Freezing nitrogen ethanol composite reduces periprosthetic infection caused by Staphylococcus aureus contaminated metal implants: An animal study.

Background: Implant-associated infection remains a major complication of orthopedic surgery. The treatment of such infection is complicated by bacterial biofilm formation on the metal surfaces of implants. Biofilm surrounds and protects the bacteria against the organism's endogenous defense system and from external agents such as antibiotics and mechanical debridement. This study aims to evaluate whether freezing nitrogen ethanol composite (FNEC), the combination of liquid nitrogen and 95% ethanol in a 3 to 1 ratio, used frequently in bone tumor surgery, is capable of disinfecting Staphylococcus aureus contaminated implants.

Methods: The femurs of six New Zealand white rabbits were implanted with S. aureus-contaminated screws, half of which were treated with FNEC before implantation. The femurs were harvested 14 days after implantation. Histological analysis and TUNEL assay were conducted. The autoclaved screw, contaminated screw, and FNEC-treated contaminated screw were investigated using scanning electron microscopy to evaluate the biofilm structure.

Results: The FNEC-treated group had significantly lower relative C-reactive protein levels. An obvious periosteal reaction at the implant site was observed in all rabbits in the non-FNEC group but none was observed in the FNEC-treated group. The FNEC-treated group exhibited fewer empty lacunae, less inflammatory infiltration, and less bone necrosis. Immunohistochemical analysis showed no S. aureus in bone tissue from the FNEC-treated group. Scanning electron microscopy showed disruption of the biofilm on the contaminated screw treated with FNEC.

Conclusion: FNEC showed potential in disinfecting S.aureus-contaminated implants. Further investigation is warranted, such as the effect on the implant-cement-bone interface, for FNEC to be used clinically in treating implant-associated infection.