Biocompatibility and Efficiency of Biodegradable Magnesium-based Plates and Screws in Fractures of Zygoma of Beagles

Abstract

The purpose of this study was to evaluate the biocompatibility and efficiency of biodegradable magnesium-based plates and screws (magnesium alloy implant) for fixation of zygomatic arch fractures in beagle dogs.<br/> Methods: Plates and screws were fixed in zygomatic arch fractures in beagles. Fracture healing, degradation, and bone formation were evaluated using mechanical tests, micro computed tomography, histomorphometric analysis, and histopathological analysis to compare biodegradable magnesium alloy implants with poly -L- lactide implants<br/> Results: The fracture line was well maintained until 26 weeks in both groups. Inflammatory reactions were not significantly increased in any of the animals. Histomorphometric results showed significantly smaller normalized implant areas and larger normalized void areas in the magnesium alloy group than in the PLLA group (p < 0.05). The micro CT scans also showed that the void area around the implant was greater in the magnesium alloy group than in the control group until 26 weeks. The hydrogen gas around the magnesium implant increased at 4 and 12 weeks but showed a decrease at 26 weeks. Regarding the ultimate load, the magnesium alloy group exhibited significantly higher stiffness and structural stiffness at 4 weeks than the control group. At 12 and 26 weeks, the stiffness and structural stiffness were maintained in the magnesium alloy group. In the histopathological analysis, the number of osteoclasts was significantly higher in the magnesium alloy group than in the PLLA group at 4 weeks after fixation. The magnesium alloy group exhibited a significantly higher number of osteoblasts and extent of neovascularization than the PLLA group at 26 weeks.<br/> Conclusion: Our results show that the magnesium alloy implant had higher strength at 4 weeks after fixation, but no significant difference was observed between the 2 groups at 12 and 26 weeks. On the basis of the histological data, we speculate that the magnesium alloy implant contributed to bone regeneration in this study. These results show the possibility of future development of magnesium alloy plates and screws for human craniofacial fixation. However, the corrosion rate of magnesium alloys needs to be optimized.<br/>