Multiscale morphological analysis of bone microarchitecture around Mg-10Gd implants

Sandra Sefa; Jonathan Espiritu; Hanna Ćwieka; Imke Greving; Silja Flenner; Olga Will; Susanne Beuer; D C Florian Wieland; Regine Willumeit-Römer; Berit Zeller-Plumhoff

doi:10.1016/j.bioactmat.2023.07.017

Multiscale morphological analysis of bone microarchitecture around Mg-10Gd implants

Bioact Mater. 2023 Aug 1:30:154-168. doi: 10.1016/j.bioactmat.2023.07.017. eCollection 2023 Dec.

Affiliations

¹ Institute of Metallic Biomaterials, Helmholtz Zentrum Hereon, Geesthacht, Germany.
² Syntellix AG, Hannover, Germany.
³ Institute of Materials Physics, Helmholtz Zentrum Hereon, Geesthacht, Germany.
⁴ Molecular Imaging North Competence Center, Kiel University, Kiel, Germany.
⁵ Fraunhofer Institut für Integrierte Systeme und Bauelementetechnologie (IISB), Erlangen, Germany.

Abstract

The utilization of biodegradable magnesium (Mg)-based implants for restoration of bone function following trauma represents a transformative approach in orthopaedic application. One such alloy, magnesium-10 weight percent gadolinium (Mg-10Gd), has been specifically developed to address the rapid degradation of Mg while enhancing its mechanical properties to promote bone healing. Previous studies have demonstrated that Mg-10Gd exhibits favorable osseointegration; however, it exhibits distinct ultrastructural adaptation in comparison to conventional implants like titanium (Ti). A crucial aspect that remains unexplored is the impact of Mg-10Gd degradation on the bone microarchitecture. To address this, we employed hierarchical three-dimensional imaging using synchrotron radiation in conjunction with image-based finite element modelling. By using the methods outlined, the vascular porosity, lacunar porosity and the lacunar-canaliculi network (LCN) morphology of bone around Mg-10Gd in comparison to Ti in a rat model from 4 weeks to 20 weeks post-implantation was investigated. Our investigation revealed that within our observation period, the degradation of Mg-10Gd implants was associated with significantly lower (p < 0.05) lacunar density in the surrounding bone, compared to Ti. Remarkably, the LCN morphology and the fluid flow analysis did not significantly differ for both implant types. In summary, a more pronounced lower lacunae distribution rather than their morphological changes was detected in the surrounding bone upon the degradation of Mg-10Gd implants. This implies potential disparities in bone remodelling rates when compared to Ti implants. Our findings shed light on the intricate relationship between Mg-10Gd degradation and bone microarchitecture, contributing to a deeper understanding of the implications for successful osseointegration.

Keywords: Biodegradable magnesium implants; Lacunar-canalicular network (LCN); Synchrotron radiation micro computed tomography (SRμCT); Transmission x-ray microscopy (TXM); Vascular porosity.