Post-Operative Infection Following Multi-Level Posterior Lumbar Spinal Instrumentation in the Vancomycin Powder Era

<b><i>Background:</i></b> Since the early 2010s, prophylactic vancomycin powder has been widely adopted in spine surgery, with many surgeons crediting it for low surgical site infection (SSI) rates (1%-2%). However, its efficacy remains debated. <b><i>Purpose:</i></b> To compare post-operative SSI and related complications in multi-level posterior lumbar spinal surgery before and after the widespread use of vancomycin powder. <b><i>Design:</i></b> Retrospective study using the TriNetX Research Network. <b><i>Patient Sample:</i></b> Adult patients undergoing posterior spinal instrumentation (≥3 levels) for lumbar stenosis or spondylolisthesis. <b><i>Outcome Measures:</i></b> Primary: Composite rate of post-operative infections (superficial/deep incisional SSI, organ/space SSI, sepsis). Secondary: Incidence of incision and drainage (I&D) for SSIs. <b><i>Methods:</i></b> Patients were divided into two cohorts: 2003-2013 (pre-vancomycin era) and 2014-2023 (vancomycin era). Propensity matching was controlled for age, gender, race, and comorbidities. Post-operative infections requiring I&D within 90 days were identified using procedural and diagnostic codes. <b><i>Results:</i></b> Of 33,320 patients (mean age: 63.6 y; 43.3% male), 28,649 (86.0%) underwent surgery in 2014-2023 and 4,671 (14.0%) in 2003-2013. After propensity matching (4,668 patients per cohort), the 2014-2023 group had significantly lower odds of requiring I&D (odds ratio [OR] = 0.337) and developing post-operative infections (OR = 0.606). <b><i>Conclusion:</i></b> This large-scale, propensity-matched analysis suggests that the likelihood of post-operative infections or requiring I&D following multi-level posterior lumbar spinal instrumentation is approximately 40%-60% lower in the vancomycin era compared with the pre-vancomycin period.