Clinical Characteristics and Follow-Up of Children with Primary Haematogenous Osteomyelitis and Septic Arthritis: Eight Years of Experience from Hungary.

Introduction: Paediatric acute haematogenous bone and joint infections (BJIs) are serious conditions. This study aimed to analyse the characteristics of paediatric acute haematogenous osteomyelitis (AHO) and septic arthritis (SA) in Hungary, with a focus on causative pathogens, clinical outcomes, and long-term complications. Methods: A retrospective cohort study was conducted at a Hungarian tertiary referral centre between 2015 and 2022. Children aged 18 years or younger diagnosed with acute haematogenous osteomyelitis (AHO) or septic arthritis (SA) within two months of symptom onset were included. Exclusion criteria were chronic infection, post-operative infections, or wound-related infections. Complicated AHO was defined by intraosseous abscess or necrosis confirmed radiologically or intraoperatively. The primary outcome was surgical intervention beyond 30 days after diagnosis; secondary outcomes included long-term complications. Results: Forty patients were included (77.5% male, median age 8.7 years). AHO was diagnosed in 8 patients (20.0%), complicated AHO in 22 (55.0%), and SA in 10 (25.0%). MRI had the highest diagnostic sensitivity (97.0%). Pathogens were identified in 72.5% of cases; Staphylococcus aureus (S. aureus) was most common (57.5%), followed by Salmonella and Streptococcus pyogenes (5% each). Surgery was required in 90.0% of SA cases, 77.2% of complicated AHO, and 37.5% of uncomplicated AHO. Long-term complications occurred in 10%, mainly with S. aureus and complicated AHO. Conclusions: Paediatric BJIs, especially due to S. aureus, often require surgery and cause long-term sequelae.