In vivo assessment of the host reactions to the biodegradation of the two novel magnesium alloys ZEK100 and AX30 in an animal model

However, since rare earths are a mixture of elements and their toxicity is unclear, a reduced content of rare earths is favorable. The present study assesses the in vivo biocompatibility of two new magnesium alloys which have a reduced content (ZEK100) or contain no rare earths at all (AX30).24 rabbits were randomized into 4 groups (AX30 or ZEK100, 3 or 6 months, respectively) and cylindrical pins were inserted in their tibiae. To assess the biodegradation μCT scans and histological examinations were performed.The μCT scans showed that until month three ZEK100 degrades faster than AX30, but this difference is leveled out after 6 months. Histology revealed that both materials induce adverse host reactions and high numbers of osteoclasts in the recipient bone. The mineral apposition rates of both materials groups were high.Both alloys display favorable degradation characteristics, but they induce adverse host reactions, namely an osteoclast-driven resorption of bone and a subsequent periosteal formation of new bone. Therefore, the biocompatibility of ZEK100 and AX30 is questionable and further studies, which should focus on the interactions on cellular level, are needed.Recently, magnesium alloys returned to the focus of research as potential material for degradable metallic implants [1-10]. Besides problems like rapid corrosion, accumulation of subcutaneous gas and insufficient mechanical stability, adverse host reactions and toxic effects had also been limiting factors of the magnesium implants used by first researchers [11-15] and were reasons why magnesium had been abandoned. In modern magnesium alloys ligands are used to modify the corrosion properties and the mechanical characteristics of the alloy [5,6,16,17] and that is why modern magnesium alloys have favorable mechanical characteristics [1,3]. The magnesium alloys most commonly researched on are magnesium-calcium-alloys and magnesium-aluminum-rare earth-alloys [3,18-21]. They were shown to be of good in vivo