Lordotic interbody spinal fusion implants

• US 5,609,635 A
• Filed: 06/07/1995
• Issued: 03/11/1997
• Est. Priority Date: 06/28/1988
• Status: Expired due to Term

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: Gary K. Michelson
• Inventors: Michelson, Gary K.
• Primary Examiner(s): SHAY, RANDY CITRIN
• Application Number:
  US08/482,146
• Time in Patent Office: 643 Days
• Field of Search: 623/17, 606/60, 606/61
• US Class Current: 623/17.16
• CPC Class Codes: A61F 2/30744 End caps, e.g. for closing an endoprosthetic cavity
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/44 for the spine, e.g. vertebrae, spinal discs
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2/447 substantially parallelepipedal, e.g. having a rectangular or trapezoidal cross-section
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/30143 hexagonal
• CPC Class Codes: A61F 2002/30153 rectangular
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/30261 parallelepipedal
• CPC Class Codes: A61F 2002/3037 Translation along the common longitudinal axis, e.g. piston
• CPC Class Codes: A61F 2002/30398 Sliding
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30433 using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/30556 for adjusting thickness
• CPC Class Codes: A61F 2002/30579 with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30593 : hollow
• CPC Class Codes: A61F 2002/30599 : stackable
• CPC Class Codes: A61F 2002/30604 : modular
• CPC Class Codes: A61F 2002/30774 : internally-threaded
• CPC Class Codes: A61F 2002/30777 : Oblong apertures
• CPC Class Codes: A61F 2002/30785 : parallel
• CPC Class Codes: A61F 2002/30787 : inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/30789 : perpendicular with respect to each other
• CPC Class Codes: A61F 2002/30797 : internally-threaded
• CPC Class Codes: A61F 2002/30836 : knurled
• CPC Class Codes: A61F 2002/30841 : Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/30843 : Pyramidally-shaped
• CPC Class Codes: A61F 2002/30904 : serrated profile, i.e. saw-toothed
• CPC Class Codes: A61F 2002/3092 : having an open-celled or open-pored structure
• CPC Class Codes: A61F 2002/4485 : comprising three or more adjacent spinal implants
• CPC Class Codes: A61F 2002/449 : comprising multiple spinal implants located in different intervertebral spaces or in different vertebrae
• CPC Class Codes: A61F 2002/4629 : connected to the endoprosthesis or implant via a threaded connection
• CPC Class Codes: A61F 2210/0004 : bioabsorbable
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0033 : made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2220/0041 : using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2230/0017 : Angular shapes
• CPC Class Codes: A61F 2230/0019 : rectangular
• CPC Class Codes: A61F 2230/0026 : trapezoidal
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2250/0009 : for adjusting thickness
• CPC Class Codes: A61F 2250/0063 : Nested prosthetic parts
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite
• CPC Class Codes: Y10S 606/90 : Lumbar stabilizer
• CPC Class Codes: Y10S 606/907 : Composed of particular material or coated
• CPC Class Codes: Y10S 606/908 : Bioabsorbable material

Abstract

The present invention is directed to interbody spinal fusion implants having a structural configuration that provides for the maintaining and creating of the normal anatomic angular relationship of two adjacent vertebrae of the spine to maintain and create spinal lordosis. The spinal fusion implants of the present invention are sized to fit within the disc space created by the removal of disc material between two adjacent vertebrae and conform wholly or in part to the disc space created. The spinal fusion implants of the present invention have upper and lower surfaces that form a support structure for bearing against the end plates of the adjacent vertebrae. The upper and lower surfaces are disposed in a converging angular relationship to each other such that the implants of the present invention have an overall "wedged-shape" in an elevational side view. The angular relationship of the upper and lower surfaces places and maintains the vertebrae adjacent to those surfaces in an angular relationship to each other, creating and maintaining the desired lordosis.

Claims

1. An interbody spinal fusion implant for fusion of two adjacent vertebrae in the human spine in which said implant to be interposed between the vertebral endplates of said adjacent vertebrae, comprising:

upper and lower walls, insertion and trailing walls, and side walls;

a plurality of openings in at least said upper and lower walls, at least some of said plurality of openings allowing for communication between said upper wall and said lower wall so as to be capable of containing fusion promoting materials for promoting bone ingrowth is continuity through said implant from the vertebral endplate of one of said adjacent vertebrae to the vertebral endplate of the other of said adjacent vertebrae for fusion of said adjacent vertebrae;

said upper and lower walls forming a support structure including at least a portion of the surfaces of said upper and lower walls between said plurality of openings and between said insertion, trailing, and side walls for bearing against the vertebral endplates of the adjacent vertebrae, said upper and lower walls being disposed at least in part in a diverging angular relationship to each other from said insertion wall to said trailing wall, said upper and lower walls being spaced apart at a distance from each other that is greater at said trailing wall than at said insertion wall;

whereby the insertion of said implant between the vertebral endplates of the two adjacent vertebrae supports the two adjacent vertebrae in an angular relationship and allows for bone growth to occur through said implant from one vertebral endplate adjacent to said implant to the other vertebral endplate adjacent to said implant.

2. The implant of claim 1 in which the depth of said implant is substantially the same as the depth of a space created by the removal of the nucleus pulposus from between the two adjacent vertebrae.

3. The implant of claim 1 in which the width of said implant is substantially equal to the transverse width of a space created by the removal of the nucleus pulposus from between the two adjacent vertebrae.

4. The implant of claim 1 in which said implant has substantially the same height, width and depth as a space created by the removal of at least generally the nucleus pulposus and at least a portion of the annulus fibrosus from between the two adjacent vertebrae.

5. The implant of claim 1 in which said implant has substantially the same shape as a space created by the removal of at least a substantial portion of the nucleus pulposus and a portion of the annulus fibrosus from between the two adjacent vertebrae.

6. The implant of claim 1 in which said upper wall has a fixed shape which is generally configured to match the contours of the endplate of one of the two adjacent vertebrae.

7. The implant of claim 1 in which said lower wall has a fixed shape which is generally configured to match the natural contours of the endplate of one of the two adjacent vertebrae.

8. The implant of claim 1 in which said upper wall has a fixed shape which is generally configured to match the natural contours of the endplate of a first of the two adjacent vertebrae, and said upper wall has a fixed shape which is generally configured to match the natural contours of the endplate of a second of the two adjacent vertebrae.

9. The implant of claim 1 in which at least a portion of said insertion wall is tapered for facilitating insertion of the implant between the two adjacent vertebrae.

10. The implant of claim 1 in which said implant comprises an insertion end and a trailing end, said insertion end comprising at least one tapered portion.

11. The implant of claim 1 in which said insertion wall is convex and conforms to a space created by the removal of at least generally the nucleus pulposus and a portion of the annulus fibrosus from between the two adjacent vertebrae.

12. The implant of claim 1 in which said trailing wall is curved.

13. The implant of claim 12 in which said trailing wall is convex.

14. The implant of claim 1 in which said side walls are curved.

15. The implant of claim 1 in which the shape of said side walls is generally trapezoidal.

16. The implant of claim 1 in which said implant is substantially rectangular.

17. The implant of claim 1 in which at least some of said openings are approximately 1 mm to 3 mm in diameter.

18. The implant of claim 1 in which at least some of said plurality of openings are greater than microscopic in size.

19. The implant of claim 1 in which at least a portion of said plurality of openings are microscopic in size.

20. The implant of claim 1 in which at least some of said plurality of openings pass through said upper and said lower walls forming a plurality of channels through said implant.

21. The implant of claim 1 in which said implant has at least one interior chamber and having at least one of said plurality of openings in said upper wall and at least one of said plurality of openings in said lower wall being in communication with said at least one interior chamber.

22. The implant of claim 21 in which said implant includes an access opening for accessing said at least one interior chamber, said access opening being larger than the largest of said plurality of openings.

23. The implant of claim 22 including a covering means for closing said access opening.

24. The implant of claim 23 in which said covering means for closing said access opening comprises a slidable door.

25. The implant of claim 1 having a plurality of openings capable of retaining fusion promoting material.

26. The implant of claim 25 in which said plurality of openings comprise wells.

27. The implant of claim 1 in which said implant includes bone engaging means for engaging said implant to adjacent vertebrae of the spine.

28. The implant of claim 27 in which said bone engaging means includes a plurality of surface roughenings for engaging said adjacent vertebrae and for maintaining said implant in place, said surface roughenings being present on at least a portion of said upper and lower walls.

29. The implant of claim 28 in which said surface roughenings comprises a plurality of ridges.

30. The implant of claim 29 in which said a plurality of ridges are facing the direction of insertion for preventing said implant from backing out once inserted between said adjacent vertebrae.

31. The implant of claim 28 in which said surface roughenings comprise at least one groove.

32. The implant of claim 28 in which said surfaces roughenings comprise a plurality of spike projections.

33. The implant of claim 32 in which said implant includes means for retracting and extending said plurality of spike projections.

34. The implant of claim 28 in which said surface roughenings include knurling.

35. The implant of claim 1 in which said implant comprises a mesh-like material having a plurality of interstices for receiving fusion promoting material.

36. The implant of claim 1 in which said implant has an exterior surface that is porous at least in part.

37. The implant of claim 1 in which said implant has at least a portion of its surface treated to promote bone ingrowth between said surface and a vertebrae.

38. The implant of claim 1 in which said implant comprises a bone ingrowth material for promoting bone ingrowth between said implant and said two adjacent vertebrae.

39. The spinal fusion implant of claim 1 in which said implant is at least in part bioabsorbable.

40. The implant of claim 1 in which said implant includes driving engaging means for engaging a driving instrument for implanting said implant within the disc space between the two adjacent vertebrae.

41. The implant of claim 1 which said implant comprises a plurality of modular members, each of said modular members having a height substantially equal to the height of the space created by the removed disc material from between two adjacent vertebrae and a width substantially less than the transverse width of the vertebrae.

42. The implant of claim 1 in which said implant dimensionally corresponds to the space created by the removal of at least generally all of the nucleus pulposus and a portion of the annulus fibrosus when said adjacent vertebrae are distracted and placed in angular relationship to each other.

43. The implant of claim 1 for use in the cervical spine in which the depth of said implant is in the range of approximately 11 mm to 21 mm.

44. The implant of claim 1 for use in the cervical spine in which the width of said implant is in the range of approximately 14 mm to 28 mm.

45. The implant of claim 1 for use in the cervical spine in which said implant has a height in the range of approximately 5 mm to 10 mm, a width in the range of approximately 14 mm to 28 mm, and depth in the range of approximately 11 mm to 21 mm.

46. The implant of claim 1 for use in the lumbar spine in which the depth of said implant is in the range of approximately 20 mm to 34 mm.

47. The implant of claim 1 for use in the lumbar spine in which the width of said implant is in the range of approximately 28 mm to 48 mm.

48. The implant of claim 1 for use in the lumbar spine in which said implant has a height in the range of approximately 8 mm to 16 mm, a width in the range of approximately 28 mm to 48 mm, and depth in the range of approximately 20 mm to 34 mm.

49. The implant of claim 1 including expanding means for moving said upper and lower walls apart in said diverging angular relationship.

50. An interbody spinal fusion implant for fusion of two adjacent vertebrae in the human spine in which said implant to be interposed between the vertebral endplates of said adjacent vertebrae, comprising:

upper and lower walls, insertion and trailing walls, and side walls, said upper and lower walls forming a support structure including at least a portion of the surfaces of said upper and lower walls between said insertion, trailing and side walls for conforming to and bearing against the vertebral end plates of the adjacent vertebrae;

said upper and lower wall being disposed at least in part in a diverging angular relationship to each other, said upper and lower walls being spaced apart at a distance from each other that is greater at said trailing wall than at said insertion wall; and

means for permitting bone ingrowth through said implant for fusion of said adjacent vertebrae;

whereby the insertion of said implant between the vertebral endplates of the two adjacent vertebrae supports the two adjacent vertebrae in an angular relationship and allows for bone growth to occur through said implant from one vertebral endplate adjacent to said implant to the other vertebral endplate adjacent to said implant.

51. The implant of claim 50 in which said implant dimensionally corresponds to the space created by the removal of at least generally all of the nucleus pulposus and a portion of the annulus fibrosus when said adjacent vertebrae are distracted and placed in angular relationship to each other.