Studies have shown that Polyvinyl alcohol (PVA) can be made into biocompatible, lubricous, and tough hydrogels that can survive the loading environment in joints, making them ideal biomaterials for cartilage replacement therapy. Due to the nature of skeletal loading, creep is one of the more physiologically relevant means to quantify mechanical properties of artificial cartilage constructs. Creep is investigated either in a confined setting, as is the case with a hydrogel osteochondral plug that is replacing a focal cartilage defect, or in an unconfined setting, as with an interpostional device that is replacing a damaged meniscus. Under a 3-parameter biphasic viscoelastic Kelvin-Voight model, creep behavior can be described in terms of the immediate elastic response of the cartilage matrix, and the time-dependent viscoelastic response due to fluid pressurization within the cartilage. The theoretical elastic and viscoelastic values of various PVA hydrogels and swine cartilage under confined and unconfined conditions were compared to experimental data.
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