Temporal trends in incidence, clinical characteristics and outcomes of pyogenic vertebral osteomyelitis in Southern Denmark from 2009 to 2022: a retrospective population-based cohort study

OBJECTIVES: Pyogenic vertebral osteomyelitis (PVO) is a severe infection with increasing incidence. We aimed to describe long-term population-based temporal trends in incidence, clinical presentation, diagnostic approaches, microbiology, and outcomes. MATERIALS AND METHODS: We conducted a retrospective population-based cohort study including 1,017 adults with multidisciplinary team-verified PVO diagnosed at a tertiary infectious diseases referral centre in the Region of Southern Denmark between 2009 and 2022. Incidence rates (IRs) per 100,000 person-years (PY) were calculated using regional population data and compared across three calendar periods (2009-2013, 2014-2018, 2019-2022). Temporal changes in clinical characteristics, microbiology, diagnostic strategies, and outcomes were assessed. RESULTS: F]FDG-PET/CT) increased over time. Median hospital stay remained 33 days. One-year mortality increased from 9.5% to 18.2%, while relapse declined, resulting in a stable composite risk of death or relapse (20.7%). CONCLUSIONS: The incidence of PVO increased markedly from 2009 to 2022, predominantly in older patients with comorbidities. Despite improved diagnostics, microbiologically-negative cases remain frequent. Mortality remained high and increased over time.