IN-VITRO EVALUATION OF ANTIBIOTIC DIFFUSI ON FROM ANTIBIOTIC-IMPREGNATED XENOGRAFTS

Purpose of the study The purpose of the study was to evaluate xenograf ts as a slow release antibiotic delivery system, as xenografts also ha ve excellent biocompatibility and osteogenesis-stimulating effect. Mat erial 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. Methods In the pilot study, xenograf t 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 mu g/ml was 8 hours. The 8 hours contact time was used in th e main study to evaluate gentamicin sulphate, ciprofloxacin and penici llin G. The method was the same as in the pilot study. Results All ant ibiotics showed similar release patterns reaching their peaks on the 5 th day and then gradually decreasing below the effective level (0.5 mu g/ml) approximately on day 10. Discussion Although various materials have been used to deliver antibiotics, they have some certain disadvan tages especially reduced biocompatibility. The superiority of xenograf ts over other materials, is not only biocompatibility but also to faci litate osteogenesis. The only objection may be the relatively short du ration of release (10 days) but the length of antibiotherapy is contro versial and standard 6 weeks of administration has no documented super iority over other time intervals. Conclusion Our delivery system is su perior to others as its function is not only to deliver antibiotics bu t has its place in orthopedic practice to fill defects and stimulate o steogenesis. Also the preparation of this system is not time and skill consuming.