Background:The incidence of Septic arthritis (SA) in adults is rising, but few data are available for children (1). SA symptomatology in young children is often atypical and delayed diagnosis can cause significant morbidity.Objectives:To describe the incidence, risk factors and long-term outcomes in children hospitalised with septic arthritis (SA) in Western Australia (WA).Methods:We extracted population-based longitudinally linked administrative health data for patients under 16 years with a first inpatient primary or secondary code of 711.xx (ICD9-CM) and M00.xx (ICD10-AM) in WA for the study period 1990-2010 (to allow a minimum 5 year followup). We report annual incidence rates per 100.000 (AIR), prior conditions during lookback (median 15 months, IQR 5-45) as well as joint and other comorbidities including Charlson comorbidity index (CCI) and standardised mortality rates (SMR) during a median follow-up of 10 years. Age and gender speficic population and mortality rate data were obtained from the Australian Bureau of Statistics.Results:A total of 891 patients (62% male, median age 6.4 (IQR 1.9-10.6) years with 34% <3 years of age) had a first admission for SA. AIR was 9.85 (CI 4.79-14.41) overall with higher rates in males (11.9 vs 7, p<0.01) and no apparent period (Figure 1) or seasonal variation. Knees (43.9%), hips (34.6%), and ankles (13.3%) were most frequently affected with Staphylococci (49%) the predominant organism in patients with positive cultures (41.5%). Prior infections (40.4%) and respiratory disease (7 %) were the main preexisting morbidities. Mean hospital stay was 5.78 (± 6.4) days with ICU admission required in 1.9%, while 30-day readmittance rate was 10.4%. During follow-up 25 patients (3%) had recurrent/persistent osteomyelitis, nine patients were diagnosed with osteoarthrosis (1.1%) and five patients (0.6%) underwent joint replacement. More female patients developed new comorbidity (CCI>0, 34.6 vs 27.2%, p=0.02) including diabetes (4.2% vs 0%, p=0.001), cardiovascular events (4.2 vs 1.4%, p=0.002) and chronic arthritis (1% vs 0, p=0.05). While the crude mortality rate was low (0.3%) SMR was significantly increased for female patients (10.52, CI 1.59-41.6).Conclusion:The statewide incidence of septic arthritis in children in WA is similar to a recent report (1) and did not change over a 20-year period. In this large population based study, subsequent bone/joint disease occured in 4.6 %, while a third of patients developed other comorbidity before the age of 18. Such (subclinical) comorbidity may thus be a contributing factor to SA development and to the increased mortality risk in female SA patients.References:[1]Cohen E, Katz T, Rahamim E, Bulkowstein S, Weisel Y, Leibovitz R, Fruchtman Y, Leibovitz E. Septic arthritis in children: Updated epidemiologic, microbiologic, clinical and therapeutic correlations. Pediatr Neonatol. 2020 Jun;61(3):325-330. doi: 10.1016/j.pedneo.2020.02.006Figure 1.Annual incidence of septic arthritis per 100,000 population <16 years in Western Australia over period 1990-2010 by gender.Acknowledgements:The authors wish to thank the Arthritis Foundation of WA for their support and would like to acknowledge the support of the Western Australian Data Linkage Branch, the Western Australian Department of Health, and the data custodians of, the Hospital and Morbidity Data Collection, the Emergency Department Data Collection the WA Cancer Register and the WA Death Register for their assistance with data collection.Disclosure of Interests:None declared.
Septic Arthritis in Children: A Longitudinal Population-Based Study in Western Australia