In vivo biocompatibility evaluation of Zn-0.05Mg-(0, 0.5, 1wt%)Ag implants in New Zealand rabbits.

Bio-absorbable Zn alloys have been attractive replacements for the traditionally permanent implants due to their reasonable mechanical strength and elongation, degradation rate, and biocompatibility. The hybridization addition of Mg and Ag elements could greatly improve the mechanical properties and antibacterial ability of Zn, respectively. In the present paper, in vivo biocompatibility for the Zn-0.05Mg-(0, 0.5, 1 wt%) Ag implants in New Zealand rabbit was qualitatively evaluated during the implantation periods of 4, 12, and 24 weeks. The blood serum biochemical parameters and in vivo integrity of the implants in the live rabbits were monitored by using clinical chemistry analyzing and X-ray radiographic imaging techniques during the implantation process, respectively. There is no great difference in the serum biochemical indicator between the implanted rabbits and the control group. Especially the levels of serum Zn and serum Mg normalize after implantation of 24 weeks. The interfacial adherence between the implants and newly formed bones, and the histopathological morphology of heart, liver, and kidney were observed morphologically under the microscope. The new bones formed and grew surrounding the implants after 12 weeks' post-operation, which were well joined with the original cortical bones after post-implantation of 24 weeks. The heart, liver and kidney were not negatively influenced as evidenced from the serum biochemical indicators and morphologies of the tissues. Zn-0.05Mg-(0, 0.5, 1 wt%) Ag alloys are proved to be in vivo biocompatible and potential candidates for the biodegradable medical implants.

[Restoration of segmental bone defect by calcium sulfate pellet: experiment with rabbit].

OBJECTIVE: To compare the effects of different calcium sulfate pellets made by different methods in treating segmental defect of bone. METHODS: Eighty New Zealand white rabbits underwent cutting off a segment in the middle part of radius so as to establish models of radial segmental defect, and than were divided into 4 groups: Group A as control group, Group B with calcium sulfate pellet made by routine method implanted into the defect, Group C with chitosan coated pressed calcium sulfate pellet implanted into the defect, and Group D with chitosan coated pressed calcium sulfate pellet combined with recombinant human bone morphogenetic protein (rhBMP)-2 implanted into the defect: X-ray photography was done every 4 weeks to observe the new bone formation. Four, 8, and 12 weeks 5 rabbits from each group were killed. The defect segments with parts of normal bone at both ends were cut off to undergo fluorescence microscopy and biomechanic three point bending test. RESULTS: X-ray photography and histological examination showed that new bone formation of cortex and reconstruction of marrow cavity were seen in Groups D and C, especially in Group D. The new bone mineralization rate of Group D was significantly higher than that of Group C (P<0.05) which was significantly higher than that of Group B (P<0.01). The anti-bending strength ratio of Group D was (47.5%+/-2.1%, significantly higher than that of Group C [(39.6+/-1.7)%, F=125.3, P<0.01], and the anti-bending strength ratios of Groups D and C were both significantly higher than those of Groups B and A [(23.6+/-3.3)% and (21.3+/-2.7)%]. CONCLUSION: Chitosan coated pressed calcium sulfate pellet shows relatively higher anti-bending strength and slightly slower resorption that closely coincide with the growth rate of new bone. It can be used to restore segmental bone defect, and particularly when combined with rhBMP-2.

Biocompatible Porous Tantalum Metal Plates in the Treatment of Tibial Fracture.

Fractures of the tibia represent a common class of injuries in orthopedics. The blood supply to the tibia is poor due to the small subcutaneous muscle tissues inside. Consequently, the tibia is prone to delayed fracture healing and nonunion of the fracture after surgery. In this case, we used porous tantalum metal plate to treat nonunion of a tibial fracture and achieved satisfactory therapeutic effects. For the first time in the field, we used 3D printing technology to fabricate porous tantalum metal plates for the treatment of tibial fractures. The resulting porous tantalum metal exhibited excellent mechanical and biological properties, and improved the therapeutic effects for the treatment of a tibial fracture nonunion. Porous tantalum metal plates have great application potential as a new implant material for internal fixation.