Arthroplasty device

1 . A prosthetic device for placement at least partially between a superior vertebra and an inferior vertebra, comprising:

a single piece of material having an upper portion adapted to engage the superior vertebra; a lower portion adapted to engage the inferior vertebra; and a first motion segment having a first shape to allow relative movement between the superior vertebra and the inferior vertebra.

2 . The prosthetic device of claim 1 , wherein the first motion segment is disposed at a posterior portion of the single piece of material.

3 . The prosthetic device of claim 1 , wherein the first shape of the first motion segment comprises a single curve.

4 . The prosthetic device of claim 1 , wherein the first shape of the first motion segment comprises a plurality of curves.

5 . The prosthetic device of claim 1 , wherein the first shape of the first motion segment includes an opening.

6 . The prosthetic device of claim 1 , wherein the first shape of the first motion segment is non-symmetrical.

7 . The prosthetic device of claim 1 , further including a second motion segment having a second shape to allow movement between the upper portion and the lower portion.

8 . The prosthetic device of claim 7 , wherein the first motion segment and the second motion segment function together.

9 . The prosthetic device of claim 1 , wherein the first motion segment is configured to create an articulation point in a posterior portion of a space between the two vertebrae.

10 . The prosthetic device of claim 1 , further including a stop portion adapted to engage a vertebral body of either the superior or inferior vertebra.

11 . The prosthetic device of claim 10 , wherein the stop portion is adapted to be secured to either the superior or inferior vertebra.

12 . The prosthetic device of claim 11 , the stop portion is adapted to be secured by one or more screws.

13 . The prosthetic device of claim 1 , wherein the upper portion includes a superior surface configured to enhance engagement with the superior vertebra.

14 . The prosthetic device of claim 13 , wherein the lower portion includes an inferior surface configured to enhance engagement with the inferior vertebra.

15 . The prosthetic device of claim 14 , wherein at least one of either the superior surface or the inferior surface includes a keel.

16 . The prosthetic device of claim 14 , wherein at least one of the superior surface and the inferior surface is treated with an osteoconductive material.

17 . The prosthetic device of claim 14 , wherein at least one of the superior surface and the inferior surface is treated with an osteoinductive material.

18 . The prosthetic device of claim 1 , wherein the first motion segment allows flexion motion between the superior vertebra and the inferior vertebra.

19 . The prosthetic device of claim 1 , wherein the first motion segment allows extension motion between the superior vertebra and the inferior vertebra.

20 . The prosthetic device of claim 1 , wherein the first motion segment allows axial rotation between the superior vertebra and the inferior vertebra.

21 . The prosthetic device of claim 1 , wherein the first motion segment allows lateral bending motion between the superior vertebra and the inferior vertebra.

22 . The prosthetic device of claim 1 , wherein the first motion segment is further adapted to provide load bearing support.

23 . A prosthetic device for placement at least partially between a superior vertebra and an inferior vertebra, comprising:

a first portion having a first length that extends along a substantial portion of an endplate of the superior vertebra;

a second portion having a second length that extends along a substantial portion of an endplate of the inferior vertebra;

a motion portion connected between distal ends of the first and second portions, the motion portion being configured to allow relative movement between the first and second portions.

24 . The prosthetic device of claim 23 , wherein the first, second and motion portions are a monolithic structure.