Antimicrobial Effect Of Visible Blue Light Used In A Minimally Invasive Intramedullary Fracture Stabilization System

Introduction: Since 2009, the IlluminOss^® System is being used as an intramedullary fracture treatment. The system is characterized by the use of blue light to polymerize liquid monomer after its infusion in a polyethylene terephthalate balloon. Very few infections of the material have been observed, which might be explained by the possible antimicrobial side-effect of the blue light used in this intramedullary fracture stabilization system. This study aimed to assess this antimicrobial (side-)effect on S. aureus. Methods: A suspension of 1.5 x 10³ CFU/ml of 8325-4 S. aureus was placed into five, custom made, black delrin cylinders. The implant was placed into the cylinders and the light source was activated for 200, 400, 600, 800, or 1,000 seconds. 100 µL of the light exposed suspension was grafted on blood agar and placed in a 35 degrees Celsius incubator for 24 hours. Colonies on each agar plate were counted and compared to the control plates (no blue light exposure). Results: The control plates showed a mean of 85 ± 15 colonies per plate. A statistically significant decrease was observed after 600 seconds of exposure time; mean colony count of 63 ± 4 (p <0.05). The absolute reduction was 24 ± 14 after 600 seconds exposure time. At 800 and 1,000 seconds, no statistically significant reduction was found compared with the control plates (means 72 ± 10 and 83 ± 14 colonies, respectively). Conclusions: In this study only a temporary reduction of S. aureus was observed. If future research regarding the antimicrobial characteristics of blue light used in the IlluminOss^® System is desired, it should focus on the need for oxygen and its availability and the dose and manner of applying the light.