Patent ID: 7591853

Claim:
A modular disc prosthesis that is adapted to be implanted in an evacuated disc nucleus space, the prosthesis comprising: a first modular segment having a width and having a first rail extending at least partially along one side of the width; a second modular segment having a width and slidably connected to the first rail on one side of the width and having a second rail extending at least partially along another side of the width; a third modular segment having a width and slidably connected to the second rail on one side of the width; wherein the prosthesis has an expanded position in which the modular segments are extended along the first and second rails and positioned in a generally end to end configuration spaced apart by the rails prior to implantation and an implanted position in which the modular segments are positioned in a generally side by side configuration; wherein each modular segment comprises an inner portion including structure that mates with one of the rails and an outer portion substantially surrounding the inner portion except for the side having one of the rails and the side having structure that mates with one of the rails; wherein the inner portion of each modular segment and the outer portion of each modular segment are made of polymers of different durometers, the inner portion of each modular segment having a compressive modulus that is greater than a compressive modulus of the outer portion of each modular segment, the compressive modulus of the outer portion being in the range from about 6-20 MPa; and wherein the inner portion of each modular segment has a compressive modulus in the range from about 70 MPa to about 100 MPa.