[The in vitro observational investigation of antibiotic coating on implants]

To investigate the characteristics of antibiotic poly (D, L-lactide) (PDLLA) coating of implants, including its quantity, mechanical stability, sterility and antibiotic release in vitro.

The weight of the total coating mass was determined with an electronic semimicro balance before and after coating. Thickness of the coating was documented by scanning electronic microscopy. The stability and the loss of coating mass after implantation and extraction into the intramedullary canal was measured by electronic semimicro balance and the regularity and possible damage of the coating was examined by scanning electronic microscopy. Sterility of the coating procedure was tested by bacteria incubation. A group of coated implants were incubated in PBS to test the coating decrease and the release of gentamicin at different time points.

The quantification of the total coating mass was (7.2 +/- 0.9) mg and the thickness of coating was (13.5 +/- 1.7) microm. After explantation of the coated implants from the tibia medullary, the mean loss of coating mass was (3.5 +/- 1.3)%. Scanning electronic microscopy confirmed no defects of the coating layer extending to the metallic surface in any implant. None of the tested samples presented bacterial growth after incubation on blood agar and tryptic soy broth. The PDLLA depicted a weight reduction of about 6.4% after 6 weeks. Within the first 4 h, the release of gentamicin experienced an initial peak period, then a constant and gradual release was found for at least 6 weeks.

The antibiotic PDLLA coating on implants can meet the demands of the mechanical stability and sterility, and gentamicin releases quickly in the first hour and the release can last at least 6 weeks. These characteristics undoubtedly justify the feasibility of the coating usage in clinics.