Surgical Humidification (HumiGard™) Reduces Bacterial Load in an Open Spine Animal Infection Model

Purpose Surgical site infections (SSIs) are a leading cause of revision operations, impacting patient outcomes and healthcare costs. Exposure of surgical wounds to the conventional dry and cold theatre environment has been overlooked as a modifiable factor in reducing SSIs. The F&P HumiGard™ system is designed to deliver warm and humidified air to the wound bed during surgery. This study investigates the potential for HumiGard™ to reduce bacterial load in a porcine model of spinal surgery. Methods Pigs were randomised to the Control and HumiGard groups (n = 6 per group). A 160 mm midline incision was made along the lumbar spine and dissected to the depth of the lumbar lamina to simulate open spine surgery, and the wound surface was inoculated with ~ 10 ⁶ CFU/ml of Staphylococcus aureus. Infected wounds were exposed to the ambient theatre conditions (Control) or warm humidified air (HumiGard) for 180 min before wound closure. Wounds were re-opened three days post-surgery and bacterial enumeration and histological analyses were performed on biopsies. Results The increase in bacterial load from the day of surgery to three days post-surgery was significantly higher in the Control group (100-fold) than the HumiGard group (16-fold). Wound tissue biopsies at Day 3 post-surgery revealed large bacterial colonies infiltrating the deeper tissues in Control, while the HumiGard group tissues had smaller bacterial colonies confined to the superficial zone. Distribution of white blood cells varied significantly between the Control and HumiGard groups at Day 3 post-surgery. Neutrophil proportion in the HumiGard group (34% ± 5.1%) was significantly lower than the Control group (65% ± 6.1%). In contrast, the proportion of mononuclear cells was significantly higher in HumiGard tissues (66% ± 5.1%) than Control (35% ± 6.1%), implying a transition from the pro-inflammatory to the reparative stage of wound healing. Conclusion In this animal study, HumiGard offered a protective benefit against bacterial growth, indicated by the lower bacterial load and an advancement in the wound healing process. By maintaining physiological temperature and humidity of the wounds, HumiGard may substantially reduce the risk of SSIs following orthopaedic surgery.