Patent ID: 7578846

Claim:
A selectively expandable composite intervertebral disc prosthesis, comprising: an outer shell comprised of a non-hydrogel polymer material; and at least one core positioned within the outer shell, the core comprised of a hydrophilic polymer; where the at least one core expands upon hydration, thereby deforming the outer shell and selectively expanding the intervertebral disc prosthesis; and wherein the intervertebral disc prosthesis is selectively expanded due to one or more of the group consisting of: (a) the shape of the core; (b) the position of the core within the outer shell; (c) the thickness of the outer shell; (d) the concentration and/or composition of the non-hydrogel polymer material in the outer shell; (e) the concentration and/or composition of the hydrophilic polymer in the core; (f) use and amount of a reinforcing element in the outer shell; and (g) combinations thereof.