Spinal motion preservation assemblies

• US 20060079898A1
• Filed: 10/24/2005
• Published: 04/13/2006
• Est. Priority Date: 10/23/2003
• Status: Active Grant

• Current Assignee: Mis Ip Holdings LLC
• Original Assignee: TranS1 Incorporated (Baxano Surgical, Inc.)
• Inventors: Assell, Robert L., Wessman, Bradley J., Ainsworth, Stephen D., Dickhudt, Eugene A.
• Granted Patent: US 7,601,171 B2
• Time in Patent Office: Days
• US Class Current: 623/17.120
• CPC Class Codes: A61B 17/025 Joint distractors
• CPC Class Codes: A61B 17/70 Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
• CPC Class Codes: A61B 17/8888 at its central region
• CPC Class Codes: A61B 2017/0256 for the spine
• CPC Class Codes: A61F 2/30742 Bellows or hose-like seals; Sealing membranes A61B17/8808 takes precedence; sealing membranes for retaining bone substitute A61F2/2846
• CPC Class Codes: A61F 2/30744 End caps, e.g. for closing an endoprosthetic cavity
• CPC Class Codes: A61F 2/441 made of inflatable pockets or chambers filled with fluid, e.g. with hydrogel
• 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 2/4425 made of articulated components
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2/4637 for connecting or disconnecting two parts of a prosthesis
• CPC Class Codes: A61F 2002/30014 differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2002/30075 swellable, e.g. when wetted
• CPC Class Codes: A61F 2002/30224 cylindrical
• CPC Class Codes: A61F 2002/30289 helically-coiled
• CPC Class Codes: A61F 2002/30327 differing in diameter
• CPC Class Codes: A61F 2002/30331 made by longitudinally pushing a protrusion into a complementarily-shaped recess, e.g. held by friction fit
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/30462 retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2002/30495 using a locking ring
• CPC Class Codes: A61F 2002/30507 : using a threaded locking member, e.g. a locking screw or a set screw
• CPC Class Codes: A61F 2002/3055 : 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 2002/30566 : Helical springs
• CPC Class Codes: A61F 2002/30571 : Leaf springs
• CPC Class Codes: A61F 2002/30579 : with mechanically expandable devices, e.g. fixation devices
• CPC Class Codes: A61F 2002/30581 : having a pocket filled with fluid, e.g. liquid
• CPC Class Codes: A61F 2002/30583 : filled with hardenable fluid, e.g. curable in-situ
• CPC Class Codes: A61F 2002/30588 : filled with solid particles
• CPC Class Codes: A61F 2002/30601 : telescopic
• CPC Class Codes: A61F 2002/30604 : modular
• CPC Class Codes: A61F 2002/30649 : Ball-and-socket joints
• CPC Class Codes: A61F 2002/30677 : Means for introducing or releasing pharmaceutical products, e.g. antibiotics, into the body
• CPC Class Codes: A61F 2002/3085 : with a threaded, e.g. self-tapping, bone-engaging surface, e.g. external surface
• CPC Class Codes: A61F 2002/30859 : having threaded portions of different pitches
• CPC Class Codes: A61F 2002/30863 : the entry end surface having flutes, relief grooves, starter notches or bevelled indentations
• CPC Class Codes: A61F 2002/443 : having two transversal endplates and at least one intermediate component
• CPC Class Codes: A61F 2002/444 : for replacing the nucleus pulposus
• CPC Class Codes: A61F 2002/4495 : having a fabric structure, e.g. made from wires or fibres
• 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 2210/0061 : swellable
• CPC Class Codes: A61F 2210/0085 : hardenable in situ, e.g. epoxy resins
• 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 2220/0075 : sutured, ligatured or stitched, retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2230/0069 : cylindrical
• CPC Class Codes: A61F 2230/0091 : helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
• CPC Class Codes: A61F 2250/0018 : differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2250/0039 : differing in diameter
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium

Abstract

Spinal motion preservation assemblies adapted for use in a spinal motion segment are disclosed including the process for delivering and assembling the spinal motion preservation assemblies in the spinal motion segment via an axial channel created with a trans-sacral approach. The spinal motion preservation assemblies make use of a dual pivot. A number of different embodiments of spinal motion preservation assemblies are disclosed which include at least one component adapted for elastic deformation under compressive loads. The disclosed mobility preservation assemblies provide for dynamic stabilization (DS) of the spinal motion segment.

Claims

1. A spinal motion preservation assembly adapted for use in a spinal motion segment the spinal motion preservation assembly comprising:

a distal bone anchor comprising;

a distal end;

a proximal end;

a cavity in the interior of the distal bone anchor accessible from the proximal end, the cavity adapted for receipt of a corresponding driver head; and

a set of threads on the exterior of the distal bone anchor, the threads adapted to engage a distal vertebral body in the motion segment;

a pivot comprising;

a distal end;

a proximal end; and

a middle between the distal end and the proximal end;

a distal pivot cap comprising;

an exterior corresponding to a portion of the cavity in the interior of the distal bone anchor; and

a cavity at the proximal end of the distal pivot cap for receiving the distal end of the pivot;

a proximal bone anchor comprising;

a distal end;

a proximal end;

a cavity that runs through the interior of the proximal bone anchor from the distal end to the proximal end, the cavity adapted for receipt of a corresponding driver head; and

a set of threads on the exterior of the proximal bone anchor adapted to engage a proximal vertebral body in the motion segment;

a proximal pivot cap comprising;

a distal end;

a proximal end; and

a cavity at the distal end of the proximal pivot cap for receiving the proximal end of the pivot; and

at least one component located between the distal bone anchor and the proximal bone anchor that is elastically deformable.

2. The spinal motion preservation assembly of claim 1 wherein the distal bone anchor is adapted to be engaged by a driver tool to retain the distal bone anchor on the driver head.

3. The spinal motion preservation assembly of claim 2 wherein the proximal bone anchor is adapted to be engaged by the driver tool to retain the proximal bone anchor on a portion of the driver tool.

4. The spinal motion preservation assembly of claim 3 wherein the distal bone anchor engaged by the driver tool and the proximal bone anchor engaged by the driver tool can be delivered to the distal vertebral body and the proximal vertebral body by an axial channel in the spine without cross-threading a thread path cut into proximal vertebral body by the passage of the bone anchors.

5. The spinal motion preservation assembly of claim 3 wherein:

the major diameter of the set of threads on the exterior of the distal bone anchor is less than the major diameter of the set of threads on the exterior of the proximal bone anchor;

the handedness of the set of threads on the exterior of the distal bone anchor is the same as the handedness on the set of threads on the proximal bone anchor;

the pitch of the set of threads on the exterior of the distal bone anchor is finer than the set of threads on the proximal bone anchor such that rotation of the distal bone anchor and the proximal bone anchor at the same time and at the same rate by the driver tool will cause the distal vertebral body engaged with the distal bone anchor to move relative to a proximal vertebral body engaged with the proximal bone anchor to distract the intervertebral disc space.

6. The spinal motion preservation assembly of claim 1 wherein the cavity in the distal bone anchor extends from the proximal end to the distal end along the longitudinal axis such that the distal bone anchor can be deployed over a guide wire.

7. The spinal motion preservation assembly of claim 1 wherein the proximal pivot cap further comprises a set of external threads corresponding to the first threaded portion of the proximal bone anchor cavity and a driver cavity in the proximal end of the proximal pivot cap, the driver cavity adapted to receiver a corresponding driver head so that the driver head can impart torque to the proximal pivot cap to selectively advance the proximal pivot cap along the longitudinal axis of the proximal bone anchor to move the pivot towards the distal bone anchor to increase the distance between the distal vertebral body and the proximal vertebral body.

8. The spinal motion preservation assembly of claim 7 further comprising a jam nut which in turn comprises:

a distal end,

a proximal end,

a jam nut body between the distal end and the proximal end, the jam nut body being at least partially threaded along the exterior of the jam nut with threads that can engage with the threaded cavity of the proximal bone anchor; and

a driver cavity open on at least the proximal end of the jam nut so that a corresponding driver can engage the driver cavity to impart torque and cause the jam nut to axially advance along the longitudinal axis of the proximal bone anchor to move the proximal end of the jam nut into contact with the proximal end of the proximal pivot cap.

9. The spinal motion preservation assembly of claim 1 wherein a spinal motion segment with an implanted spinal motion preservation assembly can move in flexion, extension, lateral bending to the right, lateral bending to the left, clockwise axial rotation, and counterclockwise axial rotation.

10. The spinal motion preservation assembly of claim 9 wherein the spinal motion segment with an implanted spinal motion preservation assembly can move in about 12 degrees of flexion, about 8 degrees of extension, about 9 degrees of lateral bending to the right, about 9 degrees of lateral bending to the left, about 2 degrees of clockwise axial rotation, and about 2 degrees of counterclockwise axial rotation.

11. The spinal motion preservation assembly of claim 10 wherein the distal vertebral body can translate relative to the proximal vertebral body in the anterior/posterior direction and in the lateral right/lateral left direction as well as translation arising from the elastic deformation and recovery of at least one component of the spinal preservation assembly.

12. The spinal motion preservation assembly of claim 1 wherein at least one component that can undergo elastic deformation is made from a material selected from the group consisting of fluoropolymer elastomer, polyurethane elastomer, and silicone rubber.

13. The spinal motion preservation assembly of claim 1 wherein at least one component that can undergo elastic deformation is a spring adapted to recoverably deform in compression.

14. The spinal motion preservation assembly of claim 1 wherein at least one component that can undergo elastic deformation is located between the distal pivot cap and the distal bone anchor.

15. The spinal motion preservation assembly of claim 1 wherein at least one component that can undergo elastic deformation is located between the proximal pivot cap and the proximal bone anchor.

16. The spinal motion preservation assembly of claim 1 wherein at least a portion of the pivot can undergo elastic deformation.

17. The spinal motion preservation assembly of claim 16 wherein the pivot is at least partially comprised of a fabricated spring.

18. The spinal motion preservation assembly of claim 1 wherein at least a portion of the distal pivot cap can undergo elastic deformation.

19. The spinal motion preservation assembly of claim 18 wherein the distal pivot cap is at least partially comprised of a fabricated spring.

20. The spinal motion preservation assembly of claim 1 wherein at least a portion of the proximal pivot cap can undergo elastic deformation.

21. The spinal motion preservation assembly of claim 20 wherein the proximal pivot cap is at least partially comprised of a fabricated spring.

22. The spinal motion preservation assembly of claim 1 wherein the proximal pivot cap is adapted to move longitudinally relative to the distal end of the cavity of the proximal bone anchor without having to rotate in order to move longitudinally into the distal end of the cavity;

wherein the spinal motion preservation assembly further comprises;

an expandable membrane extending from the proximal end of the distal anchor to the distal end of the proximal anchor such that when filled with prosthetic nucleus material serves as a prosthetic nucleus to distribute forces to the annulus fibrosis;

a threaded cap, the threaded cap comprising;

a distal end;

a proximal end;

a body between the distal end and the proximal end, the external surface of the body threaded for at least a portion of the external surface with threads corresponding to the first threaded portion of the proximal bone anchor cavity; and

a driver cavity in the proximal end of the threaded cap such that a driver head inserted into the proximal end of the proximal bone anchor can engage within the driver cavity of the threaded cap to rotate the threaded cap relative to an implanted proximal bone anchor to advance the threaded cap distally towards that distal bone anchor to press against the pivot to cause an increase in the longitudinal distance between the proximal bone anchor and the distal bone anchor to selectively change the distribution of shared axial compressive loads assumed by the prosthetic nucleus and the external threads on the proximal bone anchor and the external threads on the distal bone anchor.

23. The spinal motion preservation assembly of claim 1 wherein the pivot is comprised of:

a material having a first set of biomechanical properties optimized for wear and that is used in configuring the distal end and the proximal end, and

a material having a second set of biomechanical properties optimized for fatigue resistance and that is used in configuring the pivot body between the distal end and the proximal end.

24. The spinal motion preservation assembly of claim 1 wherein the spinal motion preservation assembly further comprises an expandable membrane extending from the proximal end of the distal anchor to the distal end of the proximal anchor such that when filled with prosthetic nucleus material serves as a prosthetic nucleus to distribute forces to the annulus fibrosis.

25. A spinal motion preservation assembly of claim 24 wherein the proximal pivot cap is adapted for threaded engagement with the proximal bone anchor such after a motion preservation assembly that has been implanted in the proximal and distal vertebral bodies and the expandable membrane has been filled with prosthetic nucleus material that has cured, rotation of the proximal pivot cap within the proximal bone anchor can be used to advance the threaded proximal pivot cap distally towards that distal bone anchor to press against the pivot to selectively change the distribution of loading between A) the prosthetic nucleus and annulus fibrosus and B) the external threads on the proximal bone anchor and the external threads on the distal bone anchor.

26. The spinal motion preservation assembly of claim 24 wherein the expandable membrane is adapted for contact of a membrane material of a first stiffness with at least a portion of the annulus fibrosis and a membrane material of a second stiffness with at least a portion of the proximal vertebral body and at least a portion of the distal vertebral body where the first stiffness is more stiff than the second stiffness such that after expansion, the expanded membrane is configured to be circumferentially radially stiffer in its middle section where it contacts the annulus fibrosus than on its end portions which contact the vertebral endplates of the proximal vertebral body and the distal vertebral body.

27. The spinal motion preservation assembly of claim 24 further comprising an elastomeric collar that abuts the annulus fibrosus and encircles at least a portion of the expanded membrane after expansion.

28. The spinal motion preservation assembly of claim 1 further comprising a volume of prosthetic nucleus material deployed in the intervertebral disc space.

29. The spinal motion preservation assembly of claim 28 wherein the spinal motion segment comprises an intervertebral disc space between the distal vertebral body and the proximal vertebral body, the spinal motion preservation assembly further comprising a layer of barrier-sealant material that is in conformal contact with the surfaces of the intervertebral disc space.

30. The spinal motion preservation assembly of claim 1 further comprising a flexible intermediate section connected to the proximal end of the distal bone anchor and the distal end of the proximal bone anchor so that a range of movement of the distal vertebral body relative to the proximal vertebral body along the longitudinal axis of the assembly causes a reversible alteration in the shape of the flexible intermediate section.

31. The spinal motion preservation assembly of claim 30 wherein the flexible intermediate section is a helical spring connecting the proximal bone anchor to the distal bone anchor.

32. The spinal motion preservation assembly of claim 31 wherein the helical spring is fabricated from a single piece of material.

33. The spinal motion preservation assembly of claim 1 further comprising an expandable flexible membrane providing a sealed-volume between the distal end of the proximal bone anchor and the proximal end of the distal bone anchor.

34. The spinal motion preservation assembly of claim 33 further comprising prosthetic nucleus material deployed in the expandable flexible membrane and to expand the expandable flexible membrane into the intervertebral disc space.

35. The spinal motion preservation assembly of claim 34 wherein the expandable flexible membrane is expanded by prosthetic nucleus material to fill the intervertebral disc space and conformably contact the distal vertebral body, the proximal vertebral body and the annulus fibrosus.

36. The spinal motion preservation assembly of claim 1 wherein the distal pivot cap has a set of external threads which correspond to a set of internal threads on at least a portion of the cavity in the interior of the distal bone anchor.

37. The spinal motion preservation assembly of claim 1 wherein the cavity in the distal bone anchor has an alignment slot and the cavity in the proximal bone anchor has an alignment slot such that the distal bone anchor and the proximal bone anchor can be axially advanced into the spinal motion segment by a driver that maintains the relative position of the distal bone anchor to the proximal bone anchor.

38. The spinal motion preservation assembly of claim 37 wherein:

the major diameter of the set of threads on the exterior of the distal bone anchor is the substantially the same as the major diameter of the set of threads on the exterior of the proximal bone anchor;

the pitch of the set of threads on the exterior of the distal bone anchor is the same as the pitch of the set of threads on the exterior of the proximal bone anchor;

the handedness of the threads on the exterior of the distal bone anchor is the same as the set of threads on the proximal bone anchor; and

the alignment slots in the distal bone anchor and the proximal bone anchor assist in the timed delivery of the proximal bone anchor so that a start of the set of threads on the proximal bone anchor enters into the proximal vertebral body into a thread path cut into the proximal vertebral body by the set of threads on the exterior of the distal bone anchor.

39. The spinal motion preservation assembly of claim 1 wherein the distal bone anchor has driver assembly engagement means and the proximal bone anchor has a driver assembly engagement means such that the distal bone anchor and the proximal bone anchor can be retained by a driver assembly so that both bone anchors while retained on the driver assembly can be axially advanced into the spinal motion segment as the driver assembly maintains the relative position of the distal bone anchor to the proximal bone anchor so that the proximal bone anchor is provided to the proximal vertebral body via timed delivery to engage a helical thread path in the proximal vertebral body previously cut by the passage of the distal vertebral bone anchor.

40. A spinal motion preservation assembly adapted for use in a spinal motion segment the spinal motion preservation assembly comprising:

a distal bone anchor comprising;

a distal end;

a proximal end;

a cavity in the interior of the distal bone anchor accessible from the proximal end, the cavity adapted for receipt of a corresponding driver head; and

a set of threads on the exterior of the distal bone anchor, the threads adapted to engage a distal vertebral body in the motion segment;

a pivot comprising;

a distal end;

a proximal end; and

a middle between the distal end and the proximal end;

a distal pivot cap comprising;

an exterior corresponding to a portion of the cavity in the interior of the distal bone anchor; and

a cavity at the proximal end of the distal pivot cap for receiving the distal end of the pivot;

a proximal bone anchor comprising;

a distal end;

a proximal end;

a cavity that runs through the interior of the proximal bone anchor from the distal end to the proximal end, the cavity adapted for receipt of a corresponding driver head; and

a set of threads on the exterior of the proximal bone anchor adapted to engage a proximal vertebral body in the motion segment;

an expandable membrane extending from the proximal end of the distal anchor to the distal end of the proximal anchor such that when filled with prosthetic nucleus material serves as a prosthetic nucleus to distribute forces to the annulus fibrosis;

a proximal pivot cap comprising;

a distal end;

a proximal end; and

a cavity at the distal end of the proximal pivot cap for receiving the proximal end of the pivot; and

at least one component located between the distal bone anchor and the proximal bone anchor that is elastically deformable.

41. A spinal motion preservation assembly adapted for use in a spinal motion segment, the spinal motion preservation assembly comprising:

a distal bone anchor comprising;

a distal end;

a proximal end;

a cavity in the inferior of the distal bone anchor accessible from the proximal end, the cavity adapted for receipt of a corresponding driver head

a set of threads on the exterior of the distal bone anchor, the threads adapted to engage a distal vertebral body in the motion segment;

a pivot comprising;

a distal end;

a proximal end; and

a middle between the distal end and the proximal end;

a distal pivot cap comprising;

an exterior corresponding to a portion of the cavity in the interior of the distal bone anchor; and

a cavity at the proximal end of the distal pivot cap for receiving the distal end of the pivot;

a proximal bone anchor comprising;

a distal end;

a proximal end;

a cavity that runs through the interior of the proximal bone anchor from the distal end to the proximal end, the cavity adapted for receipt of a corresponding driver head; and

a set of threads on the exterior of the proximal bone anchor, the threads adapted to engage a proximal vertebral body of the motion segment; and

a proximal pivot cap comprising;

a distal end;

a proximal end; and

a cavity at the distal end of the proximal pivot cap for receiving the proximal end of the pivot.

42. The spinal motion preservation assembly of claim 41 wherein the distal pivot cap has a set of external threads which correspond to a set of internal threads on at least a portion of the cavity in the interior of the distal bone anchor.

43. A spinal motion preservation assembly adapted for use in a spinal motion segment the spinal motion preservation assembly comprising:

a distal bone anchor comprising;

a distal end;

a proximal end;

a cavity in the interior of the distal bone anchor accessible from the proximal end, the cavity adapted for receipt of a corresponding driver head and the cavity adapted to receive the distal end of the pivot and to serve as a bearing surface to the distal end of the pivot; and

a set of threads on the exterior of the distal bone anchor, the threads adapted to engage a distal vertebral body of the motion segment;

a pivot comprising;

a distal end;

a proximal end; and

a middle between the distal end and the proximal end;

a proximal bone anchor comprising;

a distal end;

a proximal end;

a cavity that runs through the interior of the proximal bone anchor from the distal end to the proximal end, the cavity adapted for receipt of a corresponding driver head; and

a set of threads on the exterior of the proximal bone anchor, the threads adapted to engage a proximal vertebral body of the motion segment; and

a proximal pivot cap comprising;

a distal end;

a proximal end; and

a cavity at the distal end of the proximal pivot cap for receiving the proximal end of the pivot; and

at least one component located between the distal bone anchor and the proximal bone anchor that is elastically deformable in compression.

44. A spinal motion stabilization assembly for providing dynamic stabilization to a motion segment within a spine;

the spinal motion stabilization assembly comprising;

a distal implant device assembly;

a proximal implant device assembly;

a dual pivot in contact with the distal implant device assembly via an unconstrained pivot contact with a bearing surface in the distal implant device assembly and also in contact with the proximal implant device assembly via an unconstrained pivot contact with a bearing surface in the proximal implant device assembly; and

a prosthetic nucleus encircling at least a portion of the dual pivot.

45. The spinal motion stabilization assembly of claim 44 wherein a spinal motion segment with an implanted spinal motion stabilization assembly can move in flexion, extension, lateral bending to the right, lateral bending to the left, clockwise axial rotation, and counterclockwise axial rotation.

46. The spinal motion stabilization assembly of claim 45 wherein a motion segment with an implanted spinal motion stabilization assembly can move in about 12 degrees of flexion, about 8 degrees of extension, about 9 degrees of lateral bending to the right, about 9 degrees of lateral bending to the left, about 2 degrees of clockwise axial rotation, and about 2 degrees of counterclockwise axial rotation.

47. The spinal motion stabilization assembly of claim 44 wherein the motion segment comprises a superior vertebral body and an inferior vertebral body and wherein the superior vertebral body can translate relative to the inferior vertebral body in the anterior/posterior direction, in the lateral right/lateral left direction as well as translation arising from elastic deformation and recovery of at lest one component of the spinal motion stabilization assembly.

48. The spinal motion stabilization assembly of claim 44 wherein the proximal implant device assembly is adapted to move the bearing surface within the proximal implant device assembly towards the distal implant device assembly in response to torque applied during assembly of the spinal motion stabilization assembly to selectively change the distribution of loading between A) the prosthetic nucleus and annulus fibrosus and B) external threads on the proximal implant device assembly engaged with the proximal vertebral body and the external threads on the distal device assembly and the distal vertebral body.

49. A method for deploying a spinal motion preservation assembly in a motion segment accessed by an axial trans-sacral approach, the implanted spinal motion preservation assembly comprising a distal component and a proximal component both with external threads, an implant subassembly extending between the distal and proximal components which comprises a pivot adapted for unconstrained engagement by means of dual pivot ends within both the distal component and the proximal component, and an expandable membrane which is expanded with a prosthetic nucleus material, the method comprising:

rotating a driver which simultaneously deploys the distal component and the proximal component to engage the distal component with a distal vertebral body and to engage the proximal component with a proximal vertebral body while maintaining a predetermined separation distance between the distal component and the proximal component and without cross threading the thread path cut into the proximal vertebral body;

inserting a distal end of the pivot into the proximal end of the distal implant device assembly; and

selectively advancing a portion of the proximal implant device assembly to push the pivot against the distal implant device assembly to change the distribution of loading between A) the prosthetic nucleus and B) the external threads on the proximal component and the external threads on the distal component.

50. The method of claim 49 further comprising the step of engaging the distal component with at least one component adapted to elastically deform under compressive load.

51. The method of claim 49 further comprising the step of engaging the proximal component with at least one component adapted to elastically deform under compressive load.

52. The method of claim 51 further comprising the step of engaging the distal component with at least one component adapted to elastically deform under compressive load.

53. A method of providing dynamic stabilization to a motion segment in a spine, the method comprising;

deploying into the motion segment by an axial channel created with a trans-sacral approach a spinal motion stabilization assembly with a pair of unconstrained pivot points and at least one component capable of elastic deformation such that motion segment after receipt of the spinal motion stabilization assembly can undergo motion that enables the normal range of motion in all six degrees of freedom.

54. The method of claim 53 further comprising the steps of:

expanding a membrane connected to the spinal motion stabilization assembly with prosthetic nucleus material to form a prosthetic nucleus; and

selectively varying the loading between the prosthetic nucleus and sets of threads on the spinal motion stabilization assembly engaged with vertebral bodies on the superior and inferior ends of the motion segment.

55. The method of claim 54 wherein prosthetic nucleus material is provided to the membrane through a distractor/injector tool after distraction of the motion segment and before removal of the distractor/injector tool.