Perifocal Soft Tissue Reactions in Response to Contaminated Implants With a Composite Antibacterial Coating: Experimental Study

Background. Protection against microbial colonization of surface fixators for metal osteosynthesis can reduce the number of infectious complications. The aim of the study was to experimentally assess early perifocal tissue reactions to metal implants with a composite antibacterial coating under microbial load. Methods. Fragments of steel pins for osteosynthesis (diameter 1 mm) with a four-component antibacterial coating based on polylactide, polyurethane, ciprofloxacin and silver nanoparticles were contaminated by methicillin-resistant S. aureus (MRSA) 43431. They were implanted in rats within the quadriceps femoris. Contaminated uncoated pins were used as a control. The animals were withdrawn from the experiment on the 2nd, 4th, 7th day after implantation. Histopathological specimens from tissue around implants were prepared. A semiquantitative assessment of reactions was performed. Results. The microbial load before implantation was (1.120.26)106 S. aureus cells for the control implants and (0.860.31)106 cells for implants with antibacterial coating. Tissue inflammatory reactions on the second day of implantation were equally evident in the control and investigated groups. There was a significant reduction in the number of immune cells and necrotic detritus, as well as increased growth of connective tissue and neoangiogenesis in the experimental group by the 4th day. The appearance of a less pronounced well-vascularized fibrous capsule around the experimental implants was noted by the 7th day. It indicates a more favorable healing of soft tissues in comparison with the control. Conclusion. Weak morphological manifestations of tissue reactions in response to the fitting of contaminated implants with an antibacterial coating can be associated with both the direct antimicrobial effect of the coating components and the anti-inflammatory activity of silver nanoparticles and ciprofloxacin included in its composition.