Knee tuberculosis: an overlooked clinical entity.

INTRODUCTION: The most common anatomic sites affected by extrapulmonary tuberculosis are lymph nodes, pleura, bones, and joints, urogenital tract, and meninges. Tuberculous arthritis is difficult to diagnose early because of its atypical insidious clinical manifestations and non-specific imaging findings. CASE REPORT: A 59-year-old male presented with progressive swelling in his left knee for over two months. The patient was initially misdiagnosed with pigmented villonodular synovitis (PVNS) and had undergone total knee arthroplasty (TKA) two years ago, however, the TKA did not completely alleviate his symptoms. Comprehensive radiological and laboratory assessments, including X-rays, magnetic resonance imaging and computed tomography scans, and an interferon-γ release assay (IGRA), pointed towards a diagnosis of tuberculous knee arthritis. Definitive diagnosis was established through the detection of Mycobacterium tuberculosis (MTB) DNA in the synovial fluid via polymerase chain reaction (PCR) and a positive IGRA result. CONCLUSIONS: The case underscores the importance of considering MTB infection in the differential diagnosis of chronic unilateral knee arthritis, especially given the atypical clinical manifestations and imaging findings that can mimic other conditions like PVNS.

Metagenomic next-generation sequencing promotes pathogen detection over culture in joint infections with previous antibiotic exposure.

Objective: To investigate the diagnostic value of metagenomic next-generation sequencing (mNGS) in detecting pathogens from joint infection (JI) synovial fluid (SF) samples with previous antibiotic exposure. Methods: From January 2019 to January 2022, 59 cases with suspected JI were enrolled. All cases had antibiotic exposure within 2 weeks before sample collection. mNGS and conventional culture were performed on SF samples. JI was diagnosed based on history and clinical symptoms in conjunction with MSIS criteria. The diagnostic values, including sensitivity, specificity, positive/negative predictive values (PPV/NPV), and accuracy, were in comparison with mNGS and culture. Results: There were 47 of the 59 cases diagnosed with JI, while the remaining 12 were diagnosed with non-infectious diseases. The sensitivity of mNGS was 68.1%, which was significantly higher than that of culture (25.5%, p<0.01). The accuracy of mNGS was significantly higher at 71.2% compared to the culture at 39.0% (p <0.01). Eleven pathogenic strains were detected by mNGS but not by microbiological culture, which included Staphylococcus lugdunensis, Staphylococcus cohnii, Finegoldia magna, Enterococcus faecalis, Staphylococcus saprophytics, Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, Acinetobacter pittii, Brucella ovis, andCoxiella burnetii. Antibiotic therapy was adjusted based on the mNGS results in 32 (68.1%) patients, including 12 (25.5%) and 20 (42.6%) patients, in whom treatment was upgraded and changed, respectively. All JI patients underwent surgery and received subsequent antibiotic therapy. They were followed up for an average of 23 months (20-27 months), and the success rate of treatment was 89.4%. Out of the 33 patients who had positive results for pathogens, reoperation was performed in 1 case (3.03%), while out of the 14 cases with negative results for both mNGS and cultures, reoperation was performed in 4 cases (28.6%). Conclusions: mNGS has advantages over conventional culture in detecting pathogens in SF samples from JI patients previously treated with antibiotics, potentially improving clinical outcomes.

Synovial Fluid Cutibacterium acnes Antigen Is Detected Among Shoulder Samples with High Inflammation and Early Culture Growth.

BACKGROUND: An emerging paradigm suggests that positive Cutibacterium acnes shoulder cultures can result from either true infection or contamination, with true infections demonstrating a host inflammatory response and early culture growth. This clinical retrospective study examines the relationship between C. acnes antigen, C. acnes culture results, and inflammation. METHODS: From January 2021 to July 2023, 1,365 periprosthetic synovial fluid samples from 347 institutions were tested for shoulder infection at a centralized clinical laboratory. A biomarker scoring system based on the 2018 International Consensus Meeting (ICM) definition was utilized to assign each sample an inflammation score. Associations between inflammation, culture results, and C. acnes antigen results were assessed utilizing cluster and correlation analyses. RESULTS: Of 1,365 samples, 1,150 were culture-negative and 215 were culture-positive (94 C. acnes and 121 other organisms). Among the 94 C. acnes culture-positive samples, unsupervised clustering revealed 2 distinct sample clusters (silhouette coefficient, 0.83): a high-inflammation cluster (n = 67) and a low-inflammation cluster (n = 27). C. acnes antigen levels demonstrated moderate-strong positive correlation with inflammation (Spearman ρ, 0.60), with 166-fold higher levels of C. acnes antigen in high-inflammation samples (16.6 signal/cutoff [S/CO]) compared with low-inflammation samples (0.1 S/CO) (p < 0.0001). The days to C. acnes culture positivity demonstrated weak-inverse correlation with inflammation (Spearman ρ = -0.38), with 1.5-fold earlier growth among the 67 high-inflammation samples (6.7 compared with 10.4 days; p < 0.0001). Elevated C. acnes antigen was observed in only 4 (0.38%) of 1,050 low-inflammation culture-negative samples and in only 5 (4.9%) of 103 high-inflammation non- C. acnes -positive cultures. However, 19.0% of high-inflammation, culture-negative samples demonstrated elevated C. acnes antigen. CONCLUSIONS: Synovial fluid C. acnes antigen was detected among shoulder samples with high inflammation and early culture growth, supporting the emerging paradigm that these samples represent true infection. Future research should explore antigen testing to differentiate contamination from infection and to identify culture-negative C. acnes infections. LEVEL OF EVIDENCE: Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Prosthetic joint infection caused by Mediterraneibacter gnavus following total knee arthroplasty, challenges in anaerobic bacteria identification.

BACKGROUND: Mediterraneibacter gnavus is a Gram positive, non-sporulated, obligate anaerobe diplococci. It was first described in 1974 by Moore et al. (under the name Ruminococcus gnavus) from faeces and contents of the gastrointestinal tract of humans. It is a relatively common member of the human gut microbiota, nevertheless its role as a pathogenic bacterium has not been completely elucidated yet and it seems to depend on numerous factors, including those of the host. Here we present a case of prosthetic joint infection following total knee arthroplasty by M. gnavus. CASE PRESENTATION: A 74 years old patient was admitted to the emergency department presenting with acute onset of left knee pain and swelling 20 days after total left knee arthroplasty. Follow-up revealed erythema and oedema without signs of fluctuation or purulent discharge from the surgical wound and elevated inflammatory reactants. Synovial fluid was taken for bacterial culture and antibiotic treatment with ceftazidime and daptomycin was established. Examination of the synovial fluid revealed abundant polymorphonuclear leucocytes, without visualizing bacteria. After four days of incubation, anaerobic culture exhibit growth of small, grey, umbilicated colonies in pure culture on Schaedler agar. The microorganism was identified as R. gnavus by MALDI-TOF (Bruker Daltonics) and M. gnavus by 16S ribosomal bacterial sequencing. The isolated showed susceptibility to the most commonly used anaerobicidal antibiotics except for clindamycin. Surgical treatment and infection source control included DAIR (debridement, antibiotics, and implant retention) and vacuum assisted therapy. The patient was discharged after six weeks with a 3-month course of oral amoxicillin as consolidation therapy. Subsequent follow-up revealed adequate wound healing with no signs of infection. CONCLUSIONS: Mediterraneibacter gnavus have been reported as the causal microorganism in a range of human infections, nevertheless its identification remains challenging. Infection of prosthetic joints by anaerobic microorganisms is uncommon and is not considered in its empirical antibiotic treatment, thus, correct and swift identification of anaerobic bacteria in these cases is paramount.

Propensity of Candida spp. prosthetic joint infection clinical isolates to form aggregates in synovial fluid and the clinical ramifications.

BACKGROUND: Bacterial aggregation has been shown to occur in synovial fluid which are resistant to high concentrations of antibiotics. Yet the propensity of Candida spp. to form aggregates is unknown. OBJECTIVE: To assess the ability of numerous Candida spp. to form synovial fluid aggregates and the clinical ramifications of the aggregates. METHODS: Nine different Candidal prosthetic joint infection clinical isolates were evaluated for their ability to form aggregates at static and dynamic conditions and their resistance to high concentrations of amphotericin. Furthermore, the ability of tissue plasminogen activator (TPA) to disrupt the aggregates and enhance amphotericin activity was assessed. RESULTS: The results show that all species of Candida spp. evaluated formed aggregates in synovial fluid under dynamic conditions that were resistant to amphotericin. Yet no aggregates formed in tryptic soy broth under any conditions or in synovial fluid under static conditions. As well, when TPA was combined with amphotericin there was a statistically significant decrease (p < .005) in the amount of colony forming units per mL for all Candidal species evaluated. Interestingly, for Candida krusei there was no colony forming units observed after exposure to TPA and amphotericin. CONCLUSION: Our findings suggest that Candidal species form synovial fluid aggregates that are resistant to high dose amphotericin similar to those that occur with bacteria. However, the varying ability of the different Candida spp. to form hyphae and pseudohyphae compared to yeast cells may have direct impacts on the hardiness of the aggregates and thereby have clinical ramifications with respect to treatment durations.

The predictive value and reliability of ultrasound-guided synovial aspiration and biopsies for diagnosing periprosthetic shoulder infections.

INTRODUCTION: Preoperative diagnosis of periprosthetic shoulder infections (PSI) is difficult. Infections are mostly caused by low virulence bacteria and patients do not show typical signs of infection. The aim of this study was to determine the diagnostic value and reliability of ultrasound-guided biopsies for cultures alone and in combination with multiplex polymerase chain reaction (mPCR), serum markers, and/or synovial markers for the preoperative diagnosis of PSI in patients undergoing revision shoulder surgery. MATERIALS AND METHODS: A prospective explorative diagnostic cohort study was performed including 55 patients undergoing revision shoulder replacement surgery. A shoulder puncture was performed preoperatively before incision to collect synovial fluid for mPCR analysis and for measurement of interleukin-6, calprotectin, white blood cell count (WBC), and polymorphonuclear cells. Also prior to revision surgery, six ultrasound-guided synovial tissue biopsies were collected for culture and two for mPCR analysis. A blood sample was obtained to determine serum C-reactive protein, WBC, and erythrocyte sedimentation rate. Six routine care tissue biopsies were taken during revision surgery and served as reference standard. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV; the primary outcome measure), and accuracy were calculated for ultrasound-guided biopsies, blood and synovial markers, mPCR, and combinations thereof. RESULTS: Routine tissue cultures were positive for infection in 24 patients. Cultures from ultrasound-guided biopsies diagnosed infection in 7 of these patients, yielding a sensitivity, specificity, PPV, NPV, and accuracy of 29.2%, 93.5%, 77.8%, 63.0%, and 65.6%, respectively. The best diagnostic value was found for the combination of ultrasound-guided biopsies for culture, synovial WBC, and calprotectin with a sensitivity of 69.2%, specificity of 80.0%, PPV of 69.2%, and NPV of 80.0%. CONCLUSION: Ultrasound-guided biopsies for cultures alone and in combination with mPCR, and/or blood and/or synovial markers are not reliable enough to use in clinical practice for the preoperative diagnosis of PSI. LEVEL OF EVIDENCE: Diagnostic study level II.

Predicting Septic Arthritis in the Setting of Crystalline Arthropathy in the Native Joint Using Laboratory Data.

Background: Septic arthritis is an orthopedic emergency. Diagnosis is difficult in patients with concomitant crystalline arthropathy (gout or pseudogout). The symptomatology of crystal arthritis mimics septic arthritis, clouding clinical diagnosis. Arthrocentesis and synovial fluid analysis are the standard diagnostic tests for both pathologies. Crystals on microscopy are diagnostic of crystal arthritis, however their presence does not rule out septic arthritis. Septic arthritis is diagnosed by positive microbiology culture. Though septic arthritis is associated with elevated synovial total nucleated count (TNC), TNC elevations can also occur with gout. The literature suggests that a TNC count of > 50,000 cells in a crystal-positive joint should raise suspicion for concurrent septic arthritis, however data is limited. Further diagnostic indicators are needed to help clinicians promptly identify crystal positive septic arthritis as the treatments and prognoses are different. Methods: Patients were retrospectively identified who had arthrocentesis of a native joint positive for monosodium urate (MSU) and/or (CPPD) crystals. Laboratory data was collected including synovial fluid cultures, total nucleated cell count (TNC), percent polymorphic neutrophils (%PMN), and crystal analysis; and serum CRP, ESR, and white blood cell count (WBC). Statistical analysis performed using Spearman correlation, Univariate-Fischer's exact and Wilcoxon tests, and multivariate analysis. Results: 442 joints identified with positive CPPD and/or MSU crystals, 31% female, 69% male. Of 442 aspirates, 58 had positive cultures. Patients were more likely to have positive cultures if synovial TNC > 50,000 (odds ratio 7.7), CRP > 10 mg/dL (OR 3.2), PMN > 90% (OR 2.17), and if the patient was female (OR 1.9), all were statistically significant with p < 0.05. There were 55 patients who underwent irrigation and debridement based on clinical suspicion or a positive gram stain, 37 of these ultimately had a positive culture (67%), the remaining 18 had negative cultures. Conclusion: Results are consistent with the literature, a TNC > 50,000 warrants a high suspicion for concurrent septic arthritis and should prompt providers to critically evaluate other patient laboratory data. Results further suggests that a patient with positive crystals, synovial TNC > 50,000 cells, PMN > 90%, and serum CRP > 10mg/dL is at high risk for having a concurrent septic arthritis and may warrant urgent irrigation and debridement and antibiotic therapy. This data serves as a supporting to develop an infection risk calculator for crystal positive septic arthritis. Level of Evidence: III.

Effect of silica-sprayed collection tubes on synovial fluid bacterial culture.

INTRODUCTION: Silica-sprayed tubes (SSTs) are often used to transport synovial fluid samples in equine practice. They promote the coagulation of the sample. The objective of the study is to evaluate the effect of SST on bacterial culture. MATERIALS AND METHODS: The study was divided into two parts: sterile saline (Part A) and synovial fluid (Part B). Four common bacteria associated with equine synovial sepsis were used: Streptococcus pyogenes, Escherichia coli, Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). Three collection tubes were used: STT, plain (no-additives) and brain and heart infusion (BHI) broth. Bacteria were cultured in horse blood agar plates for 48 h. Outcome variables were negative culture, positive culture and total number of colony-forming units (CFUs). Statistical analysis was performed using Mann-Whitney U test, and significance was set at p < 0.05. RESULTS: The total number of agar plates read was 1557 (779 saline; 778 synovial fluid). Total negative cultures were 25/779 on saline and 3/778 on synovial fluid. In broth, maximum growth CFU was achieved after 8 h for both saline and synovial fluid for all bacteria. S. pyogenesand E. coli produced a significantly lower number of CFU when in SST compared to plain or broth after 4 h, whereas S. aureus (American Type Culture Collection [ATCC] and MRSA) only after 24 h. DISCUSSION: Silica-containing tubes reduced bacterial proliferation, whereas the use of a BHI broth provided the highest bacterial load in the sample. The use of SST may have a negative effect on bacterial proliferation in samples obtained from clinical cases.

Concomitant septic and crystal arthropathy: a single-centre 10-year retrospective observational study in New Zealand.

AIM: To quantify and characterise patients with coexistent septic arthritis (SA) and crystal arthritis (CA) (SACA) in an emergency department (ED) setting. METHODS: A single-centre, retrospective, 10-year observational study was conducted at a major referral centre. Patients with a positive joint aspirate for CA or SA carried out in ED, were included. The Newman criteria were utilised to define SA. RESULTS: Of the 567 patients included in the final analysis, 427 had CA and 140 had a final diagnosis of SA. Twenty-three point six percent of patients diagnosed with SA had concomitant CA, while 7.2% of patients diagnosed with CA had concomitant SA. The greatest predisposing factors for SACA were previous history of gout, rheumatoid arthritis, being immunocompromised or having joint metalware. Synovial fluid (SF) white cell count (WCC) showed excellent predictive capability for joint infection with the area under the receiver operating characteristic curves (AUROCs) of 0.81 and 0.87 for SA and SACA respectively. The receiver operating characteristic curves (ROCs) reported a SF WCC cutoff of 32,000/mm3 allowed for 100% sensitivity and approximately 50% specificity. CONCLUSIONS: SACA remains a small but important sub-group of patients at risk of misdiagnosis of CA alone. SF WCC of 32,000/mm3 may be a better cutoff than the traditionally accepted 50,000/mm3, possibly warranting inpatient admission for investigation and management of presumed SA.

Differentiating Lyme arthritis: a case-based review.

The incidence or prevalence of Lyme arthritis (LA) in Denmark is unknown and assumed very low. No published cases of polymerase chain reaction (PCR)-confirmed LA from Denmark exist. Clinically, LA does not differ from other rheumatic oligoarthritic disorders posing a differential diagnostic challenge. To review the incidence and prevalence of LA to our knowledge and to present a case series of PCR-confirmed LA cases from Denmark. We conducted a systematic literature review via MEDLINE and EMBASE to explore incidence and prevalence rates of LA. Additionally, we present six cases of patients diagnosed with LA in Denmark. Our literature review identified 23 studies reporting prevalence or incidence, yet only ten studies provided estimates ranging from 1.1 to 280/100.000 in the general population. Our case series identified six patients with LA from a localized region in Southern Denmark; all confirmed by Borrelia-specific real-time PCR from synovial fluid. The diagnostic delay was up to 38 months. All patients except one had a history of previous tick bites; none had erythema migrans lesions. All presented with recurrent arthritis in the knee joint, and two had arthritis in the wrist. The literature review showed an incidence of LA ranging from 1.1 to 15.8 per 100.000 in Europe. Our case series suggests a potentially higher prevalence of LA in Denmark than previously believed. Lack of tick exposure history, antibody assessments and test of Borrelia burgdorferi sensu lato DNA in synovial fluid might lead to misdiagnosed cases potentially explaining the assumed low incidence of LA in Denmark.

Specific discrimination of pathogenic bacteria causing septic arthritis using Raman spectroscopy: In-vitro study.

In this study we performed preliminary experiments using Raman spectroscopy as an evolving technology in biofluid and microbial characterization, to explore its potential for rapid diagnosis of pathogenic bacteria in an in-vitro synovial fluid infection model. Normal human synovial fluids samples were collected from patients undergoing knee surgery and the three most common pathogenic bacteria introduced in-vitro into the samples. The bacterial growth was systematically monitored using a Raman spectroscopy. Multivariate regression analysis of acquired spectra showed bacterial characteristic Raman bands related to bacterial cell membranes and DNA structures to increase continuously as the incubation period was increased. Spectra signature recorded from cultured synovial fluid samples showed a significant loss in synovial quality and protein morphology over time compared to control samples. In this study, Raman spectroscopy shows promise for rapid pathogenic bacteria identification in synovial fluid. Marker peaks distinguished inoculated bacteria, while chemical changes reveal infection dynamics.

A case study: Lecanicillium infection detected in the human body.

Lecanicillium dimorphum and Lecanicillium psalliotae are fungi that exist naturally in plants or insects, and are generally considered non-pathogenic to humans. However, in this case, we cultured Lecanicillium from the synovial fluid of a patient, and identified it through genome sequencing and sequence alignment as Lecanicillium dimorphum or Lecanicillium psalliotae. Due to the conservation of sequences, we can only identify the genus and not the species. There are very few reports on the human infection and pathogenicity of these two fungi, and this case also cannot completely prove that the pathogenic agent is this fungus. But this case also holds clinical significance, as the discovery of Lecanicillium in a human sample can alert the clinician to the presence of an uncommon mold with unclear clinical significance.

Development of a multiplex Loop-Mediated Isothermal Amplification (LAMP) for the diagnosis of bacterial periprosthetic joint infection.

BACKGROUND: Periprosthetic joint infection (PJI) is one of the most serious and debilitating complications that can occur after total joint arthroplasty. Therefore, early diagnosis and appropriate treatment are important for a good prognosis. Recently, molecular diagnostic methods have been widely used to detect the causative microorganisms of PJI sensitively and rapidly. The Multiplex Loop-Mediated Isothermal Amplification (LAMP) method eliminates the complex temperature cycling and delays caused by temperature transitions seen in polymerase chain reaction (PCR) methods, making it faster and easier to perform compared to PCR-based assays. Therefore, this study developed a multiplex LAMP assay for diagnosing bacterial PJI using LAMP technology and evaluated its analytical and clinical performance. METHODS: We developed a multiplex LAMP assay for the detection of five bacteria: Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, Pseudomonas aeruginosa, and Escherichia coli, frequently observed to be the causative agents of PJI. The method of analytical sensitivity and cross-reactivity were determined by spiking standard strains into the joint synovial fluid. The analytical sensitivity of the multiplex LAMP assay was compared with that of a quantitative real-time PCR (qPCR) assay. Clinical performance was evaluated using 20 joint synovial fluid samples collected from patients suspected of having bacterial PJI. RESULTS: The analytical sensitivity of the gram-positive bacterial multiplex LAMP assay and qPCR were 105/104 CFU/mL, 103/103 CFU/mL, and 105/104 CFU/mL against S. agalactiae, S. epidermidis, and S. aureus, respectively. For P. aeruginosa and E. coli, the analytical sensitivity of the multiplex LAMP and qPCR assays were 105/104 and 106/104 CFU/mL, respectively. The multiplex LAMP assay detects target bacteria without cross-reacting with other bacteria, and exhibited 100% sensitivity and specificity in clinical performance evaluation. CONCLUSIONS: This multiplex LAMP assay can rapidly detect five high-prevalence bacterial species causing bacterial PJI, with excellent sensitivity and specificity, in less than 1 h, and it may be useful for the early diagnosis of PJI.

An elderly male with septic arthritis and bacteremia.

Rhodococcus hoagii is a gram positive actinomycete found in horses and cattle. Humans can be infected by ingestion or inhalation through contaminated food or soil. The organism usually infects immunosuppressed hosts with pneumonia being the common presentation. We present a case of an 89 years old, apparently immunocompetent host presenting with fever, encephalopathy and arthritis who grew Rhodococcus hoagii in blood and synovial fluid, The patient responded well to a combination of vancomycin, azithromycin and imipenem-cilastatin. Our case demonstrates that extra-pulmonary manifestations such as septic arthritis and bacteremia can be seen in immune competent hosts.

Upcoming evidence in clinical practice of two-stage revision arthroplasty for prosthetic joint infection.

Total joint arthroplasty is the recommended treatment for patients with end-stage osteoarthritis, as it reduces disability and pain and restores joint function. However, prosthetic joint infection is a serious complication of this procedure, with the two-stage exchange being the most common treatment method. While there is consensus on diagnosing prosthetic joint infection, there is a lack of agreement on the parameters that can guide the surgeon in performing definitive reimplantation in a two-stage procedure. One approach that has been suggested to improve the accuracy of microbiologic investigations before definitive reimplantation is to observe a holiday period from antibiotic therapy to improve the accuracy of cultures from periprosthetic tissues, but these cultures report some degree of aspecificity. Therefore, several pieces of evidence highlight that performing reimplantation using continuous antibiotic therapy should be considered a safe and effective approach, leading to higher cure rates and a shorter period of disability. Dosage of C-reactive protein (CRP), erythrocyte sedimentation rate (ERS) and D-dimer are helpful in diagnosing prosthetic joint infection, but only D-dimer has shown sufficient accuracy in predicting the risk of infection recurrence after a two-stage procedure. Synovial fluid analysis before reimplantation has been shown to be the most accurate in predicting recurrence, and new cutoff values for leukocyte count and neutrophil percentage have shown a useful predictive rule to identify patients at risk of unfavourable outcome. A new scoring system based on a numerical score calculated from the beta coefficient derived through multivariate analysis of D-dimer levels, synovial fluid leukocytes and relative neutrophils percentage has demonstrated high accuracy when it comes to guiding the second step of two-stage procedure. In conclusion, reimplantation may be a suitable option for patients who are on continuous therapy without local symptoms, and with CRP and ERS within the normal range, with low synovial fluid leukocytes (< 952/mL) and a low relative neutrophil percentage (< 52%) and D-dimer below 1100 µg/mL. A numerical score derived from analysing these three parameters can serve as a valuable tool in determining the feasibility of reimplantation in these patients.

An update on the study of synovial fluid in the geriatric patient / Panorama actual del estudio de líquido sinovial en el paciente geriátrico

Background: The characteristics of synovial fluid (SF) in geriatric patients differ from those in younger patients. In Mexico, epidemiologic data on the incidence of different rheumatic diseases in geriatric patients are scarce. Objective: To describe the physical characteristics of geriatric SF and the prevalence of crystals in knee and other joint aspirates from patients with previously diagnosed joint disease. Materials and methods: A retrospective study was performed with a baseline of 517 SF samples between 2011 and 2023. White blood cell count was performed by Neubauer chamber and crystals were identified by polarized light microscopy. Descriptive statistical analysis was performed and prevalence was reported as a percentage. Results: The mean age of the adults was 73.5±5.0 years, 54.4% were women and 45.6% were men. The mean SF volume was 6.3±9.5mL in older adults and 15.3±24.9mL in those younger than 65 years. The mean viscosity in older adults was 9.5±4.5mm and the mean leukocyte count was 7352±16,402leukocytes/mm3. Seventy percent of the older adults’ SFs were referred to the laboratory for osteoarthritis (OA), with lower proportions for rheumatoid arthritis (RA) (14.6%) and gout (5.1%). Of the crystals observed in the geriatric population, 14.6% corresponded to monosodium urate crystals (CUM) and 18.9% to calcium pyrophosphate crystals (CPP). Conclusions: The characteristics of LS in older adults were smaller volume, increased viscosity, and non-inflammatory. The main diagnoses were OA, RA, and gout. The crystal content of the SF of the geriatric population corresponded mainly to CPP.(AU)

Antecedentes: Las características del líquido sinovial (LS) en pacientes geriátricos varían en comparación con pacientes más jóvenes. En México, los datos epidemiológicos sobre la incidencia de diversas enfermedades reumáticas en el paciente geriátrico son escasos. Objetivo: Describir las características físicas del LS geriátrico y la prevalencia de cristales en aspirados de rodilla y otras articulaciones de pacientes con enfermedades articulares previamente diagnosticadas.Materiales y métodos: Se realizó un estudio retrospectivo con una base de 517 muestras de LS entre 2011 y 2023. El recuento de glóbulos blancos se realizó con cámara de Neubauer, y los cristales se identificaron por microscopia de luz polarizada. Se realizó un análisis estadístico descriptivo y la prevalencia se reportó como porcentaje. Resultados: La edad promedio en los adultos fue de 73,5±5,0 años; el 54,4% fueron mujeres y el 45,6%, hombres. El volumen promedio del LS en adultos mayores fue de 6,3±9,5ml, mientras que en menores de 65 años fue de 15,3±24,9ml. La viscosidad promedio fue de 9,5±4,5mm en los adultos mayores, y una cuenta de 7.352±16.402 leucocitos/mm3. El 70% de los LS de los adultos mayores fueron remitidos a laboratorio por osteoartritis (OA), u una proporción más baja, por artritis reumatoide (AR) (14,6%) y gota (5,1%). En cuanto a los cristales observados en los LS de la población geriátrica, el 14,6% correspondieron a cristales de urato monosódico (CUM) y el 18,9%, a cristales de pirofosfato de calcio (CPP). Conclusiones: Las características del LS en los adultos mayores fueron menor volumen, viscosidad incrementada y no inflamatorios. Los principales diagnósticos fueron OA, AR y gota. El contenido de los cristales en los LS de la población geriátrica correspondió principalmente a CPP.(AU)

Commercial Synovial Antigen Testing is Inferior to Traditional Culture for the Diagnosis of Periprosthetic Joint Infection in Patients Undergoing Revision Total Knee Arthroplasty.

BACKGROUND: Despite its limitations, a culture remains the "gold standard" for pathogen identification in patients who have periprosthetic joint infection (PJI). Recently, a synovial fluid antigen test has been introduced by a commercial entity. The purpose of this multicenter study was to determine the accuracy of the antigen test in the diagnosis of PJI. METHODS: This retrospective study identified 613 patients undergoing revision total knee arthroplasty who had undergone preoperative synovial fluid analysis. A PJI was defined using the 2018 International Consensus Meeting (ICM) criteria. Patients who had an extended period (> 180 days) from aspiration to revision procedure (n = 62), those presenting within 90 days of their index arthroplasty procedure (n = 17), and patients who had an inconclusive ICM score (n = 8) were excluded. Using receiver operator characteristic curve analyses, we examined the utility of the microbial identification (MID) antigen test and any positive culture (either preoperative or intraoperative) in the diagnosis of PJI. RESULTS: A total of 526 patients were included. Of these, 125 (23.8%) were ICM positive and 401 (76.2%) were ICM negative. Culture demonstrated an area under the curve (AUC) of 0.864, sensitivity of 75.2%, and specificity of 97.5%. On the other hand, the MID test exhibited an AUC of 0.802, sensitivity of 61.6%, and specificity of 98.8%. The AUC of culture was significantly higher than that of the MID test (P = .037). The MID test was positive in 41.9% of culture-negative PJI cases. We also observed a high rate of discordance (29.7%) when both culture and the MID test were positive in the ICM-positive group. CONCLUSIONS: Synovial fluid antigen testing does not provide additional clinical benefit when compared to traditional cultures for the diagnosis of PJI. The antigen test had low sensitivity in the diagnosis of PJI and a relatively high rate of discordance with culture. LEVEL OF EVIDENCE: Level III.

Associations with unplanned repeat irrigation and debridement of native septic arthritis.

PURPOSE: To identify associations with unplanned repeat irrigation and debridement (I&D) after arthrotomy for native septic arthritis. METHODS: A retrospective review identified patients with native septic arthritis treated with open arthrotomies. The primary outcome was unplanned repeat I&D within 90 days. Associations evaluated for included comorbidities, ability to bear weight, fever, immunosuppressed status, purulence, C-reactive protein, erythrocyte sedimentation rate, white blood cell count (synovial fluid and serum levels), and synovial fluid polymorphonuclear cell percentage (PMN%). RESULTS: There were 59 arthrotomies in 53 patients involving the knee (n = 32), shoulder (n = 10), elbow (n = 8), ankle (n = 6), and hip (n = 3). The median patient age was 52, and a 71.2% were male. An unplanned repeat I&D was required in 40.7% (n = 24). The median time to the second I&D was 4 days (interquartile range 3 to 9). On univariate analysis, unplanned repeat I&Ds were associated with fever (p = 0.03), purulence (p = 0.01), bacteria growth on cultures (p = 0.02), and the use of deep drains (p = 0.05). On multivariate analysis, the only variables that remained associated with unplanned repeat I&Ds were fever (odds ratio (OR) 5.5, 95% confidence interval (CI) 1.3, 23.6, p = 0.02) and purulence (OR 5.3, CI 1.1, 24.4, p = 0.03). CONCLUSIONS: An unplanned repeat I&D was required in 40.7% of patients and was associated with fever and purulence. These findings highlight the difficulty of controlling these infections and support the need for future research into better methods of management. LEVEL OF EVIDENCE: Diagnostic, Level III.

Utility of Synovial Fluid Biomarkers for Culture-Positive Septic Arthritis in a Lyme Disease-Endemic Region.

OBJECTIVE: To evaluate the performance of synovial fluid biomarkers to identify children with culture-positive septic arthritis. METHODS: We identified children 6 months to 18 years old presenting to a single emergency department between 2007 and 2022 undergoing evaluation for septic arthritis defined by having a synovial fluid culture obtained. Our primary outcome was septic arthritis defined by a positive synovial fluid culture. We evaluated the ability of synovial fluid biomarkers to identify children with septic arthritis using area under the receiver operating characteristic curve (AUC) analyses. We measured the sensitivity and specificity of commonly used synovial fluid biomarkers. RESULTS: We included 796 children, of whom 79 (10%) had septic arthritis. Compared with synovial white blood cell count (AUC, 0.72; 95% confidence interval [CI], 0.65-0.78), absolute neutrophil count (AUC, 0.72; 95% CI, 0.66-0.79; P = 0.09), percent neutrophils (AUC, 0.66; 95% CI, 0.60-0.71; P = 0.12), and glucose (AUC, 0.78; 95% CI, 0.67-0.90; P = 0.33) performed similarly, whereas protein (AUC, 0.52; 95% CI, 0.40-0.63, P = 0.04) had lower diagnostic accuracy. Synovial fluid white blood cell count ≥50,000 cells/µL had a sensitivity of 62.0% (95% CI, 50.4%-72.7%) and a specificity of 67.0% (95% CI, 63.4%-70.4%), whereas a positive synovial fluid Gram stain had a sensitivity of 48.1% (95% CI, 36.5%-59.7%) and specificity of 99.1% (95% CI, 98.1%-99.7%) for septic arthritis. CONCLUSIONS: None of the routinely available synovial fluid biomarkers had sufficient accuracy to be used in isolation in the identification of children with septic arthritis. New approaches including multivariate clinical prediction rules and novel biomarkers are needed.

Joint Fluid Cell Count in Acute Bacterial Arthritis Patients Proven Positive Culture in Children.

BACKGROUND: Acute bacterial arthritis (ABA) is a serious, pediatric infection that can result in motor comorbidities. Normally, a joint fluid white blood cell (WBC) count of 50,000 or more cells/mm 3 is used to make a presumptive diagnosis of ABA. This study evaluated the utility of the joint fluid WBC count for diagnosing pediatric ABA confirmed by a positive culture result. METHODS: Patients with ABA between March 2010 and March 2023 at Tokyo Metropolitan Children's Medical Center were included. ABA was confirmed by positive joint fluid culture results for a pathogenic organism. Patients with negative results and those without a joint fluid WBC count were excluded. Electronic medical records were retrospectively reviewed for demographic data, timing of arthrocentesis, culture results and the joint fluid WBC count. RESULTS: Ninety-five patients with ABA were identified; of these, 22 were included. The median age was 5 years [interquartile range (IQR): 2-10 years]. Males comprised 55% of the population. The median joint fluid WBC count was 19,575 (IQR: 6806-47,388) cells/mm 3 , and 23% of the patients had 50,000 cells/mm 3 or more. The median time from symptom onset to arthrocentesis was 3 days (IQR: 2-5 days). The isolated organisms were methicillin-susceptible Staphylococcus aureus (50%), methicillin-resistant S. aureus (9%), Streptococcus pyogenes (27%), Streptococcus pneumoniae (5%), Klebsiella pneumoniae (5%) and Salmonella spp. (5%). CONCLUSIONS: Most of the patients with ABA confirmed by positive results of a joint fluid culture had a joint fluid WBC count of less than 50,000 cells/mm 3 .