In Vivo Degradation Behavior of the Magnesium Alloy LANd442 in Rabbit Tibiae

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.

In vivo evaluation of a magnesium-based degradable intramedullary nailing system in a sheep model

“…The volume of the calculated implant parts seems to decrease over time while the density showed a slight increase after 24 weeks. Also Ullmann et al [86] found no significant changes in LANd442 implant volume but a significant decrease in density after 26 weeks. Additionally, they reported a significant decrease in maximum force as corrosion magnesium usually undergoes if exposed to chloride ions in nonoxidizing solutions [87] and was observed by several authors examining different magnesium-based alloys in vivo [44] or in vitro [88].…”

Magnesium alloys: A stony pathway from intensive research to clinical reality. Different test methods and approval‐related considerations

“…Using a three‐point bending test of pins with the same geometry (diameter: 2.5 mm, length: 25 mm), the mechanical stability (maximal force F max ) was highest for the LAE442 alloy (255.67 N), followed by ZEK100 (240.79 N), and WE43 (238.05 N) . The alloys MgCa0.8 (178.76 N), AX30 (177.42 N), and LANd442 (194.5 N) have low initial stability. Three months after in vivo implantation, the mechanical stability of these magnesium alloys was further reduced by 30–50% .…”

Influence of the grain size on the in vivo degradation behaviour of the magnesium alloy LAE442

“…It displays the homogeneity of the overall degradation of an implant. 3,22 The implant's corrosion rate was calculated using the in vivo mCT data according to the following formula: CR = DV/(A 3 t). 23 Here, CR (mm/year) is the corrosion rate, DV (mm 3 ) is the volume loss, A (mm 2 ) is the area that was exposed to the corrosion and t (days) is the implantation period.…”