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.

Children with Primary Septic Arthritis Have a Markedly Lower Risk of Adverse Outcomes Than Those with Contiguous Osteomyelitis.

BACKGROUND: It is widely believed that septic arthritis poses a risk of joint destruction and long-term adverse outcomes for children if not treated emergently. In the present study, children who had primary confirmed septic arthritis were compared with those who had septic arthritis and adjacent osteomyelitis to evaluate differences that affect the relative risk of adverse outcomes. METHODS: Children who underwent multidisciplinary treatment for septic arthritis with or without contiguous osteomyelitis between 2009 and 2019 were retrospectively studied. Clinical, laboratory, treatment, and outcome data were compared between cohorts of children with primary confirmed septic arthritis and children with septic arthritis and contiguous osteomyelitis. RESULTS: One hundred and thirty-four children had primary confirmed septic arthritis, and 105 children had septic arthritis with contiguous osteomyelitis. Children with osteomyelitis were older (median, 7.4 versus 2.4 years), had higher initial C-reactive protein (median, 15.7 versus 6.4 mg/dL), and had a higher rate of thrombocytopenia (21.0% versus 1.5%). They also had a higher rate of bacteremia (69.5% versus 20.2%) for a longer duration (median, 2.0 versus 1.0 days). Detected pathogens in children with osteomyelitis as compared with those with primary septic arthritis were more likely to be Staphylococcus aureus (77.1% versus 32.1%) and less likely to be Kingella kingae (2.9% versus 32.1%). Children with contiguous osteomyelitis had longer hospitalizations (median, 8.0 versus 4.0 days), a higher rate of intensive care (21.0% versus 1.5%), a higher readmission rate (17.1% versus 5.2%), and a higher complication rate (38.1% versus 0.7%). CONCLUSIONS: Primary septic arthritis in children is dissimilar to septic arthritis associated with osteomyelitis. The present study demonstrates that long-term adverse outcomes in children with septic arthritis are likely due to the contiguous osteomyelitis. Children with primary septic arthritis are sufficiently distinguishable from those who have contiguous osteomyelitis to guide decisions for magnetic resonance imaging acquisition, duration of antibiotic therapy, and length of outpatient follow-up in order to recognize and address adverse outcomes. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Primary Septic Arthritis Among Children 6 to 48 Months of Age: Implications for PCR Acquisition and Empiric Antimicrobial Selection.

INTRODUCTION: Primary septic arthritis requires unique evaluation and treatment considerations for children in the 6- to 48-month age range because of the spectrum of identified pathogens and high rate of negative cultures. The purpose of this study is to evaluate primary septic arthritis in this age group in order to differentiate children with infection caused by Kingella kingae from those with other confirmed pathogens and those with no identified pathogen. METHODS: Preschool children who underwent multidisciplinary evaluation and treatment for septic arthritis between 2009 and 2019 were retrospectively studied. Three cohorts were established for comparison of clinical and laboratory features of primary septic arthritis: (1) confirmed K. kingae, (2) confirmed other pathogen, and (3) presumed (without identified pathogen). RESULTS: Among 139 children with septic arthritis, 40 (29%) were confirmed K. kingae, 29 (21%) other pathogen, and 70 (50%) presumed. Children with Kingella and those with presumed septic arthritis had significantly lower initial C-reactive protein (4.8 and 4.5 vs. 9.3 mg/dL) and fewer febrile hospital days (0.2 and 0.4 vs. 1.3 d) than children with other confirmed pathogens. Children with other pathogens had higher rates of bacteremia (38% vs. 0%) and positive joint fluid cultures (86% vs. 15%) than that of children with Kingella. The rate of polymerase chain reaction (PCR) acquisition was 38 of 40 (95.0%) Kingella cases, 18 of 29 (62.1%) other pathogen cases, and 33 of 70 (47.1%) presumed cases. CONCLUSIONS: K. kingae was the most commonly identified pathogen among 6-month to 4-year-old children. The Kingella and other identified pathogens in this study serve to guide empiric antimicrobial recommendations for this age range. Because of similarities between children with septic arthritis because of K. kingae and those with no identified pathogen, it is likely that an unrecognized burden of Kingella resides in culture negative cases, particularly if no PCR is sent. Systematic evaluation, including PCR acquisition, and a high index of suspicion for K. kingae are recommended to thoroughly evaluate septic arthritis in preschool children. LEVEL OF EVIDENCE: Level III-Retrospective cohort comparison.