Banana cage

1. An intervertebral fusion device comprising:

a) an anterior wall and a posterior wall defining a width therebetween, wherein the anterior wall has a convex shape and the posterior wall has a concave shape to define a banana shape adapted for non-linear insertion from a posterior side of a spine,

b) first and second end walls between the anterior and posterior walls and defining a length therebetween, and

c) an upper bearing surface and a lower bearing surface, each having a midline having a recessed ridge running in the anterior-posterior direction and bisecting a right and left side of the device,

c) a internal planar wall extending transversely from the anterior wall to the posterior wall, and from the upper bearing surface to the lower bearing surface, to define first and second graft chambers,

wherein the anterior wall has a middle portion, lateral end portions, each having a maximum height, and the maximum height of the middle portion is greater than the maximum height of the lateral end portions,

wherein the width of the device is less than the length of the device, and

wherein the length is less than ½ a width of a disc space.

2. The device of claim 1 wherein the length is less than one-third of the width of the disc space.

3. The device of claim 1 wherein a posterior portion of each bearing surface is adapted to bear against an anterior one-third of the disc space.

4. The device of claim 1 being an integral unit.

5. The device of claim 1 wherein the posterior wall has a concave horizontal cross section.

6. The device of claim 1 wherein the anterior wall has a maximum height, the posterior wall has a maximum height, and wherein the maximum height of the anterior wall is greater than the maximum height of the posterior wall.

7. The device of claim 1 wherein the first end wall is a leading end wall adapted for insertion into the disc space, and the leading end wall is tapered.

8. An intervertebral fusion device adapted for non-linear insertion into a disc space comprising:

a) an anterior wall having a convex shape,

b) a posterior wall,

c) first and second end walls between the anterior and posterior walls

d) an upper bearing surface between the anterior and posterior walls, and having an anterior portion and a posterior portion, and

e) a lower bearing surface between the anterior and posterior walls,

f) first and second transverse struts extending from the anterior portion of the upper bearing surface to the posterior portion of the upper bearing surface,

wherein the anterior wall has a middle portion having a maximum height and lateral end portions each having a maximum height, and the maximum height of the middle portion is greater than the maximum height of the lateral end portions to provide a dome shape,

wherein the upper and lower bearing surfaces each have a midline having a recessed ridge running in the anterior-posterior direction and bisecting a right and left side of the device.

9. The device of claim 8 wherein the posterior portion of each bearing surface is adapted to bear against an anterior one-third of the disc space.

10. The device of claim 8 being an integral unit.

11. The device of claim 8 wherein the posterior wall has a concave horizontal cross section.

12. The device of claim 8 adapted for non-linear insertion from a posterior side of the spine.

13. The device of claim 8 wherein the anterior wall has a maximum height, the posterior wall has a maximum height, and wherein the maximum height of the anterior wall is greater than the maximum height of the posterior wall.

14. The device of claim 8 wherein the first end wall is a leading end wall adapted for insertion into the disc space, and the leading end wall is tapered.

15. The device of claim 8 wherein the upper bearing surface comprises at least one upper opening comprising between 30 areal % and 60 areal % of the upper surface.

16. The device of claim 8 wherein the anterior wall has a middle portion, lateral end portions, each having a maximum height, and the maximum height of the middle portion is greater than the maximum height of the lateral end portions.

17. An intervertebral fusion device comprising:

a) an anterior wall having a leading end and a trailing end

b) a posterior wall having a leading end and a trailing end,

c) a leading end wall connecting the leading ends of the anterior and posterior walls and having a leading insertion hole,

d) a trailing end wall connecting the anterior and posterior walls and having a trailing insertion hole,

e) an upper bearing surface between the anterior and posterior walls, and having an anterior portion and a posterior portion, and

f) a lower bearing surface between the anterior and posterior walls,

wherein the anterior and posterior walls define a centerline therebetween, and

wherein the leading and trailing insertion holes are disposed asymmetrically about the centerline

wherein the upper and lower bearing surfaces each have a midline having a recessed ridge running in the anterior-posterior direction and bisecting a right and left side of the device.

18. The device of claim 17 being an integral unit.

19. The device of claim 17 wherein the posterior wall has a concave horizontal cross section.

20. The device of claim 17 adapted for non-linear insertion from a posterior side of a spine.

21. The device of claim 17 wherein the anterior wall has a maximum height, the posterior wall has a maximum height, and wherein the maximum height of the anterior wall is greater than the maximum height of the posterior wall.

22. The device of claim 17 wherein the leading end wall is tapered.

23. The device of claim 17 wherein the anterior wall has a middle portion, lateral end portions, each having a maximum height, and the maximum height of the middle portion is greater than the maximum height of the lateral end portions.

24. An intervertebral fusion device comprising:

a) an anterior wall having a horizontal cross section having a convex shape and a recessed portion,

b) a posterior wall,

c) first and second end walls between the anterior and posterior walls,

d) an upper bearing surface between the anterior and posterior walls having at least one upper opening therethrough adapted to promote bony fusion, wherein the at least one upper opening comprises between 30 areal % and 60 areal % of the upper surface, and

e) a lower bearing surface between the anterior and posterior walls having at least one lower opening therethrough adapted to promote bony fusion,

wherein the anterior wall has a convex shape and the posterior wall has a concave shape to define a banana shape adapted for non-linear insertion from a posterior side of a spine, and

wherein the upper and lower bearing surfaces each have a midline having a recessed ridge running in the anterior-posterior direction and bisecting a right and left side of the device.

25. The device of claim 24 wherein a posterior portion of each bearing surface is adapted to bear against an anterior one-third of a disc space.

26. The device of claim 24 being an integral unit.

27. The device of claim 24 wherein the posterior wall has a concave horizontal cross section.

28. The device of claim 24 adapted for non-linear insertion from a posterior side of a spine.

29. The device of claim 24 wherein the anterior wall has a maximum height, the posterior wall has a maximum height, and wherein the maximum height of the anterior wall is greater than the maximum height of the posterior wall.

30. The device of claim 24 wherein the first end wall is a leading end wall adapted for insertion into a disc space, and the leading end wall is tapered.

31. The device of claim 24 wherein the anterior wall has a middle portion, lateral end portions, each having a maximum height, and the maximum height of the middle portion is greater than the maximum height of the lateral end portions.

32. An intervertebral fusion device comprising:

a) an anterior wall having a convex shape, and a maximum height,

b) a posterior wall having a concave shape,

c) first and second end walls connecting the anterior and posterior walls

d) an upper bearing surface between the anterior and posterior walls and having a middle portion having a recess, lateral end portions, and at least one upper opening therethrough adapted to promote bony fusion, wherein the at least one upper opening comprises between 30 areal % and 60 areal % of the upper surface, and

e) a lower bearing surface having an anterior portion below the anterior wall, a posterior portion below the posterior wall, and at least one lower opening therethrough adapted to promote bony fusion,

wherein the anterior wall has a convex shape and the posterior wall has a concave shape to define a banana shape adapted for non-linear insertion from a posterior side of a spine, and

wherein the upper and lower bearing surfaces each have a midline having a recessed ridge running in the anterior-posterior direction and bisecting a right and left side of the device.

33. The device of claim 32 wherein a posterior portion of each bearing surface is adapted to bear against an anterior one-third of a disc space.

34. The device of claim 32 being an integral unit.

35. The device of claim 32 wherein the posterior wall has a concave horizontal cross section.

36. The device of claim 32 adapted for non-linear insertion from a posterior side of a spine.

37. The device of claim 32 wherein the anterior wall has a maximum height, the posterior wall has a maximum height, and wherein the maximum height of the anterior wall is greater than the maximum height of the posterior wall.

38. The device of claim 32 wherein the first end wall is a leading end wall adapted for insertion into a disc space, and the leading end wall is tapered.

39. The device of claim 32 wherein the at least one upper opening comprises between 30 areal % and 60 areal % of the upper surface.

40. The device of claim 32 wherein the anterior wall has a middle portion, lateral end portions, each having a maximum height, and the maximum height of the middle portion is greater than the maximum height of the lateral end portions.