Arthritis in children: comparison of clinical and biological characteristics of septic arthritis and juvenile idiopathic arthritis

Investigation and Management of Lower Limb Septic Arthritis in Children: An Update Using the Latest British Orthopaedic Association Standard for Trauma (BOAST) Guidelines

Septic arthritis is a serious condition in children, with the hip and knee joints most typically affected. Patients typically present with pain, joint swelling, fever, and an inability to bear weight. Early recognition and treatment are crucial, as untreated septic arthritis can lead to serious complications, including sepsis, irreversible joint damage, growth problems, and early-onset arthritis. Clinical signs, inflammatory markers, and imaging are used for the diagnosis of septic arthritis. The mainstay of management includes antibiotic therapy and surgical washout. Long-term follow-up is essential to monitor for complications.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA): 2023 Guideline on Diagnosis and Management of Acute Bacterial Arthritis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute bacterial arthritis (ABA) in children was developed by a multidisciplinary panel representing the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with ABA, including specialists in pediatric infectious diseases and orthopedics. The panel's recommendations for the diagnosis and treatment of ABA are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of ABA in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) (see Figure 1). A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Antibiotic therapy for osteoarticular infections in 2023: Proposals from the Pediatric Infectious Pathology Group (GPIP)

Most osteoarticular infections (OAI) occur via the hematogenous route, affect children under 5 years of age old, and include osteomyelitis, septic arthritis, osteoarthritis and spondylodiscitis. Early diagnosis and prompt treatment are needed to avoid complications. Children with suspected OAI should be hospitalized at the start of therapy. Surgical drainage is indicated in patients with septic arthritis or periosteal abscess. Staphylococcus aureus is implicated in OAI in children at all ages; Kingella kingae is a very common causative pathogen in children from 6 months to 4 years old. The French Pediatric Infectious Disease Group recommends empirical antibiotic therapy with appropriate coverage against methicillin-sensitive S. aureus (MSSA) with high doses (150 mg/kg/d) of intravenous cefazolin. In most children presenting uncomplicated OAI with favorable outcome (disappearance of fever and pain), short intravenous antibiotic therapy during 3 days can be followed by oral therapy. In the absence of bacteriological identification, oral relay is carried out with the amoxicillin/clavulanate combination (80 mg/kg/d of amoxicillin) or cefalexin (150 mg/kg/d). If the bacterial species is identified, antibiotic therapy will be adapted to antibiotic susceptibility. The minimum total duration of antibiotic therapy should be 14 days for septic arthritis, 3 weeks for osteomyelitis and 4-6 weeks for OAI of the pelvis, spondylodiscitis and more severe OAI, and those evolving slowly under treatment or with an underlying medical condition (neonate, infant under 3 months of old, immunocompromised patients). Treatment of spondylodiscitis and severe OAI requires systematic orthopedic advice.

Diagnostic Utility of Synovial Fluid Cell Counts and CRP in Pediatric Knee Arthritis: A 10-Year Monocentric, Retrospective Study

Background: Orthopedic surgeons often use the intra-articular white blood counts (WBCs) and the percentage of polymorphonuclear cells (PMN) in the diagnosis of an acute swollen and painful knee joint in children. Today, there is no established threshold for the synovial WBC, and their differentiation, as indicative of native joint knee bacterial arthritis. We determine the sensitivity and specificity of synovial WBCs and PMN percentages in the prediction of a community-acquired, acute bacterial native joint septic arthritis (SA) in the pediatric population. Methods: A retrospective study on healthy children 0–16 years of age who underwent knee joint aspiration for a community-acquired, acute irritable knee effusion in our tertiary-care children’s hospital between May 2009 and April 2019 was conducted. We divided the study population into two groups according to the detection of bacterial arthritis in the synovial fluid (bacterial arthritis versus its absence) and compared the intra-articular leukocyte and C-reactive protein (CRP) levels. Results: Overall, we found a statistically significant difference regarding the total CRP (p = 0.017), leukocyte or PMN counts (p ≤ 0.001 in favor of a bacterial arthritis). In contrast, the percentage of the neutrophils was not determinant for the later confirmation of bacterial pathogens, and we were unable to establish diagnostically determining minimal thresholds of the intra-articular CRP and leukocyte levels. Conclusions: This pilot study suggests that either the leukocyte or PMN counts may be associated with a bacterial origin of knee arthritis in children. We plan a larger prospective interventional study in the future to confirm these findings including the investigation of other joint aspirate biomarkers.

Primary Septic Arthritis in Children Demonstrates Presumed and Confirmed Varieties Which Require Age-specific Evaluation and Treatment Strategies

BACKGROUND

There is uncertainty involved in the evaluation and treatment of children suspected to have septic arthritis particularly when no causative pathogen is confirmed. This study evaluates children with primary septic arthritis to refine the processes of evaluation and treatment and improve the rate of pathogen confirmation.

METHODS

Children suspected to have septic arthritis from 2009 to 2019 were retrospectively studied. Diagnosis of primary septic arthritis, defined as hematogenous joint infection without associated osteomyelitis, was established by clinical evaluation, radiology and laboratory results, including joint fluid analysis. Excluded cases were categorized by etiology. Children with primary septic arthritis were divided into confirmed and presumed cohorts for statistical comparison.

RESULTS

A total of 355 children (average age 4.4 y, range 0.05 to 18 y) were initially treated as septic arthritis. Eighty-seven (24.5%) were excluded due to other conditions, including 34 (9.6%) with noninfectious conditions. Among 268 children with primary septic arthritis, 134 were confirmed and 134 were presumed. A higher rate of 16S polymerase chain reaction (PCR) acquisition (71.6% vs. 45.5%) occurred in the confirmed cohort. Overall yield for various methods of pathogen identification were 27 of 239 (11.3%) by blood culture, 83 of 268 (31.0%) by joint fluid culture and 85 of 157 (54.1%) by PCR. PCR identified a pathogen in 87.5% of children with confirmed septic arthritis. Antibiotic pretreatment was associated with a lower rate of joint fluid culture positivity. Pathogens aggregated within specific age groups. The 4 to 9-year-old age group displayed the widest spectrum of pathogens with limited predictability.

CONCLUSIONS

This study emphasizes the need for systematic processes of evaluation and treatment for children suspected to have primary septic arthritis, including minimization of antibiotic pretreatment, age-based empiric antibiotic selection, and sufficient follow-up to ensure noninfectious conditions are distinguished in culture-negative cases. Extended observation, before intervention, may be appropriate for some children.

LEVEL OF EVIDENCE

Level III-retrospective control study.

Acute Arthritis in Children: How to Discern between Septic and Non-Septic Arthritis?

The term septic arthritis refers to an infection of the synovial space. This is an infrequent condition in healthy children, but it should be considered a medical emergency potentially leading to irreversible articular damage. Therefore, prompt diagnosis and antimicrobial treatment play a crucial role in improving the prognosis. Although septic arthritis is the most common cause of acute arthritis, many other diseases may mimic a similar clinical picture, constituting a diagnostic challenge for the clinician who first approaches the patient. Herein we analyze the main features of septic arthritis, offering an overview of the main conditions involved in the differential diagnosis and suggesting a diagnostic workup plan.

Clinical presentations of Kingella kingae musculoskeletal infections in South Australian children

AIM

This study aimed to alert clinicians to the spectrum of presentations of Kingella kingae musculoskeletal infections.

METHODS

Between August 2010 and March 2018, 55 children presented with positive K. kingae polymerase chain reaction on joint fluid, bone or deep soft tissue collections involving the limbs and subsequently underwent retrospective medical record, radiological and laboratory review. Demographics and clinical information are presented.

RESULTS

Median age at presentation was 15.9 months (range 4.3 months-10.7 years) and 64% were male. Septic arthritis was the most common diagnosis (95%), median duration of symptoms was 4 days, 65% had a preceding infection (e.g. upper respiratory or gastrointestinal) and 22% re-presented to emergency departments after prior discharge. The lower limb was involved in 84%, with the knee being most affected (55%). If the lower limb was involved, 82% of previously weight-bearing children had a limp or were unable to weight bear. On presentation, median temperature was 36.7°C and inflammatory markers were mildly elevated. No blood cultures grew K. kingae. Five synovial fluid cultures were positive for K. kingae. Plain radiography showed effusion, soft tissue swelling or a lesion in 53% of patients. All 41 ultrasounds showed effusion, soft tissue swelling or synovial thickening. One patient with delayed diagnosis later presented with avascular necrosis of the femoral head.

CONCLUSION

Kingella kingae is difficult to diagnose due to non-specific symptoms, absence of fevers and often unremarkable blood tests. Despite generally having good long-term outcomes, our case of avascular necrosis suggests accurate diagnosis and treatment are important.

A Neonatal Hip Septic Arthritis Caused by Klebsiella pneumonia at Hawassa University Comprehensive Specialized Hospital Neonatal Unit, Hawassa, Sidama, Ethiopia

BACKGROUND

Neonatal hip septic arthritis is one of the rarest clinical conditions epidemiologically but with momentous long-term sequelae. Early detection and proper intervention have a paramount role in alleviating the shattering long-term effects. The clinical presentation of neonatal hip septic arthritis is very non-specific, with limited movement of the extremities and excessive crying during manipulations such as diaper changing. Our case was a 17-day-old male newborn who presented to our hospital after a family noticed decreased left leg movement and crying while changing diapers for 5 days, with the associated complaint of holding the left leg in a flexed position. The newborn then underwent all the available investigations and the diagnosis of hip septic arthritis was made. We were stunned by the culture result, which isolated Klebsiella pneumonia from the sample that had been taken from joint fluid, which is a very unusual isolate.

CONCLUSION

Hip septic arthritis is an orthopedic emergency, especially in neonates. It should be considered in newborns presenting with pseudoparalysis as the presentation is non-specific. Considering a less common microorganism with culture and sensitivity is very important, especially if the response to treatment is delayed. We endorse proper workup and timely intervention as hip arthritis has a poor prognosis when the management is delayed.

Acute monoarthritis in young children: comparing the characteristics of patients with juvenile idiopathic arthritis versus septic and undifferentiated arthritis

Acute arthritis is a common cause of consultation in pediatric emergency wards. Arthritis can be caused by juvenile idiopathic arthritis (JIA), septic (SA) or remain undetermined (UA). In young children, SA is mainly caused by Kingella kingae (KK), a hard to grow bacteria leading generally to a mild clinical and biological form of SA. An early accurate diagnosis between KK-SA and early-onset JIA is essential to provide appropriate treatment and follow-up. The aim of this work was to compare clinical and biological characteristics, length of hospital stays, duration of intravenous (IV) antibiotics exposure and use of invasive surgical management of patients under 6 years of age hospitalized for acute monoarthritis with a final diagnosis of JIA, SA or UA. We retrospectively analyzed data from < 6-year-old children, hospitalized at a French tertiary center for acute mono-arthritis, who underwent a joint aspiration. Non-parametric tests were performed to compare children with JIA, SA or UA. Bonferroni correction for multiple comparisons was applied with threshold for significance at 0.025. Among the 196 included patients, 110 (56.1%) had SA, 20 (10.2%) had JIA and 66 (33.7%) had UA. Patients with JIA were older when compared to SA (2.7 years [1.8–3.6] versus 1.4 [1.1–2.1], p < 0.001). Presence of fever was not different between JIA and SA or UA. White blood cells in serum were lower in JIA (11.2 × 10⁹/L [10–13.6]) when compared to SA (13.2 × 10⁹/L [11–16.6]), p = 0.01. In synovial fluid leucocytes were higher in SA 105.5 × 10³ cells/mm³ [46–211] compared to JIA and UA (42 × 10³ cells/mm³ [6.4–59.2] and 7.29 × 10³ cells/mm³ [2.1–72] respectively), p < 0.001. Intravenous antibiotics were administered to 95% of children with JIA, 100% of patients with SA, and 95.4% of UA. Arthrotomy-lavage was performed in 66.7% of patients with JIA, 79.6% of patients with SA, and 71.1% of patients with UA. In children less than 6 years of age with acute mono-arthritis, the clinical and biological parameters currently used do not reliably differentiate between JIA, AS and UA. JIA subgroups that present a diagnostic problem at the onset of monoarthritis before the age of 6 years, are oligoarticular JIA and systemic JIA with hip arthritis. The development of new biomarkers will be required to distinguish JIA and AS caused by Kingellakingae in these patients.

Short-course antibiotic treatment of bone and joint infections in children: a retrospective study at Montpellier University Hospital from 2009 to 2013

BACKGROUND

Acute haematogenous bone and joint infections (AHBJI) represent a diagnostic and therapeutic emergency in children, with significant potential sequelae in the case of delayed treatment. Although historically the recommendations for treatment have been based on surgery and prolonged antibiotic therapy, recent studies have demonstrated that short-course antibiotic therapy is also effective.

OBJECTIVES

We evaluated a short-term antibiotic protocol for both osteomyelitis and septic arthritis in a 6 year retrospective study at the University Hospital of Montpellier.

METHODS

This protocol was based on an initial intravenous treatment with a re-evaluation after 48 h and an early switch to oral therapy in the case of a favourable clinical course for a minimum total duration of 15 days. Antibiotics were selected based on local microbiological epidemiology and systematically adapted to bacteriological results.

RESULTS

One hundred and seventy-six cases of AHBJI were included, comprising 56 patients with osteomyelitis, 95 with septic arthritis and 25 who had both of these. The aetiological agent was identified in 42% of the cases, with the main pathogens being Staphylococcus aureus (39%) and Kingella kingae (27%). The mean intravenous treatment duration was 4 days, while the total treatment duration was 15 days. There were no treatment failures, mild sequelae occurred in 1% of the cases and the secondary surgical revision rate was 7%.

CONCLUSIONS

The results of this study are comparable to those reported for evaluations of prolonged antibiotic therapy protocols, thus indicating that a common short-term antimicrobial therapy for the management of both osteomyelitis and septic arthritis (minimum of 15 days) is a viable option for treating AHBJI in children. Further prospective studies to confirm these findings are hence warranted.

Septic Arthritis: An Evidence-Based Review of Diagnosis and Image-Guided Aspiration

OBJECTIVE. The purpose of this evidence-based review is to equip radiologists to discuss and interpret findings obtained with various imaging modalities, guide patient selection for percutaneous aspiration, and safely perform arthrocentesis to assess for infection in both native and prosthetic joints. CONCLUSION. Septic arthritis is an emergency that can lead to rapidly progressive, irreversible joint damage. Despite the urgency associated with this diagnosis, there remains a lack of consensus regarding many aspects of the management of native and periprosthetic joint infections.

Differential Accumulation and Activation of Monocyte and Dendritic Cell Subsets in Inflamed Synovial Fluid Discriminates Between Juvenile Idiopathic Arthritis and Septic Arthritis

Despite their distinct etiology, several lines of evidence suggest that innate immunity plays a pivotal role in both juvenile idiopathic arthritis (JIA) and septic arthritis (SA) pathophysiology. Indeed, monocytes and dendritic cells (DC) are involved in the first line of defense against pathogens and play a critical role in initiating and orchestrating the immune response. The aim of this study was to compare the number and phenotype of monocytes and DCs in peripheral blood (PB) and synovial fluid (SF) from patients with JIA and SA to identify specific cell subsets and activation markers associated with pathophysiological mechanisms and that could be used as biomarkers to discriminate both diseases. The proportion of intermediate and non-classical monocytes in the SF and PB, respectively, were significantly higher in JIA than in SA patients. In contrast the proportion of classical monocytes and their absolute numbers were higher in the SF from SA compared with JIA patients. Higher expression of CD64 on non-classical monocyte was observed in PB from SA compared with JIA patients. In SF, higher expression of CD64 on classical and intermediate monocyte as well as higher CD163 expression on intermediate monocytes was observed in SA compared with JIA patients. Moreover, whereas the number of conventional (cDC), plasmacytoid (pDC) and inflammatory (infDC) DCs was comparable between groups in PB, the number of CD141⁺ cDCs and CD123⁺ pDCs in the SF was significantly higher in JIA than in SA patients. CD14⁺ infDCs represented the major DC subset in the SF of both groups with potent activation assessed by high expression of HLA-DR and CD86 and significant up-regulation of HLA-DR expression in SA compared with JIA patients. Finally, higher activation of SF DC subsets was monitored in SA compared with JIA with significant up-regulation of CD86 and PDL2 expression on several DC subsets. Our results show the differential accumulation and activation of innate immune cells between septic and inflammatory arthritis. They strongly indicate that the relative high numbers of CD141⁺ cDC and CD123⁺ pDCs in SF are specific for JIA while the over-activation of DC and monocyte subsets is specific for SA.

C-Reactive Protein Level at Time of Discharge Is Not Predictive of Risk of Reoperation or Readmission in Children With Septic Arthritis

Purpose: C-reactive protein (CRP) level is used at our tertiary pediatric hospital in the diagnosis, management, and discharge evaluation of patients with septic arthritis. The purpose of this study was to evaluate the efficacy of a discharge criterion of CRP < 2.0 mg/dL for patients with septic arthritis in preventing reoperation and readmission. We also aimed to identify other risk factors of treatment failure.

Methods: Patients diagnosed with septic arthritis between January 1, 2007 and December 31, 2017 were identified with ICD 9/10 and related CPT codes. Systematic chart reviews were performed to obtain demographic data, infection characteristics, and treatment details. Bivariate tests of associations between potential risk factors and readmission and reoperation were performed. Quantitative variables were analyzed using Mann-Whitney tests and categorical variables were analyzed using Chi-square tests.

Results: One hundred and eighty-three children with septic arthritis were included in the study. Seven (3.8%) were readmitted after hospital discharge for further management, including six who required reoperation. Mean CRP at discharge for single-admission patients was 1.71 mg/dL (± 1.07) and 1.96 mg/dL (± 1.19) for the readmission group (p = 0.664). Forty-eight children (25.9%) had CRP values greater than the recommended 2.0 mg/dL at discharge. Only three of these patients (6.2%) were later readmitted. The only common variable of the readmitted children was an antibiotic-resistant or atypical causative bacteria.

Conclusions: CRP levels are useful in monitoring treatment efficacy of septic arthritis in children but are not reliable as a discharge criterion to prevent readmission or reoperation. We recommend determining discharge readiness on the basis of clinical improvement and down-trending CRP values. There was a higher risk of readmission in children with an antibiotic-resistant or atypical causative bacteria. Close monitoring of these patients and those with negative cultures at time of discharge is suggested to identify signs of persistent infection.

Level of evidence: III, retrospective cohort study.

Synovial-Fluid miRNA Signature for Diagnosis of Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) is the most common chronic inflammatory rheumatism in childhood; microRNAs (miRNAs) have been proposed as diagnostic biomarkers. Although joints are the primary targets for JIA, a synovial fluid-based miRNA signature has never been studied. We aim to identify miRNA biomarkers in JIA by comparing synovial fluid and serum samples from children with JIA and K. kingae septic arthritis (SA). With next-generation high-throughput sequencing, we measured the absolute levels of 2083 miRNAs in synovial fluid and serum from an exploratory cohort of children and validated differentially expressed miRNAs in a replication study by using RT-qPCR. We identified a 19-miRNA signature only in synovial fluid samples that was significantly deregulated, with at least 2-fold change in expression, in JIA versus SA (p < 0.01). The combination of miR-6764-5p, miR-155, and miR-146a-5p expression in synovial fluid yielded an area under the receiver operating characteristic curve of 1 (95% CI 0.978 to 1), thereby perfectly differentiating JIA from SA in children. We propose, for the first time, a synovial fluid-specific miRNA signature for JIA and associated signaling pathways that may indicate potential biomarkers to assist in the classification and differential diagnosis of JIA and help in understanding JIA pathogenesis.

Pediatric Septic Arthritis: An Update

Septic arthritis in children is a surgical emergency, and prompt diagnosis and treatment are mandatory. If diagnosed quickly and treated correctly, the outcomes can be good. With delay in diagnosis and without proper treatment, outcomes often are quite devastating, with growth disturbance and joint destruction.

Synovial fluid cell counts and its role in the diagnosis of paediatric septic arthritis

PURPOSE

Clinical presentation of paediatric septic arthritis (SA) can be similar to other joint pathologies. Despite potential for infection in all major joints, most diagnostic criteria are based on values from the hip. This study identifies the best joint aspirate values in diagnosing SA in all joints.

METHODS

In all, 166 patients who underwent 172 joint aspirations at the authors' institution between 01 September 2004 and 01 September 2014 were retrospectively identified. Recorded measures included age, sex, duration of symptoms, fever history, weight-bearing status, aspiration results, serum results and antibiotic administration. Patients were placed in the following four categories: 'culture confirmed SA' (C-SA), 'suspected SA' (S-SA), 'Other' and 'Other-rheumatologic' (Other-R), a subcategory of 'Other'.

RESULTS

Most common sites of aspiration were the knee (55%) and hip (29%). Diagnostic grouping was as follows: C-SA = 44, S-SA = 45, Other = 83 (Other-R = 21). Fever and non-weight-bearing prior to admission were useful predictors of SA, though in C-SA patients, 21% did not have a fever and 23% could weight bear at the time of admission. Aspirate white blood cell (WBC) count was significantly greater in both C-SA (92 000 cells/hpf) and S-SA (54 000) than in Other (10 000) and Other-R (18 000) patients. The percentage of polymorphonuclear (%PMN) was also significantly greater in C-SA (81.1%) and S-SA (80.9%) than in Other (57.9%) and Other-R (63.3%).

CONCLUSION

Joint aspirate values, especially %PMN, are valuable in diagnosing SA. Additionally, antibiotics pre-aspiration did not affect %PMN, facilitating subsequent diagnosis of infection. Lastly, while aspirate WBC count was a valuable indicator of SA, this finding is not as definitive as previous research suggests.

LEVEL OF EVIDENCE

IV Case Series.

[Characteristics of synovial fluid in patients with juvenile idiopathic arthritis]

INTRODUCTION

Synovial fluid (SF) analysis is an important tool for the diagnosis of patients with juvenile idiopathic arthritis (JIA).

PATIENTS AND METHODS

A retrospective analysis was carried out of cytological features of SF samples obtained from patients with JIA during the period 2008-2016.

RESULTS

A total of 102 SF samples from 59 patients were analysed. JIA was more common in females (66%). The most frequent form was persistent oligoarticular JIA (52.5%). The median age at onset was 5 years (IQR 2.4-11.8). SF usually showed an inflammatory pattern (median white blood cells count 11,757/mm³; IQR 4,543-18,800), with a predominance of polymorphonuclear (PMN) cells (61%; IQR 30-75). Eight patients (14%) had white blood cells counts of less than 2,000 cells/mm³, with predominance of mononuclear cells (80%), whereas 3 patients (5%) had white blood cells counts higher than 50,000 cells/mm³, with a predominance of PMN cells (90%). Synovial white blood cells count did not show significant differences among the different forms of JIA. The median synovial white blood cells count in ANA-positive patients was 20% lower than in ANA-negative (9,340 vs. 11,600/mm³; P=.23). The proportion of PMN increased with increasing levels of ESR (P<.001) and/or CRP (P=.03). No significant correlation was found between JADAS-10 and synovial white blood cells count (P=.4). SF obtained from different joints in simultaneous arthrocentesis showed a significant correlation P=.001).

CONCLUSION

SF from JIA patients usually had inflammatory characteristics, although 19% of the patients showed white blood cells counts below 2,000cells/mm³ or higher than 50,000cells/mm³. SF cell count was non-significantly lower in ANA-positive patients, and the proportion of PMN increased with increasing levels of ESR/CRP.