Abstract
STUDY DESIGN: Retrospective cohort study. OBJECTIVE: Although surgical risk factors for developing spine surgical site infections (S-SSI) have been identified, the impact of such knowledge in its prevention has not been demonstrated. METHODS: We evaluated in 500 patients undergoing spine surgery between 2011 and 2019 at Hospital 12 de Octubre the changes in S-SSI rates over time. Surgical variables independently related to S-SSI were analyzed by univariate and multivariate analysis using binary logistic regression models. A case-control sub-analysis (1:4), matched by the surgical variables identified in the overall cohort was also performed. RESULTS: Twenty cases of S-SSI were identified (4%), with a significant decrease in the incidence rate across consecutive time periods (6.6% [2011-2014] vs .86% [2015-2019]; P-value <.0001)). Multivariate analysis identified arthrodesis involving sacral levels (odds ratio [OR]: 2.57; 95% confidence interval [95%CI]: 1.02-6.47; P-value = .044) and instrumentation over 4-8 vertebrae (OR: 2.82; 95%CI: 1.1-7.1; P-value = .027) as independent risk factors for S-SSI. The reduction in the incidence of S-SSI concurred temporally with a reduction in instrumentations involving 4-8 vertebrae (55% vs 21.8%; P-value <.0001) and sacral vertebrae (46.9% vs 24.6%; P-value <.0001) across both periods. The case-control analysis matched by these surgical variables failed to identify other factors independently related to the occurrence of S-SSI. CONCLUSIONS: Spinal fusion of more than 4 levels and the inclusion of sacral levels were independently related to the risk of S-SSI. Optimization of surgical techniques by reducing these two types of instrumentation could significantly reduce S-SSI rates.