Methods of antibiotic instillation in porous orbital implants

Soaking porous implants in antibiotic solution at the time of implantation is often recommended to promote fibrovascular ingrowth and reduce risk of infection. This study evaluated antibiotic penetration in porous implants using different instillation techniques.

Penetration of methylene blue in three 20-mm diameter porous implants (hydroxyapatite, porous polyethylene, and aluminum oxide) was measured using 4 different techniques: 1) soaking in dye for 5 minutes; 2) compressing the implant in dye in a 60-ml syringe for 1 and 2 minutes; 3) aspirating dye through the implants in a 60-ml syringe for 1 and 2 minutes; and 4) direct injection of dye in the center of the implants. Each implant was cut in half to measure penetration in 4 quadrants by 2 independent observers.

Soaking the implants for 5 minutes resulted in 6 mm penetration of dye from the surface in hydroxyapatite and no penetration in the others. Compressing or aspirating implants in dye for both 1 minute and 2 minutes resulted in complete penetration to the center in all implants. Direct injection resulted in complete distribution in hydroxyapatite, localized within 4 mm of the injection site in porous polyethylene, and no penetration in aluminum oxide.

Best penetration of fluid in all implants was achieved with aspiration or compression within a syringe. If an implant becomes infected, topical instillation of antibiotic is unlikely to reach the sites of infected pores. Direct injection of antibiotic may be helpful for porous implants providing the needle pore does not get blocked while penetrating the implant as it did with the 3 aluminum oxide implants tested in this study.