Antibiotic impregnation of cartilage implants

Background: Antibiotic impregnation of cartilage implants may reduce the ri sk of bacterial infection and subsequent absorption. The aim of this study was to investigate the penetration kinetics of two quinolone antibiotics in to fresh cartilage and the concentrations in the core of lyophilized cartil age after rehydration. Methods: Fresh human costal cartilage was impregnate d with ofloxacin and ciprofloxacin (2 mg/ml) for 2, 15 and 90 min. Concentr ations were measured in 6 levels (0.5 mm each) from the surface to 3 mm ben eath the surface with high performance liquid chromatography (HPLC). Lyophi lized human costal cartilage was rehydrated in ofloxacine and ciprofloxacin e solutions (2 mg/ml, 0.2 mg/ml and 0.02 mg/ml) for 18 hours and concentrat ions in the core of the rib segment were measured. Results: Quinolone antib iotics penetrate into cartilage by free diffusion. We found no evidence of significant binding to cartilage. After 2 and 15 min of impregnation, conce ntrations above the minimal inhibitory concentration (MIC90) for pseudomona s species are found from 0-0.5 mm below the surface of fresh cartilage. Aft er 90 min concentrations above the MIC90 were found 1.0-1.5 mm below surfac e of the implant. In lyophilized rib grafts which were rehydrated in 1/10 d iluted intravenous solutions (0.2 mg/ml), concentrations in the core of the specimen were above MIC90. Differences between the penetration characteris tics of ofloxacine and ciprofloxacine were minor. Conclusion: Intraoperativ e impregnation of cartilage implants with ofloxacin or ciprofloxacin probab ly offers only short-term protection against bacterial infection. Rehydrate d rib grafts, however, contain high quinolone concentrations which may be e ffective even in infected implant beds for several hours.