Impact of a History of COVID-19 Infection on Postoperative Complications in Spinal Surgery: A Nationwide Cohort Study

<b>Background/Objectives</b>: The postoperative implications of a history of coronavirus disease 2019 (COVID-19) in patients undergoing spinal surgery remain inadequately defined. This study investigated whether a history of COVID-19 is associated with increased postoperative complication risk and assessed how surgical timing after infection influences outcomes. <b>Methods</b>: Patients who underwent spinal surgery in 2020 were identified. Individuals with a confirmed history of COVID-19 were matched 1:3 by age and sex to uninfected controls. Patients were categorized by the interval between COVID-19 diagnosis and the index surgical date (≤1 month, >1-≤3 months, or >3-≤6 months). Postoperative pulmonary, cardiovascular, thromboembolic, infectious, and mortality outcomes were evaluated. Cumulative risks were estimated using Kaplan-Meier analysis, and adjusted hazard ratios (HRs) were determined using multivariable Cox proportional hazards models controlling for demographic and clinical factors. <b>Results</b>: Surgery performed ≤1 month after COVID-19 diagnosis was associated with significantly higher risks of pneumonia within 3 months (HR 3.91; <i>p</i> = 0.031) and 6 months postoperatively (HR 3.12; <i>p</i> = 0.049). Patients undergoing surgery >1-≤3 months after COVID-19 demonstrated increased risk of spinal and implant-related infections within 3 months (HR 2.12; <i>p</i> = 0.040), and this elevated risk persisted when surgery occurred >3-≤6 months after infection (HR 2.00; <i>p</i> = 0.022). No significant differences were observed in cardiovascular, thromboembolic, or mortality outcomes. <b>Conclusions</b>: A history of COVID-19 infection was associated with postoperative pneumonia and spinal and implant-related infections following spinal surgery. These findings suggest that prior COVID-19 infection may be a relevant consideration in perioperative risk assessment and surgical planning.