| Objective To probe the treatment of infected bone defects with bone morphogentic protein (BMP) and gentamicin-loaded fibrin glue (FG) drug delivery system, controlling the infection and speeding bony growth and healing at one stage to relieve patients of the trouble of several operations. Methods (1 Preparation of BMP and gentamicin-loaded FG drug delivery system and its release characteristic in vivo. Fibrinogen and gentamicin solution mixed with BMP was blended with thrombin solution in model and made into a cylindrical composite. Even' composite contained 3.2 mg gentamicin and 2.5 mg BMP. The composites were implanted into the muscle pouch of mice in right thighs. 6 mice were randomly selected after 0.5,l,2,3,5,7,10,14d postoperatively respectively, and implanted composites and surrounding 2 mm thick soft tissue were removed from the mice and weighed respectively. Their antibiotic concentrations were determined by using the methods of microassay in the standard agar diffusion. (2)Experimental treatment of infected bone defects with the composites. Animal models of chronic osteomyelitis were made in 48 rabbits. One month later, all foci were debrided thoroughly, and 1.5 cm long half-annular bone defects were made in the proximal tibias. 48 rabbits were randomly divided into 3 groups (A, B and C). Animals in group A were implanted with FG, BMP and gentamicin composites, and group B with FG/BMP composites. Animals in group C that was taken as blank control one were implanted nothing postoperatively. The situation of experimental animals were observed postoperatively, and the healing of infected bone defects was measured radiologically, histologically within 1 2 weeks following the surgery. Bone culture and bacterial counts were made in 6 rabbits selected from every group.?57!iResults (l)The initial concentration of the antibiotic in the muscle tissue around the composite was high and the concentration at 12h reached 111.3 U g/g. Most antibiotic was delivered within three 3 days, but the concentration remained above the minimum inhibitory concentration of Staphylococcus aureus lasted for two weeks. (2) Among 3 groups, only 3 animals in group A had infection in tibias, and 11 animals in group B,C respectively. The rates of bone infection controlled of group A, B and C were 12/15,1/12 and 0/11 respectively. The rate of group A was superior to that of group B or C. The bacterial count of infected bone in group A was lower than that of group B or C remarkably. Obvious bone healing was observed in group A and B, but new bone formation in group A was shown more than that in group B radiologically. Bone repair in group C was not obvious, a little callus could be observed after 8 to 12 weeks postoperatively in the edge of the bone defects. Conclusion The FG, BMP and gentamicin composites have the effects of anti-infection and speeding bony growth and healing .It can not only be used to treat infected bone defects, but also be used to treat severely polluted bone defects caused by open fracture. |
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