[In vitro evaluation of antibiotic diffusion from antibiotic impregnated xenografts]

The purpose of the study was to evaluate xenografts as a slow release antibiotic delivery system, as xenografts also have excellent biocompatibility and osteogenesis-stimulating effect.

Xenograft (Unilab Surgibone) blocks of 5 x 5 x 5 mm were used in the study. Antibiotics used for impregnation were gentamicin sulphate, ciprofloxacin and penicillin G.

In the pilot study, xenograft blocks impregnated with gentamicin sulphate solution and the contact time was between 1/2 to 10 hours. Then the grafts were incubated and the antibiotic concentration was measured in the elution fluid changed every day. The minimum contact time to release the antibiotic 10 days over 0.5 microgram/ml was 8 hours. The 8 hours contact time was used in the main study to evaluate gentamicin sulphate, ciprofloxacin and penicillin G. The method was the same as in the pilot study.

All antibiotics showed similar release patterns reaching their peaks on the 5th day and then gradually decreasing below the effective level (0.5 microgram/ml) approximately on day 10.

Although various materials have been used to deliver antibiotics, they have some certain disadvantages especially reduced biocompatibility. The superiority of xenografts over other materials, is not only biocompatibility but also to facilitate osteogenesis. The only objection may be the relatively short duration of release (10 days) but the length of antibiotherapy is controversial and standard 6 weeks of administration has no documented superiority over other time intervals.

Our delivery system is superior to others as its function is not only to deliver antibiotics but has its place in orthopedic practice to fill defects and stimulate osteogenesis. Also the preparation of this system is not time and skill consuming.