In vivo evaluation of antibiotic impregnated beads in a rat osteomyelitis model

The biocompatibility, release and efficacy of gentamicin released from poly (lactic acid) (PLA) beads in an osteomyelitis model were evaluated. Microsp here particles of PLA containing gentamicin were compressed into 2.5 mm bea ds. Osteomyelitis was induced in the tibia by a gentamicin resistant Staphy lococcus aureus in 32 Sprague-Dawley rats. Following debridement at 8 weeks , rats were randomized into four groups: 1) gentamicin-impregnated PLA bead implant, 2) PLA bead without gentamicin, 3) once-daily gentamicin injectio ns (5 mg/kg) subcutaneously for 14 days, and 4) no treatment (control). Rat s were sacrificed at 7 weeks, and the tibias were sampled for quantitative culture, histologic scoring and gentamicin concentration. Radiography and c ulture in 31 of the 32 rats confirmed osteomyelitis. A low level of gentami cin was measured in the serum of group 1 rats up to day 42. Gentamicin was not detectable in bone samples. There was no significant difference in radi ographic scores, histologic scores or quantitative culture results between the groups. This study confirmed the consistency of this model, the biocomp atibility of the PLA implants and the low level release of gentamicin from implanted beads.