Abstract
In former studies the magnesium alloy LAE442 showed promising in vivo degradation behavior and biocompatibility. However, reproducibility might be enhanced by replacement of the rare earth composition metal “E” by only a single rare earth element. Therefore, it was the aim of this study to examine whether the substitution of “E” by neodymium (“Nd”) had an influence on the in vivo degradation rate. LANd442 implants were inserted into rabbit tibiae and rabbits were euthanized after 4, 8, 13 and 26 weeks postoperatively. In vivo µCT was performed to evaluate the in vivo implant degradation behaviour by calculation of implant volume, density true 3-D thickness and corrosion rates. Additionally, weight loss, type of corrosion and mechanical stability were appraised by SEM/EDS-analysis and three-point bending tests. Implant volume, density and true 3-D thickness decreased over time, whereas the variance of the maximum diameters within an implant as well as the corrosion rate and weight loss increased. SEM examination revealed mainly pitting corrosion after 26 weeks. The maximum bending forces decreased over time. In comparison to LAE442, the new alloy showed a slower, but more uneven degradation behavior and less mechanical stability. To summarize, LANd442 appeared suitable for low weight bearing bones but is inferior to LAE442 regarding its degradation morphology and strength.
Highlights
Implant materials must exhibit adequate strength, good biocompatibility as well as a reliable quality for their applications in osteosynthesis.Hitherto, non-resorbable titanium and its alloys as well as surgical steel and alloys based on cobalt-chromium were employed for loaded bone [1,2]
Non-resorbable titanium and its alloys as well as surgical steel and alloys based on cobalt-chromium were employed for loaded bone [1,2]
Owing to undesirable effects, such as the so-called “stress shielding”, foreign-body reactions, mutagenicity and inflammations caused by the release of toxic metal ions, these materials must frequently be removed in a second procedure [2,3,4,5]
Summary
Implant materials must exhibit adequate strength, good biocompatibility as well as a reliable quality for their applications in osteosynthesis.Hitherto, non-resorbable titanium and its alloys as well as surgical steel and alloys based on cobalt-chromium were employed for loaded bone [1,2]. In order to avoid these disadvantages, current research focuses on resorbable materials for osteosynthesis [2,3,6,7,8,9] Polymers, such as PGA and PLA, as well as ceramics, such as β-TCP, or hydroxylapatite are employed as degradable materials [3,9,10]. Early studies carried out at the beginning of the 20th century using magnesium as an implant material demonstrated copious gas production due to a too rapid degradation of the magnesium material [13,14,15] This lead to insufficient biocompatibility and, to a premature loss in strength [16,17]. Further research using magnesium as a material for osteosynthesis played a minor role, presumably because of the development of stainless steel, and later titanium, as a medical product [8]
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