2. Outline
• Bearings choices for hard on soft articulation
• OXINIUM™ Oxidized Zirconium
• OXINIUM knee – laboratory studies
• OXINIUM knee – clinical studies
• OXINIUM hip – laboratory studies
• OXINIUM hip – clinical studies
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3. Desired attributes of hard bearings
in hard on soft articulation
Bulk material attributes Bearing surface attributes
• Biocompatible to reduce PE wear
• Corrosion resistant • Low friction and wettable
• Suitability for metal sensitive patients • Scratch or abrasion resistant to third
body debris such as bone cement
• Chemically and mechanically stable
over extended period of time • Macro-damage resistance
(instrument damage, chipping,
taper damage-compatibility,
fracture risk, etc)
4. Choices of hard bearing materials
• CoCr alloy (as-cast, forged or wrought)
• Surface hardened CoCr
• Surface hardened Ti6Al4V alloy (wrought or forged)
• Ceramic coatings
• Monolithic ceramic such as yttria stabilized zirconia, alumina
(Forte), zirconia toughened alumina (Delta)
• OXINIUM™ Oxidized Zirconium
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5. CoCr Alloy
• Long clinical history
• Does contain Nickel which
is known to cause allergic Allergic response Ni content for Ti and CoCr
to a CoCr knee femoral
response in some patients (Nasser et al., AAOS 2007)
is permissible content per
ASTM, actual content
• Less scratch resistant to bone may be less, Internal
cement debris compared to some Specification of Ni for
Zr2.5Nb <0.0035%
of the advanced bearing materials
Scratches on retrieved CoCr
due to bone cement debris
6. Ion treated CoCr
• Increase surface hardness of CoCr to improve
wettability and abrasion resistance
• Sold by Stryker under trade name “LFIT”
(Low Friction Ion Treated)
• Small depth of hardening (~0.2 micron)
• Retrieval analysis has shown that ion
treated layer can disappear over time*
*McGrory et.al., AAOS 2005
7. Ti6Al4V alloy
• Not a favored material
for bearing application
• Promoted as an alternate
to CoCr for metal sensitive
patients by some companies
• Nitrogen diffusion hardened
Ti6Al4V sold by Zimmer
• Depth of hardening is small and
hardened layer will eventually wear Scratching of nitrogen ion implanted
through and scratch the femoral Ti6Al4V during knee simulator test
(Shetty et.al., ASTM- STP, 1272,1996)
leading to increased wear
of polyethylene
8. Ceramic coatings
• Ceramic coating
to improve hardness
and abrasion resistance
• Coating adhesion critical to the
performance, third body debris can Endotec TiN Aesculap ZrN
wear the coating, coating debris can coating on Ti6Al4V coated CoCr
scratch CoCr and will increase wear
of polyethylene Coating delamination
TiNbN ZrN
Wear through of the coating during bone cement abrasion test TiNbN coating* – Vanguard-Biomet
(Hunter et al., MPMD, 2004) *Haider et. Al. Trans. 54th ORS, poster 2007, 2008
9. Monolithic ceramics
• Yttria stabilized zirconia, Alumina
and zirconia toughened alumina
(ZTA or Delta) are preferred materials
of choice Yttira stabilized Biolox Delta-CeramTec AG
zirconia ceramic
• Difficult to put porous structure for JMM, Japan
non-cemented use in knee femoral !"90
ß=#=90
a!c
• Ceramic knees not cleared in US
#
• Finite fracture risk 5% Volume increase
c
• Phase transformation leading to
roughening or fracture pose long ß
term concern on stability a !
Tetragonal
Monoclinic
Metastable phase of zirconium Stable phase of zirconium
dioxide in ytrria stabilized oxide in the oxide of
zirconia and Delta OXINIUM™ Oxidized Zirconium
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10. OXINIUM™ Oxidized Zirconium
• Base alloy of the OXINIUM material is
zirconium-2.5 wt% niobium (Zr-2.5Nb)
• Oxidized to form a hard ceramic surface
• Zirconium is one of the five
most biocompatible elements
(titanium, zirconium, niobium,
tantalum and platinum)
• Ni content of Zr2.5Nb alloys is extremely
low making it suitable
for metal sensitive patients
• Other uses of Zirconium alloys
– Chemical industries
(valves and seals)
– Nuclear fuel rods
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11. OXINIUM™ Oxidized Zirconium
• Wrought zirconium-2.5 niobium device is heated in air
• Surface transforms to stable ceramic (~5 !m), not a coating
• The OXINIUM alloy is durable with toughness of metal and high strength
Air
Oxygen 500oC
Diffusion
Original Surface
Oxygen Enriched Metal
Ceramic Oxide
Oxygen Enriched Metal
Metal Substrate
*Hunter et al., J ASTM Intl 2005
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12. Hardness
Hardness of Oxide of OXINIUM™ devices is twice that of CoCr
*Long et al., SFB 1998
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13. Oxide integrity
Adhesion and cohesion of the oxide excellent
• “Brick-like” structure perpendicular to surface
• No pores or segregation internally or at interface
TEM Image*
Rectangular
Ceramic Monoclinic
Oxide Crystals of
Zirconia
Zr2.5Nb
*Hobbs et al., J Appl Ceram Tech 2005
14. Strength
• Supports 4.4 kN (~1000 lbf)
for 10 million cycles – equivalent to CoCr
• Bends with 19.8 kN (~4500 lbf) – does not break or delaminate
Tsai et al., SFB 2001
15. Abrasion resistance
4,900 times less volumetric wear in bone cement abrasion test
compared to CoCr, Ceramic coated disks show wear through
OXINIUM CoCr
TiNbN ZrN
Wear through of the coating during bone cement abrasion test
(Hunter et al., MPMD, 2004) Hunter and Long, WBC 2000
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16. Damage tolerance
Resists oxide removal even if damaged
• 10 Mcycle bone cement abrasion test
across a groove milled through the oxide*
Milled Pin Motion
Groove
Oxide
Surface
Metal
Substrate
*Hunter, SFB 2001
*Hunter, SFB 2001
17. Coefficient of friction
• Lower coefficient of friction against
polyethylene and against cartilage ™
• Lower coefficient of friction means
less adhesive wear of polyethylene
Poggie et al., ASTM STP 1145
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18. Interfacial friction and heat generation*
• Lower friction leads to lower
interfacial temperature
• Thermal conductivity
(heat dissipation also critical)
• OXINIUM™-ceramic surface provides
lower friction and bulk metal 45
provides higher thermal conductivity 40
HEAD LINER
Alumina
Temperature Difference (degC)
OxZr
• Alumina and OXINIUM heads 35
CoCr
30
generated less heat compared to 25
Zirconia
yttria stabilized zirconia. 20
15
10
5
0
1.0Hz 0.5 Hz 1.0Hz 0.5 Hz
*Tsai et al., Key Eng. Matls. 2006 Test Frequency Test Frequency
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19. Wettability
• A drop of fluid beads up more on a
CoCr surface
• A drop of fluid lies down more on a
ceramic surface Drop of fluid on a CoCr surface
• The ceramic surface of Oxidized
Zirconium slides better than Cobalt
Chrome because it lubricates better
Drop of fluid on a ceramic surface
20. Chemical and mechanical stability
• Chemically stable after 20 hrs of steam autoclave
(~simulated ageing of >80 years in-vivo)*
• Does not shatter in crush test with 89 kN (20,000 lbf) load
– Flattens slightly with 89 kN side load without stem
– Oxide maintains integrity on slightly flattened head
Zirconia OXINIUM™ head
*Sprague et al., ISTATop load
2003 Side load
*Sprague et al., ISTA 2003
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21. OXINIUM™ Oxidized Zirconium – key messages
• Ceramic bearing surface without a risk of fracture
• Surface transformation, not a coating
• Suitable for metal sensitive patients
• Highly wettable, abrasion resistant
and low friction ceramic surface
• Long term mechanical and chemical stability
• Like other surfaces can get damaged
intraoperatively, care needs to be exercised
with all the bearing surfaces
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22. OXINIUM™ knee – laboratory studies
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23. Knee simulator test (benign)
OXINIUM™ femorals reduced conventional PE wear rate by 85%
Spector et al., JBJS, 2001
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24. Independent Wear Study: Scripps Institute
• Testing done at Independent Lab (Scripps Institute in San Diego)
• 42% wear reduction – benign conditions*
• 40–60% wear reduction – high rotation & high varus**
40
CoCr
Wear Rate (mm3 / Mcycle)
35
OxZirc
30
25
20
15
10
5
0
Benign HiRot HiVarus
*Ezzet et.al., CORR 2004, ** Ezzet et.al., Trans. ORS, 2005
25. VERILAST™ Technology:
OXINIUM™ Knee Femoral and 7.5 XLPE*
VERILAST Technology provides the lowest wear
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26. OXINIUM™ knee – clinical studies
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27. OXINIUM™ knee and hip implantations
As of 2009, over 200,000 knee femorals
and 100,000 femoral heads implanted
• First total knee in December 1997
• First total hip in October 2002
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28. Clinical study knees – 5 year clinical results
• First Study
72 Patients with OXINIUM™ knees OXINIUM CoCrMo
mean follow-up 5.6 years, safety study
• Second study (randomized) Mean flex 119º 116º
compare CoCr and OXINIUM knees Knee
(38 patients) 91 92
score
• No specific complications Function
associated with OXINIUM knees 76 72
score
Laskin, Tech. Knee Surgery 6(4), 220-226,2007
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29. Clinical study knees >5 year clinical results
• 98 Patients, minimum follow-up 5 years,
Implanted between April 2001 to December 2003
• 98.7% survival rate at 7 years (95% CI , 90.3%–99.8%)
• Worst case scenario of patients losing follow-up,
gives 94.5% survivorship at 7 years
*
*Innocenti et al.,CORR, DOI 10.1007/s11999-009-1109-y, 2009
30. In-vivo temperature measurements*
Increase in temperature in the joint space for healthy knee,
arthritic knee, different designs and OXINIUM™ knee
femoral components was measured
OXINIUM knee
*Pritchett, CORR, 442,2006,195-198
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31. Metal sensitivity case study*
• 56 year old homemaker,
cannot wear jewelry
• Left Knee: 3 years post TKA (CoCr)
– Pain & stiffness
– Persistent rash
• Revised to Alumina
– Rash went away
• Right knee primary with OXINIUM™
material: Rash did not appear
*Nasser et al., AAOS 2007
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32. Retrieval analysis*
90
80
• Matched pair analysis of OXINIUM™ 70
Tibial Insert Wear Score
60
Oxidized Zirconium and CoCr knee 50
femorals and tibial inserts 40
30
• In-vivo time similar 20
10
• Wear score of inserts and of femoral 0
Inserts/CoCr Inserts/OXINIUM
components graded
12
• Lower wear score of OXINIUM
femorals and corresponding inserts
Femoral Damage Wear Score
10
8
6
4
2
0
CoCr OXINIUM
*Heyse et al., ESSKA, 2010, Oslo, Norway
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33. Retrieval analysis
• 9 OXINIUM™ and 9 CoCr knee
femoral components*
• In-vivo time
– OXINIUM (1.2 to 5.6 yrs)
– CoCr (0.7 to 4.6 yrs)
• Articulating surface roughness
measurements
• CoCr components rougher than
OXINIUM knee femorals
*Sebastian et al., Trans. 54th ORS, 2008
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34. OXINIUM™ hip – laboratory studies
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36. Hip simulator wear test with abraded heads
20
• CoCr and OXINIUM™ heads
Wear Rate (mm3/Mcycle)
Against OXINIUM heads
roughened to simulate presence Against CoCr heads
of third body debris in the joint
10
• Tumbled OXINIUM head has same
wear rate as new CoCr head
0
Smooth Rough
Good et al., JBJS 2003
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37. Hip simulator wear test (jogging protocol)
30
HL001123 Verse CoCr Head
25 Against CoCr heads
HL001125 Verse CoCr Head
HL001127 Verse CoCr Head
HL001122 Verse Oxinium Head
HL001124 Verse Oxinium Head heads
Against OXINIUM
20 HL001126 Verse Oxinium Head
Cumulative Wear (mm3)
15
10
5
0
0 1 2 3 4 5 6 7 8
-5
Cycles (millions)
-10
Parikh et al., Trans. 55th ORS, 2340, 2009
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38. CoCr/CPE, OXINIUM™/XLPE and Delta/XLPE
under jogging protocol
60
50
Wear Rate mm3/Mcycle
40
30
~95%
20
10
0
32mm CoCr/CPE 36mm Delta/XLPE 36mm Ox/XLPE
32 mm CoCr/CPE: Parikh et al., ORS 2009, 36 mm Delta/XLPE and Ox/XLPE –Data on file
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39. Large heads against XLPE
• Large heads offer more joint 4.5
stability and range of motion 4
• Wear of 44mm OXINIUM™/XLPE 3.5
Cumulative Wear (mm 3)
is less than 36mm CoCr/XLPE 3
(p<0.05)* 2.5
2
1.5
1
0.5
0
Against 36mm CoCr heads Against 44mm OXINIUM heads
Parikh et al., ISTA 2010
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40. OXINIUM™ hips – clinical studies
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41. Linear wear
• RSA study in Australia:
– 30 patients with 32mm OXINIUM™/XLPE (10Mrad)
– 28mm CoCr/XLPE (5 and 10 Mrad)
– 28mm CoCr/ETO sterilized UHMWPE
• OXINIUM/XLPE-10 shows promising results
Li et al., Trans. 52nd ORS, 0643,2006
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42. Linear wear
• 2 year follow-up,
– CoCr/XLPE
– OXINIUM™/CPE
– OXINIUM/XLPE
• 270 patients prospectively
randomized consecutive,
all heads 32 mm
• Reviewers blinded CoCr/XLPE Ox/CPE Ox/XLPE
• OXINIUM/XLPE shows lowest wear
Haddad et.al., Proc. AAOS, P067, 2010
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43. Clinical Outcome*
• Randomized study
– 50 patients received OXINIUM™ femoral heads
– 50 patients received CoCr femoral heads
• Minimum follow-up 2 years
• Authors conclude use of OXINIUM heads is safe and effective
*Lewis et.al., ISTA 2009
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44. Retrieval analysis: phase stability
Raman spectra**
• Comparison of OXINIUM™, yttria
stabilized zirconia (YTZ) and
Delta (contains yttria stabilized
zirconia~17 volume %)*,**
• Monoclinic content and surface
roughness measured
• Both YTZ and Delta showed
phase transformation,
• OXINIUM is stable monoclinic Tetragonal peak absent for OXINIUM
so no phase transformation
observed
*Medel et al., Trans. 55th ORS,2300, 2009
**Sakona et al., Trans. 56th ORS, 2358A, 2010
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