In this SBIR Phase II project, the mechanical and fatigue-related properties of ultrahigh molecular weight polyethylene (UHMWPE) joint implant materials will be improved by creating a composite material with carbon reinforcements. UHMWPE has long been widely used as wear surfaces in joint implants, and further improvements to its wear resistance have been obtained by cross-linking the polyethylene chains. However, the cross-linking process also degrades some mechanical properties, including toughness, fatigue and yield strengths. Incorporating carbon reinforcements into UHMWPE through the manner described will improve the strength, crack propagation resistance and creep resistance of UHMWPE without compromising its low wear rate. The carbon reinforcements will impart unmatched dimensional stability and toughness to the UHMWPE matrix. Moreover, as the wear surface remains (primarily) UHMWPE, the outstanding wear resistance of UHMWPE will be maintained, if not improved through the mechanical enhancements. Several of these hypotheses were validated during Phase I by preparing composite materials under various formation conditions, and then assessing their mechanical and tribological properties. Should the new UHMWPE materials perform according as expected, the benefits would include longer-lasting implants that are less prone to mechanically-induced failure. The composite materials would therefore require fewer revision procedures and maintain functionality longer, a critical need as life expectancy increases are causing people to outlive their implants.
Joint implants are an effective treatment for those with rheumatoid arthritis, osteoarthritis, osteonecrosis, and other severe destructive injuries; within the U.S. alone, roughly 900,000 joint replacements are performed each year. As life expectancy increases, patients more frequently outlive the circa 15 year lifetime of their implant. This projet will introduce a new material from which prosthetics with longer lifetimes can be fabricated.