Comparing Biodegradation of Three Families of Additively Manufactured Porous Bone Implants

Abstract (2020)

Authors

H. Jahr University Hospital RWTH Aachen
Y. Li Biomaterials & Tissue Biomechanics - Mechanical, Maritime and Materials Engineering
P. Pavanram University Hospital RWTH Aachen
Karel Lietaert 3D Systems – LayerWise NV
Julia Schenkel University Hospital RWTH Aachen
M.A. Leeflang Biomaterials & Tissue Biomechanics - Mechanical, Maritime and Materials Engineering
J. Zhou Biomaterials & Tissue Biomechanics - Mechanical, Maritime and Materials Engineering
T. Pufe University Hospital RWTH Aachen
A.A. Zadpoor Biomaterials & Tissue Biomechanics - Mechanical, Maritime and Materials Engineering
Research Group
Biomaterials & Tissue Biomechanics (Mechanical, Maritime and Materials Engineering) (TU Delft)
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Published Date

2020

Language

English

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Faculty

Mechanical, Maritime and Materials Engineering

Department

Biomechanical Engineering

Research Group

Biomaterials & Tissue Biomechanics

Abstract

Bioabsorbable metals hold a lot of potential as orthopaedic implant
materials. Three metal families are currently being investigated: iron
(Fe), magnesium (Mg) and zinc (Zn). Currently, however, biodegradation
of such implants is poorly predictable. We thus used Direct Metal
Printing to additively manufacture porous implants of a standardized
bone-mimetic design and evaluated their mechanical properties and
degradation behaviour, respectively, under in vivo-like conditions.
Atomized powder was manufactured to porous implants of repetitive
diamond unit cells, using a ProX DMP 320 (Layerwise, Belgium) or a
custom-modified ReaLizer SLM50 metal printer. Degradation behaviour was
characterized under static and dynamic conditions in a custom-built
bioreactor system (37ºC, 5% CO2 and 20% O2) for up of 28 days. Implants were characterized by micro-CT before and after in vivo-like
degradation. Mechanical characterization (according to ISO 13314: 2011)
was performed on an Instron machine (10kN load cell) at different
immersion times in simulated body fluid (r-SBF). Morphology and
composition of degradation products were analysed (SEM, JSM-IT100,
JEOL). Topographically identical titanium (Ti-6Al-4V, Ti64) specimen
served as reference.
Micro-CT analyses confirmed average strut sizes (420 ± 4 μm), and
porosity (64%), to be close to design values. After 28 days of in vivo-like
degradation, scaffolds were macroscopically covered by degradation
products in an alloy-specific manner. Weight loss after cleaning also
varied alloy-specifically, as did the change in pH value of the r-SBF.
Corrosion time-dependent changes in Young's moduli from 1200 to 800 MPa
for Mg, 1000 to 700 MPa for Zn and 48-8 MPa for iron were statistically
significant.
In summary, DMP allows to accurately control interconnectivity
and topology of implants from all three families and micro-structured
design holds potential to optimize their degradation speed. This first
systematic report sheds light into how design influences degradation
behaviour under in vivo-like conditions to help developing new standards for future medical device evaluation.