The goal of the study by Berit Zeller-Plumhoff from the Helmholtz Zentrum Geesthacht, Germany, and her international team was to compare the bone ultrastructure formed around two non-degradable implants that are already used in the clinic (titanium and polyether ether ketone, PEEK) with the tissue that developed around two magnesium-gadolinium alloys (Mg-10Gd and Mg-5Gd, with 10 or 5 weight percent Gd, respectively). They surgically implanted screws of the materials into rats and sampled thin sections along the implant axis after 4, 8, and 12 weeks of healing.
The samples were analyzed using small angle X-ray scattering (SAXS), and X-ray diffraction (XRD) experiments set up at the P03 nano-focus end station at PETRA III, Deutsches Elektronen-Synchrotron (DESY). For the XRD experiments, they placed a LAMBDA 750k detector next to the flight tube, 18–19 cm from the focal point. “We chose the LAMBDA detector for our XRD experiments, because the space around the sample was very confined due to the flight tube for the SAXS setup. The combination of a high spatial resolution (small detector pixels) and a compact detector design enabled us to position the detector close to the sample. Thus, we could measure the X-ray diffraction signal of the hydroxyapatite crystals at a high resolution and with good quality”, said Florian Wieland, one of the authors of the study. From the collected images, the team determined crystal size and crystal lattice spacing for different regions around the implant; the SAXS results were used to retrieve HAP orientation and thickness.