title: Reaction of bone nanostructure to a biodegrading Magnesium WZ21 implant - A scanning small-angle X-ray scattering time study.
abstract: Understanding the implant-bone interaction is of prime interest for the development of novel biodegrading implants. Magnesium is a very promising material in the class of biodegrading metallic implants, owing to its mechanical properties and excellent immunologic response during healing. However, the influence of degrading Mg implants on the bone nanostructure is still an open question of crucial importance for the design of novel Mg implant alloys. This study investigates the changes in the nanostructure of bone following the application of a degrading WZ21 Mg implant (2wt% Y, 1wt% Zn, 0.25wt% Ca and 0.15wt% Mn) in a murine model system over the course of 15months by small angle X-ray scattering. Our investigations showed a direct response of the bone nanostructure after as little as 1month with a realignment of nano-sized bone mineral platelets along the bone-implant interface. The growth of new bone tissue after implant resorption is characterized by zones of lower mineral platelet thickness and slightly decreased order in the stacking of the platelets. The preferential orientation of the mineral platelets strongly deviates from the normal orientation along the shaft and still roughly follows the implant direction after 15months. We explain our findings by considering geometrical, mechanical and chemical factors during the process of implant resorption.
  
  
  CONCLUSIONS
  The advancement of surgical techniques and the increased life expectancy have caused a growing demand for improved bone implants. Ideally, they should be bio-resorbable, support bone as long as necessary and then be replaced by healthy bone tissue. Magnesium is a promising candidate for this purpose. Various studies have demonstrated its excellent mechanical performance, degradation behaviour and immunologic properties. The structural response of bone, however, is not well known. On the nanometer scale, the arrangement of collagen fibers and calcium mineral platelets is an important indicator of structural integrity. The present study provides insight into nanostructural changes in rat bone at different times after implant placement and different implant degradation states. The results are useful for further improved magnesium alloys.
authors.affiliation: Institute of Physics and Materials Science, University of Natural Resources and Life Science (BOKU), Peter-Jordan Straße 82, 1190 Vienna, Austria.
authors.forename: T A
authors.initials: TA
authors.lastname: Grünewald
authors.affiliation: Institute of Physics and Materials Science, University of Natural Resources and Life Science (BOKU), Peter-Jordan Straße 82, 1190 Vienna, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Ogier
authors.affiliation: Faculty of Physics, University of Vienna, 1090 Vienna, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Akbarzadeh
authors.affiliation: Institute of Physics and Materials Science, University of Natural Resources and Life Science (BOKU), Peter-Jordan Straße 82, 1190 Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Meischel
authors.affiliation: Faculty of Physics, University of Vienna, 1090 Vienna, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Peterlik
authors.affiliation: Institute of Physics and Materials Science, University of Natural Resources and Life Science (BOKU), Peter-Jordan Straße 82, 1190 Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Stanzl-Tschegg
authors.affiliation: Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: J F
authors.initials: JF
authors.lastname: Löffler
authors.affiliation: Department of Orthopaedics, Medical University Graz, 8036 Graz, Austria.
authors.forename: A M
authors.initials: AM
authors.lastname: Weinberg
authors.affiliation: Institute of Physics and Materials Science, University of Natural Resources and Life Science (BOKU), Peter-Jordan Straße 82, 1190 Vienna, Austria. Electronic address: helga.lichtenegger@boku.ac.at.
authors.forename: H C
authors.initials: HC
authors.lastname: Lichtenegger
mesh_terms: D020341:Absorbable Implants; D000497:Alloys; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D001862:Bone Resorption; D001842:Bone and Bones / Q000737:chemistry*; D003343:Corrosion; D008274:Magnesium / Q000737:chemistry*; D008297:Male; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D012542:Scattering, Radiation; D014965:X-Rays
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; D019904:Polymethyl Methacrylate; D008274:Magnesium
keywords: Bioresorbable; Bone nanostructure; Implant; Magnesium; X-ray scattering