| 1. |
- Kruger, D., et al.
(författare)
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High-resolution ex vivo analysis of the degradation and osseointegration of Mg-xGd implant screws in 3D
- 2022
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Ingår i: Bioactive Materials. - : Elsevier BV. - 2452-199X. ; 13, s. 37-52
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Tidskriftsartikel (refereegranskat)abstract
- Biodegradable magnesium (Mg) alloys can revolutionize osteosynthesis, because they have mechanical properties similar to those of the bone, and degrade over time, avoiding the need of removal surgery. However, they are not yet routinely applied because their degradation behavior is not fully understood. In this study we have investigated and quantified the degradation and osseointegration behavior of two biodegradable Mg alloys based on gadolinium (Gd) at high resolution. Mg-5Gd and Mg-10Gd screws were inserted in rat tibia for 4, 8 and 12 weeks. Afterward, the degradation rate and degradation homogeneity, as well as bone-to-implant interface, were studied with synchrotron radiation micro computed tomography and histology. Titanium (Ti) and polyether ether ketone (PEEK) were used as controls material to evaluate osseointegration. Our results showed that Mg-5Gd degraded faster and less homogeneously than Mg-10Gd. Both alloys gradually form a stable degradation layer at the interface and were surrounded by new bone tissue. The results were correlated to in vitro data obtained from the same material and shape. The average bone-to-implant contact of the Mg-xGd implants was comparable to that of Ti and higher than for PEEK. The results suggest that both Mg-xGd alloys are suitable as materials for bone implants.
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| 2. |
- Moosmann, Julian, et al.
(författare)
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A load frame for in situ tomography at PETRA III
- 2019
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Ingår i: Developments in X-Ray Tomography XII. - : SPIE. - 0277-786X .- 1996-756X. - 9781510629196 ; 11113
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A load frame for in situ mechanical testing is developed for the microtomography end stations at the imaging beamline P05 and the high-energy material science beamline P07 of PETRA III at DESY, both operated by the Helmholtz- Zentrum Geesthacht. The load frame is fully integrated into the beamline control system and can be controlled via a feedback loop. All relevant parameters (load, displacement, temperature, etc.) are continuously logged. It can be operated in compression or tensile mode applying forces of up to 1 kN and is compatible with all contrast modalities available at IBL and HEMS i.e. conventional attenuation contrast, propagation based phase contrast and differential phase contrast using a grating interferometer. The modularity and flexibility of the load frame allows conducting a wide range of experiments. E.g. compression tests to understand the failure mechanisms in biodegradable implants in rat bone or to investigate the mechanics and kinematics of the tessellated cartilage skeleton of sharks and rays, or tensile tests to illuminate the structure-property relationship in poplar tension wood or to visualize the 3D deformation of the tendonbone insertion. We present recent results from the experiments described including machine-learning driven volume segmentation and digital volume correlation of load tomography sequences.
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| 3. |
- Moosmann, Julian, et al.
(författare)
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Biodegradable magnesium-based implants in bone studied by synchrotron radiation microtomography
- 2017
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Ingår i: Developments in X-Ray Tomography XI. - : SPIE - International Society for Optical Engineering. ; 10391
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Konferensbidrag (refereegranskat)abstract
- Permanent implants made of titanium or its alloys are the gold standard in many orthopedic and traumatological applications due to their good biocompatibility and mechanical properties. However, a second surgical intervention is required for this kind of implants as they have to be removed in the case of children that are still growing or on patient's demand. Therefore, magnesium-based implants are considered for medical applications as they are degraded under physiological conditions. The major challenge is tailoring the degradation in a manner that is suitable for a biological environment and such that stabilization of the bone is provided for a controlled period. In order to understand failure mechanisms of magnesium-based implants in orthopedic applications and, further, to better understand the osseointegration, screw implants in bone are studied under mechanical load by means of a push-out device installed at the imaging beamline P05 of PETRA III at DESY. Conventional absorption contrast microtomography and phasecontrast techniques are applied in order to monitor the bone-to-implant interface under increasing load conditions. In this proof-of-concept study, first results from an in situ push-out experiment are presented.
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| 4. |
- Willumeit-Roemer, Regine, et al.
(författare)
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The Comparability of In Vitro and In Vivo Experiments for Degradable Mg Implants
- 2022
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Ingår i: MAGNESIUM TECHNOLOGY 2022. - Cham : Springer. - 9783030925338 - 9783030925321 ; , s. 8-15
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Konferensbidrag (refereegranskat)abstract
- Mg implants possess a great potential for clinical applications. Thousands of patients are already successfully treated with Mg implants and the number of approved products increases. Despite the fact that the implants generally work, we know that we have not yet reached a full understanding of all processes which occur during the degradation of the material and tissue regeneration. A prerequisite for a comprehensive description is the visualization and analysis of the in vivo processes with high resolution, while avoiding metal artefacts during imaging and taking care of different imaging properties of inorganic and organic matrices. Here, synchrotron radiation-based micro-computed tomography was utilized to determine the degradation rates for two implant materials (Mg-5Gd and Mg-10Gd, wt. %) in vitro and in vivo. The comparison for in vitro and in vivo degradation in terms of degradation rate and pitting factor shows that in vitro experiments predict in vivo results the error. As a second aspect, push-out experiments revealed a better integration into bone for Mg-10Gd and the improvement of implant stability over time. Finally, micro X-ray fluorescence spectrometry was applied to determine the elemental composition of degradation products around the Mg-5Gd specimen in vivo. This technique shows that the Mg content of the degrading specimen is decreasing while the Gd content stays constant.
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| 5. |
- Willumeit-Römer, Regine, et al.
(författare)
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Visualization of Implant Failure by Synchrotron Tomography
- 2018
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Ingår i: TMS 2018 147th Annual Meeting & Exhibition Supplemental Proceedings. - Cham : Springer. - 9783319725253 - 9783319725260 ; , s. 275-284
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Konferensbidrag (refereegranskat)abstract
- Magnesium (Mg) and its alloys degrade under physiological conditions. But how strong is the connection between the implant, the corrosion layer and the surrounding tissue, namely bone? Biomechanical tests like push-out tests have shown that a degraded Mg-pin is surprisingly well integrated with the bone “as reported by Castellani et al. (Acta Biomater 7(1):432–440, 2011) [1]”. High-resolution synchrotron tomography offers a deep look into the microstructure of the material as well as of the bone during deformation until fracture happens. Here we present first data from an in situ tomography experiment of a biodegradable Mg-based implant under compressive load showing how Mg implants are incorporated into bone.
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| 6. |
- Zeller-Plumhoff, Berit, et al.
(författare)
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Nanotomographic evaluation of precipitate structure evolution in a Mg-Zn-Zr alloy during plastic deformation
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1, s. 16101-16101
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Tidskriftsartikel (refereegranskat)abstract
- Magnesium and its alloys attract increasingly wide attention in various fields, ranging from transport to medical solutions, due to their outstanding structural and degradation properties. These properties can be tailored through alloying and thermo-mechanical processing, which is often complex and multi-step, thus requiring in-depth analysis. In this work, we demonstrate the capability of synchrotron-based nanotomographic X-ray imaging methods, namely holotomography and transmission X-ray microscopy, for the quantitative 3D analysis of the evolution of intermetallic precipitate (particle) morphology and distribution in magnesium alloy Mg-5.78Zn-0.44Zr subjected to a complex multi-step processing. A rich history of variation of the intermetallic particle structure in the processed alloy provided a testbed for challenging the analytical capabilities of the imaging modalities studied. The main features of the evolving precipitate structure revealed earlier by traditional light and electron microscopy methods were confirmed by the 3D techniques of synchrotron-based X-ray imaging. We further demonstrated that synchrotron-based X-ray imaging enabled uncovering finer details of the variation of particle morphology and number density at various stages of processing-above and beyond the information provided by visible light and electron microscopy.
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| 7. |
- Zeller-Plumhoff, Berit, et al.
(författare)
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Oxygen-sensitive nanoparticles reveal the spatiotemporal dynamics of oxygen reduction during magnesium implant biodegradation
- 2022
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Ingår i: npj Materials Degradation. - : Springer Science and Business Media LLC. - 2397-2106. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Magnesium (Mg) alloys are becoming increasingly important in the biomedical field as temporary bone implants. However, the biodegradation process of Mg alloys is highly complex and recent findings suggest that oxygen (O2) consumption is non-negligible. In this study, we give experimental proof of O2 consumption during Mg degradation under physiological conditions. Specifically, we study pure Mg, Mg–6 wt%Ag and Mg–5 wt%Gd in Hanks’ balanced salt solution and Dulbecco’s modified Eagle’s medium. We show that O2 consumption and hydrogen evolution are inversely correlated and that O2 concentrations remain below 7.5% in certain cases, which could have significant implications for bone healing.
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