The influence of storage and heat treatment on a magnesium-based implant material: an in vitro and in vivo study.
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 48 weeks on the biomechanical, structural, and degradation properties of the degradable magnesium alloy LAE442.


METHODS
Extruded implants (n = 104; Ø 2.5 mm × 25 mm) were investigated after storage periods of 0, 12, 24, and 48 weeks in three different sub-studies: (I) immediately after the respective storage duration and after an additional (II) 56 days of in vitro corrosion in simulated body fluid (SFB), and (III) 48 weeks in vivo corrosion in a rabbit model, respectively. In addition, the influence of a T5-heat treatment (206 °C for 15 h in an argon atmosphere) was tested (n = 26; 0 week 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 48 weeks, no significant changes occurred in the implant properties.


CONCLUSIONS
LAE442 implants can be safely used after up to 48 weeks of storage.
Small Animal Clinic, School of Veterinary Medicine Hannover, Bünteweg 9, 30559, Hannover, Germany. katja.bracht@tiho-hannover.de.
Katja
K
Bracht
Small Animal Clinic, School of Veterinary Medicine Hannover, Bünteweg 9, 30559, Hannover, Germany. nina.angrisani@tiho-hannover.de.
Nina
N
Angrisani
Department of Materials Science and Engineering, Michigan Technological University, 1400 Townsend Dr, Houghton, MI, 49931, USA. jseitz@mtu.edu.
Jan-Marten
JM
Seitz
Institute of Material Science, Leibniz University Hannover, An der Universität 2, 30823, Garbsen, Germany. eifler@iw.uni-hannover.de.
Rainer
R
Eifler
Hannover Medical School, CrossBIT, Center of Biocompatibility and Implant-Immunology, Feodor-Lynen-Straße 31, 30625, Hannover, Germany. weizbauer.andreas@mh-hannover.de.
Andreas
A
Weizbauer
Small Animal Clinic, School of Veterinary Medicine Hannover, Bünteweg 9, 30559, Hannover, Germany. reifenrath.janin@mh-hannover.de.
Janin
J
Reifenrath
D000497:Alloys / Q000737:chemistry; D000818:Animals; D001696:Biomechanical Phenomena; D006358:Hot Temperature; D008274:Magnesium / Q000737:chemistry* / Q000494:pharmacology; D008422:Materials Testing; D055595:Mechanical Phenomena; D011184:Postoperative Period; D019736:Prostheses and Implants; D011817:Rabbits; D013977:Tibia / Q000000981:diagnostic imaging / Q000187:drug effects / Q000601:surgery; D013997:Time Factors; D055114:X-Ray Microtomography
D000497:Alloys; D008274:Magnesium