[Antibiotic impregnation of cartilage implants: diffusion kinetics of fluoroquinolones]

Antibiotic impregnation of cartilage implants may reduce the risk of bacterial infection and subsequent absorption. The aim of this study was to investigate the penetration kinetics of two quinolone antibiotics into fresh cartilage and the concentrations in the core of lyophilized cartilage after rehydration.

Fresh human costal cartilage was impregnated with ofloxacin and ciprofloxacin (2 mg/ml) for 2, 15 and 90 min. Concentrations were measured in 6 levels (0.5 mm each) from the surface to 3 mm beneath the surface with high performance liquid chromatography (HPLC). Lyophilized human costal cartilage was rehydrated in ofloxacine and ciprofloxacine solutions (2 mg/ml, 0.2 mg/ml and 0.02 mg/ml) for 18 hours and concentrations in the core of the rib segment were measured.

Quinolone antibiotics penetrate into cartilage by free diffusion. We found no evidence of significant binding to cartilage. After 2 and 15 min of impregnation, concentrations above the minimal inhibitory concentration (MIC90) for pseudomonas species are found from 0-0.5 mm below the surface of fresh cartilage. After 90 min concentrations above the MIC90 were found 1.0-1.5 mm below surface of the implant. In lyophilized rib grafts which were rehydrated in 1/10 diluted intravenous solutions (0.2 mg/ml), concentrations in the core of the specimen were above MIC90. Differences between the penetration characteristics of ofloxacine and ciprofloxacine were minor.

Intraoperative impregnation of cartilage implants with ofloxacin or ciprofloxacin probably offers only short-term protection against bacterial infection. Rehydrated rib grafts, however, contain high quinolone concentrations which may be effective even in infected implant beds for several hours.