[Novel nano-hydroxyapatite/polyurethane composite scaffold in the treatment of chronic osteomyelitis]

To evaluate the bone repair efficacy of the new nano-hydroxyapatite (n-HA)/polyurethane (PU) composite scaffold in the treatment of chronic osteomyelitis in tibia.

A novel levofloxacin@mesoporous silica microspheres (Lev@MSNs)/n-HA/PU was successfully synthesized. Its surface structure was observed by scanning electron microscopy (SEM). Fifty adult female New Zealand rabbits were randomly selected, and osteomyelitis was induced in the right tibia of the rabbit by injecting bacterial suspension ( Staphylococcus aureus; 3×10 ⁷ CFU/mL), which of the method was described by Norden. A total of 45 animals with the evidence of osteomyelitis were randomly divided into 4 groups, and the right medullary cavity of each animal was exposed. Animals in the blank control group (group A, n=9) were treated with exhaustive debridement only. The remaining animals were first treated by exhaustive debridement, and received implantations of 5 mg Lev@PMMA (group B, n=12), 1 mg Lev@MSNs/n-HA/PU (group C, n=12), and 5 mg Lev@MSNs/n-HA/PU (group D, n=12), respectively. At 12 weeks postoperatively, the right tibia of rabbits were observed by X-ray film, and then gross observation, methylene blue/acid fuchsin staining, and SEM observation of implant-bone interface, as well as biomechanical test (measuring the maximal compression force) were performed.

X-ray films showed that the infection were severer than those of preoperation in group A, while the control of inflammation and bone healing of rabbits in group D were obviously better than those at preoperation. The gross observation showed extensive bone destruction in group A, a significant gap between bone tissue and the material in groups B and C, and close combination between bone tissue and the material in group D. The histology of the resected specimens showed that there was no obvious new bone formation around the materials in groups B and C, and there was abundant new bone formation around the periphery and along the voids of the materials and active bone remodeling in group D. The SEM observation of the bone-implant interface demonstrated that no new bone formation was observed at the bone-implant interface in groups B and C. However, bony connections and blurred boundaries were observed between the material and host bone tissue in group D. The biomechanical test showed the maximal compression force of groups B and D were significantly higher than that of groups A and C ( P<0.05), but there was no significant difference between groups B and D ( P>0.05).

The novel synthetic composite Lev@MSNs/n-HA/PU exhibit good antibacterial activities, osteoconductivity, and biomechanical properties, and show great potential in the treatment of chronic osteomyelitis of rabbits.