title: Long-term in vivo degradation behavior and near-implant distribution of resorbed elements for magnesium alloys WZ21 and ZX50.
abstract: We report on the long-term effects of degrading magnesium implants on bone tissue in a growing rat skeleton using continuous in vivo micro-Computed Tomography, histological staining and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Two different magnesium alloys-one rapidly degrading (ZX50) and one slowly degrading (WZ21)-were used to evaluate the bone response and distribution of released Mg and Y ions in the femur of male Sprague-Dawley rats. Regardless of whether the alloy degrades rapidly or slowly, we found that bone recovers restitutio ad integrum after complete degradation of the magnesium implant. The degradation of the Mg alloys generates a significant increase in Mg concentration in the cortical bone near the remaining implant parts, but the Mg accumulation disappears after the implant degrades completely. The degradation of the Y-containing alloy WZ21 leads to Y enrichment in adjacent bone tissues and in newly formed bone inside the medullary space. Locally high Y concentrations suggest migration not only of Y ions but also of Y-containing intermetallic particles. However, after the full degradation of the implant the Y-enrichment disappears almost completely. Hydrogen gas formation and ion release during implant degradation did not harm bone regeneration in our samples.
  
  
  
  Magnesium is generally considered to be one of the most attractive base materials for biodegradable implants, and many magnesium alloys have been optimized to adjust implant degradation. Delayed degradation, however, generates prolonged presence in the organism with the risk of foreign body reactions. While most studies so far have only ranged from several weeks up to 12months, the present study provides data for complete implant degradation and bone regeneration until 24months, for two magnesium alloys (ZX50, WZ21) with different degradation characteristics. μCT monitoring, histological staining and LA-ICP-MS illustrate the distribution of the elements in the neighboring bony tissues during implant degradation, and reveal in particular high concentrations of the rare-earth element Yttrium.
authors.affiliation: Department of Orthopedic and Orthopedic Surgery, Medical University of Graz, 8036 Graz, Austria.
authors.forename: F
authors.initials: F
authors.lastname: Amerstorfer
authors.affiliation: Department of Trauma Surgery, Medical University of Graz, 8036 Graz, Austria.
authors.forename: S F
authors.initials: SF
authors.lastname: Fischerauer
authors.affiliation: University of Natural Resources and Life Sciences, Department of Chemistry, Division of Analytical Chemistry - IACM Laboratory, 1190 Vienna, Austria.
authors.forename: L
authors.initials: L
authors.lastname: Fischer
authors.affiliation: Department of Orthopedic and Orthopedic Surgery, Medical University of Graz, 8036 Graz, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Eichler
authors.affiliation: University of Natural Resources and Life Sciences, Department of Chemistry, Division of Analytical Chemistry - VIRIS Laboratory, 3430 Tulln, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Draxler
authors.affiliation: University of Natural Resources and Life Sciences, Department of Chemistry, Division of Analytical Chemistry - VIRIS Laboratory, 3430 Tulln, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Zitek
authors.affiliation: Department of Material Sciences and Process Engineering, Institute of Physics and Materials Science, University of Natural Resources and Life Sciences, 1190 Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Meischel
authors.affiliation: Department of Orthopedic and Orthopedic Surgery, Medical University of Graz, 8036 Graz, Austria.
authors.forename: E
authors.initials: E
authors.lastname: Martinelli
authors.affiliation: Department of Pediatric Orthopedics, Medical University of Graz, 8036 Graz, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Kraus
authors.affiliation: University of Natural Resources and Life Sciences, Department of Chemistry, Division of Analytical Chemistry - IACM Laboratory, 1190 Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Hann
authors.affiliation: Department of Material Sciences and Process Engineering, Institute of Physics and Materials Science, University of Natural Resources and Life Sciences, 1190 Vienna, Austria.
authors.forename: S E
authors.initials: SE
authors.lastname: Stanzl-Tschegg
authors.affiliation: Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: P J
authors.initials: PJ
authors.lastname: Uggowitzer
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 Orthopedic and Orthopedic Surgery, Medical University of Graz, 8036 Graz, Austria. Electronic address: anneliemartina.weinberg@medunigraz.at.
authors.forename: A M
authors.initials: AM
authors.lastname: Weinberg
authors.affiliation: University of Natural Resources and Life Sciences, Department of Chemistry, Division of Analytical Chemistry - VIRIS Laboratory, 3430 Tulln, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Prohaska
mesh_terms: D000497:Alloys / Q000737:chemistry*; D000818:Animals; D002118:Calcium / Q000032:analysis; D020007:Implants, Experimental; D008274:Magnesium / Q000737:chemistry*; D008297:Male; D013058:Mass Spectrometry; D010758:Phosphorus / Q000032:analysis; D017207:Rats, Sprague-Dawley; D055114:X-Ray Microtomography; D015019:Yttrium / Q000032:analysis
chemical_list: D000497:Alloys; C000624401:WZ21 alloy; C000624402:ZX50 alloy; D010758:Phosphorus; D015019:Yttrium; D008274:Magnesium; D002118:Calcium
keywords: Alloy; Degradation; Distribution; Long-term; Magnesium; Yttrium