Associated factors for surgical site infection with spinal instrumentation surgery

Surgical site infection (SSI) after spinal instrumentation surgery is a serious complication that is difficult to eliminate. We examined the associated factor for SSI in our institution. This retrospective study was conducted at a single institution. We included 483 patients aged ≥ 18 years who underwent spinal instrumentation surgery at our hospital between January 2016 and March 2021 and who were available for follow-up for at least 30 days. Patient factors were age, sex, malignant disease, diabetes, skin disease, hemodialysis, smoking, steroid and immunosuppressive drug use, BMI, albumin, total protein, CRP, American Society of Anesthesiologists (ASA) classification, and nasal culture, whereas surgery-related factors were re-operation, scheduled/emergency surgery, dural injury, number of fusion segments, fixation over the pelvis, vancomycin spray, operative time, and blood loss. Statistical analysis was performed using univariate analysis in the infected and uninfected groups and multivariate logistic analysis for factors showing an associated trend (P < 0.2). Eleven of 483 patients (2.3%) were infected, with nine having deep infections and two having superficial infections. In the univariate analysis, the patient factors were albumin level (4.1 ± 0.6: 3.7 ± 0.8 mg/dL) and CRP level (0.74 ± 1.8: 3.2 ± 5.3 mg/dL) in the uninfected group and emergency surgery rate (27.8%: 63.6%) in the infected group. Logistic analysis identified emergency surgery as a risk factor for SSI (odds ratio: 4.6, 95% confidence interval: 1.3-15.9, P = 0.016). Although not statistically significant, SSIs tend to recur sequentially within 3 months. Currently, SSI countermeasures are strictly implemented at all facilities, including our hospital. Thus, diabetes mellitus and immunosuppressive drugs were not risk factors, but emergency surgery was an associated factor, which may be due to the lack of sufficient infection control measures in emergencies. Once SSIs occur, they recur sequentially, suggesting that SSIs may result from complications in perioperative management.