Primary Septic Arthritis in the elderly – A Forgotten Killer? Five-Year Survival and Risk Factors in a Retrospective Cohort Study

Introduction: Primary septic arthritis is an acute emergency associated with high morbidity and mortality in older adults. Rapid diagnosis and treatment are crucial. The study evaluates 5-year survival and identifies prognostic risk factors in elderly patients with primary septic arthritis, including age, ASA Physical Status (ASA PS) classification, joint involvement, implants, and pathogen spectrum. Methods: 50 patients aged ≥ 60 years treated for primary septic arthritis at two hospitals between 2008 and 2020 were included. Demographic, clinical, and microbiological data were collected retrospectively. Survival was assessed by Kaplan–Meier analysis, with log-rank tests to compare subgroups. Results: The mean age was 71.2 years. Overall survival was 76% at 1 year and 54% at 5 years. Survival declined significantly with increasing age (p = 0.004), higher ASA PS classification (p < 0.001), joint involvement (p = 0.027), and presence of implants (p < 0.001). Diabetes mellitus, osteoarthritis, and synovial culture status showed no significant effect. By joint, mean survival was 1331 days for the knee, 879 days for the shoulder, 935 days for the hip, 1825 days for the ankle and 36 days for the sacroiliac joint. Patients with implants had markedly shorter survival (402 vs. 1400 days). Pathogens were isolated in 72% of cases, most frequently Staphylococcus aureus (38%). Conclusion: Primary septic arthritis in older adults remains a life-threatening condition with high early- and mid-term mortality. Survival is strongly determined by age, ASA PS classification, joint involvement, and presence of implants, while comorbidities and pathogen detection show no prognostic relevance.