This Phase I SBIR project is designed to develop new zwitterionic graft methodology for orthopedic surfaces with enhanced durability. As Americans live longer and more active lives, total joint replacement is becoming more common. Current orthopedic joints have average lifespans of approximately 20 years. By that point wear on the joint causes particulate formation, with subsequent pain and inflammation, requiring eventual revision. Revision surgeries to replace joint implants are more difficult, painful, and expensive than initial joint replacement. The work proposed extends academic research on photochemically grafting biomimetic phosphoryl choline (PC) monomers to ultrahigh molecular weight polyethylene (UHWMPE). Grafting PC monomers creates 100-200 nm polymer coatings which reduce wear significantly while also decreasing pro-inflammatory cytokine release and macrophage recruitment in vivo. However, grafting process times are unwieldy for high volume manufacturing. This proposal focuses on using our proprietary photocrosslinker TriLite(R) to form an intermediate layer which bonds to the polyethylene surface, crosslinks the surface, and initiates graft polymerization. The TriLite(R) layer will not desorb from the surface under the graft conditions, leading to a more uniform and faster graft. The novelty of the proposal is the use of a new photocrosslinker to speed graft time, increase crosslinking, and improve uniformity, as well as use of several different zwitterionic monomers and copolymer coating methodologies. The resulting coating will be optimized for lubricity, uniformity, thickness and wear durability. The graft processes developed in this work will foster longer lasting, more biocompatible implant materials for many Americans.
Project Narrative Approximately 600,000 Americans receive knee and hip implants annually in the US, over 1 million worldwide. These implants have a lifetime of approximately 20 years, less for more active recipients. This proposal is designed to increase the product lifetime of orthopedic implants. This market is already large, over $5.4 billion in 2006, and more than a fivefold increase in the number of total joint replacements is expected in the next 20 years. Improved orthopedic materials with better wear characteristics would not only contribute to the US economy, but also improve the lives of many Americans by eliminating the need for painful revision surgeries in their later years.