Presentazione di PowerPoint

1
New Technologies in MultiFit System
DuraStar Lorenza Draghi Politecnico di
Milano Italy
2
Modular THR system studies rationale

• To exploit the benefit of using modular
  prosthesis, special care must be dedicated to
  prevent stem/neck corrosion
• For this reason both design of the prosthesis and
  material must be carefully considered

3
Modular THR system studies rationale

• To exploit the benefit of using modular
  prosthesis, special care must be dedicated to
  prevent stem/neck corrosion
• For this reason both design of the prosthesis and
  material must be carefully considered

4
Modular THR system studies rationale

• Couplings of modular prostheses may be source of
  metallic debris
• The amount of debris produced depends on the
  geometry of the coupling and of the entire
  implant
• Good design, however, can reduce the phenomenon
  to negligible compared to other potential debris
  sources (stem surface or prosthetic head).

Chir Organi Mov. 1997 Jul-Sep82(3)231-8.
5
Modular THR system studies rationale

• An accurately designed taper connection can
  minimize or eliminate the problem (JBMR vol. 30,
  181)
• The design of Multifit was based on specific
  studies on wear and fretting developed by
  Politecnico di Milano and CNR, the National
  Council of Research

6
Modular THR system taper connection
Gravimetric Wear
7
Modular THR system studies rationale

• To exploit the benefit of using modular
  prosthesis, special care must be dedicated to
  prevent stem/neck corrosion
• For this reason both design of the prosthesis and
  material must be carefully considered

8
1_Titanium

• Titanium has a lot of advantages, (is
  biocompatible, load bearing etc.)
• To improve its performances, a specific surface
  treatment was developed

9
1_TiHard

• TiHard is a combined electrochemical-mechanical
  treatment of titanium alloys that enable to
  ceramize titanium surface.

mechanical finishing phase

?
electrochemical
10
1_TiHard

• step 1 Anodic Spark Deposition (ASD)
• ASD offers the possibility to generate ceramic
  oxides on the surface of valve metals, like
  Titanium.
• The growing ceramic layer is created by
  conversion of the substrate, where elements in
  the electrolitic bath can be included. Therefore
  Ti Hard is not a coating.

11
1_TiHard

• step 2 Mechanical finishing

12
1_TiHard
Titanium Alloy
Resin

• Scanning Electron Micrograph of TiHard treated
  Ti6Al4V

13
1_TiHard
Polished
TiHard

• Water contact angle of TiHard treated Ti6Al4V

Vickers micro-hardness
HV 965 35
HV 450 30
Water contact angle of untreated Ti
14
1_TiHard

• Main advantages of TiHard for biomedical
  applications
• Reduced fretting corrosion
• Galling prevention
• Improved fatigue resistance
• without coatings, with no influence on cell
  biocompatibility

15
Fretting resistance

• Weight loss is significantly reduced

Manually polished Electrochemically
polished Tumbler polished TiHard
Thin Layer Activation Joint study with European
Commission, Joint Research Centre Institute for
Health and Consumer Protection, Cyclotron
Laboratory Ispra, Italy
16
Fatigue resistance

• Fatigue resistance of Ti6Al4V is improved

Polished
TiHard
859 MPa
762 MPa
10 milions bending cycles (UNI 3964)
17
Fatigue resistance
TiHard
Ti6Al4V
Producer A
Producer B
18
1_TiHard

• TiHard allows to significantly improve titanium
  alloy performance, and can be exploited also for
  modular components
• TiHard titanium appears as an optimal choice
  especially for revision prosthesis and for
  allergic patients

19
Modular THR system

• To exploit the benefit of using modular
  prosthesis, special care must be dedicated to
  prevent stem/neck corrosion
• For this reason both design of the prosthesis and
  material must be carefully considered

20
2_CrCoMo

• Compared to Ti alloys, CoCrMo has superior
  mechanical properties

CrCoMo
Statical Mechanical Resistance
Ti6Al4MV
1600 1200 800 400 0
Ultimate tensile strenght (MPa)
21
2_CrCoMo

• Compared to Ti alloys, CoCrMo has superior
  mechanical properties

22
2_CrCoMo Durastar

• To safely use CoCrMo alloys, but the release of
  debris and/or ions needed to be investigated
• DuraStar is a special CoCrMo alloy (ISO 5832/12)
  with exceptional mechanical resistance
• A controlled shot peening process allows to even
  increase its performance (higher mechanical
  resistance and reduced wear)

23
2_CrCoMo Durastar
Safety assessment
Analysis done in SAMO (SAMO Labs) and coordinated
by scientific personnel from Politecnico di
Milano
24
2_CrCoMo Durastar
No detectable Co or Cr ions were in testing
environment
25
2_CrCoMo Durastar

• Superior CrCoMo performance make them a vey
  attractive opportunity for modular components
• Conducted studies sowed very low corrosion
  profiles and no appreciable Cr or Co ions release

26
2_CrCoMo Durastar

• Higher CoCrMo is justified by the superior
  performance
• CrCoMo appears as the safer choice for primary
  surgery modular components, and other producer
  have recently moved to this option (e.g. Stryker,
  BBrown-Aesculap)

27
New Technologies in MultiFit System
DuraStar Lorenza Draghi, Politecnico di
Milano Italy