bioactive trabecular-like coatings to improve the

8th Combined Meeting of Orthopaedic Research Societies – October 13-16, 2013, Venice, Italy
BIOACTIVE TRABECULAR-LIKE COATINGS TO IMPROVE THE
OSTEOINTEGRATION OF CERAMIC PROSTHETIC DEVICES
www.match-euproject.com
Chiara Vitale-Brovarone1, Francesco Baino1, Enrica Verné1, Polytimi Perdika1, Feza Korkusuz2, Maria Angeles
Montealegre3, Joaquim Minguella4
Contact: [email protected]
; [email protected]
1Institute
of Materials Physics & Engineering, Department of Applied Science and Technology, Politecnico di Torino , Italy
MEDICAL Ltd, Ankara, Turkey
3 AIMEN Tecnology Centre, Porriño, Spain
4 Fundacio Privada CIM, Barcelona, Spain
2 FAME-MED
Basic concepts: The potential of bioactive glasses
Since the invention of 45S5 Bioglass® by Larry Hench and associates in 1969 [1], bioactive glasses have been considered ideal biomaterials for bone repair, as they exhibit the unique property to bond to bone
and to stimulate bone regeneration while dissolving over time. Today, biomedical glasses are commercialized and clinically used mainly as bone fillers or bioactive thin coatings on prosthetic metal stems to
promote implant osteointegration, but in the experimental research they are often designed and processed to act as porous scaffolds to support tissue growth and remodelling in 3-D [2].
New perspectives and aim of the activity
Hip joint prosthesis (HJP): state of the art
Acetabular
element
Metal
Back
Advantages [3,4]:
 Improved osteointegration
 No risk of elements malpositioning
 No risk of elements mobility
 Easier fabrication of small-sized
prostheses (children)
 Easier coupling with high-diameter
femur heads
CHALLENGE: “biological” fixation by using
POROUS BIOACTIVE GLASS
 DIRECT BOND between acetabular
cup and pelvic bone
Cup
Prosthetic
femur head
PATENT: E. Verné, C. Vitale-Brovarone,
L. Robiglio, F. Baino. Monoblock ceramic
prosthetic members. WO 2008/146322 A2.
Prosthetic
femur neck
Composite cup machining
Analogous concepts can be
applied for knee prosthesis
Dense coating manufacturing
Starting materials: Al2O3 and ZrO2 powders mixed according to a 75/25 weigth ratio
(as BIOLOX Delta ® by CeramTec)
The intermediate coatings were manufactured by using powdered glasses (oxide systems: SiO2-CaO-Na2O-P2O5-B2O3-Al2O3) as starting materials.
Press into a mould to obtain
Al2O3/ZrO2 composite cylinders
Surface machining
(subtractive manufacturing)
Pre-sintering
phase
Slurry preparation
(glass powders sieved below
32 µm + PVA + water)
Soaking of the ceramic
composite cup
into the slurry
Final coatings on cups of different size obtained by
high-temperature thermal treatment.
Manual rotation to avoid
unwanted accumulation and
coating inhomogeneity
Cutting and fine
surface machining
Sintering
SEM micrograph of the
coating (thickness ~150 µm)
Two prototypes were finally obtained:
- small cups with a 29.5-mm external diameter
- large cups with a 39.5-mm external diameter
EDS analysis showing the chemical joining
between cup and coating: Al3+ migrates from
the cup into the coating and Na+ migrates
from the coating into the cup.
Micro-CT investigation
demonstraing the
homogeneity of the coating.
Microindenations at the coating/cup
interface: the cracks do not propagate
along the interface.
ADHESION STRENGTH: 30 MPa
Full prototype fabrication
First approach: sponge replication method
PU sponge preforming
by thermal shaping
Dipping of the system into a glass
slurry, so that glass particles can
adhere to polymer struts
Squeezing of the impregnated sponge to remove the
exceeding slurry out of the sponge pores
Final sintered 3-layer prototype:
alumina/zirconia composite cup + dense glass layer +
trabecular coating
«Green» full prototype
(glass–impregnated sponge
joined to the glass-coated cup)
Thermal treatment
(polymer burning-out and
glass particles sintering)
In vitro bioactivity:
the osteointegration potential
Second approach: laser cladding
Intermediate glass layer
manufactured by laser cladding
Dense coating by laser cladding
Pre-coating by a glass slurry (PVA as
porogen agent) + laser beam
Final 3-layer prototype after laser
cladding
7 days
in SBF
28 days
in SBF
Ca
P
Conclusions
• Al2O3/ZrO2 composite cups were successfully obtained by subtractive manufacturing
• The intermediate dense coating was successfully manufactured by using two different
techniques, i.e. dipping method and laser cladding
• Different prototypes of the whole ceramic cup with the trabecular-like coating were
successfully obtained
• The trabecular-like coating mimicked the 3-D porous architecture of cancellous bone and
was highly bioactive in SBF  enhanced osteointegration potential
Globular CaP agglomerate, typical of the
HA formed on bioactive glasses, are
well distiguishable and forms a 20-µm
thick layer visible in the cross-section.
References
[1] Hench LL, J Mater Sci: Mater Med 17 (2006) 967-978.
[3] Baino F & Vitale-Brovarone C, J Biomed Mater Res A 97 (2011) 514-535.
[4] Verné E et al., Single-piece ceramic prosthesis elements. WO 2008/146322 A2.
[4] Vitale-Brovarone C et al., J Mater Sci: Mater Med 23 (2012) 2369-2380.
Funding
EC-funded project MATCh (“Monoblock acetabular cup with trabecular-like coating”) – EU Seventh Framework
Programme (FP7/2007-2013) under grant agreement no. [286548].

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