Product Overview
Renovis E-MAX Highly Crosslinked Polyethylene with Vitamin E for hip bearings builds on the successes of first generation XLPE by incorporating two innovative technologies: Vitamin E and mechanical annealing.
• Vitamin E is added to inhibit in vivo oxidation, which can cause degradation of the polymer material.
• The mechanical anneal—as opposed to melting—helps maintain mechanical properties.
Thus, Renovis E-MAX Highly Crosslinked Polyethylene provides excellent wear properties, like first generation XLPE, plus oxidative stability and improved mechanical properties.
Renovis E-MAX†underwent extensive laboratory evaluations, including mechanical, material characterization, and wear simulator testing. Performance was compared to both conventional (3.5 Mrad sterilized) and 10 Mrad highly crosslinked polyethylene (XLPE).
Excellent Wear Properties
The crosslinking density of Renovis E-MAX for hip was fine-tuned to be about the same as 10 Mrad XLPE
and has demonstrated similarly low wear in hip simulator testing: 89% less wear than conventional polyethylene.
Improved Mechanical Properties
Compared 10 Mrad melt-annealed XLPE, Renovis E-MAX for hip demonstrated significant tensile strength and impact toughness improvements.
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.
• Renovis E-MAX had an overall decreased crack propagation rate compared to melt-annealed XLPE.
Oxidative Stability under Harsh Testing Conditions
The mechanical anneal process eliminates free radicals to near the detection threshold of the testing equipment (electron spin resonance testing). After accelerated aging, Renovis E-MAX showed minimal change in free radical content, indicating that the Vitamin E stabilized the free radicals, preventing them from reacting with oxygen. To further test oxidation resistance 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 Renovis E-MAX.
Evenly Distributed Vitamin E
Chemical analysis demonstrated that the Vitamin E profile is constant throughout Renovis E-MAX, indicating that it is evenly distributed throughout the material. This is because vitamin E is blended with UHMWPE powder before creating the UHMWPE barstock. In contrast, materials into which the vitamin E is diffused after UHMWPE consolidation (e.g. Biomet E1), result in more concentrated levels of vitamin E near the surface.
Stability with large diameter heads
Larger diameter heads have been shown to lead to improved range of motion and lower dislocation rates. Renovis E-MAX acetabular inserts are available for use with heads up to 40 mm in diameter.
(http://www.renovis-surgical.com/)
