Use of antibiotic-impregnated bone grafts in a rabbit osteomyelitis model

Both osteomyelitis and prosthetic joint infection can be treated surgically with the use of antibiotic loaded bone grafts, as part of local antimicrobial therapy.

The purpose of the study was to evaluate and to report on a novel, biodegradable, long-acting (4-6 weeks) antibiotic-impregnated bone graft (AIBG). A novel drug delivery system, containing vancomycin, was utilized in a rabbit osteomyelitis model in order to evaluate the antimicrobial efficacy of the antibiotic bone graft.

Forty adult New Zealand rabbits were used. The animals were randomized into three Groups: healthy animals without osteomyelitis, where AIBG was used to fill a defect (Group I); osteomyelitis caused with a methicillin-resistant S.aureus strain (MRSA) treated with AIBG (Group II); osteomyelitis caused with MRSA and treated with bone grafts without local antibiotics (Group III). At six weeks post-operation, the animals were sacrificed and histological, laboratory and radiologic evaluations were performed.

Of the 24 operated rabbits, osteomyelitis was confirmed in 18 animals. In groups with osteomyelitis, only minor radiological changes were observed on day 21 post-op. Radiographs taken on day 42 post-op showed radiological signs of chronic osteomyelitis in Group III, whereas in Group II, bone healing was observed. Bacterial cultures taken on day 42 post-op revealed the original MRSA strain in Group III, whereas no bacteria were detected in Group II. Histological examinations showed the presence of macrophage cells which slowly break down the DDS matrix. The presence of DDS did not inhibit re-ossification.

The drug delivery system was effective against MRSA-induced osteomyelitis without negative effect on osteointegration. This biodegradable technology has the potential to be a powerful tool in fighting bone infections.