Optimal time window for initiating cefuroxime surgical antimicrobial prophylaxis in spinal fusion surgery: a nested case-control study

BACKGROUND CONTEXT Surgical site infections (SSI) are one of the common complications following spinal fusion surgery. Unfortunately, several studies had shown conflicting results regarding optimal timing of surgical antimicrobial prophylaxis (SAP) administration. Due to limitations in population homogeneity and sample size, these studies have not provided significant statistical correlations or clear practical recommendations. PURPOSE The purpose of the study was to investigate the impact of timing of cefuroxime SAP on the risk of SSI in patients undergoing spinal fusion surgery, and to determine the optimal timing of administration. DESIGN Retrospective nested case-control study. PATIENT SAMPLE We retrospectively analyzed consecutive patients who underwent spinal fusion surgery at our institution between October 2011 and October 2021. OUTCOME MEASURE In the current study, the primary outcome measure was SSI. METHODS This was a retrospective nested case-control study. All consecutive patients who underwent spinal fusion surgery at our institution between October 2011 and October 2021 formed a retrospective cohort. For each SSI case, 2 controls free of SSI at the time of the index date of their corresponding case were selected, matched by age, sex, and calendar year. Electronic record and radiographic data were reviewed retrospectively in electronic database. SAP related data included timing of administration, preoperative dose, intraoperative second dose, and postoperative use. To examine the effects of mismatched variables, we further adjusted for possible confounding factors using conditional logistic regression models. Subsequently, subgroup analyses were conducted to assess the robustness of the statistical associations. RESULTS According to the pre-planned statistical scheme and matching factors, we matched 236 controls for these SSI cases, and the subsequent statistical analysis was performed on these 354 patients. After adjusting for confounding factors, the results indicated that the risk of SSI was 70% higher in the group receiving SAP 31 to 60 minutes before incision compared to the group receiving SAP 0 to 30 minutes before incision (OR=1.732, 95%CI 1.031–2.910, p=.038). Additionally, the risk of SSI was 150% higher in the group receiving SAP 61 to 120 minutes before incision compared to the group receiving SAP 0 to 30 minutes before incision (OR=2.532, 95%CI 1.250–5.128, p=.010). In subgroup analysis, this statistical trend persisted for both deformity surgeries and different SSI classifications. CONCLUSION Administering cefuroxime SAP within 30 minutes before skin incision significantly reduces the risk of SSI, whether they are deep or superficial, in spinal fusion surgery. This pattern remains consistent among spinal deformity patients.