Rheumatology and Therapy | 2021
Septic Arthritis in Children: A Longitudinal Population-Based Study in Western Australia
Abstract
To describe the incidence, risk factors and long-term outcomes in children hospitalised with septic arthritis (SA) in Western Australia (WA). We extracted state-wide longitudinally linked administrative health data for patients aged < 16 years with a first diagnostic code of 711.X (ICD9-CM) and M00.X (ICD10-AM) in WA in the period 1990–2010. Annual incidence rates (AIR) per 100,000 with 95% confidence intervals (CIs), prior conditions during a median lookback period of 63.2 [interquartile range (IQR) 19.8–117.1] months and outcomes, including standardised mortality rates (SMR), during a median follow-up of 10 years are reported. A total of 891 patients [62% male, median age 6.4 (IQR 1.9–10.6) years with 34%\u2009aged <\u20093 years] were admitted for SA during the observation period. The overall AIR (per 100,000) was 9.85 (95% CI 4.79–14.41), and was higher in Indigenous Australians [34.9 vs. 5.5 (non-Indigenous), p\u2009<\u20090.001] and in males [11.9 vs. 7 (females), p\u2009<\u20090.01]; AIR showed no temporal or seasonal variation. Knees (43.9%), hips (34.6%) and ankles (13.3%) were most frequently affected, with Staphylococci predominant (49%) in patients with positive cultures (41.5%). Prior infection(s) (40.4%) and respiratory disease (7%) were the main pre-existing morbidities. Median hospital stay was 4.0 (IQR 2–8) days, with 1.9% requiring admission to the intensive care unit and 10.4% requiring readmission within 30 days. During follow-up, 26 patients (3.1%) developed osteomyelitis, nine patients were diagnosed with osteoarthrosis (1.1%) and five patients (0.6%) underwent joint replacement. Female patients developed other serious infections more often than male patients (40.5 vs. 27.1%, p\u2009<\u20090.01), as well as other comorbidities (Charlson Comorbidity Index\u2009>\u20090: 34.6 vs. 27.2%, p\u2009=\u20090.02), including diabetes (4.2 vs. 0%; p\u2009=\u20090.001), cardiovascular events (4.2 vs 1.4%, p\u2009=\u20090.002) and chronic arthritis (1 vs. 0%, p\u2009=\u20090.05). The crude mortality rate was low (0.3%), with 99.4% survival at 180 months and no increase in the SMR. The incidence of SA in children in WA did not change over the 20-year observation period. SA did not lead to excess mortality, but bone and joint complications developed in 5% of patients. The high propensity to comorbid conditions in this young cohort suggests an underlying role of comorbidity in SA development. As more children are living with complex and chronic conditions, we investigated whether children in Western Australia (WA) have become more prone to joint infections. During a 20-year observation period we collected health data for all children admitted to any hospital in the state with an infected joint and recorded their health outcomes. We found that joint infection occurs in nearly ten out of 100,000 children each year, but we saw no change in the frequency over time. We did observe higher rates in Indigenous children (35/100,000) than in non-indigenous children (6/100,000) but found no noticeable influence of the seasons on the frequency of joint infections. Knees, hips and ankles were most often affected, and 15% had additional bone infection. Children needed to be treated in hospital for 4–5 days, and only a small minority (1.2%) were so ill they needed intensive care. Joint infections led to chronic, long-term complications in about 5% of patients, but we found no evidence that joint infections increased the risk of death compared to children in the general population.