Friday, September 28, 2018 10:30 AM–12:00 PM abstracts: innovation, surface technology and biomechanics: 178. Excising the guesswork: fluorescence-guided infection debridement surgery within a mouse model of spine infection

Abstract

BACKGROUND CONTEXT Surgical debridement of spine infections consists of excising tissue at the surgeon's discretion. Surgeon's rely on visual cues such as abnormal tissue coloration and consistency to determine the extent of debridement. However, complete and accurate debridement is difficult to assess given the lack of objective data with regard to location and extent of residual infection. PURPOSE The purpose of this study is to apply two emerging technologies: (1) novelStaphylococcus aureustargeting fluorescently labeled probes and (2) “OR ready” real-time fluorescent imaging system, in a proof of principle study evaluating the feasibility of image-guided debridement surgery. STUDY DESIGN/SETTING This is a basic science investigation utilizing a mouse model of spinal implant infection. BioluminescentStaphylococcus aureusis used for longitudinal quantification of bacterial burden. Once infections were established, an open-air, “OR ready” fluorescent imaging system was utilized for image guided surgery. PATIENT SAMPLE Thirty-six 12-week-oldC57BL/6 wild type mice were utilized, 10 for each experimental group. OUTCOME MEASURES Utilizing an established mouse model of spinal implant infection,in vivobioluminescence and fluorescence imaging was performed to quantify emitted signals. A recently developed open-air, fluorescence input image-guided surgery system was utilized to for debridement surgery and to evaluate residual bacterial burden on debrided tissue. METHODS Three groups of mice were subjected to a previously established spine implant infection model: (1) five mice with implants inoculated withS. aureusand one sterile control mouse 60 days prior to image-guided debridement, (2) 10 inoculated and five sterile mice 30 days prior, (3) 10 inoculated and five sterile control mice 7 days prior. A total of 24 hours prior to debridement surgery, aS. aureusImmunodominant Staphylococcal Antigen A (IsaA) antibody fluorescent probe was administered via tail vein injection. Fluorescent imaging was completed to confirm co-localization of the probe to bioluminescent bacteria. Mice were then subjected to a fluorescence image-guided surgery system for debridement. RESULTS Two of five mice from the 60-day group, 8/10 of the 30-day group, and 10/10 of the 7-day group established an infection confirmed by bioluminescence imaging. Subsequent fluorescence imaging following IsaA-antibody probe injection revealed co-localization of fluorescent probe to bioluminescent bacteria with high fidelity. Radical debridement of fluorescent material under the image-guided surgery system was completed which revealed fluorescently labeled tissue with continued light emissionex-vivo.No fluorescence remained in mice status post debridement, indicating successful infection excision. CONCLUSIONS The novel,S. aureusspecific fluorescent probe successfully labelled bacteria in chronic and acute spine implant infections.Furthermore, this probe was successfully applied to the image-guided surgery system.This technology has the potential to shift the paradigm in excision surgery with applications in infection and negative margin tumor surgery.