Suspected contaminant source and early deep wound infections in posterior instrumented fusion involving the lumbosacral region: a multicenter analysis.

Abstract

PurposeEarly deep wound infection complicates an estimated 4% of posterior lumbosacral fusions, increasing mortality and hospitalization costs. The objective of this study was to characterize causative organisms and risk factors of deep wound infections following spine surgery.MethodsRetrospective data were collected from six institutions regarding adults (> 18 years) who underwent posterior instrumented fusion crossing the lumbosacral junction between 2015 and 2022. Demographics, comorbidities, operative details, debridements, and microbiology results were recorded. Pathogens were grouped as "outside-in" (i.e., consistent with direct local contamination from feces or urine) or "inside-out" (i.e., consistent with hematogenous/surgical contamination). The interval from index procedure to debridement was compared between the two groups using multivariable linear regression with log transformation.Results99 patients met all study criteria. Intraoperative cultures isolated outside-in pathogens in 50 (51%) cases, inside-out pathogens in 33 (33%) cases, and negative cultures in 16 (16%) cases. Compared to inside-out infection, outside-in infection was associated with a 50% shorter time to debridement (95% CI [0.4, 0.6], p < 0.01). An index procedure involving five or more levels was associated with a 42% longer time to debridement (95% CI [1.0, 1.9], p = 0.03), while diabetes was associated with a 26% shorter time to debridement (95% CI [0.6, 0.9], p = 0.01).ConclusionOutside-in infections constituted a higher percentage of deep wound infections in comparison to inside-out infections and present earlier after lumbosacral surgery. Safety precautions and proper hygiene that limit enteric contamination should be encouraged in postoperative spinal fusion patients to reduce the risk of deep wound infection.