3D nanoscale analysis of bone healing around degrading Mg implants studied by X-ray scattering tensor tomography

Abstract The nanostructural adaptation of bone is crucial for its compatibility with orthopedic implants. The bone’s nanostructure determines its mechanical properties, however little is known about its temporal and spatial adaptation in degrading implants. This study presents insights into this adaptation by applying electron microscopy, elemental analysis, and small-angle X-ray scattering tensor-tomography (SASTT). We extend the SASTT reconstruction to multiple radii of the reciprocal space vector q , providing a 3D reciprocal-space map per voxel. Each scattering curve is spatially linked to one voxel in the volume, and properties such as the thickness of the mineral particles are quantified. This reconstruction provides information on nanostructural adaptation during healing around a degrading ZX10 magnesium implant over the course of 18 months, using a sham as control. The nanostructural adaptation process is observed to start with an initially fast interfacial organization towards the implant direction, followed by a substantial reorganization of the volume around the implant, and an adaptation in the later degradation stages. The study sheds light on the complex bone-implant interaction in 3D, allowing a more guided approach towards the design of future implant materials, which are expected to be of great interest for further clinical studies on the bone-implant interaction. TOC text and figure Degrading Magnesium implants are mechanically and chemically well adapted orthopedic implant materials and ensure a gradual load transfer during bone healing due to their degradation. The impact of the implant degradation on the bone nanostructure is however not fully understood. This study unveils the processes 3D and shows different stages of bone healing.