Expandable spinal fusion cage and associated instrumentation

• US 20060206207A1
• Filed: 01/19/2006
• Published: 09/14/2006
• Est. Priority Date: 01/20/2005
• Status: Active Grant

• Current Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Original Assignee: Warsaw Orthopedic Incorporated (Medtronic Plc)
• Inventors: Lange, Eric C., Berry, Bret M., Dryer, Randall F.
• Granted Patent: US 7,655,046 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 2/446 having a circular or elliptical cross-section substantially parallel to the axis of the spine, e.g. cylinders or frustocones
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/2817 Bone stimulation by chemical reactions or by osteogenic or biological products for enhancing ossification, e.g. by bone morphogenetic or morphogenic proteins [BMP] or by transforming growth factors [TGF]
• 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 2002/30507 using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/30522 releasable, e.g. using a releasable ratchet
• CPC Class Codes: A61F 2002/30538 for adjusting angular orientation
• 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 2002/30594 slotted, e.g. radial or meridian slot ending in a polar aperture, non-polar slots, horizontal or arcuate slots
• CPC Class Codes: A61F 2002/30624 Hinged joint, e.g. with transverse axle restricting the movement
• CPC Class Codes: A61F 2002/30774 internally-threaded
• CPC Class Codes: A61F 2002/30777 Oblong apertures
• CPC Class Codes: A61F 2002/30789 perpendicular with respect to each other
• CPC Class Codes: A61F 2002/30841 Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/30858 Threads interrupted by grooves or sidewalls, e.g. flat sidewalls
• CPC Class Codes: A61F 2002/4627 with linear motion along or rotating motion about the instrument axis or the implantation direction, e.g. telescopic, along a guiding rod, screwing inside the instrument
• 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 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 2250/0006 : for adjusting angular orientation
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: A61F 2310/00359 : Bone or bony tissue

Abstract

An expandable spinal implant comprising a cage body including at least two movable branches having first end portions that are interconnected to one another and second end portions that are movable relative to one another. The movable branches include a first shell portion having a first pair of longitudinal edges and defining a first hollow region therebetween, and a second shell portion having a second pair of longitudinal edges and defining a second hollow region therebetween, with the first and second hollow regions cooperating to define at least a portion of a hollow interior of the cage body. An expansion member co-acts with the first and second shell portions to transition the cage body to an expanded configuration as the expansion member is axially displaced along said first and second pairs of longitudinal edges. In one embodiment, at least one of the shell portions defines a plurality of retention elements positioned at select axial locations along a corresponding one of the longitudinal edges, with the expansion member engaged with one or more of the retention elements to retain the expansion member at a select axial position to maintain the implant in the expanded configuration.

Claims

1. An expandable spinal implant, comprising:

a cage body extending along a longitudinal axis and including at least two movable branches having first end portions that are interconnected to one another and opposite second end portions that are movable relative to one another, said movable branches cooperating to define a hollow interior of said cage body and including;

a first shell portion having a first pair of longitudinal edges and defining a first hollow region between said first pair of longitudinal edges;

a second shell portion having a second pair of longitudinal edges and defining a second hollow region between said second pair of longitudinal edges, said first hollow region of said first shell portion cooperating with said second hollow region of said second shell portion to define at least a portion of said hollow interior of said cage body; and

an expansion member co-acting with said first and second shell portions to transition said cage body toward a transversely expanded configuration as said expansion member is axially displaced between opposing ones of said first and second pairs of longitudinal edges.

2. The implant of claim 1, wherein said first and second pairs of longitudinal edges are arranged transversely opposite one another.

3. The implant of claim 1, wherein said first pair of longitudinal edges extend generally along a first plane, said second pair of longitudinal edges extending generally along a second plane.

4. The implant of claim 3, wherein said first and second planes are angled relative to one another along said longitudinal axis to define an inward taper.

5. The implant of claim 1, wherein at least one of said longitudinal edges of said first and second shell portions defines a plurality of retention elements positioned at select axial locations, said expansion member engaged with at least one of said retention elements to retain said expansion member at a select axial position between said first and second shell portions and to maintain said cage body in said transversely expanded configuration.

6. The implant of claim 5, wherein said retention elements comprise ratchets.

7. The implant of claim 5, wherein each of said first and second pairs of longitudinal edges of said first and second shell portions defines a plurality of retention elements positioned at select axial locations, said expansion member engaged with at least one of said retention elements defined by each of said longitudinal edges to retain said expansion member at a select axial location between said first and second shell portions and to maintain said cage body in said transversely expanded configuration.

8. The implant of claim 1, wherein said cage body defines external threads configured for engagement with adjacent vertebral bodies.

9. The implant of claim 8, wherein said cage body has a generally circular outer cross section having truncated side portions arranged generally opposite one another and interrupting said external threads.

10. The implant of claim 1, wherein said cage body includes a pair of arcuate outer surfaces arranged generally opposite one another, said cage body defining a pair of substantially planar outer surfaces arranged generally opposite one another and extending between said pair of outer arcuate surfaces.

11. The implant of claim 10, wherein said pair of arcuate outer surfaces are threaded.

12. The implant of claim 1, wherein each of said first and second shell portions defines a transverse opening extending therethrough in communication with said hollow interior.

13. The implant of claim 12, further comprising a bone growth promoting substance positioned within said hollow interior of said cage body to facilitate bone ingrowth though said transverse openings and into said hollow interior.

14. The implant of claim 12, wherein said transverse opening has a length extending along at least about one half of an overall length of said cage body, said transverse opening having a width extending across at least about one half of an overall width of said cage body.

15. The implant of claim 1, wherein said second end portions of said movable branches are configured to provide said cage body with a rounded leading end portion to facilitate insertion of said cage body between adjacent vertebral bodies.

16. The implant of claim 15, wherein said rounded leading end portion is bullet-shaped.

17. The implant of claim 1, wherein said expansion member is sized to engage each of said longitudinal edges of said first and second shell portions as said expansion member is axially displaced between said first and second pairs of longitudinal edges to transition said cage body toward said transversely expanded configuration.

18. The implant of claim 1, wherein said expansion member has a length extending substantially entirely across an overall width of said cage body.

19. The implant of claim 1, wherein said expansion member includes a rounded leading end portion to facilitate sliding engagement between opposing ones of said first and second pairs of longitudinal edges to transition said cage body toward said transversely expanded configuration.

20. An expandable spinal implant, comprising:

a cage body extending along a longitudinal axis and including at least two movable branches having first end portions that are interconnected to one another and opposite second end portions that are movable relative to one another, said movable branches including first and second branch portions separated from one another by a longitudinal slot extending through said second end portions to a location adjacent said first end portions, said slot defining a first longitudinally extending surface associated with said first branch portion and an opposing second longitudinally extending surface associated with said second branch portion, at least one of said first and second branch portions defining a plurality of retention elements positioned at select axial locations along a corresponding one of said first and second longitudinally extending surfaces; and

an expansion member positioned within said slot and co-acting with said first and second branch portions to transition said cage body toward a transversely expanded configuration as said expansion member is axially displaced through said slot and along said first and second longitudinally extending surfaces, said expansion member engaged with at least one of said retention elements to retain said expansion member at a select axial location between said first and second branch portions and to maintain said cage body in said transversely expanded configuration.

21. The implant of claim 20, wherein said retention elements comprise ratchets.

22. The implant of claim 21, wherein each of said first and second branch portions defines a plurality of said retention elements positioned at select axial locations along said first and second longitudinally extending surfaces.

23. The implant of claim 20, wherein said first and second branch portions each have a shell-like configuration and cooperate with one another to define at least a portion of a hollow interior of said cage body.

24. The implant of claim 23, wherein said first branch portion includes a first pair of longitudinal edges defining a first hollow region therebetween, at least one of said first pair of longitudinal edges defining said first longitudinally extending surface, said second branch portion including a second pair of longitudinal edges defining a second hollow region therebetween, at least one of said second pair of longitudinal edges defining said second longitudinally extending surface, said first hollow region of said first branch portion cooperating with said second hollow region of said second branch portion to define at least a portion of said hollow interior of said cage body;

and

wherein said expansion member co-acts with said first and second branch portions to transition said cage body to said transversely expanded configuration as said expansion member is axially displaced along said first and second pairs of longitudinal edges.

25. The implant of claim 24, wherein said first and second pairs of longitudinal edges are arranged transversely opposite one another;

and

wherein said first pair of longitudinal edges extends generally along a first plane, said second pair of longitudinal edges extending generally along a second plane, said first and second planes angled relative to one another along said longitudinal axis to define an inward taper.

26. The implant of claim 20, wherein said cage body includes a pair of arcuate outer surfaces arranged generally opposite one another, said cage body defining a pair of substantially planar outer surfaces arranged generally opposite one another and extending between said pair of outer arcuate surfaces.

27. The implant of claim 26, wherein said pair of arcuate outer surfaces are threaded.

28. The implant of claim 20, wherein each of said first and second branch portions defines a transverse opening extending therethrough in communication with a hollow interior of said cage body;

and

the implant further comprising a bone growth promoting substance positioned within said hollow interior of said cage body to facilitate bone ingrowth though said transverse openings and into said hollow interior.

29. The implant of claim 20, wherein said second end portions of said movable branches are configured to provide said cage body with a bullet-shaped leading end portion to facilitate insertion of said cage body between adjacent vertebral bodies.

30. An instrument for manipulating an expandable spinal implant, the spinal implant being transitionable to an expanded configuration by displacement of an expansion element between two or more branch portions of the implant, the instrument extending generally along a longitudinal axis and comprising:

an elongate support member;

an actuator member displaceable relative to said support member; and

an engagement member extending from said support member; and

wherein displacement of said actuator member relative to said support member results in displacement of the expansion element between the branch portions of the implant to transition the implant toward the expanded configuration, said displacement of said actuator member results in transverse movement of said engagement member into engagement with the spinal implant to couple the instrument to the spinal implant.

31. The instrument of claim 30, wherein said displacement of said actuator member relative to said support member comprises axial displacement;

and

wherein said displacement of the expansion element between the branch portions of the implant comprises axial displacement.

32. The instrument of claim 31, wherein said transverse movement of said engagement member comprises pivotal movement.

33. The instrument of claim 31, wherein said actuator member includes a threaded portion positioned in threaded engagement with a corresponding portion of the instrument such that rotation of said actuator member about the longitudinal axis results in said axial displacement of said actuator member.

34. The instrument of claim 30, wherein said engagement member is pivotally coupled to said support member such that said displacement of said actuator member results in pivotal movement of said engagement member into engagement with the spinal implant to couple the instrument to the spinal implant.

35. The instrument of claim 30, further comprising a pair of said engagement members extending from said support member;

and

wherein said displacement of said actuator member results in transverse movement of said pair of engagement members in generally opposite directions and into engagement with the spinal implant to couple the instrument to the spinal implant.

36. The instrument of claim 35, wherein said pair of engagement members are pivotally coupled to said support member such that said displacement of said actuator member results in pivotal movement of said pair of engagement members in generally opposite directions and into engagement with the spinal implant to couple the instrument to the spinal implant.

37. The instrument of claim 30, wherein said engagement member comprises an axial portion extending from said support member and a flange portion extending transversely from said axial portion;

and

wherein said transverse movement of said engagement member results in engagement of said flange portion with a corresponding portion of the spinal implant to couple the instrument to the spinal implant.

38. A surgical method, comprising:

providing an expandable spinal implant, the spinal implant extending along a longitudinal axis and defining an outer cross section having a first transverse dimension and a second transverse dimension greater than the first transverse dimension;

inserting the spinal implant into an intervertebral space with the first transverse dimension generally aligned along a height of the intervertebral space;

orienting the spinal implant within the intervertebral space to generally align the second transverse dimension along the height of the intervertebral space; and

expanding the spinal implant along at least the second transverse dimension.

39. The method of claim 38, wherein the orienting comprises rotating the expandable spinal implant 90 degrees about the longitudinal axis.

40. The method of claim 38, wherein the expanding occurs subsequent to the orienting.

41. The method of claim 38, further comprising:

reorienting the spinal implant within the intervertebral space to generally realign the first transverse dimension along the height of the intervertebral space; and

removing the spinal implant from the intervertebral space.

42. The method of claim 41, wherein the reorienting is accomplished without collapsing the spinal implant along the second transverse dimension.

43. The method of claim 41, further comprising reinserting the spinal implant into the intervertebral space with the first transverse dimension generally aligned along the height of the intervertebral space and reorienting the spinal implant within the intervertebral space to generally align the second transverse dimension along the height of the intervertebral space.

44. The method of claim 38, wherein the expandable spinal implant defines an outer cross section having a pair of opposite arcuate surfaces and a pair of opposite generally planar surfaces extending between said pair of arcuate surfaces;

and

wherein a distance between the pair of planar surfaces defines the first transverse dimension and a distance between the pair of arcuate surfaces defines the second transverse dimension.

45. The method of claim 38, wherein the expandable spinal implant defines an inner chamber extending along the longitudinal axis;

and

further comprising positioning a bone growth promoting material within the inner chamber.

46. The method of claim 45, wherein the positioning of the bone growth promoting material within the inner chamber occurs prior to the inserting.