Risk factors for surgical site infections after spinal surgery: a systematic review and meta-analysis

Surgical site infections (SSIs) are a serious complication of spinal surgery, leading to prolonged hospital stays, increased healthcare costs, and worse patient outcomes. This review aimed to synthesise current evidence on modifiable risk factors for SSIs in spinal surgery to identify targets for intervention, perioperative optimisation, and improve patient care. A systematic search of MEDLINE, Embase, Scopus, Academic Search Ultimate, and CINAHL was conducted on 10 March 2024. Risk of bias was assessed using the Newcastle-Ottawa Scale, ROBINS-E, and the Oxford Centre for Evidence-Based Medicine: Levels of Evidence. A random-effects meta-analysis generated pooled odds ratios (ORs) with 95% confidence intervals (CI). Heterogeneity was assessed using I², Cochran’s Q, and associated p-values. Sensitivity and influence analyses evaluated the robustness. Forty-four studies were included, comprising 637,032 patients and 9,745 SSIs. Modifiable risk factors associated with increased SSI risk included body mass index, diabetes mellitus (including insulin-dependent), smoking, low preoperative haematocrit (< 33–39%), and chronic steroid use. Subcutaneous fat thickness > 30 mm and operative time > 2 h were also considered partially modifiable. Intraoperative vancomycin powder significantly reduced SSI risk. Non-modifiable risk factors included (American Society of Anaesthesiologists) ASA ≥ 3, female sex, coronary artery disease, revision surgery and procedures involving ≥ 3 vertebral levels. Age, alcohol use, albumin levels, instrumentation and blood transfusion were not significantly associated. High heterogeneity was noted for several variables, particularly BMI and diabetes. Several modifiable risk factors for SSIs were identified. Intraoperative vancomycin powder showed a protective effect. These findings offer perioperative strategies including glycaemic control, smoking cessation, anaemia management, and steroid dose adjustments to reduce SSI incidence and improve outcomes.