to septic complications compared to 5.7% (4/70) in the non-AB group (survival log-rank: p=0.691). In total, 30/70 (42.9%) of patients in the AB-group and 23/70 (32.9%) of patients in the non-AB group were diagnosed as having an “infection likely” according to the PJI diagnostic criteria of EBJIS (p=0.223). All UPICs comprised low virulent microorganisms and were considered as a contaminant. In total, 68/70 (97.1%) of the patients in the AB-group received a dual antibiotic treatment for a mean duration of 41 (IQR: 23.5-56.5) days. Conclusion. Postoperative antibiotic treatment did not result in a decreased re-revision rate compared to non-antibiotic treatment in patients with UPIC in presumed aseptic rTHA and rTKA. UPICs with pathogens are likely to be a containment and therefore the classification of “infection likely” according to the EBJIS definition can be safely ignored

Aim. Several options to standardize the definition of periprosthetic joint infection (PJI) have been created including the 2013 Musculoskeletal Infection Society (MSIS), 2018 Intentional Consensus Meeting (ICM), and the 2019 proposed European Bone and Joint Infection Society (EBJIS) criteria. Synovial fluid biomarkers have been investigated in an effort to simplify and improve the diagnosis of PJI. The aim of this study was to test the sensitivity, specificity, positive, and negative predicted values (PPV and NPV, respectively) of a calprotectin point of care (POC) test for diagnosing PJI in revision total knee arthroplasty (TKA) patients comparing different sets of criteria (2013 MSIS, 2018 ICM, and 2019 EBJIS criteria) used to define patients as with or without infection. Method. From October 2018 to January 2020 and under IRB approval 123 intraoperative samples of synovial fluid were prospectively collected at two academic hospitals in the same institution from revision TKA patients. All patients underwent standard clinical and laboratory evaluation for PJI at our institution, allowing for categorization using the 3 criteria. Patients were adjudicated by 2 blinded and independent reviewers for the 3 sets of criteria. The 3 criteria agreed 91.8% of the time. Four likely cases by the 2019 proposed EBJIS were considered unlikely and 1 inconclusive case by the 2018 ICM was considered not infected for the purposes of analysis. Calprotectin POC testing followed manufacturer's instructions using a threshold of >50 mg/L to indicate PJI. Sensitivities, specificities, PPV, NPV, and areas under the curve (AUC) were calculated for the 3 sets of criteria. Results. Using 2013 MSIS criteria the calprotectin POC test demonstrated a sensitivity, specificity, PPV, NPV AUC of 98.1%, 95.7%, 94.5%, 98.5%, and 0.969, respectively. Using 2018 ICM the POC test demonstrated a sensitivity, specificity, PPV, NPV and (AUC) of 98.2%, 98.5%, 98.2%, 98.5%, and 0.984, respectively. Using the 2019 proposed EBJIS criteria the POC test demonstrated a sensitivity, specificity, PPV, NPV and area under the curve (AUC) of 93.2%, 100.0%, 100.0%, 94.2%, and 0.966, respectively. Conclusions. The calprotectin lateral flow POC test has an excellent sensitivity and specificity regardless of the set of criteria used to define PJI. These results are promising and suggest that the calprotectin lateral flow test may be used as a rule out test in a cost-conscious health care model or when conventional diagnostic tools may not be available. Further investigations of the calprotectin PCO test must be completed to validate these results

Aim. Prosthetic joint infection (PJI) represents the second most frequent complication of total joint arthroplasty (TJA) with up to 20% of low-grade PJI treated as aseptic failure. Sensitive diagnostic criteria have been provided by EBJIS. However, to date there is no single test to reliably diagnose all PJIs. Studies of Mazzucco et al. and Fu et al. suggest that synovial fluid (SF) viscosity could be considered as an important marker for PJI. The primary aim of our study was to determine if SF viscosity is a more reliable diagnostic criterion of PJI than the SF cell count with differential (CCD), and the combined diagnostic value of SF viscosity and CCD. Method. We prospectively analysed the viscosity of SF samples obtained during TJA of hip and knee revisions. We sampled 2.5–5mL of SF for viscosity and CCD. Intraoperatively, 1mL of the sample was analysed for the CCD. The remaining SF was centrifuged for 4min at 7000rpm. The viscosity of the supernatant was determined on Ostwald viscometer as the time required to pass the viscometer at 20°C. During each surgery at least 5 microbiological and multiple histopathological samples were harvested, and explant sonication was performed. The diagnosis was based on EBJIS definition. The viscosity threshold for detecting PJI was set at 65 seconds. Results. Between December 2020 and January 2023, we analysed 65 knee and 47 hip TJA revision procedures. There were 55 septic and 57 aseptic diagnoses. As a diagnostic marker of PJI, SF viscosity achieved 100% sensitivity and 82.5% specificity, with area under the receiver operating characteristic curve (AUC) of 0.832 (95% CI 0.739, 0.925). The specificity and sensitivity of SF CCD were 98.2% and 78.2%, respectively, with AUC of 0.921 (95% CI 0.869, 0.974). Of the 10 cases incorrectly diagnosed as aseptic based on SF viscosity, 2 were acute traumas and 8 metalloses. The SF CCD in all these cases was <0.5. Of the 12 cases incorrectly diagnosed as aseptic based on SF CCD, 6 cases were culture negative, 4 C. acnes and 2 S. epidemidis isolates in microbiology. Taken together, SF viscosity and CCD achieved a combined AUC of 0.953 (95% CI 0.919, 0.987). Conclusions. Our study is the first to report that SF viscosity is more sensitive but slightly less specific for PJI than SF CCD. The study demonstrates diagnostic value of combining SF viscosity with CCD in decision making in TJA revision surgery

Aim. Synovial fluid investigation is the best alternative to diagnose prosthetic joint infection (PJI) before adequate microbiological/histology sampling during revision surgery. Although accurate preoperative diagnosis is certainly recommended, puncturing every patient before revision arthroplasty raises concerns about safety and feasibility issues especially in difficult to access joint (e.g., hip), that often require OR time and fluoroscopy/ultrasound guidance. Currently there is no clear guidelines regarding optimal indications to perform preoperative joint aspiration to diagnose PJI before revision surgery. The main goal of this study is to determine the accuracy of our institutional criteria using the new European Bone and Joint Infection Society (EBJIS) PJI definition. Method. We retrospectively evaluated every single- or first-stage for presumed aseptic or known infected revision total hip/knee arthroplasty procedures between 2013–2020. Preoperative clinical and laboratory features were systematically scrutinized. Cases with insufficient information for accurate final PJI diagnosis (i.e., no perioperative synovial fluid examination or no multiple cultures including sonication of removed implant) were excluded. Preoperative joint aspiration is recommended in our institution if any of the following criteria are met: 1) elevated CRP and/or ESR; 2) early failure (<2 years) or repeat failure; 3) high clinical suspicion/risk factors are present. Performance of such criteria were compared against final postoperative EBJIS definition PJI diagnosis. Results. A total of 364 revision THAs or TKAs were performed during the study period. After excluding 258 cases with insufficient information, a total of 106 patients were ultimately included. 38 (35,8 %) were classified as confirmed infections, 10 (9.4 %) as likely infected and 58 (54.7%) as infection unlikely. Of those, 37 confirmed infection cases, 9 likely infected cases and 32 infection unlikely cases did have indication for preoperative synovial fluid collection before revision surgery. Institutional criteria showed 95.8 % Sensitivity, 44.83 % Specificity, 92.9 % Negative Predictive Value (NPV) and 59 % Positive Predictive Value (PPV). Conclusions. Sensitivity and NPV of the aforementioned institutional criteria are very high even with the use of the more sensitive EBJIS PJI definition. As such they seem to be a valid alternative in selecting patients that should be punctured before revision arthroplasty. They identify the vast majority of infected patients while saving a significant number of patients from unnecessary procedures

Background. The identification of novel biomarker which is highly specific and sensitive for periprosthetic joint (PJI) have the potential to improve diagnostic accuracy and ultimately improve patient outcomes. Thus, the aim of this systemic review is to identify and evaluate novel biomarkers for the preoperative diagnostics of PJI. Methods. MEDLINE, EMBASE, PubMed and Cochrane Library databases identified from 1. st. of January 2018 to 30. th. of September. 2022. We used “periprosthetic joint infection” OR “prosthetic joint infection” OR “periprosthetic infection” as the diagnosis of interest and the target index applied AND “marker”. To focus on novel biomarkers already used biomarkers of the established PJI diagnostic criteria of MSIS, ICM and EBJIS were not included in the analysis. These three criteria were considered the reference standard during quality assessment. Results. A total of 19 studies were included. In these, fourteen different novel biomarkers were analyzed. Fifteen studies (79%) had prospective designs and the other four (22%) were retrospective studies. Six studies (33%) included only periprosthetic knee infections and thirteen (67%) included periprosthetic knee and hip infections. Proteins were analyzed in most cases (nine studies), followed by molecules (three studies), exosome (two studies) as well as DNA (two studies), interleukin (one study) and lysosome (one study). One novel and promising marker that had been frequently analyzed is calprotectin. Conclusion. No marker demonstrated higher sensitivity and specificity than already known parameters used for standardized treatment based on established PJI definitions. Further studies are needed to elucidate the benefit and usefulness of implementing new biomarkers in diagnostic PJI settings

Aim. Diagnosing low-grade periprosthetic joint infections (PJI) can be very challenging due to low-virulent microorganisms capable of forming biofilm. Clinical signs can be subtle and may be similar to those of aseptic failure. To minimize morbidity and mortality and to preserve quality of life, accurate diagnosis is essential. The aim of this study was to assess the performance of various diagnostic tests in diagnosing low-grade PJI. Methods. Patients undergoing revision surgery after total hip and knee arthroplasty were included in this retrospective cohort study. A standardized diagnostic workup was performed using the components of the 2021 European Bone and Joint Infection Society (EBJIS) definition of PJI. For statistical analyses, the respective test was excluded from the infection definition to eliminate incorporation bias. Receiver-operating-characteristic curves were used to calculate the diagnostic performance of each test, and their area-under-the-curves (AUC) were compared using the z-test. Results. 422 patients undergoing revision surgery after total hip and knee arthroplasty were included in this study. 208 cases (49.3%) were diagnosed as septic. Of those, 60 infections (28.8%) were defined as low-grade PJI (symptoms >4 weeks and caused by low-virulent microorganisms (e. g. coagulase-negative staphylococci, Cutibacterium spp., enterococci and Actinomyces)). Performances of the different test methods are listed in Table 1. Synovial fluid (SF) - WBC (white blood cell count) >3000G/L (0.902), SF - %PMN (percentage of polymorphonuclear neutrophils) > 65% (0.959), histology (0.948), and frozen section (0.925) showed the best AUCs. Conclusion. The confirmatory criteria according to the EBJIS definition showed almost ideal performances in ruling-in PJI (>99% specificity). Histology and synovial fluid cell count (SF-WBC and SF-%PMN) showed excellent accuracies for diagnosing low-grade PJI. However, a reduced immune reaction in these cases may necessitate lower cut-off values. Intraoperative frozen section may be valuable in cases with inconclusive preoperative diagnosis. For any tables or figures, please contact the authors directly

Aim. While 16S rRNA PCR - Sanger sequencing has paved the way for the diagnosis of culture-negative bacterial infections, it does not provide the composition of polymicrobial infections. We aimed to evaluate the performance of the Nanopore-based 16S rRNA metagenomic approach using partial-length amplification of the gene, and to explore its feasibility and suitability as a routine diagnostic tool for bone and joint infections (BJI) in a clinical laboratory. Method. Sixty-two clinical samples from patients with BJI were sequenced on MinION* using the in-house partial amplification of the 16S rRNA gene. BJI were defined based on the ICM Philly 2018 and EBJIS 2021 criteria. Among the 62 samples, 16 (26%) were culture-positive, including 6 polymicrobial infections, and 46 (74%) were culture-negative from mono- and polymicrobial infections based on Sanger-sequencing. Contamination, background noise definition, bacterial identification, and time-effectiveness issues were addressed. Results. Results were obtained within one day. Setting a threshold at 1% of total reads overcame the background noise issue and eased interpretation of clinical samples. The partial 16S rRNA metagenomics approach had a greater sensitivity compared both to the culture method and the Sanger sequencing. All the 16 culture-positive samples were confirmed with the metagenomic sequencing. Bacterial DNA was detected in 32 culture-negative samples (70%), with pathogens consistent with BJI. The 14 Nanopore negative samples included 7 negative results confirmed after implementation of other molecular techniques and 7 false-negative MinION results: 3 Kingella kingae infections detected after targeted-PCR only, 2 Staphylococcus aureus infections and 2 Pseudomonas aeruginosa infections sterile on agar plate media and detected only after implementation of blood culture media, advocating for the very low inoculum. Conclusions. The results discriminated polymicrobial samples, and gave accurate bacterial identifications compared to Sanger-based results. They confirmed that Nanopore technology is user-friendly as well as cost- and time-effective. They also indicated that 16S rRNA targeted metagenomics is a suitable approach to be implemented for routine diagnosis of culture-negative samples in clinical laboratories. * Oxford Nanopore Technologies

Aim. Currently, gram-negative bacteria (GNB), including multidrug-resistant (MDR-GNB) pathogens, are gaining importance in the aetiology of prosthetic joint infection (PJI). To characterize the antimicrobial resistance patterns of Gram-negative bacteria (GNB) causing hip prosthetic joint infections in elderly patients treated at a Brazilian tertiary academic hospital. Method. This is a retrospective, cross-sectional study of patients over 60 years of age undergoing hip arthroplasty from 2018 to 2023 at a tertiary academic trauma, which were diagnosed with hip prosthetic joint infection. PJI diagnosed was based on EBJIS criteria, in which intraoperative tissue cultures identified the pathogens. Demographics, reason for arthroplasty, type of implant and susceptibility patterns using disk diffusion method were analysed. Results. Overall, among 17 elderly patients diagnosed with hip infected arthroplasty, 45 bacterial isolated were identified. Debridement, irrigation, antibiotic and implant retention (DAIR) procedures due to uncontrolled infection occurred in 47.0% (n=8/17), and five patients underwent more than two DAIR surgeries. Tissue cultures yielded eleven different bacterial species, with GNB accounted for 64.4% (n=29/45) of pathogens. Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, and Pseudomonas aeruginosa were identified in 34.5% (n=10/29), 17.25% (n=5/29), 13.8% (n=4/29), and 13.8% (n=4/29), respectively. In the resistance profile analysis, E. coli was most sensitive to antibiotics, whereas K. pneumoniae showed resistance rates higher than 70% for cephalosporins, carbapenems, and quinolones. All A. baumannii isolates were resistant to meropenem, and 80% of these isolates were resistant to amikacin. Conclusions. This study emphasizes the role of GNB in the microbiological profile of PJI among elderly patients at a tertiary hospital in a Brazilian centre. The present study portrays a worryingly higher rates of MDR-GNB, mainly to quinolones and cephalosporins resistance which have been the cornerstone of PJI antibiotic treatment. In addition, higher rates carbapenems and aminoglycosides resistance shows a threat to antibiotic treatment of PJI. More global studies need to be carried out to show a likely change in the microbial epidemiology of PJI

Aim. To classify Fracture-related Infection (FRI) allowing comparison of clinical studies and to guide decision-making around the main surgical treatment concepts. Method. An international group of FRI experts met in Lisbon, June 2022 and proposed a new FRI classification. A core group met during the EBJIS Meeting in Graz, 2022 and on-line, to determine the preconditions, purpose, primary factors for inclusion, format and the detailed description of the elements of an FRI Classification. Results. Historically, FRI was classified by time from injury alone (early, delayed or late). Time produces pathophysiological changes which affect the bone, the soft-tissues and the patient general health, over a continuum. No definitive cut-off is therefore possible. Also, in several studies, time was not identified as an independent predictor of outcome. The most important primary factors were characteristics of the fracture (F), relevant systemic co-morbidities of the patient (R) and impairment of the soft-tissue envelope (I). These factors determine FRI severity, choice of treatment method and are predictors of outcome. For the fracture (F), the state of healing, the potential for bone healing and the presence or absence of a bone defect are critical factors. Co-morbidities are listed and the degree of end-organ damage is important (R). The ability to close the wound directly or the need for soft tissue reconstruction determines the impairment of the soft tissue component (I). Hence the FRI Classification was designed. The final proposal of the FRI Classification is presented here. The new classification has five stages; from simple cases of infected healed fractures, in healthy individuals with good soft tissues (Stage 1), through unhealed fractures with variable potential for bone healing (Stages 2, 3 or 4) to Stage 5, with no limb-sparing or reconstructive options. For instance, the need for a free flap (I4), over a well-healed fracture (F1), in a patient with 2 co-morbidities (R2) gives a classification of F1R2I4 for that patient. Conclusions. This novel approach to FRI classification builds on previous work in osteomyelitis, PJI and chronic medical conditions. It focusses attention on the elements of the disease which need treatment. It now requires validation in large patient cohorts. On behalf of the FRI Classification Consensus Group

Aim. To compare outcomes of PJI in relation to treatment method versus classification using the JS-BACH system. Method. Patients having surgery for EBJIS Criteria Confirmed PJI between 2010–2015 were included. Index surgical procedures were 1-stage or 2-stage revision or debridement and implant retention (DAIR). Patients completed the EuroQol EQ-5D-3L questionnaire and were followed clinically to a median of 4.7 years (IQR 2.7–6.7 years). Patients were stratified using the JS-BACH classification1 into either ‘Uncomplicated’, ‘Complex’ or having ‘Limited treatment options’, by two separate classifiers, blinded to clinical outcome. Results. 216 patients met the inclusion criteria. There were 51 patients classified as Uncomplicated (23.6%), 127 (58.8%) as Complex and 38 (17.6%) having Limited treatment options. Patients underwent either DAIR (n=97), 1-stage (n=35) or 2-stage (n=84) revision. Patients classified as Uncomplicated PJI had the lowest risk of recurrence or treatment failure, regardless of index procedure performed. Complex patients were significantly more likely than Uncomplicated patients to have recurrence following 2-stage revision (Odds Ratio 1.85; p=0.040) or DAIR (OR 1.83; p=0.037), but not 1-stage revision (OR 0.518; p=0.675). Limited treatment option patients had the highest recurrence risk regardless of index procedure (1-stage: OR 2.5 p=0.036; 2-stage: OR 3.3 p=0.004; DAIR: OR 3.40 p=0.006). At one year after surgery, Uncomplicated patients had the highest EQ-index scores (a marker of Quality of Life), with all treatments (EQ-5D-3L mean index scores; Uncomp 0.773, Complex 0.512, Limited Options 0.310: p<0.01). Differences in patient-reported outcomes were greater between the JS-BACH classification groups than between any methods of treatment. Conclusions. The JS-BACH classification effectively predicted outcome after three common PJI treatments. Comparing outcomes between treatments, without stratification of the patients, may be misleading as factors other than treatment method have a major effect on outcome. Classification may allow better allocation of individual treatments to provide optimal outcome for patients