State of the art of hip joint prostheses:

PROBLEM: Fixation of the acetabular element to pelvis bone.
Question: Is it possible direct bond between acetabular cup and pelvis?
Solution: BIOLOGICAL FIXATION BY ENHANCED OSTEOINTEGRATION

ADVANTAGES:


- Improved osteointegration with pelvis bone
- No risk of elements malpositioning
- No risk of elements mobility
- Easier fabrication of small-size prostheses (children)
- Easier coupling with high-diameter femur heads

Implementation: Development of an appropriate schedule for the fabrication of whole 3-layer device (ceramic cup + glass interlayer + trabecular coating) and characterization of the obtained device.
The sample preparation can be divided in 3 main stages:

● alumina-zirconia composite cup produced by subtractive manufacturing
● glass interlayer manufactured by dipping route
● trabecular coating fabricated by sponge replication


CUP PREPARATION

Press mould to obtain alumina/zirconia composite cylinders:


Crucial issue: α's mismatch

AVAILABLE BIOACTIVE GLASSES: high α = 12-14 × 10-6 K
ALUMINA and ITS COMPOSITES: α = 8.5-8.6 × 10-6 K
It leads to an important RISK: stress at the interface with possible delamination

Solution: new glass formulation in the system SiO2-CaO-Na2O-P2O5-B2O3 (3-U) with α = 8.3 × 10-6 K

GREEN COATING

ISO international standards (ISO 13779-4, 2002. Implants for surgery - Hydroxyapatite. Part 4: Determination of coating adhesion strength), recommends a tensile stress of at least 15 MPa n the case of hydroxyapatite coatings on titanium alloys for prosthetic applications failure values of the prepared coatings are above this threshold


SPONGE SHAPING

 



CONCLUSIONS


• Alumina/zirconia composite ceramic cups were successfully obtained with subtractive manufacturing
• The intermediate dense coating was successfully obtained by a dipping method
• A reproducible method to obtain a shell-like polymeric template was developed
• The sponge replication method was properly modified and adapted to be applied to samples of complex, curved geometry
• The trabecular-like coating mimicked the 3-D porous architecture of cancellous bone and was highly bioactive in SBF
• The overall processing schedule provides interesting perspectives for application in an industrial context


    

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