Allograft implant

• US 20050240267A1
• Filed: 03/28/2005
• Published: 10/27/2005
• Est. Priority Date: 03/26/2004
• Status: Active Grant

• Current Assignee: Synthes USA LLC (Johnson & Johnson)
• Original Assignee: Synthes USA LLC (Johnson & Johnson)
• Inventors: Angelucci, Christopher M., Goodwin, Roger D., Boyer, Michael L. II, Messerli, Dominique, Delurio, Robert J., Randall, Brandon L., Myer, Jacqueline
• Granted Patent: US 7,491,237 B2
• Time in Patent Office: Days
• US Class Current: 623/17.110
• CPC Class Codes: A61F 2/28 Bones joints A61F2/30
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• CPC Class Codes: A61F 2/44 for the spine, e.g. vertebrae, spinal discs
• 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 2/4611 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 2002/30057 made from both cortical and cancellous adjacent parts
• CPC Class Codes: A61F 2002/30266 wedge-shaped parallelepipeds
• CPC Class Codes: A61F 2002/30383 made by laterally inserting a protrusion, e.g. a rib into a complementarily-shaped groove
• CPC Class Codes: A61F 2002/30387 Dovetail connection
• CPC Class Codes: A61F 2002/30492 using a locking pin
• CPC Class Codes: A61F 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/30571 Leaf springs
• CPC Class Codes: A61F 2002/30604 modular
• CPC Class Codes: A61F 2002/30617 Visible markings for adjusting, locating or measuring
• CPC Class Codes: A61F 2002/30782 inclined obliquely
• CPC Class Codes: A61F 2002/30795 Blind bores, e.g. of circular cross-section
• CPC Class Codes: A61F 2002/3082 Grooves
• CPC Class Codes: A61F 2002/30843 Pyramidally-shaped
• CPC Class Codes: A61F 2002/30904 serrated profile, i.e. saw-toothed
• CPC Class Codes: A61F 2002/4622 : having the shape of a forceps or a clamp
• CPC Class Codes: A61F 2002/4628 : with linear motion along or rotating motion about an axis transverse to the instrument axis or to the implantation direction, e.g. clamping
• CPC Class Codes: A61F 2002/4629 : connected to the endoprosthesis or implant via a threaded connection
• CPC Class Codes: A61F 2220/0025 : Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2230/0082 : parallelepipedal
• CPC Class Codes: A61F 2250/0097 : Visible markings, e.g. indicia
• CPC Class Codes: A61F 2310/00359 : Bone or bony tissue

Abstract

An allogenic implant for use in intervertebral fusion is formed from one or more two pieces. The pieces are made from bone, and are joined together to form an implant having sufficient strength and stability to maintain a desired distance between first and second vertebrae in a spinal fusion procedure. The implant pieces may be formed of cortical bone and connected by dovetail joints, and at least one cortical bone pin may be provided to lock the pieces together and to add strength to the implant. Teeth are formed on the vertebra engaging surfaces of the implant prevent short-term slippage of the implant.

Claims

1. An multipiece implant having superior and inferior surfaces comprising:

at least first and second cortical bone segments, each segment having a locking surface configured to engage the locking surface of the other segment, each segment further having a pair of vertebra-engaging surfaces and at least one fastener-engaging surface;

at least one fastener;

wherein the locking surfaces of the first and second bone segments comprise corresponding male and female surfaces, the fastener further configured to contact the fastener-engaging surfaces of the first and second bone segments to lock the segments together to form a multipiece implant having mechanical properties substantially similar to those of an implant formed of a single piece of cortical bone.

2. The multipiece implant of claim 1, wherein the locking surfaces of the first and second bone segments comprise a dovetail joint.

3. The multipiece implant of claim 1, wherein the vertebra-engaging surfaces of each cortical bone segment comprise a plurality of teeth.

4. The multipiece implant of claim 2, wherein the teeth are arranged in a two dimensional array, and at least some of the teeth have a pyramidal shape.

5. The multipiece implant of claim 1, wherein the multipiece implant has superior and inferior engaging surfaces configured to engage adjacent vertebral end plates and the superior surface has a substantially convex curvature.

6. The multipiece implant of claim 5, wherein the inferior surface has a substantially convex curvature.

7. The multipiece implant of claim 6, wherein the curvature of the superior suface lies in the anterior-posterior plane, and the curvature of the inferior surface lies in the medial-lateral plane.

8. The multipiece implant of claim 5, wherein the superior and inferior engaging surfaces each comprise a series of teeth.

9. The multipiece implant of claim 8, wherein the teeth are arranged in a two dimensional array, and the teeth have a pyramidal shape.

10. The multipiece implant of claim 1, wherein the fastener comprises a pin made of cortical bone.

11. The multipiece implant of claim 10, wherein the locking element engaging surface of each cortical bone segment comprises at least one bore configured to receive the cortical bone pin.

12. The multipiece implant of claim 11, the implant further comprising an anterior-posterior axis, the at least one bore being aligned substantially parallel to the axis.

13. The multipiece implant of claim 12, wherein the at least one bore is aligned substantially non-parallel to the axis.

14. The multipiece implant of claim 11, wherein the implant has superior and inferior engaging surfaces configured to engage adjacent vertebral end plates, the implant further comprising an opening in communication with the superior and inferior engaging surfaces and configured to receive osteogenic, osteoconductive or osteoinductive material.

15. The multipiece implant of claim 14, the implant further comprising an anterior-posterior axis, a second cortical locking pin, and a second fastener engaging surface comprising a second bore configured to receive the second cortical locking pin, wherein at least one of the first and second bores is aligned substantially non-parallel to the anterior-posterior axis.

16. The multipiece implant of claim 15, wherein the first and second bores do not intersect the opening and the bores are oriented to allow at least one dimension of the opening to be maximized

17. The multipiece implant of claim 1, wherein the fastener comprises a cortical bone pin and the fastener engaging surface of each bone segment comprises a bore configured to receive the cortical bone pin, the fastener engaging surface of at least one bone segment further comprising an abutting surface configured to engage an end surface of the cortical pin.

18. The multipiece implant of claim 17, the first and second bone segments comprising an anterior bone segment and a center bone segment, respectively the implant further comprising a posterior bone segment engaged to the center bone segment via a dovetail joint, wherein the abutting surface is located in the posterior bone segment so that when the implant is placed between vertebral end plates of a patient, the pin is thereafter prevented from migrating in the direction the posterior direction.

19. The multipiece implant of claim 17, the first and second bone segments comprising an anterior bone segment and a center bone segment, the implant further comprising a posterior bone segment engaged to the center bone segment via a dovetail joint, wherein the abutting surface is located in the anterior bone segment so that when the implant is placed between vertebral end plates of a patient, the pin is thereafter prevented from migrating in the anterior direction.

49. The multipiece implant of claim 6, wherein the convex curvatures of the superior surface and the inferior surface lie in the medial-lateral plane.

50. The multipiece implant of claim 19, wherein the dovetail joint is oriented on the superior surface and inferior surface of the implant.

20. A method of manufacturing an intervertebral implant having a superior surface, an inferior surface, and a perimeter, comprising the steps of:

forming at least first, second and third implant pieces from cortical bone;

connecting the first and second pieces using a joint having a male element disposed on one of the first and second pieces and a corresponding female element disposed on the other of the first and second pieces;

connecting the second and third pieces using a joint having a male element disposed on one of the second and third pieces and a corresponding female element disposed on the other of the second and third pieces;

locking the first, second and third pieces together using a cortical bone pin disposed within bores formed through at least a portion of each piece to form an implant configured to be inserted between adjacent vertebra of a patient'"'"'s spinal column; and

forming superior and inferior vertebra engaging surfaces on the implant, wherein the engaging surfaces each comprise a plurality of teeth.

21. The method of claim 20, wherein the step of forming a first piece further comprises forming the male portion of a first dovetail joint, the step of forming a third piece comprises forming the male portion of a second dovetail joint, and the step of forming a second piece further comprises forming opposing female portions of the first and second dovetail joints.

22. The method of claim 20, wherein the step of forming the first piece further comprises marking an indicia on a face of the first piece, the indicia providing a visual indicia of implant orientation.

23. The method of claim 22, wherein the indicia comprises an arrow.

24. The method of claim 21, wherein the teeth comprise of pyramidal teeth.

25. The method of claim 24, wherein the superior vertebra engaging surface has a convex profile.

26. The method of claim 25, wherein the inferior surface has a substantially convex curvature.

27. The method of claim 26, wherein the curvature of the superior suface lies in the anterior-posterior plane, and the curvature of the inferior surface lies in the medial-lateral plane.

28. The method of claim 20, the superior and inferior vertebra engaging surfaces being oriented substantially non-parallel with respect to each other.

29. The method of claim 20, wherein, subsequent to the step of locking the first, second and third pieces together, the implant is machined so that the implant perimeter that substantially conforms to the outer perimeter of a patient'"'"'s vertebral end plate.

30. The method of claim 29, the implant further having a medial-lateral centerline, the cortical bone pin disposed within a bore that is oriented substantially non-parallel to the medial-lateral centerline.

31. An intervertebral implant kit, comprising:

at least one implant configured for insertion between the end plates of adjacent vertebrae in the spinal column of a patient, the implant comprising at least first and second cortical bone segments, the implant further having first and second vertebra engaging surfaces and a perimeter,

at least one implant insertion tool for engaging the implant and inserting the implant between the adjacent vertebrae, the tool having at least one implant engaging end configured to grip the implant,

wherein the perimeter of the implant has an anterior segment configured to substantially conform to the anterior shape of the adjacent vertebral end plates when the implant is installed between the adjacent vertebrae, and the implant engaging end of the tool is further configured to engage the implant along a substantial portion of the anterior segment.

32. The intervertebral implant kit of claim 31, the implant further comprising a third cortical bone segment and at least a first fastener configured to lock the first, second and third bone segments together.

33. The intervertebral implant kit of claim 32, wherein the fastener comprises a cortical bone pin.

34. The intervertebral implant kit of claim 33, wherein at least one vertebra engaging surface has a convex shape.

35. The intervertebral implant kit of claim 34, the implant further comprising at least one opening in communication with at least one of the first and second vertebra engaging surfaces, the opening configured to receive osteogenic, osteoinductive, or osteoconductive material.

36. The intervertebral implant kit of claim 32, the implant further comprising an anterior-posterior centerline, the fastener having an axis oriented at an acute angle with respect to the centerline.

37. The intervertebral implant kit of claim 31, the implant further comprising a second fastener configured to lock the first, second and third bone segments together, the second fastener having an axis oriented at an acute angle with respect to the centerline.

38. The intervertebral implant kit of claim 32, wherein the axes of the first and second fasteners are oriented non-parallel with respect to each other.

39. The intervertebral implant kit of claim 32, the implant further comprising at least one opening in communication with at least one of the first and second vertebra engaging surfaces and configured to receive bone growth enhancing materials, the implant further comprising a second fastener configured to lock the first, second and third bone segments together, wherein the first and second fasteners each have an axis, the axes oriented to maximize the size of the opening.

40. The intervertebral implant kit of claim 31, the vertebra engaging surfaces further comprising a plurality of protrusions configured to engage the respective vertebral end plate.

41. The intervertebral implant kit of claim 35, wherein the protrusions comprise pyramidal shaped teeth.

42. The intervertebral implant kit of claim 31, the anterior segment of the implant having first and second recesses, and the implant engaging end of the tool further having first and second protrusions for engaging the first and second recesses, the recesses and protrusions configured to allow the tool to firmly grip the implant.

43. The intervertebral implant kit of claim 42, the tool further having first and second arms, the arms each having a proximal gripping end and distal implant-engaging end, wherein the first protrusion is disposed on the distal end of the first arm and the second protrusion is disposed on the distal end of the second arm.

44. The intervertebral implant kit of claim 43, the tool further comprising a pivot mechanism connecting the first and second arms at a location between the proximal and distal ends of the arms.

45. The intervertebral implant kit of claim 44, wherein the first and second protrusions engage the first and second recesses when the distal end of the tool contacts the anterior segment of the implant and the gripping ends of the first and second arms are moved toward each other.

46. The intervertebral implant kit of claim 45, the implant further comprising a medial-lateral dimension, the implant engaging end of the tool further comprising a medial lateral dimension that is equal to or less than the medial lateral dimension of the implant.

47. The intervertebral implant kit of claim 45, the implant further comprising a medial-lateral dimension, the implant engaging end of the tool further comprising a medial lateral dimension that is equal to or smaller than the medial lateral dimension of the implant.

48. The intervertebral implant kit of claim 31, further comprising an impacter for positioning and impacting the implant between the vertebrae, wherein the impacter comprises a distal implant-engaging end comprising an implant-engaging face sized and dimensioned to engage the anterior segment of the implant.