In vivo Comparison of Positive Microbial Culture by Wound Irrigation Methods

Abstract

Study Design Objective: This study aimed to evaluate the risk factors and prevalence of intraoperative contamination (IoC) through the microbial culture of superficial and deep samples obtained during surgery. Summary of Background Data: Surgical site infection (SSI) in spinal surgery is a serious complication. The prevalence of IoC may differ based on surgical approach and technique, even in the setting of the same procedure. Methods: In this in-vivo study, microbial cultivation was performed with superficial (ligamentum flavum, LF) and deep (nucleus pulposus, NP) surgical specimens to evaluate IoC in 132 patients undergoing single-level transforaminal lumbar interbody fusion (TLIF). Biportal endoscopic (BE) TLIF was performed under continuous wound irrigation (group A, n=66), whereas open microscopic (OM) TLIF was performed under intermittent wound irrigation (group B, n=66). LF and NP specimens were homogenized, gram-stained, and cultured in aerobic and anaerobic media for 14 days. Microbial culture results and occurrence of SSI in the two groups were assessed. The Chi-square test and Fisher’s exact test were used to determine significant differences among categorical variables. Logistic regression analysis was used to assess the influence of patient characteristics on the prevalence of positive microbial cultures. Results: Of the 132 patients, 34 (25.8%) had positive microbial cultures, and positive culture required an incubation period of 72 h to 2 weeks in all these patients except for three. Overall positive culture was significantly higher in group B than in group A (P=0.029). The subgroups of LF- and NP-positive cultures were 18.18% (n=24) and 12.88% (n=17), respectively; the SSI was 0.76% (n=1). Group A had a significantly lower subgroup of NP-positive culture than group B (P=0.035). OM technique was an independent risk factor associatd with overall positive culture (P<0.05). The most common microorganism was Cutibacterium acnes (C. acnes). Conclusion: BE-TLIF with continuous wound irrigation showed significantly lower overall, and NP-positive cultures, than OM-TLIF with intermittent irrigation. The most common strain of positive culture was C. acnes. Level of Evidence: II.