The effect of dehydration history on associating hydrogels for nucleus pulposus replacement

A replacement of the nucleus pulposus with a biocompatible, hydrogel blend of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) has been proposed. These gels are stable in physiological fluid due to physical crosslinks consisting of intramolecular hydrogen bonds within PVA crystallites and intermolecular hydrogen bonds between PVA and PVP. It has been suggested that the swelling properties of these polymer blends might allow a nucleus replacement surgery to be performed -arthroscopically through a small posteriorly placed cannula. The dehydration of an implant would allow for insertion of the nucleus substitute. Subsequent rehydration once the substitute is positioned within the disc would follow. Here we examine the effects of the extent of dehydration on the properties of the rehydrated hydrogel. It is concluded that the properties of PVA/PVP hydrogel blends are strongly dependent on the material´s dehydration history. Partial dehydration/rehydration is a viable process for allowing nucleus pulposus replacement surgery to be performed arthroscopically