Risk Factors and Outcomes of Surgical Site Infections of the Spine: A Retrospective Multi-Center Analysis

<b>Background/Objectives</b>: Surgical site infections (SSIs) in spine surgery pose significant risks, including neurological deficits, prolonged hospital stays, and increased healthcare costs. SSIs are classified by their location and include superficial, deep, and organ/space (OS) infections. In spine surgery, OS SSIs include osteomyelitis, discitis, and spinal epidural abscess. These infections are difficult to treat with conservative measures, impart significant morbidity, and incur increasing hospital costs. Despite advancements in surgical technique and infection control, the literature is conflicting on which factors are associated with a significant increase in risk of SSIs after spinal surgery. There is also a significant gap in the literature in defining the risk factors specific to OS SSIs. This study aims to identify risk factors associated with SSI after spine surgery at a single institution, as well as provide descriptive characteristics of patients with OS SSIs. <b>Methods</b>: This retrospective study analyzed spinal surgeries performed at a multi-center, single-institution between 1 January 2019 and 9 February 2025. Neurosurgical patients who underwent spine surgery were identified by ICD-10 procedure and diagnosis codes. Surgical infections were classified based on the National Healthcare Safety Network (NHSN) criteria. Univariate and multivariate analyses were performed to assess associations between patient demographics, comorbidities, and infection risk. <b>Results</b>: Of the 2363 unique spinal surgery patients, 39 developed infections, with 14 meeting the NHSN criteria for OS SSI. The overall rate of SSIs at this institution was 1.65%. Significant risk factors for developing an SSI included cardiovascular disease (<i>p</i> = 0.017) and COPD (<i>p</i> = 0.012). Multivariate analysis confirmed both risk factors identified in the univariate analysis as independent risk factors, with adjusted odds ratios of 1.97 (<i>p</i> = 0.033) and 2.072 (<i>p</i> = 0.041), respectively. The commonly cultured pathogens included <i>Staphylococcus aureus</i>, <i>Staphylococcus epidermidis</i>, and methicillin-resistant <i>Staphylococcus aureus</i>. <b>Conclusions</b>: Male sex, diabetes mellitus, gastroesophageal reflux disease, hyperlipidemia, hypertension, hardware placement, and a history of smoking were more common in patients with SSI. In the OS SSI subgroup, cardiovascular disease and COPD were associated with an increased risk of developing an OS SSI. Future research is needed to investigate more detailed risk factors and include mitigating factors of OS infection into the analysis.