Objective It is difficult to treat chronic osteomyel itis due to the formation of the Staphylococcus aureus biofilms. Liposomal gentamicin-impregnated allogeneic cortical bone can inhibit the formation of the Staphylococcus aureusbiofilms. To explore the treatment of chronic osteomyel itis of rabbit by l iposomal gentamicin-impregnated allogeneic cortical bone. Methods The l iposomal gentamicin, l iposomal gentamicin-impregnated allogeneic cortical bone and gentamicinimpregnated allogeneic cortical bone were produced. Then the chronic Staphylococcus aureus osteomyel itis models of rabbit were made in left lower l imbs of 40 6-month-old rabbits and the right lower l imbs were used as controls. After 2 weeks, the observations of gross and X-ray were done. Four rabbits died within 10 days after the models were made and other 36 rabbits were devided into 6 groups: group A (no antibiotics), group B (intravenous injection of gentamicin), group C (intravenous injection of l i posomal gentamicin), group D (implantation of gentamicin-impregnated allogeneic cortical bone), group E (implantation of l i posomal gentamicin-impregnated allogeneic cortical bone), and group F (implantation of allogeneic cortical bone). After 2 weeks of treatment, the bacterial culture, X-ray and HE staining were done. Results The chronic Staphylococcus aureus osteomyel itis model of rabbit was made successfully. The X-ray showed dissolution of bone and periosteal reaction in groups A, B, C, and F, and no obvious dissolution of bone and periosteal reaction in groups D and E. The Norden scores were (2.5 ± 0.3), (2.1 ± 0.2), (1.5 ± 0.3), (1.5 ± 0.2), (0.9 ± 0.3), and (2.7 ± 0.3) points in groups A-F, respectively; showing significant differences between group A and groups B-E (P lt; 0.05), between groups B, E, F and other groups (P lt; 0.05). The results of blood and marrow cultures for Staphylococcus aureus were positive in groups A and F, and negative in other 4 groups; the results of bone marrow culture for Staphylococcus aureus were positive in 6 rabbits of group B, 4 rabbits of group C and 3 rabitts of group D; and the results were negative in group E. HE staining showed: in groups A and F, abscess and dead bone formed, and no new bone formation were observed; in groups B and C, different degrees of neutrophil accumulation was seen; in group D, some neutrophil accumulation occurred, and osteoprogenitor cells and osteoclasts were seen around implanted bone; and in group E, no neutrophil accumulation was observed, a lot of granulation tissues formed, and osteoprogenitor cells and osteoclasts were seen around implanted bone. Conclusion Implantation of l iposomal gentamicin-impregnated allogeneic cortical bone has remarkly better effect in treating chronic osteomyel itis than intravenous injection of l iposomal gentamicin and implantation of gentamicin-impregnated allogeneic cortical bone.
Objective To extend its application in the field of bone repair by adding oxygen-carboxymethylated chitosan (O-CMC) and gentamicin for modification of the calcium sulfate cement (CSC). Methods The O-CMC/CSC was prepared by adding O-CMC with different concentrations (0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, and 1.0wt%) in the CSC liquid phase. The effect of O-CMC on the CSC was evaluated by testing the injectability, compressive strength, degradation rate, pH value, cytotoxicity and osteogenesis. After the optimal concentration of O-CMC was determined, gentamicin with different concentrations (0.5wt%, 1.5wt%, and 2.5wt%) was added in the O-CMC/CSC, and then the compressive strength and antibacterial properties were investigated. Results After adding O-CMC in the CSC liquid phase, the injection time of O-CMC/CSC was increased to more than 5 minutes; it significantly prolonged with increased concentration of O-CMC (P<0.05). The compressive strength of the modified bone cement was in the range of 11-18 MPa and it was the highest when the concentration of O-CMC was 0.5wt% (P<0.05). The degradation rate of O-CMC/CSC was not influenced obviously by O-CMC (P>0.05). The pH value was in the range of 7.2-7.4 and Ca2+ concentration was in the range of 6-8 mmol/L.In vitro mineralization experiment indicated that the induced mineralization ability of O-CMC/CSC was much higher than that of pure CSC. The 0.5wt% O-CMC/CSC had the best performance; the compressive strength of the composite bone cement was above 5 MPa after gentamicin was added, which had antibacterial effect. Conclusion O-CMC is able to effectively improve the injection, compressive strength, and osteogenic activity of CSC; in addition, antibacterial properties is obtained in the CSC after adding gentamicin.