Aim. Synovial fluid D-lactate may be useful for diagnosing septic arthritis (SA) as this biomarker is almost exclusively produced by bacteria. We evaluated the performance of synovial fluid D-lactate and determined its optimal cut-off value for diagnosing SA. Method. Consecutive patients with suspicion of septic arthritis were prospectively included. They underwent joint aspiration and synovial fluid was collected for culture, leukocyte count and D-lactate concentration (by spectrophotometry). Youden's J statistic was used for determining optimal D-lactate cut-off value on the receiver operating characteristic (ROC) curve by maximizing sensitivity and specificity. Results. A total of 155 patients were included. Using institutional criteria, 21 patients (14%) were diagnosed with SA and 134 (86%) patients with aseptic arthropathy, out of which 43 (27%) had osteoarthrosis, 80 (52%) had rheumatic arthropathy and 11 (7%) reactive arthritis. The optimal cut-off of synovial fluid D-lactate to differentiate SA from aseptic cases was 0,035 mmol/l. Synovial fluid D-lactate had a sensitivity 90% (95% CI: 70–99%) and specificity 87% (95% CI: 80–92%) compared to leukocyte count with sensitivity 81% (95% CI: 60–95%) and specificity 83% (95% CI: 76–90%). Culture was positive in only 17 (80%) out of 21 patients with SA. Conclusions. The synovial fluid D-lactate showed high sensitivity and specificity for diagnosis of SA which was higher than the current gold standard of diagnosis (culture and leukocyte count). The high sensitivity makes this biomarker useful as a point-of-care screening test for SA

Aim. In the diagnosis of prosthetic joint infection (PJI), many biomarkers have shown a sound performance in terms of accuracy, sensitivity and specificity. In this study we aimed to test the frequently used serum biomarkers C-reactive Protein (CRP), Fibrinogen, Leukocytes, Interleukin-6 (IL-6), Interferon alpha (IF-alpha) and Procalcitonin (PCT) regarding these qualities. Following that, the optimal multi-biomarker combination was calculated to further improve the diagnostic performance. Method. 124 knee or hip revision arthroplasty procedures were prospectively investigated focusing on preoperative serum blood levels of CRP, Fibrinogen, Leukocytes, IL-6, IF-alpha and PCT. The presence of PJI was determined by a blinded researcher. Logistic regression with lasso-regularization was used for the biomarkers and all their ratios. Following cross-validation on a training sample set to get optimal performance estimates, we performed the final model on a test set (25% of all samples). Results. Out of all evaluated biomarkers, CRP (AUC 0.91, p-value 0.03) and Fibrinogen (AUC 0.93, p-value 0.02) had the best performances. The optimal combination when testing multiple biomarkers in 32 cross-validation runs was calculated including Fibrinogen, CRP, the ratio of Fibrinogen to CRP and the ratio of serum Thrombocytes to CRP (AUC 0.92, accuracy 0.77, specificity 0.92, sensitivity 0.68, cut-off 0.63, p-value 0.04). Conclusions. It was not possible to increase the diagnostic performance by combining multiple biomarkers using sophisticated statistical methods. The calculated Multi-biomarker models did not improve the AUC, accuracy, sensitivity and specificity when compared to single biomarkers

INTRODUCTION:. The diagnosis of periprosthetic joint infection (PJI) remains a serious challenge. Based on previous work, we believe that biomarkers will become the mainstay of diagnosing PJI in the future. We report on completion of our 8 year comprehensive biomarker program, evaluating the diagnostic profile of the 15 most promising synovial fluid biomarkers. METHODS:. Synovial fluid was prospectively collected from 99 patients being evaluated for infection in the setting of revision hip or knee arthroplasty. All synovial fluid samples were tested by immunoassay for 15 putative biomarkers that were developed and optimized specifically for use in synovial fluid. Sensitivity, specificity and receiver operating Characteristic (ROC) curve analysis were performed for all biomarkers. RESULTS:. The MSIS criteria, including cultures, CRP, ESR, fluid WBC, PMN%, and histology, was used to classify 30 PJIs and 69 cases of aseptic failure. Four synovial fluid biomarkers (alpha-defensin, bactericidal/permeability increasing protein, neutrophil gelatinase-associated lipocalin, and resistin) correctly predicted the MSIS classification of all patients in this study, exhibiting an AUC of 1.0 with >98% sensitivity and specificity for the diagnosis of PJI. Eight other biomarkers exhibited an AUC of >0.9. These results all outperformed the tests for serum CRP (specificity 87%, sensitivity 96%) and ESR (specificity 80%, sensitivity 93%). Interestingly, the Pearson correlations comparing the biomarkers to each other and to the synovial fluid WBC in the group of infected samples revealed only weak correlations, demonstrating that these biomarkers are not simply inflammatory biomarkers. DISCUSSION AND CONCLUSION:. A comprehensive biomarker program has led to the identification of several synovial fluid biomarkers that appear to be diagnostic for PJI. The four top biomarkers are proteins that have known functional roles in the cellular response to pathogens. These biomarkers outperform our currently utilized serum tests and can be used to develop rapid bedside immunoassays for PJI

Introduction. Gelsolin (GSN) is a protein whose function in the cytoplasm is to regulate intracellular actin assembly, while circulating plasma GSN has been implicated in the clearance of cellular byproducts via the body's scavenger system. In knee synovial fluid, GSN appears to be protective of inflammation as lower levels have been found in patients with rheumatoid arthritis while higher levels have been demonstrated in hypersensitivity reactions to metallic implants. The purpose of this study is to define the role of GSN in painful total knee arthroplasty (TKA) patients as a biomarker to distinguish septic from aseptic diagnoses. Methods. After Institutional Review Board (IRB) approval, 50 patients were enrolled in the study into two cohorts. 25 patients presented with a painful TKA and 25 patients had a painful native knee with primary osteoarthritis (OA). Synovial fluid was obtained from each patient's affected knee. Appropriate lab and culture data was also obtained from the painful TKA group. An ELISA was used to determine GSN levels and the groups were compared. Two tailed Student's t tests were used to compare means while Pearson's Correlation Coefficient and linear regression analyses were used to determine association between laboratory findings and GSN levels. Results. 11 of 25 knees in the TKA group had culture positive aspirations while the remaining 14 were sterile and determined to have aseptic component loosening. There was a significant difference in the GSN levels of the entire TKA cohort when compared to the OA group (TKA = 41,218 ng/mL; OA = 84,188 ng/mL; p = 0.002), with no difference noted between the infected and sterile TKA patients (infected = 43,210 ng/mL; sterile = 39,654 ng/mL; p = 0.63). There was a high correlation of ESR and CRP to GSN in the infected TKA group (r = 0.66 and 0.93 respectively; [Fig. 1 and 2]). Discussion. GSN levels correlate highly to other commonly used markers of periprosthetic joint infection (PJI), with overall lower levels seen in PJI when compared to patients with OA. However, GSN levels may be indicative of a painful total knee arthroplasty for multiple reasons, and further study is needed to delineate its role as a biomarker of PJI as well as specific aseptic TKA diagnoses

Aim. The diagnosis of periprosthetic joint infection (PJI) remains a clinical dilemma, since presentations of PJI usually greatly overlap with aseptic failure (AF). The aim of this study is to evaluate the values of plasma fibrinogen, individually or in combination with CRP, ESR and WBC, for distinguishing PJI from AF. Method. We retrospectively enrolled 357 cases who underwent revision hip or knee arthroplasties in the Third Affiliated Hospital of Southern Medical University, Sun Yat-sen Memorial Hospital and the First Affiliated Hospital of Sun Yat-sen University from January 2013 to December 2021, including 197 AF, 116 PJI and 44 reimplantation. The diagnostic capacity of preoperative fibrinogen, CRP, ESR and WBC as well as their combinations for differentiating PJI from AF were assessed by ROC curves. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were calculated according to the optimal cutoff value based on the Youden index. All biomarkers were further investigated for their potential ability to predict optimal timing of reimplantation as well as their diagnostic capacity in the subgroups of the knee and hip PJI. Furthermore, the correlations among fibrinogen, CRP and ESR in the patients with PJI and AF were analyzed to further evaluate the potential capacity of fibrinogen in the diagnosis of PJI. Results. The levels of fibrinogen, CRP, ESR and WBC were significantly higher in PJI group than in AF group. ROC analyses showed that the AUCs of fibrinogen, CRP, ESR and WBC were 0.879, 0.903, 0.879 and 0.685, respectively. The optimal threshold of fibrinogen is 4.04 g/L (74.1% sensitivity, 85.6% specificity, 76.1% PPV, 85.0% NPV and 81.8% accuracy). Combining fibrinogen with CRP and/or ESR (AUC: 0.903∼0.914) yielded almost equivalent diagnostic efficiency compared with the combination of CRP and ESR (AUC: 0.910). Besides, fibrinogen yielded AUCs of 0.869 (cutoff: 3.44 g/L) and 0.887 (cutoff: 4.12 g/L) in the hip and knee subgroups, with higher specificity and PPV of 93.1% and 96.1% in the knee PJI. Intriguingly, as for the cases with CRP < 10mg/L and ESR ≧ 30 mm/h, the specificity and NPV of fibrinogen for diagnosing PJI were 92.2% and 83.9%. Conclusions. Plasma fibrinogen is considered as a potential first-line screening marker for PJI detection and timing of reimplantation. As for the patients with an increased ESR but normal CRP, a low fibrinogen level (below 4.04 g/L) is more likely to rule out PJI

Aim. Diagnosis of periprosthetic joint infection (PJI) is still challenging due to limitations of available diagnostic tests. Many efforts are ongoing to find out novel methods for PJI diagnosis. Recently, several studies have shown a role of the long pentraxin PTX3 as a biomarker in inflammatory diseases and infections. This pilot diagnostic study evaluated the diagnostic ability of synovial fluid and serum PTX3 for the infection of total hip arthroplasty (THA) and total knee arthroplasty (TKA). Method. Consecutive patients undergoing revision surgery for painful THA or TKA were enrolled. Patients with antibiotic therapy suspended for less than 2 weeks prior to surgery and patients eligible for spacer removal and prosthesis re-implantation were excluded. Quantitative assessment of synovial fluid and serum PTX3 was performed with ELISA method. Musculoskeletal Infection Society (MSIS) criteria were used as reference standard for diagnosis of PJI. Continuous data values were compared for statistical significance with univariate unpaired, 2-tailed Student's t-tests. Receiver operating characteristic (ROC) curve analyses was performed to assess the ability of serum and synovial fluid PTX3 concentration to determine the presence of PJI. Youden's J statistic was used to determine optimum threshold values for the diagnosis of infection. Sensitivity (Se), specificity (Sp), positive (PPV) and negative (NPV) predictive values, positive (LR+) and negative (LR-) likelihood ratio, area under the ROC curve (AUC) were calculated. Results. Sixty-two patients (M:F=28:34) with a mean age of 64 years (40–78) underwent revision of THA (n=52) or TKA (n=10). According with MSIS criteria, 10 cases were categorized as septic and 52 as aseptic revisions. The average synovial fluid concentration of PTX3 was significantly higher in patients with PJI compared to patients undergoing aseptic revision (23,56 ng/mL vs 3,71 ng/mL; P=0.0074). There was no significant difference in terms of serum concentration of PTX3 between the two groups. Synovial fluid PTX3 demonstrated an AUC of 0.93 (95%IC 0.86–0.97) with Se 100%, Sp 85%, PPV 55%, NPV 100%, LR+ 6.6 and LR- <0.01 for a threshold value of 3 ng/mL. Serum PTX3 demonstrated an AUC of 0.59 (95%IC 0.38–0.8) with Se 78%, Sp 50%, PPV 25%, NPV 90%, LR+ 1.56 and LR- 0.44 for a threshold value of 3 ng/mL. Conclusions. Synovial PTX3 demonstrated a strong diagnostic ability for PJI. PTX3 could represent a useful biomarker for detection of PJI in patients undergoing revision surgery for painful THA or TKA. Larger diagnostic studies are required to confirm these preliminary data

Post operative prosthetic joint infection (PJI) is the most common cause of failure of total joint arthroplasty, requiring revision surgery, but a gold standard for the diagnosis and the treatment of PIJ is still lacking [1]. SuPAR, the soluble urokinase plasminogen activation receptor, has been recently described as a powerful diagnostic and prognostic tool, able not only to detect sepsis but also to discriminate different grade of sepsis severity [2,3]. This study aimed to examine the diagnostic value of SuPAR in post operative PJI, in order to explore the possible application of this new biomarker in the early diagnosis of PJI. The level of SuPAR have been measured in PJI patients and controls (patients undergoing prosthesis revision without infection), and correlated with pro and anti inflammatory markers (CRP C-reactive protein, IL-6, IL-1 TNFα, IL-10, IL-12, IL-8, IL1ra and the chemokine CCL2). Statistical analysis of Receiver Operating Characteristic (ROC) curves and Area Under the Curve (AUC) was performed. As described in Figure 1, serum SuPAR displayed a strongly significative increase in PJI patients compared to not infected controls, and a significative positive correlation with C-reactive protein, IL-6, IL-1 and TNFα and the chemokine CCL2. SuPAR displayed a very good AUC, significantly higher than CRP and IL-6 AUC. This study clearly show that the measure of Serum level of SuPAR provide a extremely important benefit because it is a precise indicator of bacterial infection, and the addition of SuPAR serum level measurement to classical inflammatory markers can strongly improve the diagnosis of prosthesis joint infection. The authors acknowledge ViroGates, Denmark for providing suPARNOSTIC Standard Kit. The authors would also acknowledge the Italian Ministero dell’ Istruzione, Università e Ricerca (MIUR) and Italian Ministero della Salute for providing funds for this research project

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

Anterior cruciate ligament (ACL) injuries have been increasing, especially amongst adolescents. These injuries can increase the risk for early-onset knee osteoarthritis (OA). The consequences of late-stage knee OA include structural joint change, functional limitations and persistent pain. Interleukin-6 (IL-6) is a pro-inflammatory biomarker reflecting knee joint healing, and increasing evidence suggests that IL-6 may play a critical role in the development of pathological pain. The purpose of this study was to determine the relationship between subjective knee joint pain and function, and synovial fluid concentrations of the pro-inflammatory cytokine IL-6, in adolescents undergoing anterior cruciate ligament reconstruction surgery. Seven youth (12-17 yrs.) undergoing anterior cruciate ligament (ACL) reconstruction surgery participated in this study. They completed the Pedi International Knee Documentation Committee (Pedi-IKDC) questionnaire on knee joint pain and function. At the time of their ACL reconstruction surgery, synovial fluid samples were collected through aspiration to dryness with a syringe without saline flushing. IL-6 levels in synovial fluid (sf) were measured using enzyme linked immunosorbent assay. Spearman's rho correlation coefficient was used to determine the correlation between IL-6 levels and scores from the Pedi-IKDC questionnaire. There was a statistically significant correlation between sfIL-6 levels and the Pedi-IKDC Symptoms score (-.929, p=0.003). The correlations between sfIL-6 and Pedi-IKDC activity score (.546, p = .234) and between sfIL-6 and total Pedi-IKDC score (-.536, p = .215) were not statistically significant. This is the first study to evaluate IL-6 as a biomarker of knee joint healing in an adolescent population, reported a very strong correlation (-.929, p=0.003) between IL-6 in knee joint synovial fluid and a subjective questionnaire on knee joint pain. These findings provide preliminary scientific evidence regarding the relationship between knee joint pain, as determined by a validated questionnaire and the inflammatory and healing status of the patient's knee. This study provides a basis and justification for future longitudinal research on biomarkers of knee joint healing in patients throughout their recovery and rehabilitation process. Incorporating physiological and psychosocial variables to current return-to-activity (RTA) criteria has the potential to improve decision making for adolescents following ACL reconstruction to reduce premature RTA thereby reducing the risk of re-injury and risk of early-onset knee OA in adolescents

Reconstruction of the anterior cruciate ligament (ACL) allows to restore stability of the knee, in order to facilitate the return to activity (RTA). Although it is understood that the tendon autograft undergoes a ligamentous transformation postoperatively, knowledge about longitudinal microstructural differences in tissue integrity between types of tendon autografts (ie, hamstring vs. patella) remains limited. Diffusion tensor imaging (DTI) has emerged as an objective biomarker to characterize the ligamentization process of the tendon autograft following surgical reconstruction. One major limitation to its use is the need for a pre-injury baseline MRI to compare recovery of the graft, and inform RTA. Here, we explore the relationship for DTI biomarkers (fractional anisotropy, FA) between knees bilaterally, in healthy participants, with the hypothesis that agreement within a patient's knees may support the use of the contralateral knee as a reference to monitor recovery of the tendon autograft, and inform RTA. Fifteen participants with no previous history of knee injuries were enrolled in this study (age, 26.7 +/− 4.4 years; M/F, 7/8). All images were acquired on a 3T Prisma Siemens scanner using a secured flexible 18-channel coil wrapped around the knee. Both knees were scanned. A 3D anatomical Double Echo Steady State (DESS) sequence was acquired on which regions of interest (ROI) were placed consistent with the footprints of the ACL (femur, posteromedial corner on medial aspect of lateral condyle; tibia, anteromedial to intercondylar eminence). Diffusion images were acquired using fat saturation based on optimized parameters in-house. All diffusion images were pre-processed using the FMRIB FSL toolbox. The footprint ROIs of the ACL were then used to reconstruct the ligament in each patient with fiber-based probabilistic tractography (FBPT), providing a semi-automated approach for segmentation. Average FA was computed for each subject, in both knees, and then correlated against one another using a Pearson correlation to assess the degree of similarity between the ACLs. A total of 30 datasets were collected for this study (1/knee/participant; N=15). The group averaged FA (+/− standard deviation) for the FBPT segmented ACLs were found to equal 0.1683 +/− 0.0235 (dominant leg) and 0.1666 +/− 0.0225 (non-dominant leg). When comparing both knees within subjects, reliable agreement was found for the FBPT-derived ACL with a linear correlation coefficient (rho) equal to 0.87 (P < 0 .001). We sought to assess the degree of concordance in FA between the knees of healthy participants with hopes to provide a method for using the contralateral “healthy” knee in the comparison of autograft-dependent longitudinal changes in microstructural integrity, following ACL reconstruction. Our results suggest that good agreement in anisotropy can be achieved between the non-dominant and dominant knees using DTI and the FBPT segmentation method. Contralateral anisotropy of the ACL, assuming no previous injuries, may be used as a quantitative reference biomarker for monitoring the recovery of the tendon autograft following surgical reconstruction, and gather further insight as to potential differences between chosen autografts. Clinically, this may also serve as an index to supplement decision-making with respect to RTA, and reduce rates of re-injuries

Obesity is associated with worse outcomes following total knee/hip arthroplasty (TKA/TKA). This study aimed to determine the feasibility of a dietitian-led low-inflammatory weight-loss program for people with obesity awaiting arthroplasty. Quasi-experimental pilot study enrolled people with obesity waitlisted for primary TKA/THA into ‘usual care’ (UC) or weight-loss (low-inflammatory diet) program (Diet). Recruitment occurred between July 2019 and February 2020 at Fairfield and Campbelltown Hospitals. Assessments at baseline, pre-surgery, time of surgery and 90-days following surgery included anthropometric measurements, patient-reported outcomes, serum biomarkers and 90-day postoperative complication rate. 97 people consented to the study (UC, n=47, mean age 67, BMI 37, TKA 79%; Diet, n=50, mean age 66, BMI 36, TKA 72%). Baseline characteristics indicated gross joint impairments and poor compliance with a low-inflammatory diet. Study feasibility criteria included recruitment rate (52%), proportion of diet patients that improved compliance to low-inflammatory diet by ≥10% (57%) and had ≥60% attendance of dietitian consultations (72%), proportion of patients who undertook serum biomarkers (55%). By presurgery assessments, the diet group had more patients who cancelled their surgery due to symptom improvement (4 vs 0), reduced waist-circumference measurements, increased compliance with the Low-Inflammatory diet and preservation of physical activity parameters. More usual care participants experienced at least one postoperative complication to 90-days (59% vs 47%) and were discharged to inpatient rehabilitation (21% vs 11%). There was no difference in weight change, physical function, and patient-reported outcome measures from pre-surgery to 90-days post-surgery, and length of hospital stay. Using pre-determined feasibility criteria, conducting a definitive trial is not feasible. However, intervention audit demonstrated high intervention fidelity. Pilot data suggest our program may promote weight loss but the clinical effects for most are modest. Further research utilising a stronger intervention may be required to assess the effectiveness of a pre-arthroplasty weight-loss intervention

Background. The diagnosis of periprosthetic joint infection (PJI) remains a challenge in clinical practice and the analysis of synovial fluid (SF) is a useful diagnostic tool. Recently, two synovial biomarkers (leukocyte esterase (LE) strip test, alpha-defensin (AD)) have been introduced into the MSIS (MusculoSkeletal Infection Society) algorithm for the diagnosis of PJI. AD, although promising with high sensitivity and specificity, remains expensive. Calprotectin is another protein released upon activation of articular neutrophils. The determination of calprotectin and joint CRP is feasible in a routine laboratory practice with low cost. Purpose. Our objective was to evaluate different synovial biomarkers (calprotectin, LE, CRP) for the diagnosis of PJI. Methods. In this monocentric study, we collected SF from hip, knee, ankle and shoulder joints of 42 patients who underwent revision or puncture for diagnostic purposes. Exclusion criteria included a joint surgery in the previous 3 months and a diagnosis of a systemic inflammatory disease. PJI was diagnosed in a multidisciplinary consultation meeting (RCP) of the Reference Centers for Osteoarticular Infections of the Great West (CRIOGO). SF was analysed for LE, CRP and calprotectin. The cut-off values used were 50 mg/L for calprotectin, 8.8 mg/L for CRP and 125 WBC/µL for LE. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for these different synovial markers. Results. Of the 42 patients included, 28 were considered as infected and 14 uninfected. The statistical parameters are presented in Table 1. Conclusion. The present study shows that the synovial calprotectin assay has an excellent sensitivity and a 100% NPV for the diagnosis of PJI, suggesting that a result < 50 mg/L could exclude PJI. This promising study suggests that calprotectin should be included with synovial CRP in a new decision algorithm for the diagnosis of PJI. 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 analysis of synovial fluid has proved to be of crucial importance in the diagnostic process of prosthetic joint infections (PJI), suggesting the presence of an infection before the microbiological culture results. In this context, several studies illustrated the efficacy of synovial calprotectin in supporting the diagnosis of PJI [1, 2]. However, several testing methods have been explored to detect synovial calprotectin levels, emphasizing the need to use a standardized, rapid and rapid test. In this study, synovial calprotectin was analyzed by means of a commercial stool test [3] to explore whether the detected levels might predict PJIs and, therefore, being a promising tool for the fast and reliable diagnosis of this complication. Method. The synovial fluid of 55 patients underwent to revision of the prosthetic implant were analyzed. The measurement of calprotectin was carried out by of commercial stool test, following the protocol for liquid samples. Calprotectin levels were then compared to other synovial biomarkers of PJI such as leucocyte esterase and count and percentage of polymorphonuclear cells. Data analysis were performed using R software v4.1.1 (R Core Team) and package “pROC” [4]. Receiver operator characteristics curves were designed using culture test as gold standard to evaluate the area under curve (AUC) of each method (with DeLong method for confidence-interval calculation). Thresholds were calculated to maximize Youden's index; sensitivity and specificity were reported. One-to-one Pearson's correlations coefficient were calculated for each pair of methods. P value <0.05 were considered statistically significant. Results. Of the 55 synovial fluids analyzed, 13 patients were diagnosed with PJI and 42 with an aseptic failure of the implant. The specificity, sensitivity, and AUC of calprotectin resulted 0.90, 0.85, and 0.86 (95%CI: 0.72–0.99), respectively with a set threshold of 226.5 µg/g. The values of calprotectin had a moderate and statistically relevant correlation with the synovial leucocyte counts (r. s. = 0.54, p = 0.0003) and the percentage of polymorphonuclear cells (r. s. = 0.68, p = 0.0000). Conclusions. From this analysis, it can be concluded that synovial calprotectin is a valuable biomarker that correlates with other established indicator of local infection, delivering a rapid and reliable results and supporting the diagnostic process of PJI

Aim. Differentiation of infected (INF) nonunion from aseptic (AS) nonunion is crucial for the choice of intra- and postoperative treatment. Preoperative diagnosis of infected nonunion is challenging, especially in case of low-grade infection lacking clinical signs of infection. Standard blood markers such as C-reactive protein or leucocyte count do not aid in preoperative diagnosis. Proteomic profiling has shown promising results for differentiation of numerous chronic disease states, and in this study was applied to preoperative blood samples of patients with nonunion in an attempt to identify potential biomarkers. Method. This prospective multicenter study enrolled patients undergoing revision surgery of femur or tibia nonunion. Patients with implant removal after regular fracture healing (HEAL) were included as a control-group. Preoperative blood samples, intraoperative tissue samples, sonication of osteosynthesis material and 1-year-follow-up questionnaire were taken. Nonunion patients were grouped into INF or AS after assessing bacterial culture and histopathology of retrieved samples. Diagnosis of infection followed the fracture related infection consensus group criteria, with additional consideration of healing one year after revision surgery. Targeted proteomics was used to investigate a predefined panel of 45 cytokines in preoperative blood samples. Statistical differences were calculated with Kruskal Wallis and Dunn's post hoc test. Cytokines with less than 80% of samples being above the lower limit of detection range (LLDR) were excluded for this study. Results. We recruited 62 AS, 43 INF and 32 HEAL patients. Patients in the two nonunion groups (INF and AS) did not differ concerning smoking, diabetes or initial open or closed fracture. Thirty-two cytokines were above LLDR in >80% of patients. INF patients showed a significant difference in expression of 8 cytokines compared to AS, with greatest differences observed for Macrophage Colony Stimulating Factor 1 (MCSF-1) and Hepatocyte Growth Factor (HGF) (p<0.01). In comparing AS with HEAL patients, 9 cytokines displayed significant differences, including interleukin (IL)-6, Vascular Endothelial Growth Factor A (VEGFA), Matrix Metalloproteinase 1 (MMP-1). Comparison of INF with HEAL patients revealed significantly different expression of 20 cytokines, including. IL-6, IL-18, VEGFA or MMP-1. Conclusions. Our study revealed differences in plasma cytokine profile of blood samples from INF and AS patients. Although no single biomarker is sufficient to differentiate these patients preoperatively in isolation, future multivariant analysis of this cytokine data in combination with clinical characteristics may provide valuable diagnostic insights. Funded by German Social Accident Insurance (FF-FR 0276) and AO Trauma (AR2021_04)

The number of shoulder arthroplasty procedures performed in the United States continues to rise. Currently, the number of procedures performed per year ranges from 55,000–80,000 and is expected to increase more than 300% in the coming years. Periprosthetic joint infection (PJI) is one of the most serious complications associated with arthroplasty surgery, leading to poor outcomes, increased cost, and technically difficult revision surgery. The incidence of infection following primary shoulder arthroplasty has been reported between 0.7% and 4%, representing 2.9–4.6% of all complications. Prosthetic shoulder joint infections are unlike prosthetic joint infections of the hip and knee. Shoulder PJIs are primarily indolent in nature and difficult to diagnose using traditional methods that have been shown to be accurate for periprosthetic infections of the hip and knee. The majority of infected revision shoulder arthroplasties are associated with growth of Propionibacterium acnes (P. Acnes). This slow-growing, anaerobic organism requires longer than normal incubation times for culture (7–21 days), and typically demonstrates a subtle, non-specific clinical presentation that can make the presence of infection difficult to identify. In the reported literature, P. Acnes accounts for about 70% of cases with positive cultures associated with revision for treatment of a painful shoulder arthroplasty and due to the bacteria's slow growing nature and virulence profile, the rate of infection following shoulder arthroplasty may often be underestimated. A more recent and promising tool for evaluation of periprosthetic infection has been analysis of synovial fluid. Synovial fluid biomarkers have been identified as part of the innate response to pathogens, and include pro-inflammatory cytokines and anti-microbial peptides, and marker levels have shown promise for improved diagnostic efficacy in hip and knee PJI. Currently, no highly predictive clinical test for diagnosis of PJI in the shoulder exists, however, several of these synovial biomarkers have recently been analyzed for their diagnostic capacity in the setting of periprosthetic shoulder infection. Synovial fluid cytokine analysis shows the potential to improve diagnosis of infection in revision shoulder arthroplasty. This information can help to guide decision-making in the management of PJI of the shoulder, including the decision to perform a single- vs. two-stage revision surgery, and the need for post-operative antibiotics following an unexpected positive culture result after revision surgery. However, there are still challenges to broader use of these synovial biomarkers. Synovial α-defensin (Synovsure, CD Diagnostic) is the only marker currently available as a commercial test, and no point-of-care test is currently available for any of the biomarkers to allow for intraoperative decision-making. While a preoperative synovial aspirate is possible to send for α-defensin analysis currently, with results back in approximately 24 hours, dry fluid aspirations are frequent in the shoulder because of the predominance of indolent pathogens and may limit utility of the test. In summary, indolent infection associated with P. acnes is a common cause for the painful total shoulder arthroplasty. Pre-operative diagnosis of infection is difficult as a result of the poor diagnostic accuracy of traditional methods of testing. Synovial biomarker testing may ultimately improve our ability to more accurately diagnosis and treat prosthetic shoulder joint infections

Aim. Periprosthetic joint infections (PJI) are severe complications after total joint arthroplasty (TJA). Up to now, a gold standard in the diagnostics of PJI is missing. Small extracellular vesicles (sEVs) are secreted by all types of cells and play a key role in immune response in presence of infection (1). In this prospective study, the diagnostic accuracy of sEVs in the synovial fluid to detect PJI of knee, hip and shoulder joints was investigated. We hypothesized increased surface markers of sEVs in PJI compared to aseptic complications (e.g. implant loosening, stress shielding related pain). Method. Synovial fluid from 48 patients with painful arthroplasty was examined. The distinction between aseptic and infectious cases was made on the basis of the 2018 Definition of Periprosthetic Hip and Knee Infection (2). 35 (72,9%) probands assigned to aseptic and 13 patients (27,1%) to PJI group. Immuno-fluorescence flow cytometry served to document the concentrations of CD9, CD63, CD66b, CD82 and HLA-DR on sEVs. Results. The concentration of CD9 surface marker on sEVs in synovial fluid was significantly lower (p=0.002) in PJI group than in aseptic group. In contrast, the levels of CD82 on sEVs in synovial fluid was significantly higher (p<0.0001) in the PJI group than in aseptic group. The concentrations of CD63, CD66b and HLA-DR on sEVs in synovial fluid did not differ significantly between the two cohorts (CD63: p=0.372; CD66b: p=0.634; HLA-DR: p=0.558). Conclusions. Overall, the significance of sEVs in the diagnostics of PJI is not well enough understood and the subject of current research and scientific discussion. Our data suggest, that CD82 and CD9 on sEVs in synovial fluid are promising biomarkers to differentiate between PJI and aseptic complications

Specific and rapid detection methods for spinal tuberculosis, with sufficient sensitivity in HIV-1 co-infected individuals, are needed, to ensure early initiation of appropriate treatment to prevent physical disability and neurological fallout. In addition, understanding the systemic and local pathophysiology of spinal tuberculosis, and its interaction with HIV-1 infection, is crucial to guide future therapeutic interventions. We prospectively enrolled adult patients presenting with signs and symptoms of suspected spinal tuberculosis, at Groote Schuur Hospital, between November 2020 and December 2021. TB diagnostic testing was performed on open and CT-guided spinal biopsies using Xpert MTB/RIF Ultra compared to gold standards TB culture and histology. A highly sensitive droplet digital PCR assay for detecting and quantifying Mycobacterium tuberculosis complex (MTBC) and HIV-1 DNA was tested. Plasma inflammatory proteins were measured to assess systemic inflammation. Xpert Ultra had a high sensitivity of 94.7% and specificity of 100% for STB against TB culture and histology in both open and CT-guided biopsy samples. The ddPCR assay confirmed TB detection in 94% of patients with positive Xpert Ultra results. Four patients with negative TB diagnostic results had MTBC DNA detected by ddPCR. HIV-1 DNA was detected in the spinal tissues from all HIV-1-infected patients. MTBC DNA levels were significantly higher in HIV-1-co-infected spinal tissue samples (p< 0.01). We identified four biomarkers significantly associated with higher bacterial burden at the disease site (p< 0.01). Xpert Ultra and MTBC ddPCR improve the detection of STB. DdPCR can be utilized as an additional, highly sensitive tool for detecting and quantifying Mtb, in pathological samples that may be paucibacillary. These findings provide novel diagnostic and pathophysiologic insight into STB, in the context of HIV-1 infection, and provide rationale to include these tests in hospital and research settings for patients from communities burdened by TB and HIV-1

Aim. Low-grade infections cannot be easily distinguished from aseptic complications frequently leading to false negative diagnoses and late onset of anti-bacterial therapy. Therefore, there is a great need to establish biomarkers for early detection of low-grade infections. Method. In this study, we focused on the investigation of anti-α-defensin, anti-C3, anti-C5 and anti-C9 as potential biomarkers for infection in a cohort of hip and knee septic revision cases, taking patient characteristics and comorbidities into account. Here we included 78 patients with septic (35) and aseptic (43) (woman:37, men:42, age 50 – 93 years) revision surgeries of hip and knee. CRP serum levels and leucocyte blood values were evaluated. Patient characteristics, including age, number of prior revision surgeries and comorbidities were recorded. Periprosthetic tissue was stained histologically with Hematoxylin/Eosin and immunohistologically with different antibodies. Results. The CRP values were significantly increased in the septic cohort, but no changes were observed in leucocyte count. Interestingly, we found a strong increase in the terminal complement system component C9 (septic: 0.1% ± 0.2% aseptic: 0.01% ± 0.05%, p= 0.0004) in the septic periprosthetic tissue. The predictive value of α-defensin staining was not statistically significant (septic: 0.5% ± 0.7% aseptic: 0.1% ± 0.6%, p= 0.09). Analyzing the synovial fluid of aseptic and septic patients, the presence of C9 in the septic group (1.8 ± 0.4) was not significantly higher compared to the aseptic (1.9 ± 0.7) group. The next step was to investigate the specificity C9 detection using different joint related diseases such as chondrocalcinosis (CC), rheumatoid arthritis (RA) and metallosis. The median of C9 staining in the CC group (0 ± 0.0001) was significant lower than the infection group. Similar results have been observed in RA (0.0003 ± 0.2) and the metallosis group (0.0002 ± 0.01). Conclusions. We found a strong predictive value of anti-C9 staining for tissue infection, suggesting that C9 deposition could be a novel biomarker for the identification of periprosthetic joint infections using tissue biopsies

Aim. Despite several synovial fluid biomarkers for diagnosis of periprosthetic joint infection (PJI) have being investigated, point-of-care (POC) tests using these biomarkers are not widely available. Synovial calprotectin has recently been reported to effectively exclude diagnosis of PJI and a novel lateral flow POC test using it has shown potential to be effective. Thus, the aims of this study were to 1) validate calprotectin POC with enzyme linked immunosorbet assay (ELISA) 2) at 2 separate thresholds for PJI diagnosis in total knee arthroplasty (TKA) patients using the 2013 Musculoskeletal Infection Society (MSIS) PJI diagnosis criteria as the gold standard. Method. Intraoperative synovial fluid samples were prospectively collected from 123 patients who underwent revision TKAs (rTKA) at two academic hospitals within the same healthcare system from October 2018 to January 2020. The study was conducted under IRB approval. Included patients followed the hospital standard for their PJI diagnostic work-up. Data collection included demographic, clinical, and laboratory data in compliance with MSIS criteria. Synovial fluid samples were analysed by calprotectin POC and ELISA tests in accordance with manufacturer's instructions. Patients were categorized as septic or aseptic using MSIS criteria by two independent reviewers blinded to calprotectin assay results. The calprotectin POC and ELISA test performance characteristics were calculated with sensitivities, specificities, positive, and negative predicted values (PPV and NPV, respectively) and areas under the curve (AUC) for 2 different PJI diagnosis scenarios: (1) a threshold of >50 mg/L and (2) a threshold of >14 mg/L. Results. According to MSIS criteria, 53 rTKAs were septic while 70 rTKA were aseptic. In the (1) >50 mg/mL threshold scenario, the calprotectin POC and ELISA performance showed 100% agreement with sensitivity, specificity, PPV, NPV, and AUC, respectively, of 98.1%, 95.7%, 94.5%, 98.5%, and 0.969. In the (2) >14 mg/mL threshold scenario, the POC slightly outperformed the ELISA with sensitivity, specificity, PPV, NPV and AUC of 98.1%, 87.1%, 85.2%, 98.4%, and 0.926, respectively (ELISA values were 98.1%, 82.9%, 81.3%, 98.3%, and 0.905, respectively). Conclusions. The calprotectin POC test performed as well as the ELISA at the >50mg/L threshold and was slightly better at the >14 mg/L threshold. The >50 mg/L threshold had a better specificity while maintaining the same sensitivity as the >14 mg/L threshold. This test could be effectively implemented as a rule out test. However, further investigations with larger cohorts are necessary to validate these results