Benefits of Renovis E-MAX™

Renovis E-MAX is highly crosslinked to reduce wear and incorporates two new technologies—mechanical-anneal and Vitamin E—which address known problems with melt-annealed XLPE. Laboratory tests have verified the superior oxidative stability and improved mechanical properties of Renovis E-MAX.

Wear Resistance

The radiation doses for Renovis E-MAX hip and knee liners were fine-tuned to achieve crosslinking densities comparable to first-generation XLPE’s, which have demonstrated reduced wear rates both in simulators and in clinical use. [1-10] Simulator studies comparing Renovis E-MAX to conventional polyethylene found:

  • 89% reduction in hip wear [11]
  • 74% reduction in knee wear [11]

Mechanical Properties

Renovis E-MAX is mechanically annealed, eliminating* free radicals without the sacrifice in mechanical properties associated with melt-annealing.[12,13] Laboratory tests have verified the significantly improved strength and toughness of Renovis E-MAX compared to melt-annealed XLPE.[14] (Figure 1)

Figure 1: Tensile and IZOD impact test results for Renovis E-MAX Highly Crosslinked Polyethylene (Hip). Percentages indicate relative improvement over 10 Mrad melt-annealed XLPE [14].

(Click image to enlarge)

 

Fatigue crack propagation analysis comparing Renovis E-MAX to melt-annealed XLPE demonstrated:

  • Renovis E-MAX had a significantly higher stress intensity factor for crack initiation, meaning it is more resistant to crack initiation than melt-annealed XLPE. [15]
  • Renovis E-MAX had an overall decreased crack propagation rate compared to melt-annealed XLPE. [15]

Oxidative Stability

To address the unexpected in vivo oxidation observed in melt-annealed XLPE, Renovis E-MAX contains 0.1%-wt vitamin E. Vitamin E is a natural antioxidant that has a stabilizing effect against the oxidation of PE.[16]

The oxidative stability of Renovis E-MAX was tested under extreme conditions—samples were exhaustively extracted to remove as much Vitamin E as possible and then subjected to accelerated aging. Even under extreme conditions, no positive oxidation index was measured in E-MAX materials (hip or knee).[15]  Furthermore, mechanical testing after aging showed no decrease in tensile or impact strength. [14] (Figure 2)

Figure 2: Artificially-Aged Renovis E-MAX Highly Crosslinked Polyethylene (Hip). Strength maintained over 28 days of laboratory aging. [14]

(Click image to enlarge)

Note that adding vitamin E via the diffusion method (as with Biomet E1™†) typically results in a non-homogeneous, gradient distribution.[17] However, in Renovis E-MAX, the vitamin E powder is blended with 1020 UHMWPE resin powder, so the vitamin E is distributed evenly throughout the material.[15]


†E1 is a trademark of Biomet, Inc. Warsaw, Indiana.
*With both melt annealing and mechanical annealing, free radicals are eliminated to a level at or near the detection threshold of ESR measurement equipment.

  1. Kurtz S, Medel FJ, MacDonald D, Rimnac CM. In vivo oxidation, oxidation potential, and clinical performance of highly crosslinked UHMWPEs implanted for up to 8 years. 4th International Meeting UHMWPE for arthroplasty: From Powder to Debris 2009; Torino, Italy.
  2. Digas G, Karrholm J, Thanner J, Herberts P. 5-year experience of highly cross-linked polyethylene in cemented and uncemented sockets: Two randomized studies using radiostereometric analysis. Acta Orthop 2007; 78(6): 746-54.
  3. D’Antonio JA, Manley MT, Capello WN, et al. Five-year experience with Crossfire highly cross-linked polyethylene. Clin Orthop Relat Res 2005; 441: 143-50.
  4. Engh CA, Stepniewski AS, Ginn SD, et al. A randomized prospective evaluation of outcomes after total hip Arthroplasty using crosslinked marathon and non-cross-linked Enduron polyethylene liners. J Arthroplasty 2006; 21(6): 17-25.
  5. Olyslaegers C, Defoort K, Simon JP, Vandenberghe L. Wear in conventional and highly cross-linked polyethylene cups: a 5-year
    follow-up study. J Arthroplasty 2008; 23(4): 489-94.
  6. Garcia-Rey E, Garcia-Cimbrelo E, Cruz-Pardos A, Ortega-Chamarro J. New polyethylenes in total hip replacement: a prospective, comparative clinical study of two types of liner. J Bone Joint Surg Br 2008; 90(2): 149-53.
  7. Geerdink CH, Grimm B, Vencken W, Heyligers IC, Tonino AJ. Cross-linked compared with historical polyethylene in THA: An 8-year clinical study. Clin Orthop Relat Res 2009; 467(4): 979-84.
  8. Glyn-Jones S, Isaac S, Hauptfleisch J, McLardy-Smith P, Murray DW, Gill HS. Does highly cross-linked polyethylene wear less than conventional polyethylene in total hip arthroplasty? A doubleblind, randomized, and controlled trial using roentgen stereophotogrammetric analysis. J Arthroplasty 2008; 23(3): 337-43.
  9. Kurtz SM, Medel FJ, MacDonald DW, Parvizi J, Kraay MJ, Rimnac CM. Reasons for revision of first-generation highly cross-linked polyethylenes. J Arthroplasty. 2010 Sep;25(6 Suppl):67-74.
  10. Kurtz SM. Chapter 8 The clinical performance of UHMWPE in knee replacements. In UHMWPE Biomaterials Handbook Second Edition (ed. Kurtz SM). Elsevier: Amsterdam, 2009.
  11. University of Nebraska Medical Center. Characterization of CIMA and E-CIMA UHMWPE as a bearing against CoCr femoral hip components: A hip simulation study. Test report dated July 15, 2011. and An in-vitro wear durability study of the Renovis A200 CR Knee System: two sizes and two bearing materials.Test report dated November 11, 2011. On file with Renovis Surgical.
  12. Wannomae KK, Micheli BR, Lozynsky AJ, Muratoglu OK. A New Method of Stabilizing Irradiated UHMWPE Using Vitamin E and Mechanical Annealing. 11th Congress EFFORT. Madrid, Spain. June 2010.
  13. Bhattacharyya S, Matrisciano L, Spiegelberg S, Harris W, Muratoglu O. Mechanical elimination of residual free radicals in an irradiated UHMWPE rod: advantages over melting. 50th annual meeting of the orthopaedic research society. 2004:1474.
  14. Materials Characterization testing. Test report TP0322. On file with Renovis Surgical.
  15. Cambridge Polymer Group. Analysis of CIMA and E-CIMA Material. Test report dated July 15, 2011. On file with Renovis Surgical.
  16. Costa L, Bracco P. Chapter 21 Mechanisms of crosslinking, oxidative degradation, and stabilization of UHMWPE. In UHMWPE Biomaterials Handbook Second Edition (ed. Kurtz SM). Elsevier: Amsterdam, 2009.
  17. Gomez-Barrena E, Medel F, Puetrolas JA. Polyethylene oxidation in total hip arthroplasty: evolution and new advances. The Open Orthopedics Journal 2009; 3:115-120.

† This product is not currently cleared by the FDA for clinical use in the United States.