The influence of storage and heat treatment on a magnesium-based implant material: An in vitro and in vivo study

Abstract

Background: Magnesium alloys are recommended as a potential material for osteosynthesis. It is known that storage-induced property modifications can occur in materials like aluminum. Thus the aim of this study was to analyze the influence of storage durations of up to 48weeks on the biomechanical, structural, and degradation properties of the degradable magnesium alloy LAE442. Methods: Extruded implants (n=104; Ø 2.5mm×25mm) were investigated after storage periods of 0, 12, 24, and 48weeks in three different sub-studies: (I) immediately after the respective storage duration and after an additional (II) 56days of in vitro corrosion in simulated body fluid (SFB), and (III) 48weeks in vivo corrosion in a rabbit model, respectively. In addition, the influence of a T5-heat treatment (206°C for 15h in an argon atmosphere) was tested (n=26; 0week of storage). Evaluation was performed by three-point bending, scanning electron microscopy, radiography, μ-computed tomography, evaluation of the mean grain size, and contrast analysis of precipitations (such as aluminum or lithium). Results: The heat treatment induced a significant reduction in initial stability, and enhanced the corrosion resistance. In vivo experiments showed a good biocompatibility for all implants. During the storage of up to 48weeks, no significant changes occurred in the implant properties. Conclusions: LAE442 implants can be safely used after up to 48weeks of storage.