Treatment of osteomyelitis in rats by injection of degradable polymer releasing gentamicin.

We evaluated the potential of an injectable degradable polymer-poly(sebacic-co-ricinoleic-ester-anhydride) containing gentamicin for the treatment of osteomyelitis. Osteomyelitis of both tibiae was induced in 13 female Fischer rats by injecting a suspension containing approximately 105 (CFU)/ml of S. aureus into the tibial medullar canal. Three weeks later both tibiae were X-rayed, drilled down the medullar canal, washed with 50 microl gentamicin solution (80 mg/2 ml) and then injected with 50 microl P(SA-RA)+gentamycin 20% w/v to the right tibia and 50 microl P(SA-RA) without gentamicin to the left tibia. After an additional 3 weeks, the rats were sacrificed, and radiographs of the tibiae were taken. Histopathological evaluation of the tibiae was done in a blinded manner. X-ray radiographs showed that all tibiae developed changes compatible with osteomyelitis in 3 weeks. Histological evaluation revealed significant differences between right and left tibiae in 10 rats. In the left tibia moderate intramedullary abscess formation occurred. In most treated tibiae typical changes included the absence (or minimal grade only) of abscesses. The treated group developed significantly less intramedullary abscesses; the p value was 0.028. Locally injected degradable polymer releasing gentamicin proved to be efficient histologically in the treatment of osteomyelitis.