This was an unusual case of invasive pneumococcal disease in an immunocompetent adult without serious underlying medical conditions. Streptococcus pneumoniae bacteraemia was found with multiple distant sites of infection, including polyarticular septic arthritis, osteomyelitis, multi-level spondylodiscitis, and paravertebral, psoas and pelvic abscesses. A fit and well 56 year old woman presented with a 10 day history of fevers, rigors, and multiple hot, swollen, tender joints. Septic arthritis was initially thought unlikely, but when blood tests showed marked inflammatory response and the patient was febrile, joint aspiration was performed. Streptococcus pneumoniae was grown from blood cultures and aspirates from multiple joints. MRI confirmed distant sites of infection including left sacroiliac joint osteomyelitis, multi-level spondylodiscitis, and small paravertebral, psoas and pelvic abscesses, which were not amenable to drainage. The patient completed 11 weeks of antibiotic therapy, with IV Amoxicillin followed by IV Ceftriaxone, and made a good recovery with full resolution of joint disease. The patient had obesity but was not in a recognised risk group for invasive pneumococcal disease. No underlying medical conditions were found that would predispose her to such widespread infection. Septic arthritis can be polyarticular. Urgent joint aspiration and blood cultures should be undertaken for any patient in whom septic arthritis is considered. Patients with invasive pneumococcal disease should be investigated for predisposing risk factors and should be adequately immunised. This case provides a timely reminder of the virulence of pneumococcus, the severity of invasive pneumococcal disease, and the importance of vaccination.

Pigmented villonodular synovitis (PVNS) occurring after total knee arthroplasty (TKA) is extremely rare and has most commonly been reported within 10 years after the index procedure. Clinically, it can be difficult to distinguish from polyethylene wear-induced synovitis or aseptic loosening. We report a rare case of diffuse PVNS diagnosed 21 years after primary TKA and treated with revision arthroplasty. A 71-year-old man presented with a one-year history of left knee pain. He had undergone primary TKA 21 years earlier and maintained excellent function with full weight-bearing and unrestricted daily activities for approximately 20 years after surgery. Following this long asymptomatic period, the patient developed knee swelling and recurrent hemarthrosis, which was confirmed on three occasions by joint aspiration. Radiographic and computed tomography (CT) evaluations suggested aseptic loosening of the tibial component accompanied by extensive osteolysis on the medial side of the proximal tibia. During revision surgery, diffuse synovial hypertrophy characterized by yellowish-brown papillary projections was observed. Complete synovectomy and revision arthroplasty were performed. Histopathological examination subsequently confirmed diffuse PVNS. We report a rare case of diffuse PVNS confirmed by surgical biopsy during revision arthroplasty performed 21 years after primary TKA, representing an unusually long interval after the index procedure. In patients with TKA presenting with recurrent hemarthrosis and aseptic loosening, PVNS should be considered in the differential diagnosis and may be associated with prosthetic loosening.

Outlier patients - those residing in a ward outside that of the specialty caring for them - often experience delays due to lack of specialty-specific equipment. This study evaluated whether introducing a portable Orthopaedic 'Grab Bag' containing essential equipment improved the efficiency of reviewing and treating Orthopaedic outlier patients in a major trauma centre (MTC) and a trauma unit (TU). A prospective study was conducted at both a London MTC and a TU. Equipment retrieval times for common Orthopaedic procedures (including removal of plaster backslabs, removal of staples from a wound, joint aspiration, wound suturing, application of a polysling, skin traction) were measured under two conditions: standard collection versus use of a prepacked Orthopaedic Grab Bag. The primary outcome was total equipment retrieval time. At the MTC, modal retrieval time decreased from 5-10 minutes to 0-5 minutes post-implementation, with no retrievals exceeding 10 minutes (previously up to 30 minutes). The proportion completed within 5 minutes rose from 21.7% to 64.3%. At the TU, pre-intervention 50% of retrievals were completed within 5 minutes and 15.3% exceeded 10 minutes; post-intervention, all were completed within 5 minutes. The greatest improvements were seen in removal of plaster backslabs (437 seconds faster), polysling application (432 seconds faster) and staple removal from wounds (358 seconds faster). Implementation of an Orthopaedic Grab Bag improved equipment retrieval efficiency significantly in both MTC and TU settings. This low-cost, scalable intervention enhances the timeliness of Orthopaedic outlier care.

ObjectiveIn order to fit with National Institute for Health and Care Excellence (NICE) guidelines on arthritis, we established a ‘very early arthritis clinic’ (v-EAC) to evaluate patients within 48 h of a medical referral for any suspected arthritis of <1-month duration. We describe the characteristics of patients referred to the v-EAC from 2 October 2023 to 1 October 2024.MethodsDelay of referral was recorded. A systematic and standardized clinical, biological and ultrasound evaluation of all consecutive patients was conducted. Patients and disease characteristics are described.ResultsA total of 900 patients were evaluated within a median delay of 1 day after referral: 51% were women and the median age was 55 years (IQR 42–67). Among these patients, 37% were referred by emergency departments, 28% by rheumatologists, 18% by general practitioners and 17% by other specialists. For 46% of patients, it was the first episode of a swollen joint, with a median symptom duration of 14 days (IQR 5–44) and a mean number of 1.3 (s.d. 1.9) swollen joints. Inflammatory arthritis was confirmed in 63% of cases and diagnoses were flare of immune-mediated inflammatory disease (IMID)-related arthritis in 35% of cases (half of which represented the first manifestation of an IMID-related arthritis), crystal-related arthritis in 27% (mostly gout) and infectious disease in 8.0% (including 34 bursitis and 13 septic arthritis). Joint aspiration was performed in 414 patients (46%). Corticosteroid-derivative injections were administered to 31% of patients and hospitalization was required in 10% of cases [median stay 6 days (IQR 4–8)].ConclusionA dedicated care pathway can make the NICE guidelines regarding management of arthritis reachable.

Sacroiliac joint injury during vaginal delivery is an uncommon but important cause of acute postpartum pelvic pain. The patient is a 29-year-old gravida-6 para-3 who had an uncomplicated vaginal birth at 39.0 weeks. Shortly after delivery, the patient developed severe right-sided sacral pain. Pelvic MRI revealed tearing of the anterior sacroiliac joint capsule. CT-guided corticosteroid injection initially alleviated symptoms, but the patient developed worsening pain and recurrent fevers. Septic sacroiliitis was confirmed based on joint aspirate cultures positive for S. pneumoniae and rare Haemophilus, and the patient subsequently received intravenous antibiotics. Her recovery was protracted, requiring pain management, physical therapy, and psychiatric support. This case highlights the challenges in diagnosing postpartum sacroiliac joint injury and emphasizes the need for interdisciplinary management to prevent delayed treatment and reduce morbidity. Notably, this is the first reported case of postpartum sacroiliitis involving Haemophilus.

BackgroundSeptic arthritis (SA) and prosthetic joint infection (PJI) are common emergency referrals to orthopaedics in the United Kingdom. These infections carry a significant risk of harm due to chondrolysis and arthropathy and are a potential source of sepsis, requiring prompt assessment, investigation, and treatment. A joint aspirate is routinely sent for microscopy, culture , and sensitivities to aid treatment. In suspected PJI, this must be taken under sterile conditions to reduce the risk of iatrogenic PJI. Empirical antibiotics should then commence per the British National Formulary (BNF) or local policy. Due to the risks of delayed or ineffective treatment, evaluating local practice may identify areas to optimise treatment delivery and efficacy.AimsThis study will evaluate the incidence of SA and PJI within a tertiary orthopaedic centre over 12 months. The culprit organisms and sensitivities, delivery of timely and appropriate antibiotics, serum infection markers, length of stay (LOS), and mortality will be reviewed.MethodsAdmissions to the orthopaedic unit between November 2023 and October 2024 were screened using the ICD-10 codes for pyogenic arthritis, prosthesis infection, or infection following a procedure. Further review confirmed cases of SA or PJI, excluding unsuitable admissions. Each patient's electronic record was examined for demographics, serum infection markers, LOS, 30-day mortality, relevant imaging, time to aspirate relative to admission, culture results, and timing and type of antibiotics initiated. Antibiotics used were compared to sensitivities and BNF recommendations to determine efficacy.ResultsA total of 27 admissions with SA and 24 of PJI were seen, accounting for 51 (1.9%) of 2,670 total admissions, relative to a mean annual arthroplasty incidence of 1,204 across the health board. The median age of PJI patients was 72 years, significantly higher than the median SA patient age of 52 years (p<0.01). Median LOS was also higher in PJI patients at 13.5 days compared to nine days in SA (p=0.036). Most infections were hip and knee joints at nine (33.3%) cases in SA, and 11 (45.8%) total knee replacements in PJI cohorts. Staphylococcus aureus was the most prevalent organism in each group; however, 11 (40.7%) of the SA aspirate cultures were negative. The median aspiration time, relative to admission, was 5.6 and 10.2 hours in SA and PJI, respectively. The median time to initiate antibiotics was 7.1 and 17.9 hours in SA and PJI, respectively. The majority of admissions received appropriate antibiotics at 20 (74.1%) of SA and 17 (70.8%) of PJI patients. Culture results confirmed sensitivity to recommended antibiotics in 14 (51.8%) of SA and 18 (75%) of PJI cases. The most initiated antibiotic overall was flucloxacillin. There was no significant difference in infection markers.ConclusionThis study finds that PJI patients were typically older, with a greater LOS and comorbidity. Large joint infections, such as hips and knees, were the commonest presentation. The majority of each cohort was appropriately treated per the BNF, with S. aureus being the commonest cause. Factors such as prehospital antibiotics may reduce the bacterial yield of aspirations. Both groups show prolonged time taken to aspirate and treat, in which quality improvement interventions may reduce. Other centres may benefit from similar evaluations of the infective microbiome and the speed and efficacy of septic joint treatment.

Improvement of knee joint function through proximalisation of the patella, increase in range of motion (ROM) and reduction of anterior knee pain. Secondary patella baja following implantation of total knee arthroplasty with shortening of the patellar tendon or scarring of periarticular soft tissues (e.g. Hoffa's fat pad). Particularly in cases of functional impairment of the extensor mechanism and failure of conservative measures. Infection (preoperative joint aspiration recommended), lack of compliance, inability to undergo postoperative rehabilitation, and pseudo-patella baja due to joint line proximalisation. Release/arthrolysis: release of infrapatellar, anterolateral and femoral adhesions; tendon lengthening using Z‑plasty, if necessary. Tuberosity osteotomy: oblique osteotomy of the tibial tuberosity with distal shift of the fragment and screw fixation. Early functional physical therapy and continuous passive motion device for the knee. Full weight-bearing possible immediately after surgery. After tuberosity osteotomy, partial weight-bearing (approximately 15 kg for 6weeks) with gradual increase in weight-bearing after radiological consolidation. The literature on isolated release is limited, with isolated case reports showing functional improvements. For tuberosity osteotomy, there are case series reporting improvements in clinical scores (e.g. Kujala, Knee Society Score) and patella height indices. Nevertheless, postoperative limitations remain possible.

Abstract Background/Aims The UK incidence of tuberculosis (TB) has increased substantially in recent years. Osteoarticular (extra-axial) TB is rare, with the knee being the most affected joint. Diagnosis of osteoarticular disease can be challenging. Appropriate anti-TB treatment may provoke paradoxical inflammatory reactions of the joint, causing uncertainty as to whether this inflammatory response is infection or treatment-related. Although corticosteroid use in extra-articular TB, such as meningitis, is well-recognised and evidence-based, the role of intra-articular corticosteroids in osteoarticular TB is less clear and further clouded by this uncertainty. We present two cases of osteoarticular TB involving the knee complicated by paradoxical inflammatory reactions with very different outcomes. Methods N/A Results A 32-year-old Pakistani-born male who was previously well presented two years after migrating to the UK with constitutional symptoms and neck swelling. Cervical lymph node biopsy identified fully sensitive Mycobacterium tuberculosis, and appropriate treatment (ethambutol, rifampicin, isoniazid and pyrazinamide) was initiated. Three days later, osteoarticular TB of the knee was unmasked, confirmed through joint aspiration and imaging. The knee swelling resolved with local corticosteroid injection whilst anti-TB treatment was continued. However, four months later, both knees became painful, stiff and swollen, and the lymphangitis site also became inflamed. Imaging showed marked inflammatory changes, and a paradoxical inflammatory reaction to anti-TB treatment was diagnosed. Systemic corticosteroids were started, with rapid and significant improvement. The patient remains symptom and disease-free following treatment completion. A 29-year-old Indian-born female who was previously well presented with acute monoarthritis of the right knee. An initial joint aspirate was culture negative for TB, so she was treated for seronegative inflammatory arthritis with sulfasalazine and intra-articular corticosteroid injection. Three months later, her symptoms had not improved and repeat joint aspiration revealed isoniazid-resistant TB. Appropriate anti-TB treatment was initiated, but the right knee responded poorly with worsening pain, stiffness, swelling and progressive deformity, reflected radiographically. Subsequent joint aspirate and biopsies of synovium and bone were negative for active TB, so the consensus diagnosis was a severe paradoxical inflammatory reaction to treatment. Repeated localised intra-articular corticosteroid injections into the knee had limited and short-lived benefits. Systemic corticosteroids were not attempted. Even after successful TB treatment, this patient has right knee degeneration with persisting antalgic gait and currently awaits total joint replacement. Conclusion Our cases make clear that diagnosis and management of paradoxical reactions in the context of osteoarticular TB are not well-understood in the UK, but with TB incidence rising, they demand urgent study. We would advocate for further research into how these reactions emerge in this context, and the role of local versus systemic corticosteroid treatment in improving outcomes for such patients. Disclosure S. Sharrack: Grants/research support; SS is a recipient of the NIHR Leeds BRC Clinical Doctoral Fellowship Scheme. A.A. Notghi: None. T. Nadin: None. J.E. Meiring: None. D. Cohen: None. P. Collini: None. M.J. Petrie: None. J.R. Maxwell: None. R.S. Tattersall: None.

Role of synovial biopsy in diagnosis of chronic periprosthetic infection in total hip and knee arthroplasties.

Diagnosing periprosthetic joint infection (PJI) can be challenging, particularly in cases involving biofilm-forming organisms or low-virulence pathogens. Currently, no single test provides perfect sensitivity and specificity. However, distinguishing septic from aseptic complications is crucial for selecting an appropriate treatment strategy, reducing morbidity and mortality, and preserving joint function.The introduction of standardized infection definitions in 2011 has supported diagnostic accuracy and improved comparability between studies. Based on these PJI definitions, diagnosis relies on a combination of test methods, including clinical signs, serum parameters, joint aspiration, microbiological cultures (synovial fluid, tissue, sonication), histological analysis, and imaging.Preoperatively, the most accurate tests are the synovial leukocyte count and the percentage of polymorphonuclear neutrophils (%PMN). While synovial fluid culture may enable preoperative pathogen detection, its sensitivity is limited. Intraoperatively, 4-6 tissue samples should be collected for culture and histological evaluation. Tissue cultures are highly specific but may yield false-negative results in low-grade infections or in patients pre-treated with antibiotics. Histology (permanent sections), when performed with an optimal sampling technique, is one of the most reliable intra- and postoperative diagnostic modalities. Frozen sections allow for rapid intraoperative diagnosis. Sonication of removed implants is used to complement microbiological analysis. Additionally, molecular techniques such as next-generation sequencing (NGS) show promising results and may serve as useful adjuncts to conventional culture methods.

To the Editors: I read the recent PIDJ manuscript by Nielsen et al.1 assessing the value of a species-specific nucleic acid amplification test (NAAT) performed on an oropharyngeal swab for the diagnosis of Kingella kingae skeletal system infections. Because K. kingae frequently invades joints and bones that are too small or difficult to reach, as well as intervertebral disks, source samples such as synovial fluid or tissue from the bone and intervertebral disc are seldom available for analysis. The bacteriological diagnosis of these infections, particularly that of spondylodiscitis and sacroiliitis, is highly problematic in an uncooperative young child. Physicians are frequently hesitant to perform joint aspirations or take biopsies in pediatric patients because these invasive procedures require sedation and imaging guidance. Obtaining an intervertebral disc biopsy is considered potentially risky, and an animal experimental model has demonstrated that even the negligible damage caused by a needle puncture may result in progressive disc degeneration.2 In a retrospective study involving 124 children with spondylodiscitis, a spinal biopsy was performed in only 2 patients, and no pathogens were isolated.3 The alternative noninvasive diagnostic strategy evaluated in Nielsen et al.1 study demonstrated complete agreement in the positive detection of the bacterium in joint and bone specimens, as well as in oropharyngeal specimens. This finding supports the concept that the colonized mucosal surface serves as the portal of entry for the organism into the bloodstream, allowing for its dissemination and invasion of the skeletal system. However, the oropharyngeal swab was also positive in 33 of 112 (29.5%) of patients with unproven K. kingae disease.1 This finding is consistent with the significant prevalence of oropharyngeal carriage in the preschool population (10%) and higher among children attending daycare facilities (28%), which reduces the diagnostic usefulness of a positive test result.4 A second caveat is that NAATs targeting the rtx operon also detect the repeat-in-toxin A (RTXA)-producing Kingella negevensis.5 This recently identified species of uncertain clinical significance is also carried asymptomatically in the oropharynx by the pediatric population. Thus, oropharyngeal colonization by K. negevensis may contribute to joint or bone infections being attributed to K. kingae, further decreasing the specificity of the test. Although the positive predictive value of the oropharyngeal NAAT approach is suboptimal, as convincingly shown by Nielsen’s study, its negative predictive value is high. The failure of a sensitive molecular test to detect K. kingae DNA sequences in the oropharynx of a young child effectively rules out the bacterium as the etiology of the skeletal disease.

Periprosthetic joint infection (PJI) caused by Brucella spp. is an exceedingly rare occurrence, leading to a lack of consensus regarding its diagnosis and treatment. This review mainly aimed to assess the diagnosis and treatment strategy of Brucella-induced PJI. We summarized the data by reporting 4 cases from the Hexi area of China and conducting a systematic review. A comprehensive literature search was performed in PubMed, Web of Science, Embase, and the Chinese Biology Medicine database for relevant publications using predefined search terms. Included studies were case reports or series on human Brucella-induced PJI that described patient outcomes. Data on demographics, diagnosis, treatment, and outcomes were extracted and analyzed. A total of 61 patients of Brucella-related PJI were summarized. Serological antibody tests provided the best diagnostic yield with a 100% positive rate (35/35), compared to lower sensitivities for joint aspiration culture (53.84%, 21/39) and blood culture (41.67%, 5/12). In the presence of radiological implant loosening, 32 patients underwent one- or 2-stage revision with combination antibiotic therapy. For 29 patients without loosening, treatment included antibiotic therapy alone or combined with drainage and debridement or revision. No recurrence was reported at the end of the follow-up. Preoperative serological tests are prioritized for diagnosing Brucella PJI. Loose implants should be managed with revision surgery, while stable implants may be treated initially with antibiotics alone or combined with debridement.

Regarding patellar resurfacing in total knee arthroplasty (TKA), no consensus has been reached, but most studies have not addressed specific pathological circumstances. Evidence on the roles of patellar resurfacing and synovectomy in managing postoperative effusion in patients with severe chondrocalcinosis is limited. This single-centre observational cohort study included 160 patients who underwent the same TKA for osteoarthritis with severe chondrocalcinosis (grade 4) between January 2000 and December 2010. A matched design created four comparable groups of 40 patients each: (1) TKA without patellar resurfacing or synovectomy, (2) TKA with patellar resurfacing alone, (3) TKA with synovectomy alone, and (4) TKA with both patellar resurfacing and synovectomy. Severe chondrocalcinosis (advanced calcium pyrophosphate deposition disease) was confirmed through radiographic findings, synovial fluid analysis using polarized light microscopy, and histology. Significant postoperative effusion was diagnosed with ultrasound, quantified by sterile joint aspiration, and classified as stage I (10-20 cm3), stage II (21-30 cm3), or stage III (> 30 cm3). Postoperative joint effusion varied significantly between the strategies. In the patellar resurfacing group, 25% (10/40) of patients developed only stage I effusion without synovectomy. Conversely, 45% (18/40) of patients in the synovectomy-only group developed stage II effusion, while 62.5% (25/40) of patients without either procedure developed stage III effusion (p < 0.0001). TKA with both patella resurfacing and synovectomy resulted in either stage I (7/40) or stage II effusion (6/40). Multivariate regression confirmed patellar resurfacing as an independent protective factor against postoperative effusion (p < 0.01). Average aspirated effusion volumes further supported these findings: 39 ± 6 cm3 for TKA without additional procedures, 18 ± 8 cm3 with synovectomy, 6 ± 4 cm3 with patellar resurfacing, and 7 ± 4 cm3 with both patellar resurfacing and synovectomy. The results showed that as total knee effusion volume increased, inflammatory markers (C-reactive protein level) increased, and range of motion decreased. In severe chondrocalcinosis, patellar resurfacing may be appropriate to prevent joint effusion after TKA.

To evaluate the quality and safety of hip aspiration procedures performed by radiology residents on-call compared to those performed by supervised residents or attending radiologists during workday hours. Additionally, to identify potential areas for improving resident procedural exposure. A single-center retrospective study evaluating daytime and on-call hip joint aspirations performed on emergency or admitted patients from June 1, 2019, to May 31, 2020. Data collected included patient demographics, procedure times, performing staff, and procedural and surgical outcomes. The Mann-Whitney U-test was used to analyze quantitative data, and Fisher's exact test was used for categorical variables. Residents performed 19 (100%) of on-call procedures and 12/50 (24%) of daytime aspirations. On-call procedures had shorter median time from order to procedure start (115 compared to 294min, p = 0.004) but overall longer median procedure durations (52 versus 32min, p = 0.054). In total, 17/19 (89%) of procedures on-call versus 49/50 (98%) of daytime cases yielded sufficient sample for analysis (p = 0.18). Of these, 5/17 (26%) on-call and 16/49(34%) of daytime aspirates were culture-positive (p = 0.77). Resident-performed hip aspirations on-call were initiated more promptly but did not significantly differ in rates of aspirate yield or culture positivity. Residents performed only 24% of daytime cases, highlighting the opportunity to increase resident procedural exposure.

With the advent of recent point of care testing to evaluate for prosthetic joint infection (PJI) such as alpha-defensin and calprotectin, the diagnosis of PJI has reached a new paramount. The most widely accepted diagnostic criteria in the literature at this time is the international consensus meeting (ICM) score by Parvizi et al in 2018. One of the proposed limitations of the ICM criteria is determining if fluid analysis can be trusted for bloody joint aspirations. A proposed formula to correct red blood cells in aspirations was described in 2008 but has not been explored since then. To determine if the "true leukocytosis" formula for prosthetic joint aspirations is useful in determining PJIs. Of 158 cases with International Classification of Diseases, 10th revision diagnoses of total knee arthroplasty PJIs from 2020-2021 from a single health system were reviewed and preoperative ICM scores were calculated. Inclusion criteria involved preoperative scores indicating infection, first time diagnoses, and culture positive infections. Culture positivity remained our gold standard for infection confirmation. We compared sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve for preoperative ICM score and corrected preoperative ICM score. Of 81 cases met the inclusion criteria and had preoperative ICM scores calculated. Of the 81 cases that met inclusion criteria, no cases were found to have different preoperative ICM scores after applying the correction formula for "true leukocytosis" proposed by Ghanem et al in 2008. Given the lack of variance in ICM score following the proposed correction formula, it appears that the proposed "true leukocytosis" formula is not a useful adjuvant in treatment decision making.

Ceramic head and liner fractures in total hip arthroplasty.

Tenosynovial giant cell tumor (TGCT) is a rare, locally aggressive tumor originating in the synovial lining of the joint, bursa, and tendon sheath. TGCT typically affects individuals between 20 and 50 years of age and pediatric cases are considered ultra-rare. Research and clinical trials thus far have been largely focused on the adult TGCT population. Therefore, data are needed to understand the impact of TGCT on pediatric patients' quality of life and any differences between adults. Here we report the result of the pediatric TGCT population enrolled in an observational patient registry. A total of 122 pediatric patients (9.5%) were included in this exploratory, cross-sectional analysis of a longitudinal 1,278-patient registry from October 06, 2022 to November 26, 2024. Among pediatric patients, 73.0% had diffuse TGCT (D-TGCT; n = 89), 16.4% had localized TGCT (L-TGCT; n = 20), and 10.6% had unspecified TGCT (n = 13). Pediatric patients had a median age at diagnosis of 14.5 years. More than half of pediatric patients were initially misdiagnosed and were more likely to be misdiagnosed than adults (62.3% vs. 49.9%, p < 0.01) and received joint aspirations significantly more frequently than adult patients (47.5% [n = 58] vs. 22.5% [n = 112], p < 0.05). Most pediatric patients were diagnosed by orthopedic surgeons (n = 79, 64.8%), and 52.5% of pediatric patients were diagnosed ≥ 1 years after symptom onset. Pediatric patients with D-TGCT underwent an average of 3.4 surgeries, compared to 1.8 surgeries for those with L-TGCT. Recurrence rates were similar among adults and pediatric patients with 66.3% of pediatric patients with D-TGCT having ≥ 1 post-operative recurrence compared to 15.0% of L-TGCT pediatric patients, respectively. Despite no approved systemic therapies for pediatric use, pediatric and adult patients consulted medical oncologists in similar rates and systemic therapies were prescribed similarly but infrequently overall (n = 21, 17.2% in pediatric patients and n = 95, 19.1% in adults). Pediatric patients had significant disease burden, as compared to adults with TGCT, which severely affected their quality of life. The reliance on surgical treatment and underuse of multidisciplinary care emphasizes the unmet need for provider education and treatment advancements tailored to this population. This study was an analysis of an observational patient registry and therefore was not registered as a clinical trial; no trial registration number is available. The study protocol was approved by Advarra (protocol reference number: Pro00077310). Patient enrollment for this analysis occurred from October 6, 2022, to November 26, 2024.

BackgroundProsthetic joint infection (PJI) is a severe complication of hip or knee arthroplasty, often necessitating invasive intervention and posing a high risk of adverse outcomes. Early diagnosis and tailored antibiotic therapy are critical for the effective management of PJI. This study evaluated the utility of cell-free deoxyribonucleic acid (cfDNA) extracted from synovial fluid to diagnose PJI and identify the causative pathogens.Figure 1.Comparison of Synovial Fluid cfDNA Concentration Between PJI and Non-PJI GroupsFigure 2.ROC curve for Determining the Optimal cfDNA Concentration Cut-Off for PJI diagnosiscfDNA concentration of 1.59 ng/ul or above indicates possibility of PJI. (sensitivity, 0.90; specificity, 1.00), respectively.cfDNA, cell-free deoxyribonucleic acid; PJI, prosthetic joint infection.MethodsThis prospective, single-center study included a PJI group consisting of patients with confirmed infections based on the European Bone and Joint Infection Society criteria and a non-PJI group comprising patients without suspected PJIs who underwent joint surgery or aspiration. Synovial fluid samples were collected from all patients, and various culture methods, including conventional synovial fluid, sonication, and tissue and blood cultures, were applied along with cfDNA analysis.ResultsA total of 35 patients were included, with 20 diagnosed with PJI and 15 classified as non-PJI. The median cfDNA concentration in synovial fluid was significantly higher in the PJI group (4.560 ng/μl, interquartile range (IQR) [3.320–6.348]) compared with the non-PJI group (0.028 ng/μl, IQR [0.009–0.273]) (p < 0.001). The Youden index identified a cfDNA concentration ≥ 1.59 ng/μl as strong likelihood of PJI. Culture positivity rates in the PJI group were as follows: synovial culture (10/20, 50.0%), sonication culture (8/9, 88.9%), tissue culture (2/8, 25.0%), and blood culture (2/12, 16.7%). The bacterial detection rate of cfDNA was 65.0% (13/20).ConclusioncfDNA concentration was significantly higher in the PJI group, with synovial cultures showing substantial agreement. Additionally, cfDNA sequencing detected pathogens after antibiotic treatment and identified multiple pathogens in polymicrobial infections. These findings highlight cfDNA analysis as a valuable diagnostic tool for PJI, with the potential to enhance current diagnostic approaches.DisclosuresAll Authors: No reported disclosures

BackgroundEarly identification of the causative pathogen causing septic arthritis (SA) in children is crucial for guiding appropriate therapy; however, conventional culture methods may have low detection rates and delayed results. Molecular diagnostics have enhanced pathogen identification, potentially improving outcomes. This study aims to describe the clinical characteristics of children with SA following the implementation of the joint infection molecular panel in Costa RicaTable 1.Clinical characteristics of patients admitted for septic arthritisAbbreviations: LOS, length of hospitalization; MSSA, Meticilin-sensible Staphylococcus aureus; MRSA, Meticilin-sensible Staphylococcus aureus. Data expressed as median [25-75% IQR] for continuous variables and as numbers (%) for categorical dataMethodsIn 2024-25, we conducted a retrospective observational study including children under 13 years of age hospitalized with SA at the only tertiary pediatric hospital. All patients underwent articular fluid aspiration for conventional culture and BIOFIRE® Joint Infection (JI) Panel testing. Clinical characteristics, treatment, and outcomes were documentedResultsWe enrolled 51 pediatric patients diagnosed with SA (median age: 8.0 [IQR: 5.0–10.5] years). Median duration of symptoms prior to admission was 4 days [2–7], and a history of trauma was reported in 19 (37%) cases. Lower extremity joints were predominantly affected, with the hip/femur (n=30, 59%), knee (n=8, 16%), and tibia (n=6, 12%) as most frequently involved. All patients underwent joint aspiration and received empirical intravenous antibiotics upon admission. The median length of hospitalization was 11 [7–17] days, with a median in-hospital antibiotic duration of 9 [4–14] days. Among 35 joint samples tested by both conventional culture and molecular diagnostics, there was no statistically significant difference in positivity rates (63% vs. 54%; p=0.63). S. aureus was the most common organism (54% isolated by culture vs. 49% by PCR, p=0.81), followed by gram-negative rod (6%), and Salmonella sp. (3%). The use of PCR panel provided results faster than conventional methods (2h vs. 48-72h). Overall, complications occurred in 12 (24%) patients (Table 1)ConclusionWhile molecular diagnostics did not significantly improve pathogen detection rates compared to conventional cultures, they offered markedly faster turnaround times, which could support earlier pathogen-targeted therapy. Despite appropriate management, a proportion of patients experienced complications, highlighting the need for timely diagnosis and close follow-upDisclosuresAll Authors: No reported disclosures

Pediatric septic arthritis requires immediate recognition, as delayed diagnosis can cause severe joint damage and long-term dysfunction. In the absence of guideline-based cut-off values for laboratory markers, surgical decisions are often made on a case-by-case basis. Due to the scarcity of evidence specific to the pediatric population, treatment strategies are often based on adult data, highlighting the need for targeted research in this population. To address this gap, we developed a diagnostic algorithm that incorporated reliable predictive factors. Of 443 joint aspirations performed in our clinic (2014-2024), 132 (29.8%) were for suspected septic arthritis. After applying exclusion criteria, 80 cases were included. Clinical (fever, pain with movement, comorbidities), laboratory parameters at the time of joint aspiration (serum CRP, synovial white blood cell count [syWBC], serum white blood cell count [seWBC], synovial neutrophil perventage [syN%] and radiological data (radiographs, CT and MRI if available) were collected. Septic arthritis was defined by detection of pathogens in joint aspirate via culture or PCR. A pathogen was identified in 25% (20/80) of cases, with Kingella kingae (30%) being the most frequently detected organism, followed by Staphylococcus aureus (25%). Regression analysis revealed CRP (p < 0.01), syWBC (p = 0.04), but not syN% (p = 0.51) as predictors. ROC analysis yielded optimal cutoff values for CRP (69mg/L; AUC = 0.82; 95% CI 0.71-0.93) and syWBC (65,000 cells/µL; AUC = 0.79; 95% CI 0.66-0.92). A diagnostic algorithm using CRP > 69mg/L alone, or CRP < 69mg/L combined with syWBC > 110,000 cells/µL, predicted septic arthritis with a sensitivity of 85% (95% CI 0.62-0.97; p < 0.01) and a specificity of 90% (95% CI 0.79-0.96; p < 0.01). CRP was slightly more accurate than syWBC in predicting septic arthritis. When combined in an recursive partitioning model, these parameters demonstrated strong diagnostic performance. In cases where CRP measurements may be unreliable, an elevated syWBC count represents a CRP-independent alternative, although with reduced specificity. Level III: a retrospective case-control study.