Neutral Hypochlorous Acid Solution as an Orthopaedic Sterilization Agent

Abstract

Hypochlorous acid (HOCl) is a potent anti-bacterial agent which could reduce periprosthetic joint infection. Early infection complications in joint replacements are often considered to be due to local contamination at the time of surgery and result in a significant socioeconomic cost. Current theatre cleaning procedures produce “clean” operating theatres which still contain bacteria (colony forming units, CFU). Reducing this bacterial load may reduce local contamination at the time of surgery. HOCl is produced naturally in the human neutrophil and has been implicated as the primary agent involved in bacterial killing during this process. In vitro research confirms its efficacy against essentially all clinically relevant bacteria. The recent advent of commercial production of HOCl, delivered as a fog, has resulted in extensive use in the food industry. Reported lack of corrosion and high anti-bacterial potency are seen as two key factors for the use of HOCl in the orthopaedic environment. Prior work by the authors comparing human cell toxicity of HOCl, chlorhexidine and iodine solutions shows favourable results.This study evaluates use of neutral HOCl applied as a dry room fog to decrease bacteria in the operating theatre environment. Using an animal operating theatre as the test site, bacterial swabs were taken from ten 100cm2 sample areas before standard cleaning with detergent, after standard cleaning, and again after 60 minutes exposure to HOCl fog.After standard cleaning, 6 of 10 sample sites recorded significant bacterial growth (>10 CFU/100cm2). After exposure to HOCl fog, growth in all 10 sites was below detection limits (<10 CFU/100cm2). This was repeated with specific exposure to Staphylococcus aureus and Escherichia coli.We can conclude that HOCl is effective when used as a fogging agent to reduce bacterial loading within an operating theatre environment and as such has significant potential to reduce intraoperative contamination and periprosthetic infection.