title: Combining micro computed tomography and three-dimensional registration to evaluate local strains in shape memory scaffolds.
abstract: Appropriate mechanical stimulation of bony tissue enhances osseointegration of load-bearing implants. Uniaxial compression of porous implants locally results in tensile and compressive strains. Their experimental determination is the objective of this study. Selective laser melting is applied to produce open-porous NiTi scaffolds of cubic units. To measure displacement and strain fields within the compressed scaffold, the authors took advantage of synchrotron radiation-based micro computed tomography during temperature increase and non-rigid three-dimensional data registration. Uniaxial scaffold compression of 6% led to local compressive and tensile strains of up to 15%. The experiments validate modeling by means of the finite element method. Increasing the temperature during the tomography experiment from 15 to 37°C at a rate of 4 K h(-1), one can locally identify the phase transition from martensite to austenite. It starts at ≈ 24°C on the scaffolds bottom, proceeds up towards the top and terminates at ≈ 34°C on the periphery of the scaffold. The results allow not only design optimization of the scaffold architecture, but also estimation of maximal displacements before cracks are initiated and of optimized mechanical stimuli around porous metallic load-bearing implants within the physiological temperature range.
authors.affiliation: Biomaterials Science Center, University of Basel, c/o University Hospital Basel, 4031 Basel, Switzerland; Institute for Medical and Analytical Technologies, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, 4032 Muttenz, Switzerland.
authors.forename: Therese
authors.initials: T
authors.lastname: Bormann
authors.affiliation: Biomaterials Science Center, University of Basel, c/o University Hospital Basel, 4031 Basel, Switzerland.
authors.forename: Georg
authors.initials: G
authors.lastname: Schulz
authors.affiliation: Biomaterials Science Center, University of Basel, c/o University Hospital Basel, 4031 Basel, Switzerland.
authors.forename: Hans
authors.initials: H
authors.lastname: Deyhle
authors.affiliation: Institute of Materials Research, Helmholtz-Zentrum Geesthacht, 21502 Geesthacht, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Beckmann
authors.affiliation: Institute for Medical and Analytical Technologies, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, 4032 Muttenz, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: de Wild
authors.affiliation: Institute of Product and Production Engineering, School of Engineering, University of Applied Sciences and Arts Northwestern Switzerland, 5210 Windisch, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Küffer
authors.affiliation: Institute of Product and Production Engineering, School of Engineering, University of Applied Sciences and Arts Northwestern Switzerland, 5210 Windisch, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Münch
authors.affiliation: Institute for Medical and Analytical Technologies, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, 4032 Muttenz, Switzerland.
authors.forename: Waldemar
authors.initials: W
authors.lastname: Hoffmann
authors.affiliation: Biomaterials Science Center, University of Basel, c/o University Hospital Basel, 4031 Basel, Switzerland. Electronic address: bert.mueller@unibas.ch.
authors.forename: Bert
authors.initials: B
authors.lastname: Müller
mesh_terms: D019245:Compressive Strength; D003198:Computer Simulation; D020342:Finite Element Analysis; D021621:Imaging, Three-Dimensional; D011857:Radiographic Image Interpretation, Computer-Assisted; D013314:Stress, Mechanical; D013696:Temperature; D054457:Tissue Scaffolds / Q000737:chemistry*; D055114:X-Ray Microtomography
keywords: Digital volume correlation; NiTi; Scaffold compression; Three-dimensional displacement field; Variable temperature tomography