Method and apparatus for providing an expandable spinal fusion cage

• US 20030171813A1
• Filed: 03/05/2002
• Published: 09/11/2003
• Est. Priority Date: 03/05/2002
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Kiester, P. Douglas
• Granted Patent: US 6,893,464 B2
• Time in Patent Office: Days
• US Class Current: 623/17.11
• CPC Class Codes: A61F 2/447 substantially parallelepipedal, e.g. having a rectangular or trapezoidal cross-section
• CPC Class Codes: A61F 2/4603 for insertion or extraction of endoprosthetic joints or of accessories thereof
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/30266 wedge-shaped parallelepipeds
• CPC Class Codes: A61F 2002/30462 retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2002/30471 connected by a hinged linkage mechanism, e.g. of the single-bar or multi-bar linkage type
• CPC Class Codes: A61F 2002/30476 locked by an additional locking mechanism
• CPC Class Codes: A61F 2002/30505 spring biased
• CPC Class Codes: A61F 2002/3055 for adjusting length
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30601 telescopic
• 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 2002/4635 using minimally invasive surgery
• CPC Class Codes: A61F 2220/0025 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2220/0075 sutured, ligatured or stitched, retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2220/0091 connected by a hinged linkage mechanism, e.g. of the single-bar or multi-bar linkage type
• CPC Class Codes: A61F 2230/0082 parallelepipedal
• CPC Class Codes: A61F 2310/00023 Titanium or titanium-based alloys, e.g. Ti-Ni alloys

Abstract

The spinal fusion cage of the invention comprises two opposing end plates, and three opposing collapsible legs. The two opposing end plates and three opposing collapsible legs are adapted to be configured into an expanded cage from a collapsed configuration. The expanded cage assumes a predetermined rigid shape and volume for disposition between two adjacent vertebrae. The collapsed configuration of the cage is adapted for posterior insertion into the disk space. The apparatus further comprises locking means for at least temporarily locking the legs and maintaining the cage in an expanded configuration. One of the legs is medially disposed on a first side of the cage and the other two are laterally disposed with respect to the end plates on a second side. The three legs have differing lengths so that the cage assumes a wedge-shaped envelope in the expanded configuration. The wedge-shaped envelope reestablishes a predetermined lordosis between fused vertebrae. The invention includes an inserter comprised of a tubular member and holding clamp disposed on the distal end of the tubular member. The holding clamp holds the cage in the collapsed configuration for insertion into a confined surgical theater. The cage is then reconfigured to the expanded configuration using the inserter. Further activation of the inserter causes the cage to be temporarily locked into the expanded configuration.

Claims

1. An apparatus for spinal fusions comprising:

two opposing end plates; and

at least two opposing collapsible legs disposed between the two opposing end plates, the two opposing end plates and at least two opposing collapsible legs adapted to be arranged and configured into an expanded cage from a collapsed configuration in which the expanded cage assumes a predetermined rigid shape and volume for disposition between two adjacent vertebrae in a disk space therebetween, and in which collapsed configuration the cage is adapted to being posteriorly inserted into the disk space.

2. The apparatus of claim 1 further comprising locking means for locking the legs and maintaining the cage in an expanded configuration.

3. The apparatus of claim 1 wherein the at least two opposing collapsible legs comprise three collapsible legs in which one of the three collapsible legs is medially disposed with respect to the end plates on a first side of the cage and two of the three collapsible legs are laterally disposed with respect to the end plates on a second side of the cage.

4. The apparatus of claim 3 wherein the three legs have differing lengths so that the cage assumes a wedge-shaped envelope in the expanded configuration.

5. The apparatus of claim 4 wherein the wedge-shaped envelope in the expanded configuration reestablishes a predetermined lordosis between fused vertebrae.

6. The apparatus of claim 5 wherein the predetermined lordosis between fused vertebrae is a normal lumbar lordosis.

7. The apparatus of claim 1 wherein the at least two opposing collapsible legs are each comprised of two segments hinged together at or near one end of each segment and hinged to one of the end plates at the opposing end of each segment.

8. The apparatus of claim 7 wherein the hinge coupling the two segments together at or near one end of each segment flexibly connect the two segments of each leg together.

9. The apparatus of claim 8 wherein the hinge coupling the two segments together at or near one end of each segment comprises a flexible strap fixed to each of the two segments and extending between the two segments.

10. The apparatus of claim 9 wherein each leg has an exterior side forming part of the exterior of the envelope of the cage and wherein the strap fixed to each of the two segments and extending between the two segments is disposed on the two segments on the exterior side thereof so that the pivot of the corresponding collapsible leg is exterior to the envelope of the cage.

11. The apparatus of claim 2 wherein the locking means comprises an over-the-center toggle for each of the at least two opposing collapsible legs.

12. The apparatus of claim 1 further comprising an over-the-center toggle for each of the at least two opposing collapsible legs.

13. The apparatus of claim 11 wherein the over-the-center toggle for each of the collapsible legs comprises a resilient strap having two opposing ends, each opposing end of the resilient strap being coupled to one of the two opposing end plates, the strap being coupled to a corresponding collapsible leg so that when the cage is in the expanded configuration, the resilient strap applies a compressive force to the corresponding collapsible leg to maintain the corresponding collapsible leg in a locked configuration.

14. The apparatus of claim 13 wherein the at least two opposing collapsible legs are each comprised of two segments hinged together at or near one end of each segment and hinged to one of the end plates at the opposing end of each segment and wherein each leg has an exterior side forming part of an exterior of an envelope of the cage and wherein the resilient strap is disposed on the two segments on the exterior side thereof.

15. The apparatus of claim 7 wherein each of the two segments comprising a collapsible leg is coupled to the end plates by an open hinge.

16. The apparatus of claim 1 further comprising an inserter comprised of a tubular member having a distal end and holding clamp disposed on the distal end of the tubular member, the holding clamp adapted to hold the cage in the collapsed configuration for insertion into a confined surgical theater of operation and then on selective activation of a first type by the tubular member configure the cage from the collapsed configuration to the expanded configuration.

17. The apparatus of claim 16 wherein on selective activation of a second type by the tubular member the cage is locked into the expanded configuration.

18. The apparatus of claim 17 wherein the inserter comprises a grip, where activation of the first type by the tubular member comprises movement of the grip by a first amount to configure the cage in the expanded configuration and where activation of the second type by the tubular member comprises movement of the grip by a second successive amount to lock the cage in the expanded configuration.

19. The apparatus of claim 16 where the tubular member comprises a hollow tubular housing and a telescopic rod disposed in the hollow tubular housing, the holding clamp being resiliently coupled to the tubular housing, the telescopic rod engaging the holding clamp to manipulate the holding clamp configure the cage from the collapsed configuration to the expanded configuration when the telescopic rod engages the holding clamp.

20. The apparatus of claim 19 where the telescopic rod selectively engages the collapsible legs to configure the legs into a self-locked configuration.

28. The method of claim 9 wherein flexing a flexible strap fixed to each of the two segments comprises pivoting the two segments about the flexible strap about an axis disposed exteriorly to the envelope of the cage.

36. The method of claim 16 where the tubular member comprises a hollow tubular housing and a telescopic rod disposed in the hollow tubular housing, the holding clamp being resiliently coupled to the tubular housing, and wherein moving the grip by a first amount causes the telescopic rod to engage the holding clamp to manipulate the holding clamp configure the cage from the collapsed configuration to the expanded configuration when the telescopic rod engages the holding clamp.

37. The method of claim 36 where moving the grip by a second successive amount causes the telescopic rod to selectively engage the collapsible legs to configure the legs into a self-locked configuration.

21. A method for performing a posterior interbody spinal fusion comprising:

posteriorly disposing a fusion cage in a collapsed configuration into a disk space between two adjacent vertebrae; and

expanding the fusion cage to assume a predetermined rigid shape and volume when disposed between two adjacent vertebrae in a disk space therebetween, by locking three collapsible legs into an expanded configuration between to opposing end plates in which one of the three collapsible legs is medially disposed with respect to the end plates on a first side of the cage and two of the three collapsible legs are laterally disposed with respect to the end plates on a second side of the cage.

22. The method of claim 21 wherein locking the three legs expands the cage into a wedge-shaped envelope.

23. The method of claim 22 wherein locking the three legs into a wedge-shaped envelope reestablishes a predetermined lordosis between fused vertebrae.

24. The method of claim 23 wherein reestablishing the predetermined lordosis between fused vertebrae reestablishes a normal lumbar lordosis.

25. The method of claim 21 wherein locking the collapsible legs comprises rotating each of two segments hinged together at or near one end of each segment and hinged to one of the end plates at the opposing end of each segment.

26. The method of claim 25 wherein rotating each of two segments comprises flexing the hinge coupling the two segments together at or near one end of each segment.

27. The method of claim 26 wherein flexing the hinge coupling the two segments together comprises flexing a flexible strap fixed to each of the two segments and extending between the two segments.

29. The method of claim 21 where locking three collapsible legs into an expanded configuration comprises actuating an over-the-center toggle for each of the collapsible legs.

30. The method of claim 29 wherein actuating an over-the-center toggle comprises stretching a resilient strap having two opposing ends, each opposing end of the resilient strap being coupled to one of the two opposing end plates, the strap being coupled to a corresponding collapsible leg so that when the cage is in the expanded configuration, the stretched resilient strap applies a compressive force to the corresponding collapsible leg to maintain the corresponding collapsible leg in a locked configuration, any movement of the collapsible leg out of the locked configuration tending to further stretch the resilient strap.

31. The method of claim 30 wherein the at least two opposing collapsible legs are each comprised of two segments hinged together at or near one end of each segment to define an outwardly extending pivot point, and wherein each segment is hinged to one of the end plates at the opposing end of each segment and wherein each leg has an exterior side forming part of an exterior of an envelope of the cage and wherein the resilient strap is disposed on the two segments on the exterior side thereof, wherein moving the collapsible leg out of the locked configuration rotates the segments about the exterior pivot point causing further stretching of the resilient strap.

32. The method of claim 25 wherein rotating each of two segments comprises rotating the two segments of the collapsible leg about corresponding open hinges defined in the end plates.

33. The method of claim 21 wherein expanding the fusion cage comprises using an inserter comprised of a tubular member having a distal end and holding clamp disposed on the distal end of the tubular member, the holding clamp adapted to hold the cage in the collapsed configuration for insertion into a confined surgical theater of operation and selectively activating the tubular member to configure the cage from the collapsed configuration to the expanded configuration.

34. The method of claim 33 wherein selectively activating the tubular member also at least temporarily locks the fusion cage into the expanded configuration.

35. The method of claim 34 wherein the inserter comprises a grip, where selectively activating the tubular member the tubular member comprises moving the grip by a first amount to configure the cage in the expanded configuration and then moving the grip by a second successive amount to lock the cage in the expanded configuration.