REPLACEMENT OR SUPPLEMENTATION OF A NUCLEUS PULPOSUS USING A HYDROGEL

1 . A physiologically fully hydrated solid hydrogel intervertebral body comprising:

a polyvinyl alcohol copolymer,

wherein the solid hydrogel intervertebral body exhibits an osmotic pressure of from 0.1 to 0.3 megapascals prior to insertion into a patient, and wherein the solid hydrogel intervertebral body has a ratio of length to principal transverse dimension not less than about 5:1.

2 . The solid hydrogel intervertebral body of claim 1 , wherein the body has a ratio of length to principal transverse dimension of about 350:1.

3 . The solid hydrogel intervertebral body of claim 1 , wherein the body has an elastic modulus between about 0.05 megapascals and about 4.0 megapascals.

4 . The solid hydrogel intervertebral body of claim 1 , wherein the body has a generally cylindrical shape.

5 . The solid hydrogel intervertebral body of claim 1 , wherein the body has at least one portion with a cross-sectional area greater than a principal cross-sectional area of said body.

5 . The solid hydrogel intervertebral body of claim 1 , wherein the body has at least one end provided with a terminal portion of transverse cross-sectional area greater than a principal cross-sectional area of said body.

6 . The solid hydrogel intervertebral body of claim 1 , wherein the body has at least one end provided with a flared terminal portion of transverse cross-sectional area greater than a principal cross-sectional area of said body.

7 . The solid hydrogel intervertebral body of claim 1 , wherein the body has at least one end provided with a generally spherical terminal portion of transverse cross-sectional area greater than a principal cross-sectional area of said body.

8 . The solid hydrogel intervertebral body of claim 1 , wherein the body has at least one portion between its ends with a transverse cross-sectional area greater than a principal cross-sectional area of said body.

9 . The solid hydrogel intervertebral body of claim 1 , wherein the body further comprises poly(vinylpyrrolidone).

10 . The solid hydrogel intervertebral body of claim 1 , wherein the body comprises a radiopaque material.

11 . The solid hydrogel intervertebral body of claim 10 , wherein the radiopaque material is barium sulfate.

12 . The solid hydrogel intervertebral body of claim 1 , wherein the body has a ratio of length to principal transverse dimension of about 40:1.

13 . The solid hydrogel intervertebral body of claim 1 , wherein the body has a ratio of length to principal transverse dimension of about 100:1.

14 . The solid hydrogel intervertebral body of claim 1 , wherein the body has a ratio of length to principal transverse dimension of about 200:1.

15 . The solid hydrogel intervertebral body of claim 1 , wherein the body has a generally cylindrical shape.

16 . A physiologically fully hydrated solid hydrogel intervertebral body comprising a polyvinyl alcohol copolymer, wherein the fully hydrated solid hydrogel intervertebral body is made by a process comprising the step of:

contacting a hydrogel body comprising a polyvinyl alcohol copolymer with an aqueous isotonic solution for a period of time sufficient to achieve physiological full hydration,

wherein the solid hydrogel intervertebral body exhibits an osmotic pressure of from 0.1 to 0.3 megapascals prior to insertion into a patient, and wherein the solid hydrogel intervertebral body has a ratio of length to principal transverse dimension not less than about 5:1.

17 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the contacting step comprises immersing the hydrogel body in the aqueous isotonic solution.

18 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the aqueous isotonic solution has an osmotic pressure of about 0.2 megapascals.

19 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the aqueous isotonic solution further comprises a polymer.

20 . The fully hydrated solid hydrogel intervertebral body of claim 19 , wherein the polymer is selected from the group consisting of poly(ethylene glycol), dextran, and mixtures thereof.

21 . The fully hydrated solid hydrogel intervertebral body of claim 20 , wherein the polymer is dextran.

22 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body has a ratio of length to principal transverse dimension of about 350:1.

23 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body has an elastic modulus between about 0.05 megapascals and about 4.0 megapascals.

24 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body has a generally cylindrical shape.

25 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body further comprises poly(vinylpyrrolidone).

26 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body comprises a radiopaque material.

27 . The fully hydrated solid hydrogel intervertebral body of claim 26 , wherein the radiopaque material is barium sulfate.

28 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body has a ratio of length to principal transverse dimension of about 40:1.

29 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body has a ratio of length to principal transverse dimension of about 100:1.

30 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body has a ratio of length to principal transverse dimension of about 200:1.

31 . The fully hydrated solid hydrogel intervertebral body of claim 16 , wherein the body is isotonic with respect to surrounding physiological fluid prior to implantation within the physiological fluid.