Locking in life Evolution Conventional UHMWPE Evolution - - PowerPoint PPT Presentation

Vitamin E Technology

Locking in life

Evolution

Conventional UHMWPE

Evolution

Conventional UHMWPE

Introduced by Sir John Charnley in 1962 Moderately cross-linked due to gamma sterilisation Outstanding mechanical properties: 50-60% crystalline Good bearing material High wear characteristics (leading to

• steolysis)

Evolution

Negative:

• High wear
• Poor oxidation resistance

Positive:

• Good mechanical properties

Conventional UHMWPE

Evolution

First generation HXLPE

Evolution

Consolidation of UHMWPE powder (GUR1020, GUR1050, etc) Remelt to remove free radicals Package and sterilise (inert) - ETO Machine consolidated form Anneal to reduce free radicals Irradiate (50kGy – 100kGy) cross-linking material

First generation HXLPE – processing

First generation HXLPE

Cross linking improves wear characteristics

In vitro and in vivo wear data corroboration for polyethylene acetabular components cross-linked at various radiation dose levels1

Evolution

1. Wang, 2009.

First generation HXLPE – oxidation

Occurs in vivo with either remelt or annealed polyethylene:

0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 0,0 2,0 4,0 Oxidation Index (A.U.) Depth (mm) 0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 0,0 2,0 4,0 Oxidation Index (A.U.) Depth (mm) 0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 0,0 1,0 2,0 3,0 4,0 5,0 Oxidation Index (A.U.) Depth (mm)

• xidation: 15X↑

cross-link density: 2X↓

• xidation: 45X↑

cross-link density: 4X↓

• xidation: 2X↑

cross-link density: 1.4X↑

10-year cross-fire liner 4-year in vivo X3 liner 10-year longevity liner

• Absorption of lipids e.g. squalene
• Cyclic loading

Evolution

Negative:

• Oxidative degeneration
• Poor mechanical properties

Positive:

• Low wear

First generation HXLPE – concerns

Rim fracture:

• Tower et al., JBJS 2007
• Furmanski et al., AAOS 2008
• Moore et al., JBJS 2008
• Duffy et al., JOA 2009

In vivo oxidation:

• Currier et al., JBJS 2007
• Kurtz et al., CORR 2006
• Muratoglu et al., 2009

Evolution

Evolution

Next generation vitamin E HXLPE

Locking in life

Next generation vitamin E HXLPE

E

Locking out oxidation Vitamin E blended UHMWPE

Ci

Locking out wear Cold irradiated Mechanically annealed Locking in strength

Ma

Next generation vitamin E HXLPE

E

Locking

• ut
• xidation

Vitamin E blended UHMWPE

E

Active stabilisation

The vitamin E is grafted to the polyethylene:

• acting as a reservoir for active

stabilisation

• preventing free radical oxidation

into the long term Oxidation occurs through loading and absorption of lipids (squalene)

Locking out oxidation

Whilst some companies use a diffusion process, ECiMa™ uses a proprietary blending and consolidation process, chemically bonding the vitamin E to the polyethylene molecule at the start of the manufacturing process.

Locking out oxidation

This offers 2 distinct advantages:

• allows uniform distribution of vitamin

E across the cross section of the polyethylene

• minimises the vitamin E elution effect

seen in infused vitamin E products2

Not all vitamin E polyethylenes are created equal

2. Data held on file.

Absorbance (AU) Time (minutes)

High performance liquid chromatography chromagrams from non-polar solvent extraction

The ‘Goldilocks Enigma’

Conventional doped vitamin E polyethylene use 1% wt, which can reduce cross-linking density and wear resistance of the polyethylene The ECiMa™ grafting process allows low dosage of vitamin E to be used, 0.1% wt, optimising the cross-link density and wear resistance of the material, whilst minimising exposure to large amounts of vitamin E in the joint3

Locking out oxidation

3. Oral et al, 2008.

Oxidative shield

The free radical stabilisation effect of vitamin E provides a natural barrier to potential long-term oxidation which can occur in vivo Test results show no evidence of oxidation following intensive ageing and cyclic loading in vitro where previous HXLPE liners have failed2

2. Data held on file.

Locking out oxidation

Next generation vitamin E HXLPE

Locking

• ut wear

Cold irradiated

Ci

Low wear – test data

Designed to maximise survivorship, ECiMa™ test results indicate ultra low wear rates4 with the potential to reduce wear-related osteolysis in vivo, even with 40mm bearings

• 95% reduction

compared to UHMWPE

• 83% reduction

compared to HXLPE

• reduction in wear

compared to doped vitamin E HXLPE5

4. Traynor et al, 2012. 5. Competitor literature

Locking out wear

Next generation vitamin E HXLPE

Locking in strength Mechanically annealed

Ma

Below re-melt temperature (maintains mechanical integrity)

What is mechanical annealing?

Heat deform

Quench free radicals

Heat

Locking in strength

MPa 10 20 30 40 50 60 UHMWPE HXLPE ECiMa™ UTS

3% 34%

Test data:

Superior mechanical properties4

4. Traynor et al, 2012.

Locking in strength

Mechanical integrity vs competitor products5

Locking in strength

5. Competitor literature

Test data:

Environmental stress cracking

• Cyclical loading 10MPa, 0.5Hz, to

1.5mc

• Oxidation analysis
• All ECiMa™ samples completed

1.5mc

• 2 HXLPE failed
• Oxidisation of HXLPE 4-5X greater

than controls

ASTM F671

ECiMa™ ECiMa™ ECiMa™ ECiMa™ HXLPE HXLPE HXLPE HXLPE

Locking in strength

Mechanical integrity

UHMWPE HXLPE ECiMa™

Vitamin E doped, seq. annealed

Locking out oxidation Locking out wear Locking in strength

Locking in life

Oxidative stability (longevity)

ECiMa™ Vitamin E doped Remelted, Seq annealed HXLPE Annealed HXLPE UHMWPE

Improved wear resistance

ECiMa™ Vitamin E doped Seq annealed HXLPE HXLPE UHMWPE

Locking in life

E

Locking out oxidation

Ci

Locking out wear

Cold irradiation allows cross-linking at the optimal radiation dose providing 95% reduction in wear compared with conventional polyethylene4

M a

Locking in strength

Mechanical annealing below the melt temperature provides a 45% increase in ultimate tensile strength compared to conventional HXLPE4 Blended Vitamin E provides an ‘oxidative shield’ actively stabilising the polyethylene insert from in vivo oxidation4

4. Traynor et al, 2012.

References

1. Wang, 2009. 2. Data held on file, Corin Group PLC 3. Oral E, Godleski Beckos C, Malhi AS, Muratoglu OK. The effects of high dose irradiation on the cross-linking of vitamin E-blended ultra high molecular weight polyethylene. Biomaterials 2008:29;3557-60. 4. Traynor A, Simpson D, Collins S. ECiMa™ for low wear, optimal mechanical properties and oxidation resistance of hip bearings. Total Hip Arthroplasty – Wear Behaviour of Different Articulations, EFORT Reference in Orthopaedics and Traumatology, Springer: ISBN 978-3-642-27360-5, 2012. 5. Competitor literature review.

Vitamin E Technology

Locking in life