Selectively Expanding Spine Cage, Hydraulically Controllable in Three Dimensions for Enhanced Spinal Fusion

• US 20070093901A1
• Filed: 09/26/2006
• Published: 04/26/2007
• Est. Priority Date: 09/26/2005
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: Coalign Innovations Inc. (Stryker Corporation)
• Inventors: Pretti, Rudy, Grotz, Thomas
• Granted Patent: US 7,985,256 B2
• Time in Patent Office: Days
• US Class Current: 623/17.11
• CPC Class Codes: A61F 2/30771 applied in original prostheses, e.g. holes or grooves
• 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 2/4465 having a circular or kidney shaped cross-section substantially perpendicular to the axis of the spine
• CPC Class Codes: A61F 2/4601 for introducing bone substitute, for implanting bone graft implants or for compacting them in the bone cavity
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2/484 Fluid means, i.e. hydraulic or pneumatic
• 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 2002/30133 kidney-shaped or bean-shaped
• CPC Class Codes: A61F 2002/30235 tubular, e.g. sleeves
• CPC Class Codes: A61F 2002/30433 using additional screws, bolts, dowels, rivets or washers e.g. connecting screws
• CPC Class Codes: A61F 2002/30538 for adjusting angular orientation
• CPC Class Codes: A61F 2002/3055 for adjusting length
• CPC Class Codes: A61F 2002/30563 having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
• CPC Class Codes: A61F 2002/30579 with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30583 filled with hardenable fluid, e.g. curable in-situ
• CPC Class Codes: A61F 2002/30589 Sealing means
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30604 modular
• CPC Class Codes: A61F 2002/30617 Visible markings for adjusting, locating or measuring
• CPC Class Codes: A61F 2002/30772 Apertures or holes, e.g. of circular cross section
• 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 2002/4629 : connected to the endoprosthesis or implant via a threaded connection
• CPC Class Codes: A61F 2002/4666 : for measuring force, pressure or mechanical tension
• CPC Class Codes: A61F 2210/0085 : hardenable in situ, e.g. epoxy resins
• CPC Class Codes: A61F 2220/0041 : using additional screws, bolts, dowels or rivets, e.g. connecting screws
• CPC Class Codes: A61F 2230/0015 : Kidney-shaped, e.g. bean-shaped
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2250/0006 : for adjusting angular orientation
• CPC Class Codes: A61F 2250/0097 : Visible markings, e.g. indicia
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite

Abstract

A selectively expanding spine cage has a minimized diameter in its unexpanded state that is smaller that the diameter of the neuroforamen through which it passes in the distracted spine. The cage conformably engages between the endplates of the adjacent vertebrae to effectively distract the anterior disc space, stabilize the motion segments and eliminate pathologic spine motion. Angular deformities can be corrected, and natural curvatures restored and maintained. The cage enhances spinal arthrodesis by creating a rigid spine segment, or if filled with compressible substances, the cage can be used for motion preservation between vertebral bodies. Expanding selectively (anteriorly, along the vertical axis of the spine) rather than uniformly, the cage height increases and holds the vertebrae with fixation forces greater than adjacent bone and soft tissue failure forces in natural lordosis. Stability is thus achieved immediately, enabling patient function by eliminating painful motion. The cage shape intends to rest proximate to the anterior column cortices securing the desired spread and fixation, allowing for bone graft in, around, and through the implant for arthrodesis whereas for arthroplasty it fixes to endpoints but cushions the spine naturally.

Claims

1. An apparatus for providing spinal correction in three dimensions, comprising:

a selectively expanding spinal implant for posterior insertion between opposed superior and inferior vertebral end plates of a patient, said spinal implant comprising;

a cylinder block comprising a base resting on a first end plate and two or more slave cylinders and corresponding pistons having a corrective bone engaging surface for expanding against a second end plate.

2. The apparatus of claim 1, further comprising:

a master cylinder located away from the patient and communicating hydraulically and independently with each slave cylinder for independently operating a corresponding slave piston to impart a desired anterior/posterior spinal correction and for operating the pistons differentially for imparting desired lateral, right/left spinal correction.

3. The apparatus of claim 1 said cylinder block and pistons comprising:

a substantially incompressible, biocompatible material.

4. The apparatus of claim 3, said material comprising 6-4 titanium.

5. The apparatus of claim 1, further comprising:

a curable polymer having a fluid state for providing hydraulic communication of mechanical force from said master cylinder to said slave cylinders to elevate said pistons to a position that provides desired spinal correction;

wherein said polymer cures to a solid state to lock said pistons at said desired correction.

6. The apparatus of claim 5, said cylinder block and pistons defining a space to confine said cured polymer, wherein said position of the expanded pistons can withstand compressive forces up to a structural failure limit of the cylinder block.

7. The apparatus of claim 6 wherein said implant can withstand compressive forces in a range from 8000-12,000 Newtons, or 3000 lbs.

8. The apparatus of claim 1, said implant having a diameter substantially in a range of 0.8-1 cm in an unexpanded state to facilitate posterior insertion through a pedicle space.

9. The apparatus of claim 5, said curable polymer comprising methyl methacrylate.

10. The apparatus of claim 1, said cylinder block defining a bone graft infusion aperture that is coupled through a conduit with a source of bone graft material for infusion of said bone graft material into an intervertebral space.

11. A selectively expandable spinal implant for posterior insertion between opposed superior and inferior vertebral end plates of a patient, comprising:

a slave cylinder block defining at least first and second cylinders, said cylinders receiving corresponding pistons, each piston comprising a surface for expanding against an adjacent end plate to impart a desired spinal correction; and

a bone engaging plate moveably attached to the surface of the pistons to provide an anterior/posterior corrective angle depending on relative expansion of the pistons.

12. The spinal implant of claim 11, further comprising:

a master cylinder located away from the patient, and connected to the slave cylinders through control lines containing a hydraulic fluid said matter cylinder providing independent, selective hydraulic actuation of the slave pistons;

wherein independent operation of the slave pistons imparts a desired anterior/posterior spinal correction and wherein differential operation of the pistons with respect to one another imparts a desired lateral spinal correction.

13. The spinal implant of claim 12, said hydraulic fluid comprising a polymer that cures to a solid state to lock the slave pistons immovably in place at a desired amount of spinal correction.

14. The spinal implant of claim 13, said hydraulic fluid comprising methyl methacrylate.

15. The spinal implant of claim 13, said slave cylinder block and pistons further comprising a biocompatible, substantially incompressible material for confining the curable polymer, wherein a desired amount of spinal correction imparted by the expanded pistons is capable of withstanding compressive forces up to a structural failure limit of the cylinder block.

16. The spinal implant of claim 15, wherein the slave cylinder block and pistons comprise titanium or an alloy thereof.

17. The spinal implant of claim 15, wherein the slave cylinder block and pistons comprise stainless steel.

18. The spinal implant of claim 15, wherein the slave cylinder block and pistons comprise any of biodegradable and biologically active materials and polyarylethertherektone (PEEK)™

.

19. The spinal implant of claim 11, said pistons concurrently operable to provide medial/lateral adjustment of said patient'"'"'s spine for scoliosis with anterior/posterior adjustment of said patient'"'"'s spine to create natural lordosis, with relative anterior adjustment greater than posterior adjustment.

20. The spinal implant of claim 15, wherein the desired amount of spinal correction imparted by the pistons is capable of withstanding compressive forces substantially in a range from 8000 up to 12,000 Newtons or approximately 3000 pounds.

21. A selectively expandable spinal implant for posterior insertion between opposed superior and inferior vertebral end plates of a patient, comprising:

a cylinder block defining two or more slave cylinders;

two or more corresponding pistons positioned within said cylinders to provide a corrective bone engaging surface for expanding against a first vertebral end plate; and

said cylinder block comprising a base resting on a second vertebral end plate.

22. The spinal implant of claim 21, further comprising:

a master cylinder located away from the patient for communicating a hydraulic force over a control line to a corresponding slave cylinder for selectively operating the slave pistons to impart desired anterior/posterior spinal correction and differentially operating the slave pistons to impart lateral spinal correction.

23. The spinal implant of claim 21, further comprising:

a plate having a bone engaging surface movably provided on the pistons for expanding against a first end plate to impart a desired anterior/posterior and lateral, right/left correction as the pistons are extended.

24. The spinal implant of claim 22, further comprising:

a curable polymer having a fluid state for communicating the hydraulic force to operate the slave pistons, and curing to a solid state to lock the pistons of a desired spinal correction substantially immovably in place.

25. The spinal implant of claim 24, said cylinder block and slave cylinders comprising 614 titanium for enclosing the cured polymer, wherein the implant is able to withstand compressive forces up to a limit defined by structural failure of the 614 titanium.

26. The spinal implant of claim 25, wherein the implant is capable of withstanding compressive forces in a range of from about 8000 up to about 12,000 Newtons or approximately 3000 pounds.

27. The spinal implant of claim 21 wherein said implant is expandable to immobilize movement between said vertebral end plates to fix the patient'"'"'s spine in a physiologic position having reduced tendency toward subsidence.

28. The spinal implant of claim 27, further comprising:

filling said cylinders a compressible fluid gas for to accommodate spinal movement, by preservable motion between said vertebral end plates.

29. The spinal implant of claim 21 further comprising:

at least two transducers for sensing forces applied to the implant during spinal movement;

wherein said implant responds to sensed pressures, optimally under computer control, to operated said piston to effect corrective responsive implant shape changes that realign the patient'"'"'s spine.

30. The spinal implant of claim 29, wherein said sensors operate the pistons in accordance with any of a surgeon'"'"'s specifications and changes said patient'"'"'s spinal load.

31. The spinal implant of claim 21, wherein said piston is operated by any gas, fluid, or fluid evolving into a solid state matrix, with or without a coiled spring interior that is in itself solid or tubular, wherein movement piston comprises a combination of gas, fluid, or solid, with or without the coiled internal spring inside the piston.