Value Brief

AOX™ Antioxidant Polyethylene for SIGMA® and LCS® Rotating Platform Knee Systems

Value Summary

Advanced Technology: DePuy Orthopaedics is proud to offer AOX™ Antioxidant Polyethylene, the next generation of polyethylene for SIGMA® and LCS® Rotating Platform Knees. With our advanced blend of polyethylene resin and a unique antioxidant, COVERNOX™, DePuy Orthopaedics has created a new polyethylene material that has efficiency in trapping free radicals and scavenging oxygen. This first of its kind combination is designed to deliver wear resistance and long term oxidative stability.

Primary TKA is a successful operation associated with improvements in pain and restoration of function for the patient; however, failures of TKA may occur. Total knee arthroplasties can fail because of a variety of mechanisms, including wear, loosening, infections, instability, fracture, and mechanical failure.2 This failure can cause pain, instability, and loss of function. In order to relieve pain and restore function, revision TKAs are performed. In the US, the percentage of revision arthroplasties is expected to increase substantially

over the next several decades as the prevalence of primary arthroplasty increases, as the average age of patients who undergo primary arthroplasties decreases, and as the activity level and body mass of these patients increase.

Revision arthoplasty is required for a multitude of reasons, including those listed in the chart. Wear and lysis are related to the polyethylene materials utilized in total knee arthroplasty and are two of the top material related reasons for revision surgery. These complications may be avoided by utilizing materials such as an oxidatively stable implant like AOX Antioxidant Polyethylene.

The Projected Relative Proportion of the Younger Patient Population (Aged < 65 Years) for Primary and Revision Total Joint Arthroplasty in the United States, 2010 to 20301

TKA = total knee arthroplasty.

65

60

55

50

45

402010 2015 2020

Year

Primary TKA

Revision TKA

Perc

enta

ge

of

pat

ien

ts <

65 y

ears

of

age

2025 2020

Indication Number Percentage

Aseptic loosening 1,554 35

Infection 1,026 23

Pain 817 18

Instability 664 15

Wear of polyethylene component 509 11

Other 512 11

Lysis 448 10

Malalignment 326 7

Stiffness 255 6

Dislocation/subluxation 151 3

Periprosthetic fracture 121 3

Component dislocation 81 2

Implant fracture 45 1

Total 6,509

Indications for Knee Revision Procedures in 20093

Background

Total knee arthroplasty has been a successful treatment for severe Osteoarthritis (OA) with excellent results at 10 to 15 years. The patient demographic, however, is beginning to shift; patients undergoing TKA are increasingly likely to be younger and more active, or to be obese. These patients may demand an increased level of function compared with previous patients, who have typically been older with lower activity levels.6

The challenge of current TKA is to meet the new expectations from the emerging demographics and reduce the risk of revision, which represents a painful situation for the patient and an economic burden to the healthcare system. DePuy Orthopaedics’ SIGMA RP Knee System, which has been designed to address the leading causes of revision—specifically, instability, wear, loosening, and mechanical failure coupled with the benefits of AOX Antioxidant Polyethylene, delivers oxidative stability, and wear resistance without compromising the mechanical properties of polyethylene.4,5

Protection Against Oxidation

The addition of free radical scavengers into polyethylene enables the stabilization of the free radicals that are responsible for the oxidation of the polyethylene. By introducing COVERNOX Antioxidant into the base resin before the polyethylene is consolidated, the process enables the antioxidant to be uniformly dispersed throughout the material and remain blended for the life of the implant. The process provides an oxidatively stable polyethylene formulation. Under aggressive conditions sufficient to oxidize non-irradiated polyethylene, AOX Polyethylene is completely unaffected and oxidatively stable. Annealed polyethylenes do not similarly eliminate the potential for oxidation.4,7,8

By eliminating the annealing or remelting process, AOX Polyethylene delivers oxidative stability and wear resistance without compromising the mechanical properties of polyethylene.4,5

Antioxidant stabilized UHMWPE technology has allowed for providing robustness to an already well established orthopaedic implant material. A balanced approach to helping optimize wear performance, mechanical characteristics and oxidative stability, that is derived from judicious choices in composition and process technologies, would yield a durable and high performance material when compared to previous generations of polyethylene.

Oxidative Stability: By eliminating the annealing or remelting process, AOX Antioxidant Polyethylene delivers oxidative stability and wear resistance without compromising the mechanical properties of polyethylene, which provides a more durable material over the life of the implant. 4,5

The Next Generation of Polyethylene: Incorporation of anti-oxidant agents like COVERNOX that promote oxidative stability, while common practice in the engineering industry, has not been applied to the orthopaedic grade polyethylene until recently. This approach has yielded the fourth generation of polyethylenes. With the introduction of AOX Antioxidant Polyethylene, only DePuy Orthopaedics offers mobile bearing implant designs to accommodate the different philosophies of PCL management, wear reducing benefits of rotating platform technology and oxidative stability.

Potential Benefits

Maximizing Wear Resistance

DePuy Orthopaedics’ Rotating Platform knees were designed with polyethylene wear reduction as a core principle. SIGMA Rotating Platform features a highly polished Cobalt Chrome (CoCr) tibial tray and self aligning polyethylene insert, which by virtue of unidirectional movement results in 94% wear reduction when compared with the older design.9

Wear rates for rotating platform knees are significantly lower than for other knees.

A primary cause of osteolytic response is understood to be wear debris from polyethylene bearings.10 The rotating platform knee design allows internal and external rotation of the knee to occur between the tibial insert and the tibial tray while maintaining unidirectional motion between the articular surfaces of the femoral component and tibial insert. Wear rates for rotating platform technology continue to compare favorably against modern fixed bearing designs and materials.

Published reports demonstrate high levels of patient satisfaction with rotating platform knee implants.11,12 Maniar et al. (2011) reported that 98% of patients were happy with the outcome of their surgery with a rotating platform implant (P.F.C. SIGMA) and said they would opt to have the same surgery on the other side.

AOX Polyethylene Maintains High Material Strength

SIGMA Rotating Platform Knee Technology was designed to prevent mechanical loosening and wear—which are two primary complications of knee replacement. AOX Polyethylene maintains high material strength when compared to most other commercially available polyethylene options.

The demographics of a patient undergoing TKA are changing; patients are now younger and more likely to be obese, or to live a more active lifestyle.12,13 Maintaining mechanical properties is important as the activities high demand patients perform and subject their implant to, have the potential to deform and break down polyethylene over time. Unlike remelting, this approach to providing oxidative stability does not cause a decline of mechanical strength.14

SIgMA RPF Knee Polyethylene Wear Comparison5

Mea

n W

ear

Rat

es

GVF AOX

Strength of Materials

50

30

40

20

10

0

Ult

imat

e Te

nsi

le S

tren

gth

(M

Pa)

15

20

25

10

5

0

Yie

ld S

tren

gth

(M

Pa)

AOX Polyethylene4

10Mrad Remelted16

3x Annealed10

Vitamin E Doped15

Excellent Mechanical Toughness

Normal patient loads can impose high contact stresses on polyethylene knee components, so their toughness, or resistance to surface crack initiation and subsequent propagation leading to shear induced delamination, is critical. The findings show an advantage in toughness for AOX Polyethylene when compared against other products in the market. Standard polyethylene has the best mechanical properties but it is not used in modern implant designs due to its less than ideal wear characteristics.4,15

Proven Efficiency

Function with Wear Resistance, and Oxidative Stability

DePuy Orthopaedics continues to lead and drive the future in mobile bearing technology. The rotating platform technology with 97.7 percent survivorship at 20 years, demonstrates that its less constrained axial rotation effectively reduces wear and implant loosening forces when compared to a fixed bearing design.19–23

The demonstrated long-term survivorship of rotating platform implants and the associated low revision rates are likely to translate into economic savings through the avoidance of costly revisions.

Through advanced material and component design you can now have function with wear resistance coupled with oxidative stability of AOX Polyethylene to support implant survivorship.

Central to performance and survivorship, AOX Polyethylene is an excellent choice for your active patients where a mobile bearing knee system is preferred.

Toughness of Materials

0.6

0.8

1

1.2

1.4

1.6

0.4

0.2

0

K ∆

Ince

pti

on

AOX polyethylene18

3x Annealed (No data available)

10Mrad Remelted15

Vitamin E Doped15

60

80

100

120

40

20

0

Do

ub

le N

otc

hed

Izo

d T

ou

gh

nes

s (k

J/m

2)

AOX polyethylene4

3x Annealed17

9Mrad Remelted17

Standard8

The DePuy Orthopaedics Difference

Trusted quality and Innovation• The most orthopaedic products receiving premarket

approval in the United States of any major manufacturer24

•High-flexion femoral components paired with rotating platform technology deliver function with wear resistance for the high-demand patient25

•More than 20 years of clinical success based on DePuy Orthopaedics Rotating Platform technology19

Proven efficiency•Minimized inventory and increased operating-room

efficiency with smaller, less complex SIGMA High Performance Instrument Sets

• Strong evidence demonstrating value—with case studies, value dossiers, and data from centers of excellence

Technical Expertise & Best Practices• The only orthopaedics company with third-party, IACET-

accredited technical experts* who help you pre-plan and integrate innovative technology and techniques

• Surgical training that helps you optimize skills

•Community patient education and outreach to help meet higher levels of patient demands

Customer rewards program that offers efficient, consolidated purchasing opportunities

References:1. Bozic KJ, Kurtz SM, Lau E, Ong K, Chiu V, Vail TP, et al. The epidemiology of revision total knee

arthroplasty in the United States. Clin Orthop Relat Res. 2010;468:45-51.

2. Sharkey P, Hozack WJ, Rothman RH, Shasti S, Jacoby SM. Why are total knee arthroplasties failing today? Clin Orthop Relat Res. 2002;404:7-13.

3. National Joint Registry for England and Wales (NJR). 7th annual report. 2010. Available at: http://www.njrcentre.org.uk/njrcentre/AbouttheNJR/Publicationsandreports/Annualreports/tabid/86/Default.aspx. Accessed July 20, 2011.

4. Data on File at DePuy Orthopaedics, Inc. WR070300.

5. Data on File at DePuy Orthopaedics, Inc. WR070248.

6. Callaghan J Squire MW, Goetz DD, Sullivan PM, Johnston RC. Cemented rotating platform total knee replacement: a nine to twelve year follow-up study. J Bone Joint Surg Am. May 2000b;82(5) 705-711.

7. Muratoglu, O.K. “Grand Rounds Presentation at the Dartmouth Hitchcock Medical Center on May 16, 2007.” http://www.dnslides.org/ortho/ortho051607/msh.htm.

8. Greer, K.W. and M.S. Sharpe. “Comparison of Cross-linked UHMWPE Stabilized by Sequential Annealing or by Remelting.” Poster 1784, 53rd Annual Meeting of the Orthopaedic Research Society, February 11-14, 2007, San Diego, CA.

9. McNulty, D., S.W. Swope, D.D. Auger and T. Smith. “The Effect of Crosslinking UHMWPE on In-vitro Results in Fixed and Mobile Bearing Knees.” Presented at ASTM Symposium on Crosslinked and Thermally Treated UHMWPE for Joint Replacement,November 2002.

10. Atwood SA, Currier JH, Mayor MB, Collier JP, Van Citters DW, Kennedy FE. Clinical wear measurement on low contact stress rotating platform knee bearings. J Arthroplasty. 2008;23(3):431-40.

11. Maniar R, Gupta H, Singh A, Johorey AC, Singhi T. Five- to eight-year results of a prospective study in 118 arthroplasties using posterior-stabilized rotating-platform knee implants. J Arthroplasty. 2011;26(4):543-8.

12. Ranawat CS. Designing implants to meet evolving patient expectations. Orthopaedics Today, 2010 Aug; 3.

13. Hedley AA, Ogden CL, Johnson CL, Carroll MD, Curin LR, Flegal KM. Prevalence of overweight and obesity among US children, adolescents, and adults, 1999-2002. JAMA. 2004 Jun;291(23):2847-50.

14. Kurtz, S. M., UHMWPE Biomaterials Handbook, 2nd ed.,page 73-74.

15. Muratoglu, O.K., B.R. Burrough, A. Malhi, S. Christensen, K. Wannomac, E. Oral, S. Spiegelberg and W.H. Harris. “Two Second Generation Cross-linked UHMWPES Show Improves Mechanical Properties and Fatigue Strength.” Poster No. 1661, Presented at the 51st Annual Meeting of the Orthopaedic Research Society, Washington, DC.

16. Malhi, A.S., K.K. Wannomae, S.D. Christensen, C. Godleski and O.K. Muratoglu.“ A Novel Processing Methodology for Improvement of Mechanical Properties in Highly Cross-linked Polyethylene.” Poster No. 0657, 52nd Annual Meeting of the Orthopaedic Research Society, March 19-22, Chicago, IL.

17. Morrison, M.L., Jani, S. “Evaluation of sequentially crosslinked ultra-high molecular weight polyethylene.” Journal of Biomedical Materials Research Part B: Applied Biomaterials Volume 90B, Issue 1, July 2009, Pages: 87–100.

18. Data on File at Depuy orthopaedics, Inc. WR080219.

19. Callaghan JJ, Wells CW, Liu SS, Goetz DD, Johnston RC. Cemented rotating platform total knee replacement: a concise follow-up, at a minimum of twenty years, of a previous report. J Bone Joint Surg Am. 2010;92:1635-1639.

20. Data on File at Depuy orthopaedics, Inc. WR110006.

21. Data on File at Depuy orthopaedics, Inc. WR110009.

22. Data on File at Depuy orthopaedics, Inc. WR110010.

23. Data on File at Depuy orthopaedics, Inc. WR110024.

24. United States Food and Drug Administration web site. Premarket approval database: Http://www. Accessdata/fda.gov/scripts/cdrh/cfdocs/cfPMA.cfm (accessed August 4, 2011).

25. Meftah M, Ranawat AS, Ranawat CS. Safety and efficacy of a rotating-platform, high-flexion knee design three- to five-year follow-up. J Arthroplasty. 2011; doi:10.1016/j.arth.2011.04.013.

For more information, contact your DePuy Orthopaedics representative today.

©DePuy Orthopaedics, Inc. 2012.All rights reserved.

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www.depuy.com

* Program accredited and certified by Pfiedler Enterprises, an authorized provider for the International Association for Continuing Education and Training (IACET).