[Preparation of gentamicin-impregnated bone allograft and experimental study on treatment of infective bone defect]

To study and prepare a new kind of bone graft, which has osteogenesis, local anti-infective function and low immunogenicity.

Gentamicin-impregnated bone was prepared by means of ultrasonic and vacuum, the release of gentamicin in vivo was measured by inhibition bacteria. Ten healthy male adult sheep were made animal infection models of thigh bone or humerus defect of 6 mm x 6 mm x 20 mm at size, and the defect was inoculated into 1 ml 5 x 10(10) CFU/ml Staphylococcus aureus. The animals were randomly divided into the experimental group (n=5, the bone graft with gentamicin was implanted) and the control group (n=5, the bone graft without gentamicin). Macroscopic, WBC count, radiological, and histological investigations were carried out to evaluate the anti-infective and osteosis capability.

The concentrations of gentamicin were 46.1 microg/ml in bone allograft and 17.3 microg/ml in muscles after 1 day. The concentrations of gentamicin exceeding the minimum inhibitory concentration lasted for 14 days in vivo. WBC in the control group was higher than that in the experimental group. In the control group, 1 case died owing to septicemia 3 weeks after operation. The implanted bones were wrapped in pus 4 and 6 weeks, and the defects were filled with fibre tissue 8 and 10 weeks after operation. In the experimental group, 1 case was infected, the others had a good concrescence. The bone allografts began to integrate with adjacent bone after 4-8 weeks and integrate well after 12 weeks. The X-ray and histological observation showed that new bone formed and took the place of bone allograft.

The gentamicin-impregnated bone allograft was of a good sustained release feature in vivo, local anti-infection and osteogenesis. It might be an ideal bone grafting material for bone defects with infection.