invention is highly hydrolyzed crystalline poly vinyl alcohol pva pva cryogels may be prepared from commercially available pva powders by any of the methods known to the art preferably they are prepared by the method disclosed in u s pat nos 5 981 826 and 6 231 605 the teachings of which are incorporated herein by reference typically 25 to 50 by weight pva powder is mixed with a solvent such as water the mixture is then heated at a temperature of about 100 degrees celsius c until a viscous solution is formed the solution is then poured or injected into a metal or plastic mold such as shown in fig1 the device is allowed to cool to below u2212 10 degree c preferably to about u2212 20 degree c the device is frozen and thawed several times until a solid device is formed with the desired mechanical properties the device can them be partially or completely dehydrated for implantation the resulting prosthesis has a mechanical elasticity of 2 mpa and has a mechanical ultimate strength in tension and compression of at least 1 mpa preferably about 10 mpa the prosthesis made by this method allows for 10 degrees of rotation between the top and bottom faces with torsions greater than 1 n m without failing the device thus made does not fracture when subjected to the same load constraints as the natural intervertebral disc the device is a thus made of a single solid elastomeric material that is biocompatible by cytotoxicity.