The aims of this study are to analyse the characteristics of septic arthritis stratified by age and to identify the predictors of treatment failure and mortality in septic arthritis. A retrospective single-centre study was conducted in patients with native septic arthritis between 1994 and 2012. The primary outcome was treatment failure. Secondary outcomes included mortality, complications, endocarditis, bacteraemia, hospital readmission and the duration of the hospital stay. Logistic regression analyses with a propensity score were performed to identify the predictors of response and mortality. Additional analyses were performed according to age and the initial treatment (surgery or conservative). A total of 186 patients were studied. The median (interquartile range) age was 64 (46, 74) years, and the percentage of male patients was 68.9%. A logistic regression analysis showed that Staphylococcus aureus infection [OR 2.39 (1.20-4.77), p = 0.013], endocarditis [OR 4.74 (1.16-19.24), p = 0.029] and the involvement of joints difficult to access with needle drainage [OR 2.33 (1.06-5.11), p = 0.034] predict treatment failure and that age [OR 1.27 (1.07 = 1.50), p = 0.005], the leucocyte count at baseline [OR 1.01 (1.00-1.02), p = 0.023], bacteraemia [OR 27.66 (1.39-551.20), p = 0.030], diabetes mellitus [OR 15.33 (1.36-172.67), p = 0.027] and chronic renal failure [OR 81.27 (3.32-1990.20), p = 0.007] predict mortality. No significant differences in treatment failure by age were found. In septic arthritis, the predictors of mortality and the predictors of treatment failure differ. The predictors of treatment failure concern local factors and systemic complications, whereas conditions related to the host's immune competence, such as age and comorbidities that hamper the host's response, predict mortality.
Keywords: Age; Joint drainage; Mortality; Septic arthritis; Treatment.