Pyogenic Vertebral Column Osteomyelitis in Adults: Analysis of Risk Factors for 30-Day and 1-Year Mortality in a Single Center Cohort Study

Study Design: Retrospective cohort study. Purpose: To describe our experience in the management and outcomes of vertebral column osteomyelitis (VCO), particularly focusing on the risk factors of early and late mortality. Overview of literature: Previous reports suggest a global increase in spinal column infections highlighting significant morbidity and mortality. To date, there have been no reports from our local population, and no previous report has assessed the potential relationship of frailty with mortality in a cohort of patients with VCO. Methods: We reviewed 76 consecutive patients with VCO between 2009 and 2016 in Waikato Hospital, New Zealand. Demographic, clinical, microbiological, and treatment data were collected. Comorbidities were noted to calculate the modified Frailty Index (mFl). Mortality at 30 days and 1 year was recorded. Univariate and multivariate analyses were used to identify the predictors of mortality. Results: The mean age of patients was 64.1 years, with 77.6% being male. Most patients presented with axial back pain (71.1%), with the lumbar spine most commonly affected (46%). A mean of 2.1 vertebral bodies was involved. Methicillin-sensitive Staphylococcus aureus was the most common organism of infection (35.5%), and 15.8% of patients exhibited polymicrobial infection. Twenty patients (26.3%) underwent surgical intervention, which was more likely in patients with concomitant spinal epidural abscess (odds ratio [OR], 4.88) or spondylodiscitis (OR, 3.81). Mortality rate was 5.2% at 30 days and 22.3% at 1 year. The presence of frailty (OR, 13.62) and chronic renal failure (OR, 13.40) elevated the 30-day mortality risk only in univariate analysis. An increase in age (OR, 1.07) and the number of vertebral levels (OR, 2.30) elevated the 1-year mortality risk in both univariate and multivariate analyses. Conclusions: Although the mFI correlated with 30-day mortality in univariate analysis, it was not a significant predictor in multivariate analysis. An increase in age and the number of levels involved elevated the 1-year mortality risk.