Additive manufacturing (bioabsorbable) metal implants for ... · Additive manufacturing...
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Additive manufacturing
(bioabsorbable) metal implants for
orthopaedic applications
Holger Jahr
University Hospital
RWTH Aachen University
[email protected], [email protected]
3D Medical Conference Maastricht, 2018-01-31 1
SLS / SLM / DMP
2
Critical size bone defects
3 cm
6 cm
5 cm
5 cm
Clinical problem
Calori et al., Injury 2011:S56 3
http://en.wikipedia.org/
2.5 million graftings 1, 2
Clinical impact
8-39 % 1
1 van der Stok et al., Acta Biomater. 2011, “Bone substitutes in The Netherlands” 2 Calori et al., Injury 2011:S56 4
Porosity Pore size "Strength" (MPa)
(%) (mm) Compress. Young's Tensile
Bone N.D. N.D. 70-280 ± 1-10,000 ± 65
(Tri-)calcium salts 30-90 2-1360 1-55 3.6-3,100 4.5
Bioactive glass 1 N.D. 91-179 6,400 52
Fibrin clot N.D. N.D. << 1 0.0015 ± N.D.
"hydrogels" N.D. N.D. N.D. ± N.D. ± N.D.
Ti alloys - - N.D. 120,000 ± 800
Bone graft substitutes
.
.
van der Stok et al., Acta Biomater. 2011, “Bone substitutes in The Netherlands” Weisel, Biophys. Chem. 2004: 267-76
Gibbs et al., J Tissue Eng Regen med 2014
5
Porous anatomically shaped implant
Ti6Al4V powder
(ASTM B348, grade 23)
van der Stok et al., 2013, 2015
Amin Yavari et al. 2013, 2014
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In vivo model
Surgery
Follow-
up
µ-CT reconstruction X-ray
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Surface functionalization
Implant treatment:
• 5 M NaOH, 60°C, 24 h
• H2O, 40°C, 24 h
• 0.5 M HCl, 40°C, 24 h
• 600°C, 5°C/min
• 600°C, 60 min
• passive cooling
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• coatings
• cell attachment
• anti-microbial
• drug release systems
Ti64 scaffold + biogel e
mp
ty
Fib
rin
+ B
MP
2
Ge
lati
n +
BM
P2
9
Torsion strength
Empty Fibrin Contralateral
+ BMP2 ctrl
10 van der Stok et al., eCM 2015
Ideal solution
• Osteoinductive (actively stimulates bone formation)
• Osteoconductive (allows colonization / vascular ingrowth = porosity)
• Osteogenic (presence of bone-forming cells)
Bone Morphogenetic protein (e.g. BMP-2)
e.g.
(B)MSCs
PDCs
• high porosity
• bio-functionalized
calcium- P
metals (e.g. Ti)
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SLM product portfolio
Substrates:
• Ti alloys
• Mg alloys
Co-Cr alloy 316L chromium-nickel steel
12
50 mm struts
Why 3D printed porous metals?
3D printing allows for:
– Patient-specific perfect fit
complexity for free
– Shorter surgery time
– Longer implant lifetime
– Fast recovery
– Reduced hospitalization
– Reduced costs
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Porous scaffolds facilitate:
• Bone-ingrowth, “union”
• Good fixation through
surface roughness
• Avoiding stress-shielding
(Young’s modulus)
• May reduce or eliminate:
– Secondary removal surgery
– Long term complications, e.g.
• biofilms
• allergic reactions
• Offer higher strength and toughness over current absorbable
(polymeric/ceramic) implants
• Improve pediatric care
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Why absorbable metals?
Bio-absorbable alloys
Daily Allowance
700 mg 10-20 mg 15 mg
Y.F. Zheng et al. Materials Science and Eng R77 (2014): 1-34. 15
• pure Fe + 2 Fe-based alloys (Fe10Mn1Pd, Fe21Mn0.7C1Pd wt%)
• implanted transcortically into rat (growing) femurs
• inspected @ 4, 12, 24 and 52 wks post.
• questionable temporary implants (e.g., osteosynthesis)
Kraus + Weinberg et al. Acta Biomaterialia
10 (2014) 3346–3353 16
Ø 1.6 mm pins
rat femur, 52 w
Fe corrodes too slow ..
• stents
• zinc degradation seems to combine the
desirable aspects of Fe alloys, i.e., in vivo
longevity, with harmless degradation of Mg
alloys.
• requires further development to achieve
desired mechanical properties
• results are promising
1st paper: Bowen et al. Adv. Mater. 2013, 25, 2577–2582.
Zn-modified surfaces: Wang et al. Applied Surface Science 403 (2017) 168–176 17
Zn corrodes faster, but ..
Amerstorfer et al. Acta Biomaterialia 42 (2016) 440–450
Kraus + Weinberg et al. Acta Biomaterialia 8 (2012) 1230–1238 18
Ø 1.6 mm pins
rat femur, 24w
Mg corrodes rather fast ..
..but performed well in vivo over 24 mths
Corrosion behavior
Seitz et al. Adv. Healthcare Mater. 2015, 4,
1915–1936 19
• Anodic reaction: Fe → Fe2+ + 2e−
• Cathodic reaction: ½ O2 + H2O + 2e− → 2OH −
• Ferrous hydroxide formation: Fe2+ + 2e− → Fe(OH)2
co-formation or -precipitation of goethite (α-FeO(OH)) and magnetite (Fe3O4) possible
• Anodic reaction: 2 Zn → 2 Zn2+ 4e-
• Cathodic reaction: O2 + 2H2O + 4e- → 4OH-
• Zn(OH)2 formation: 2 Zn2+ + 4OH- → 2 Zn(OH) 2
• ZnO formation: Zn(OH) 2 → ZnO + H2O
• Anodic reaction: Mg → Mg2+ + 2e-
• Cathodic reaction: 2 H2O + 2e- → H2 + 2OH
• Mg(OH)2 formation: 2Mg2+ + 2OH- → Mg(OH)2
..neutral – alkaline pH
Material properties
Tensile/compressive strength
(MPa)
1,500
1,000
500
0 0 100 200 300 (GPa)
Polymers BONE
Mg
Ti a
lloys
Co
-Cr
allo
ys
Ste
el /
Fe
Al 2
O3
ZrO
2
Young’s modulus
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Degradation control
Necessary load-bearing strength
Bioabsorbable implant
Bone
healing
Functional phase
Absorption phase
time
sta
bil
ity
Permanent implant
SynerMag® 410
• strength and mechanical benefits
• suitable for high-load-bearing areas
• good biocompatibility
Marukawa et al., J Biomed Mater Res Part B. 2016. 104B:1282–1289. 22
anodized Mg PLLA
@ 4 wks post
ISO 13485 certification
Biotronik
Magmaris®
stent
2016
world’s 1st clinically
proven Mg-based
resorbable
scaffold;
CE mark;
in GE, B, DK,
NL, CH, E, etc.
http://www.syntellix.de/newspresse 23
• Symptomatic Hallux valgus
• 19.000 MAGNEZIX® implants
• >30 countries
July 2016
Li et al. Acta Biomater. 2017 Dec 12. pii: S1742-7061(17)30764-X 24
AM biodegradable porous Mg
Design:
• Struts = 400 mm
• Pore size = 600 mm
• Density = 67%
diamond
lattice
10 mm
11.2 mm
WE43 4 wt% yttrium
3 wt% rare earths
Topological characterization (mCT):
• as-built struts = 420 mm
• Density = 64%
Li et al. Acta Biomater. 2017 Dec 12. pii: S1742-7061(17)30764-X 25
WE43 degradation test
5% HCl/5% HNO3 (EtOH)
polishing
AC Jones 2011, Elastic Properties of the Human Proximal Femur - ANU Repository; chap. 5 26
trab. bone
WE43 mechanical properties
Instron
10 kN load cell
ISO 13314:2011
5% HCl/5% HNO3 (EtOH)
polishing
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WE43 cytocompatibility
Ti64
WE43
ISO 10993 adjustments for degradable
biomaterials needed!
Conclusions
• 1st proof-of-principle of 3D-printed porous Mg-scaffolds as bone
substituting material
• providing proper support (≤ 4 wks in vitro biodegradation)
• just 20% volume loss within 4 wks in vitro
• moderate cytotoxicity in vitro (ISO 10993)
Pure WE43 itself may not be ideal for cell adhesion, but appropriate
design and coatings may allow future orthopedic applications
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Acknowledgements
Johan van der Stok
Amir Zadpoor
Yageng Li
Harrie Weinans
Saber Amin Yavari
Lucas Jauer
Prathusha Pavanram
Jule Schenkel
Athanassios Fragoulis
Kai-Uwe Schröder
Stephan Ziegler
Maximilian Voshage
Tim Van Cleynenbreugel
Jan Schrooten