# Reduced Surgical Site Infection Risk With Overlapping Knotless Tailless Versus Buried Knot Techniques in Running Subcuticular Closure for Posterior Thoracic and Lumbar Spine Surgery

## TL;DR

This study found that a knotless tailless skin closure method may reduce surgical site infections compared to buried knot techniques in spine surgery.

## Contribution

The study introduces a knotless tailless RSAS technique and demonstrates its potential to lower deep surgical site infection rates in posterior spine surgery.

## Key findings

- The KT group had a significantly lower deep SSI rate (0.4%) compared to the BK group (2.6%).
- Multivariate analysis showed the BK method had a 6.44 times higher odds of infection compared to the KT method.

## Abstract

Background: Are small abscesses and suture reactions seen with buried knots (BK) or tails at the ends of a running subcuticular skin closure using non-barbed absorbable suture (RSAS) associated with surgical site infections (SSIs)? Would the elimination of BK and tails reduce the rate of SSI? The senior author (SK) has been using an overlapping knotless tailless (KT) RSAS method since 2013. As three spine surgeons in the same division at a tertiary referral center primarily used the BK method, we decided to compare deep SSI rates between the BK and KT methods in posterior thoracic and lumbar spine surgeries.

Methods: After IRB approval, hospital records and the research patient data registry were used to retrospectively identify consecutive posterior thoracic and lumbar surgical cases at a tertiary referral academic medical center. Inclusion criteria were open posterior thoracic and lumbar spine surgery in adult patients (age >21) and skin closure using RSAS. Exclusion criteria included previous infection in the same site, oncologic surgery, multiple procedures under the same anesthesia, and less than three months of follow-up (f/u). The KT group comprised cases closed using the overlapping KT method by the senior author (SK) from 2013 to 2023 (n=266). Power analysis suggested that more than 600 cases were needed in the BK group, comprised of cases closed using the BK method by three surgeons between 2018 and 2020 (n=613). Demographics, comorbidities, and surgical characteristics were collected. The diagnosis of SSI was made by the cultures taken and/or by the primary surgeon at the return to the operating room (ROR). We identified all patients who had ROR for deep SSI within 12 months after the index surgery. All had ROR within three months of the index surgery, had a minimum of 12 months of f/u, and were included in the study.

Results: The KT group had increased risk factors for SSI compared to the BK group, such as a higher percentage of smokers, previous surgery in the same site and instrumented fusion cases, and a greater average number of levels fused per case and case length. No differences between the groups were found for other risk factors such as age, obesity, or history of diabetes. However, the rate of deep SSI in the KT group (0.4%=1/266) was less than that in BK (2.6%=16/613); the difference was statistically significant (p=0.030). Multivariate analysis of infection risk showed that the odds ratio for BK (OR 6.44, 95% CI, 1.53 - 59.77, p=0.008) and for diabetes (OR 7.27, 95% CI, 2.79 - 20.62, p<0.001) reached statistical significance.

Conclusions: This study showed that an overlapping KT method may result in a lower rate of ROR for deep SSI in posterior thoracic and lumbar spine surgery compared to the BK method. We would recommend further studies to confirm this initial finding and to determine the optimal skin closure method in spinal surgery.