Spinal Implant-Associated Infections: Clinical-Microbiological Profile, Risk Factors and Outcomes in a Brazilian Cohort

Spinal implant-associated infections (SIAI) are complications of high clinical complexity. Despite being relatively frequent, with incidence up to 20%, the literature on risk factors and standardized guidelines remains scarce. This study aimed to describe the clinical and microbiological profile of SIAI after spinal arthrodesis, and to investigate independent risk factors for SIAI and variables associated with therapeutic outcomes. An ambispective, single-center cohort study was performed in a tertiary university center including patients undergoing spinal arthrodesis between January 2018 and December 2023. Patients who developed SIAI were classified as “cases” and the others as “controls”. The definition of SIAI followed the criteria of the Second International Consensus on Musculoskeletal Infections. Logistic regression was used for multivariable risk factor analysis, and bivariate analysis for association with outcome, with 95% CI and p<0.05 considered statistically significant. Among 150 patients included, 30 (20%) developed SIAI, mostly acute (96.7%), with median symptom onset at 16 days (SD ±146.8). Microbiological diagnosis was obtained in 56.7% of cases, with S. aureus (38.1%), P. aeruginosa (19%), K. pneumoniae (19%) and P. mirabilis (14.3%) predominating. All cases received antibiotic therapy, with a mean duration of 75.4 days (SD ±77.09). Reoperations occurred in 70% of cases, with a mean of 3.05 reoperations (SD ±2.64). Debridement with implant retention (DAIR) was the predominant approach (95.2%). Therapeutic failure occurred in 10 cases (33.3%), with 7 deaths. Independent risk factors for SIAI were body mass index (BMI) > 30 (OR = 3.890; 95% CI: 1.415–10.693; p = 0.008) and chronic alcohol use (OR = 3.289; 95% CI: 1.114–9.712; p = 0.031), while use of non–beta-lactam prophylactic antibiotic showed a protective effect (OR = 0.352; 95% CI: 0.135–0.920; p=0.033). Factors associated with therapeutic failure were persistent pain (OR = 6.6; 95% CI: 1.3–34.2; p=0.047), chronicity (p=0.041), plastic reconstruction (p=0.041) and higher number of reoperations (p = 0.012). The findings reinforce the severity of SIAI in the post-spinal arthrodesis context. The high failure rate highlights the need for standardized protocols. The associations identified may support more effective clinical guidelines.