Poster Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

INTRODUCTION: Surgical site infection (SSI) in spine surgery leads to high mortality, long hospitalization, and increased healthcare costs. This study aimed to disclose 10-year clinical features of SSI at a satellite institution of our university hospital, identify risk factors of SSI, and clarify the impacts of preventive countermeasures.

METHODS: We retrospectively reviewed 1,735 spine surgery cases from October 2014 to October 2024. Biopsy, instrumentation removal, and pyogenic spondylitis were excluded. The diagnosis with SSI followed the US Centers for Disease Control and Prevention (CDC) criteria, then in this study, additionally defined as the requirement of debridement surgery. All cases were categorized based on the presence of SSI, in which patient factors (age, sex, BMI, smoking, diabetes, hypertension, steroid use, dialysis, preoperative laboratory findings, and prior radiation therapy) and surgical factors (surgery time, blood loss, treated vertebral number, and instrumentation) were compared. Clinical characteristics of SSI (pathogen, onset timing, antibiotic regimen and duration, hospital stay, and treatment outcomes) were also assessed. In April 2022, sterilization systems were updated, and routine staff meetings began for infection prevention. The incidence and associated factors of SSI were compared before and after these interventions. The unpaired t-test and chi-squared test were used for statistical analyses.

RESULTS: The SSI occurred in 65 cases (3.7%): age (yr), 71.9±13.1; 35 men, 30 women. The incidence of SSI was as follow: 3.0%, cervical spine; 3.8%, thoracic spine; 4.4%, lumbar spine. Patients with SSI showed a more frequent >35-kg/m² BMI (6.2% vs. 0.8%, p<0.001), lower serum albumin level (3.9 vs. 4.2 g/dL, p=0.001), more frequent <3.5-g/dL hypoalbuminemia (20.3% vs. 9.4%, p=0.008), and more frequent preoperative < 11-g/dL anemia (26.2% vs. 14.0%, p=0.011). Although the presence of diabetes did not reach a statistical difference (27.7% vs. 19.4%, p=0.136), ≥7.0% HbA1c was more common in SSI (12.3% vs. 4.0%, p=0.006). Previous radiotherapy was also frequently observed in SSI (7.7% vs. 0.4%, p<0.001) (Figure 1). Statistically significant surgical factors of SSI included a longer surgery time (267.7 vs. 192.7 min, p=0.022), more frequent >500-ml blood loss (23.4% vs. 12.8%, p=0.020), and more frequent instrumentation use (86.2% vs. 68.0%, p=0.002). Bacteria of MSSA (26.2%) and MRSA (18.5%) were the primary pathogen; consequently, resistant bacteria accounted for 33.8%. Postoperative time to SSI onset was 23.5±15.1 d. Vancomycin was the most commonly used (58.5%), with the duration of 40.1±31.6 d. As outcomes, SSI was associated with a longer hospitalization (68.9 vs. 20.8 d, p<0.001), and 6 SSI cases resulted in hospital death (9.2% vs. 0.4%, p<0.001) (Figure 2). The incidence of SSI decreased from 4.3% before March 2022 to 2.0% after April 2022 (p=0.010) with a significant reduction in surgery time (208.1 vs. 175.0 min, p=0.021) and blood loss (203.3 vs. 166.0 ml, p=0.002) (Figure 3).

DISCUSSION: The SSI incidence was 3.7%. Risk factors of SSI included diabetes, hypoalbuminemia, preoperative radiotherapy, long surgery time, large blood loss, and instrumentation use. Then, SSI resulted in prolonged hospital stays and poor outcomes. Collectively, enhanced surgical skills and collaboration with co-medical workers have the potential to reduce SSI.