Oxinium oxidized zirconium and counterface review

OXINIUM™

Oxidized Zirconium and counterface

review

™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

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


Desired attributes of hard bearings in hard on soft articulationBulk material attributes

•

Biocompatible

•

Corrosion resistant

•

Suitability for metal sensitive patients

•

Chemically and mechanically stable over extended period of time

Bearing surface attributes to reduce PE wear

•

Low friction and wettable

•

Scratch or abrasion resistant to third body debris such as bone cement

•

Macro-damage resistance (instrument damage, chipping, taper damage-compatibility, fracture risk, etc)

Presenter

Most of these desired properties allude to use of ceramic surface. Ceramics are biocompatible, corrosion resistant, low friction against PE, more wettable, scratch resistant and hypoallergenic. However, ceramics do come with a drawback: fracture risk, chipping, instrument damage etc. OXINIUM proves to be a unique combination of ceramic surface with metal alloy underneath.

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


CoCr

Alloy

•

Long clinical history

•

Does contain Nickel which is known to cause allergic response in some patients

•

Less scratch resistant to bone cement debris compared to some of the advanced bearing materials

Scratches on retrieved CoCrdue to bone cement debris

Allergic response to a CoCr

knee femoral(Nasser et al., AAOS 2007)

Ni content for Ti and CoCr

is permissible content per ASTM, actual content may be less, Internal Specification of Ni for Zr2.5Nb <0.0035%

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

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 through and scratch the femoral leading to increased wear of polyethylene

Scratching of nitrogen ion implanted Ti6Al4V during knee simulator test(Shetty

et.al., ASTM-

STP, 1272,1996)

Presenter

Zimmer sells nitrogen diffusion hardened titanium knee for metal sensitive patients. Hardening depth is small and will eventually wear through. Above example is nitrogen ion implanted Ti64. Stryker sells nitrogen ion implanted CoCr (LFIT).

Ceramic coatings

•

Ceramic coating to improve hardness and abrasion resistance

•

Coating adhesion critical to the performance, third body debris can wear the coating, coating debris can scratch CoCr

and will increase wear of polyethylene

Aesculap

ZrN

coated CoCr

Endotec

TiN

coating on Ti6Al4V

TiNbN

coating* –

Vanguard-Biomet*Haider

et. Al. Trans. 54th ORS, poster 2007, 2008

Coating delamination

TiNbN ZrN

Wear through of the coating during bone cement abrasion test(Hunter et al., MPMD, 2004)

Monolithic ceramics

•

Yttria

stabilized zirconia, Alumina and zirconia

toughened alumina (ZTA or Delta) are preferred materials of choice

•

Difficult to put porous structure for non-cemented use in knee femoral

•

Ceramic knees not cleared in US

•

Finite fracture risk

•

Phase transformation leading to roughening or fracture pose long term concern on stability

Biolox

Delta-CeramTec

AGYttira

stabilized zirconia

ceramic JMM, Japan

!"90ß=#=90

!

ß

#

Monoclinic

a

c

a!c

Tetragonal

5% Volume increase

Stable phase of zirconium oxide in the oxide of OXINIUM™

Oxidized Zirconium

Metastable

phase of zirconium dioxide in ytrria

stabilized zirconia

and Delta™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

Presenter

Steve Kurtz et al., posters at ORS (2009 and 2010) showed phase transformation does occur in Delta. They did not see increase in roughness with phase transformation.

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™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

Presenter

Zirconium has been used in nuclear industry as fuel rods for decades. The oxide formed on zirconium is tenacious and well adhered. That allows the rod to be retired from the use after certain oxide growth

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

Metal Substrate

Oxygen Enriched MetalOriginal Surface

Air500oCOxygen

Diffusion

Ceramic Oxide

Oxygen Enriched Metal

*Hunter et al., J ASTM Intl 2005


Hardness

Hardness of Oxide of OXINIUM™

devices is twice

that of CoCr

*Long et al., SFB 1998™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

Oxide integrity

Adhesion and cohesion of the oxide excellent

•

“Brick-like”

structure perpendicular to surface

•

No pores or segregation internally or at interface

*Hobbs et al., J Appl

Ceram Tech 2005

Ceramic Oxide

Zr2.5Nb

Rectangular Monoclinic Crystals of Zirconia

TEM Image*

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

Abrasion resistance

Hunter and Long, WBC 2000

4,900 times less volumetric wear in bone cement abrasion test compared to CoCr, Ceramic coated disks show wear through

Wear through of the coating during bone cement abrasion test(Hunter et al., MPMD, 2004)

TiNbN ZrN

CoCrOXINIUM


Damage tolerance

Resists oxide removal even if damaged

•

10 Mcycle

bone cement abrasion test across a groove milled through the oxide*

*Hunter, SFB 2001

MilledGroove

Pin Motion

OxideSurface

MetalSubstrate

*Hunter, SFB 2001

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™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

™

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 provides higher thermal conductivity

•

Alumina and OXINIUM heads generated less heat compared to yttria

stabilized zirconia.

0

5

10

15

20

25

30

35

40

45

1.0Hz 0.5 Hz 1.0Hz 0.5 Hz

Tem

pera

ture

Diff

eren

ce (d

egC) Alumina

OxZrCoCrZirconia

Test Frequency Test Frequency

LINERHEAD

*Tsai et al., Key Eng. Matls. 2006™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

Wettability

•

A drop of fluid beads up more on a CoCr

surface

•

A drop of fluid lies down more on a ceramic surface

•

The ceramic surface of Oxidized Zirconium slides better than Cobalt Chrome because it lubricates better

Drop of fluid on a ceramic surface

Drop of fluid on a CoCr surface

*Sprague et al., ISTA 2003

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

Top load Side load*Sprague et al., ISTA 2003


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


OXINIUM™

knee –

laboratory studies


Knee simulator test (benign)

OXINIUM™

femorals

reduced conventional PE wear rate by 85%

Spector et al., JBJS, 2001™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

0

5

10

15

20

25

30

35

40

Benign HiRot HiVarus

Wea

r Rat

e (m

m3

/ M

cycl

e) CoCrOxZirc

0

5

10

15

20

25

30

35

40

Benign HiRot HiVarus

Wea

r Rat

e (m

m3

/ M

cycl

e) CoCrOxZirc

*Ezzet et.al., CORR 2004, ** Ezzet

et.al., Trans. ORS, 2005

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**

VERILAST™

Technology: OXINIUM™

Knee Femoral and 7.5 XLPE*

VERILAST Technology provides the lowest wear


OXINIUM™

knee –

clinical studies


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


Laskin, Tech. Knee Surgery 6(4), 220-226,2007

OXINIUM CoCrMo

Mean flex 119º 116º

Knee score 91 92

Function score 76 72


Clinical study knees –

5 year clinical results

•

First Study

72 Patients with OXINIUM™

knees mean follow-up 5.6 years, safety study

•

Second study (randomized) compare CoCr

and OXINIUM knees (38 patients)

•

No specific complications associated with OXINIUM knees

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

*

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

*Pritchett, CORR, 442,2006,195-198

OXINIUM knee


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™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

Retrieval analysis*

•

Matched pair analysis of OXINIUM™

Oxidized Zirconium and CoCr

knee femorals

and tibial

inserts

•

In-vivo time similar

•

Wear score of inserts and of femoral components graded

•

Lower wear score of OXINIUM femorals

and corresponding inserts

0

10

20

30

40

50

60

70

80

90

Inserts/CoCr Inserts/OXINIUM

Tibi

al In

sert

Wea

r Sco

re

*Heyse et al., ESSKA, 2010, Oslo, Norway

0

2

4

6

8

10

12

CoCr OXINIUM

Fem

oral

Dam

age

Wea

r Sco

re


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


OXINIUM™

hip –

laboratory studies


Hip simulator wear test (benign)

•

Reduces non-irradiated poly wear rate by 45%*

•

Generates approximately 30% fewer particles

0

10

20

30

40

Non-Irradiated CrosslinkedPolyethylene Liner

Agg

rega

te W

ear R

ate

(mm

3 /Mcy

cle)

CoCrOx. Zirc.

N/D N/D 0

2

4

6

8

10

Non-Irradiated CrosslinkedPolyethylene Liner

Line

r Wea

r Par

ticle

s (m

illion

s/cy

cle)

CoCrOx. Zirc.

*Good et al., JBJS-A 2003*Good et al., JBJS-A 2003

Hip simulator wear test with abraded heads

•

CoCr

and OXINIUM™

heads roughened to simulate presence of third body debris in the joint

•

Tumbled OXINIUM head has same wear rate as new CoCr head

Smooth Rough0

10

20

Wea

r Rat

e (m

m3 /M

cycl

e) Against OXINIUM heads

Against CoCr heads

Good et al., JBJS 2003™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

Hip simulator wear test (jogging protocol)

Parikh et al., Trans. 55th ORS, 2340, 2009

-10

-5

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8

Cycles (millions)

Cum

ulat

ive

Wea

r (m

m3 )

HL001123 Verse CoCr HeadHL001125 Verse CoCr HeadHL001127 Verse CoCr HeadHL001122 Verse Oxinium HeadHL001124 Verse Oxinium HeadHL001126 Verse Oxinium Head

Against CoCr heads

Against OXINIUM heads


0

10

20

30

40

50

60

32mm CoCr/CPE 36mm Delta/XLPE 36mm Ox/XLPE

Wea

r Rat

e m

m3 /M

cycl

e

CoCr/CPE, OXINIUM™/XLPE and Delta/XLPE under jogging protocol

32 mm CoCr/CPE: Parikh et al., ORS 2009, 36 mm Delta/XLPE and Ox/XLPE –Data on file

~95%


Large heads against XLPE

•

Large heads offer more joint stability and range of motion

•

Wear of 44mm OXINIUM™/XLPE is less than 36mm CoCr/XLPE (p<0.05)*

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Against 36mm CoCr heads Against 44mm OXINIUM heads

Cum

ulat

ive

Wea

r (m

m3 )

Parikh et al., ISTA 2010™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

OXINIUM™

hips –

clinical studies


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 ™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

Linear wear

•

2 year follow-up,

–

CoCr/XLPE

–

OXINIUM™/CPE

–

OXINIUM/XLPE

•

270 patients prospectively randomized consecutive, all heads 32 mm

•

Reviewers blinded

•

OXINIUM/XLPE shows lowest wear

Haddad et.al., Proc. AAOS, P067, 2010

CoCr/XLPE Ox/CPE Ox/XLPE


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 ™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.

Retrieval analysis: phase stability

•

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 so no phase transformation observed

*Medel

et al., Trans. 55th

ORS,2300, 2009**Sakona

et al., Trans. 56th

ORS, 2358A, 2010

Tetragonal peak absent for OXINIUM

Raman spectra**


Presenter

YTZ showed increased roughness (not sig) whereas Delta roughness unaltered with phase transformation

Oxinium oxidized zirconium and counterface review

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