Tensile Fatigue Characterization of High Strength Hydrogels for Soft Tissue Applications

Synthetic cartilage implants have the potential to deeply transform the treatment of articular cartilage degeneration as well as the progression of osteoarthritis in load-bearing applications of various joints in the human body. To reduce patient morbidity and enhance range of motion, surgeons and material scientists alike are looking to synthetic alternatives re-establish articular cartilage function without introducing higher cost and health burdens. These implants are rigorously tested for their compressive and wear properties over longer timeframes, with the first instance of approved human use coming in the 1st metatarsophalangeal (MTP) joint with poly(vinyl alcohol) (PVA) being the predominant polymer in composition. Despite their promise of dissipating stress and providing smooth joint movement, these synthetic cartilage implants are not well-studied for their tensile fatigue properties which are extremely critical to in vivo performance and implant survival. As a synthetic substitute to match the properties of cartilage in human beings, hydrogels are extensively researched due to their potential biocompatibility. This research describes work dedicated to the advanced mechanical study of synthetic hydrogel systems for cartilage-based applications. The materials of interest are designed to have enhanced monotonic tensile properties for supplementary investigation via tensile fatigue testing. Superior mechanical behavior was achieved through the use of bio-friendly additives, freezing-thawing cyclic processing, and fiber reinforcement. Lastly, the long-term failure mechanisms through flaw development for these synthetic hydrogel systems and biological tissue will be explored.