The present invention is a prosthetic for replacement of at least a part
of the nucleus of a intravertebral disc. The prosthetic device is
composed of at least two essentially parallel soft layers of an
elastically deformable hydrogel and at least one rigid layer, the rigid
layer having less compressibility than the soft layers, being adjacent to
the soft layers, parallel to them, and firmly attached to them. In some
embodiments, the soft layers have the same thickness and composition.
Typically, the prosthesis has more than one rigid layer and these rigid
layers have the same thickness and composition. The number of soft layers
is usually one more than the number of rigid layers, with, e.g., at least
three soft layers. The invention also includes a method of prosthesis
production, which involves prefabricating soft and rigid layers; stacking
at least two prefabricated soft and at least one prefabricated rigid
layer in a parallel fashion into their final form, and, permitting the
layers to firmly connect to one another by mutual interaction. In this
method, at least one type of the layers is prefabricated in the
dehydrated state, which is done by dehydrating stretched foil in an
apparatus preventing its contraction and thereby decreasing its area.
There is at least partial dehydration of the prosthesis under pressure
applied in a direction tangent to the planes of the layers. In preferred
embodiments, while in the state of almost full dehydration, is sterilized
using ionizing radiation or a gaseous chemical agent, after which it is
partially rehydrated within the sterile wrapper using water vapor.