Epidemiology and Risk Factors of Pediatric Osteoarticular Infections at Penn State Hershey Medical Center

Background Lyme arthritis accounts for ~30-45% of pediatric joint effusions in Lyme-endemic regions with an incidence estimated at >10 cases per 100,000 children per year while involving the knee in 90% of cases (1,2). Incidence of septic arthritis and osteomyelitis is estimated at 2-20 and about 8 per 100,000 children per year, respectively (3). The highest incidence of Lyme arthritis nationally is found among 5–9-year-olds, septic arthritis is highest in children < 4, and osteomyelitis in children < 5 (1,3,4). Early recognition of risk factors for various osteoarticular infections could allow for optimized therapy and improved outcomes and our goal was to describe the epidemiology and identify risk factors of osteoarticular infections presenting to Penn State Hershey Medical Center. Methods We conducted a retrospective review of pediatric patients treated at Penn State Hershey Medical Center from January 1, 2014 to March 1, 2024 for suspected osteoarticular infections. Demographic, clinical, diagnostic, microbiologic, and treatment data were abstracted into REDCap. Descriptive statistics characterized the cohort, and differences among Lyme arthritis, septic arthritis, and osteomyelitis were compared using Fisher’s exact tests and Wilcoxon rank-sum tests. Results 132 patients with osteoarticular infections were included in the study. 32.6% had Lyme arthritis, 11.3% with septic arthritis, and 56.1% had osteomyelitis with or without septic arthritis. 38% were female, 62% were male, 74% were White, and 75% were vaccinated. Ethnically, 11% identified as Hispanic, 73% as non-Hispanic, and 9% as other and non-Hispanic was identified in 72% of Lyme arthritis cases, 67% of septic arthritis cases and 74% of osteomyelitis cases (p = 0.029). In 30 days prior to diagnosis, 9% had surgery and occurred more frequently in osteomyelitis cases (p = 0.002). In the past year, 17% were hospitalized prior to diagnosis with all having osteomyelitis (p = 0.002). Most frequently involved joint was the knee (51%) followed by hip (27%), with knee being the most common joint for Lyme arthritis (79%, p < 0.001). No significant difference was identified in age, sex, race, or vaccination status. Conclusion In this cohort, pediatric osteoarticular infections most often affected White, non-Hispanic, vaccinated children with knee and hip involvement. Significant differences between diagnostic groups found Lyme arthritis predominately affected the knee, whereas recent surgery, prior hospitalization, and hip involvement were more associated with osteomyelitis with or without septic arthritis. Recognizing distinct epidemiologic patterns may aid in early differentiation for pediatric osteoarticular infections.