Apparatus and method for aligning vertebrae

• US 6,491,695 B1
• Filed: 11/05/1999
• Issued: 12/10/2002
• Est. Priority Date: 11/05/1999
• Status: Expired due to Fees

• Current Assignee: Carl Roggenbuck
• Original Assignee: Carl Roggenbuck
• Inventors: Roggenbuck, Carl
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): Priddy, Michael B.
• Application Number:
  US09/434,129
• Time in Patent Office: 1,131 Days
• Field of Search: 606/60, 606/61, 606/57, 606/58, 606/90, 606/99, 606/105
• US Class Current: 606/86.00A
• CPC Class Codes: A61B 17/8866 for gripping or pushing bones, e.g. approximators joint distractors A61B17/025
• CPC Class Codes: A61B 2017/0256 for the spine

Abstract

Apparatus for aligning misaligned vertebrae including a partible screw which can be threadedly coupled to misaligned vertebrae and decoupled from the vertebrae after being aligned. The screw, which is rotatable about an axis, includes axially shiftable screw halves having complementally formed partial screw thread sections which can be aligned in any one of a plurality of axially spaced apart positions to define a helical screw thread. Apparatus is provided for detachably holding the screw halves together in any one of a plurality of axially spaced apart positions with the partial screw threads on each of the halves in alignment including an alignment collar and a locking collar which can be detachably threadedly received on, and locked to, the screw thread sections in locking positions when the screw is being threadedly coupled to and uncoupled from the vertebrae. The alignment collar and locking collar can be individually unthreaded and moved to a remote position removed from the screw threads to allow the screw halves to be axially relatively shifted relative to each other.

Claims

1. Apparatus for aligning first and second vertebrae which are misaligned and have confronting portions with at least one tapped thread adapted to receive a complementally threaded fusion cage, said apparatus comprising:

a partible screw, rotatable in first and second opposite directions about a longitudinal axis, for threadedly coupling to and decoupling from, respectively, said first and second vertebrae;

said partible screw including

first and second relatively axially moveable screw halves having first and second pluralities of axially spaced, helically extending, partial screw thread sections, respectively which can be helically aligned with each other in any selected one of a plurality of different axially shifted locations to form a helical screw thread complementally formed to, and adapted to be received by, said tapped thread when said screw is turned in said first direction of rotation about said axis;

means for relatively axially shifting said first and second screw halves to first positions in which at least a first portion of said first plurality of partial screw thread sections is helically aligned with a first portion of said second plurality of partial screw thread sections when said screw is being rotated in said first direction about its axis and threadedly coupled to said first and second vertebrae,

and for relatively axially shifting said first and second screw halves from said first positions to second positions, in which said first portion of said first plurality of partial screw thread sections is helically aligned with a second axially spaced portion of said second plurality of partial screw thread sections, to shift said first vertebrae into alignment with said second vertebrae; and

locking means for detachably locking said first and second screw halves together in said second positions to preclude relative axial shifting of said first portion of said first plurality of screw threads section and said second portion of said second plurality of partial screw thread sections as said partible screw is rotated in said second direction and threadedly decoupled from said first and second vertebrae.

2. The apparatus set forth in claim 1 wherein said locking means comprises an alignment collar threadedly received by said first and second screw halves in said second positions.

3. The apparatus set forth in claim 2 wherein said locking means includes a locking collar threadedly received by said first and second screw halves in said second positions in abutting relation with said alignment collar to detachably lock said alignment collar to said first and second screw halves and preclude relative axial movement of said screw halves as said partible screw is being threadedly decoupled from said first and second vertebrae.

4. The apparatus set forth in claim 3 wherein said locking means includes means receiving first and second screw halves in said first positions for detachably locking said screw halves together in said first positions.

5. The apparatus set forth in claim 1 wherein said means for locking includes means for locking said first and second screw halves in said first positions to preclude relative axial shifting of said first and second screw halves as said partible screw is threadedly coupled to said first and second vertebrae.

6. The apparatus set forth in claim 5 wherein said locking means comprises an alignment collar axially shiftable relative to said first and second screw halves between a locking position threadedly received by said first and second screw halves in said first and second positions as said screw is being threadedly coupled to and decoupled from, respectively, said first and second vertebrae and axially spaced non-locking positions in which said screw halves can be axially relatively shifted.

7. The apparatus set forth in claim 5 wherein at least one of said first and second screw halves includes an axially spaced non-threaded dwell section for receiving said alignment collar in said non-locking position.

8. The apparatus set forth in claim 7 wherein said first and second screw halves include an additional axial spaced apart cooperating screw thread section on which said alignment collar can be threadedly coupled in said non-locking position.

9. The apparatus set forth in claim 6 in which said locking means includes a locking collar axially shiftable relative to said first and second screw halves between a locking position threadedly received by said first and second screw halves in either of said first and second positions and in abutting relation with said alignment collar as said partible screw is being threadedly coupled to and decoupled from, respectively, said first and second vertebrae, and an axially spaced, non-locking position in which said screw halves can be relatively axially shifted.

10. The apparatus set forth in claim 1 wherein said locking means includes an alignment collar threadedly receiving a first part of said first portion of said first plurality of partial screw thread sections and a first part of said first portion of said second plurality of partial screw thread sections when said first and second screw halves are in said first positions and threadedly receiving said first part of said first portion of said first plurality of partial screw thread sections and a first part of a second portion of said second plurality of partial screw thread sections when said first and second screw halves are in said second positions.

11. The apparatus set forth in claim 10 wherein said locking means includes a locking collar

threadedly receiving a second part of said first portion of said first plurality of partial screw thread sections and a second part of said first portion of said second plurality of partial screw thread sections when said first and second screw halves are in said first positions; and

threadedly receiving said second part of said first portion of said first plurality of partial screw thread sections and a second part of a second portion of said second plurality of partial screw thread sections when said first and second screw halves are in said second positions.

12. The apparatus set forth in claim 1 wherein said means for relatively axially shifting said first and second screw halves to said first and second positions comprises

a hollow body having an elongate bore therethrough and an axial end mounted to an end of said first screw half;

and

an elongate threaded rod received by said elongate bore and having an axial end mounted to an end of said second screw half; and

means threadedly coupled to said threaded rod for axially moving said threaded rod relative to said body.

13. The apparatus set forth in claim 1 wherein said means for relatively axially shifting said first and second screw halves, comprises

first and second abutting elongate bodies each having opposite ends, mounted together for relative axial sliding movement;

means mounting said first and second halves on an end of said first screw and second abutting elongate bodies, respectively, for sliding movement therewith; and

translating means coupled to opposite end portions of said first and second elongate bodies adjacent said opposite end portions of said elongate bodies.

14. The apparatus set forth in claim 13 wherein said translating means is threadedly coupled to at least one of said opposite end portions of said first and second elongate bodies.

15. The apparatus set forth in claim 14 wherein said elongate bodies each include a semi-cylindrical bar having a flat face slidingly coupled to the flat face of the other elongate body and a semi-cylindrical outer surface having a plurality of axially spaced, helically disposed rib sections which are in helical registry with the plurality of helically disposed rib sections on the other elongate body.

16. The apparatus set forth in claim 15 wherein one of said flat faces includes an elongate dove tail slot therein and the other of said flat faces includes complementally formed, dove tail slide slidingly received in said drive tail slot.

17. The apparatus set forth in claim 14 wherein at least one of said elongate bodies includes a curvilinear outer surface having a plurality of helically disposed rib sections forming a partial thread between the ends thereof;

and

translating nut means threadedly coupled to said partial thread for axially relatively shifting said elongate bodies.

18. The apparatus set forth in claim 13 wherein said locking means comprises an alignment collar which is received on said first and second elongate bodies in a non-locking position for axial movement thereon between said non-locking position and an axially outwardly spaced locking position receiving said screw halves.

19. The apparatus set forth in claim 18 wherein said locking means comprises an internally threaded collar that includes an axial outer portion which, in said locking position, threadedly receives an axially inner portion of said screw thread.

20. The apparatus set forth in claim 19 wherein said internally threaded collar includes an axially outer portion which, in said non-locking position, is threadedly coupled to a complementally threaded portion provided on at least one of said elongate bodies.

21. The apparatus set forth in claim 18 wherein at least said first elongate body includes a non-threaded dwell section axially spaced from said first plurality of screw thread sections for stowing said collar as said first and second screw halves are being relatively axially shifted between said first positions and said second positions.

22. The apparatus set forth in claim 21 further including a locking collar axially moveable on said first and second bodies between a second non-locking position received by said non-threaded dwell section and a second locking position received by said first and second pluralities of screw thread sections, in either of said first or second positions, in abutting engagement with said alignment collar.

23. The apparatus set forth in claim 1 wherein said screw has a barrel shape.

24. The apparatus set forth in claim 23 wherein each of said screw halves has a semi-cylindrical shape.

25. A vertebrae alignment tool for repositioning misaligned adjacent vertebrae into alignment comprising:

first and second elongate bodies, each having longitudinally spaced opposite ends, mounted together for relative longitudinal sliding movement;

a partible vertebrae shifting screw, having a longitudinal axis, for threadedly coupling to and decoupling from said adjacent vertebrae as said screw is turned in first and second opposite directions of rotation about said axis including;

first and second relatively longitudinally axially moveable screw halves having first and second pluralities of axially spaced, helically extending screw thread sections, respectively, which can be helically aligned with each other in any selected one of a plurality of different, longitudinally shifted positions to form a longitudinally extending helical screw thread;

said first screw half being mounted on one end of said first elongate body said second screw half being mounted on one end of said second elongate body;

shifting means threadedly coupled to at least one of said first and second elongate bodies

for longitudinally relatively moving said first and second elongate bodies to longitudinally relatively shift said first and second screw halves to first positions in which at least a first portion of said first plurality of screw thread sections is helically aligned with a first portion of said second plurality of screw thread sections as said screw is rotated in said first direction about said axis, and

for relatively longitudinally moving said first and second screw halves to second positions in which said first portion of said first plurality of screw thread sections is helically aligned with a second portion of said second plurality of screw thread sections; and

locking means detachably mounted on said screw halves to preclude axial shifting of said first portion of said first plurality of screw sections and said second portion of said second plurality of screw thread sections in said second positions when said screw is being oppositely rotated in said second direction to threadedly decouple from said vertebrae.

26. The vertebrae alignment tool set forth in claim 25 wherein said locking means is threadedly received by said first and second pluralities of screw thread sections.

27. The vertebrae alignment tool set forth in claim 26 wherein said locking means includes an alignment nut threadedly coupled to said screw when said first and second pluralities of screw thread sections are in said first positions to preclude relative longitudinal shifting thereof as said screw is rotated in said first direction and coupled to said vertebrae;

said alignment nut being moveable to a decoupled position removed from threaded engagement with said first and second pluralities of screw thread sections to a non-coupling position as said screw thread sections are being longitudinally shifted.

28. The vertebrae alignment tool set forth in claim 26 including a locking nut threadedly coupled to said partible screw in abutting relation with said alignment nut when said first and second pluralities of screw thread sections are in said first positions and decoupled from said first and second pluralities of screw thread sections as said screw thread sections are being relatively longitudinally shifted.

29. The vertebrae alignment tool set forth in claim 28 wherein at least one of said ends of said first and second elongate bodies includes a dwell section on which said alignment nut and said locking nut rest when decoupled from said screw.

30. The apparatus set forth in claim 29 wherein said shifting means includes

a helical screw rib at least one of said elongate bodies; and

a translating nut rotatably mounted for rotation about said axis on the other of said elongate bodies and threadedly coupled to at least said one elongate body for relatively axially moving said elongate bodies to relatively axially move said screw halves; and

a hand graspable handle mounted on said other elongate body for preventing rotation of said other body as said translating nut is being rotated thereon.

31. A vertebrae alignment tool for shifting misaligned adjacent vertebrae into alignment with each other comprising:

first and second elongate bodies, each having longitudinally spaced opposite ends, mounted together for relative longitudinal sliding movement;

a vertebrae shifting partible screw, having a longitudinal axis, for threadedly coupling to and decoupling from said adjacent vertebrae as said screw is turned in first and second opposite directions, respectively, about said axis including

first and second longitudinally relatively axially moveable screw halves having first and second pluralities of axially spaced, helically extending screw thread sections, respectively, which can be helically aligned with each other in any selected one of a plurality of different, longitudinally shifted positions to form a longitudinally extending helical screw thread;

said first screw half being mounted on one end of said first elongate body;

said second screw half being mounted on one end of said second elongate body;

shifting means threadedly coupled to at least one of said first and second elongate bodies

for longitudinally relatively moving said first and second elongate bodies to longitudinally relatively shift said first and second screw halves to first positions in which at least a first portion of said first plurality of screw thread sections is helically aligned with a first portion of said second plurality of screw thread sections as said screw is turned in said first direction of rotation about said axis, and

for relatively longitudinally moving said first and second screw halves to second positions in which said first portion of said first plurality of screw thread sections is helically aligned with a second portion of said second plurality of screw thread sections; and

alignment nut means detachably threadedly received by said screw when said first and second pluralities of thread sections are in either of said first positions or said second positions but moveable to an inoperative, position when said screw halves are being axially shifted.

32. The vertebrae alignment tool set forth in claim 31 including locking nut means threadedly received by said first and second pluralities of thread sections in either of said first positions or said second positions but moveable to an inoperative position removed from said first and second pluralities of thread sections as said screw halves are being axially shifted.

33. An alignment tool for shifting first and second misaligned adjacent vertebrae into alignment comprising:

a partible vertebrae shifting screw, having a longitudinal axis, for threadedly coupling to and decoupling from said adjacent vertebrae as said screw is rotated in first and second opposite directions about said axis;

said partible vertebrae shifting screw including

first and second relatively axially reciprocally moveable screw halves having first and second pluralities of axially spaced, helically extending, partial screw thread sections, respectively, which can be helically aligned with each other in any selected one of a plurality of different axially shifted locations to form a helical screw thread;

means for relatively axially shifting said first and second screw halves to first positions in which at least a first portion of said first plurality of partial screw thread sections is helically aligned with a first portion of said second plurality of partial screw thread sections to follow the same helical path when said screw is being rotated in said one direction and threadedly coupled to said first and second vertebrae,

and for relatively axially shifting said first and second screw halves to second positions in which said first portion of said first plurality of partial screw thread sections is helically aligned with a second axially spaced portion of said second plurality of partial screw thread sections to shift said first vertebrae into alignment with said second vertebrae; and

an alignment nut detachably threadedly received by said screw when said first and second pluralities of screw thread sections are in either of said first and second positions but detached from screw as screw first and second screw halves are being axially shifted.

34. The alignment tool set forth in claim 33 further including a locking nut detachably threadedly received by said first and second pluralities of screw thread sections in either of said first and second positions and abutting said alignment nut to lock said alignment nut in position to said first and second screw halves and preclude relative axial shifting of said first are second screw halves as said screw is being threadedly coupled to and decoupled from said adjacent vertebrae.

35. Apparatus for aligning first and second misaligned vertebrae which have confronting portions with at least one tapped thread adapted to threadedly receive a complementally threaded fusion cage, said apparatus comprising:

a vertebrae shifting partible screw, having a longitudinal axis for threadedly coupling to and decoupling from said first and second vertebrae when rotated in first and second opposite directions, respectively, about said axis including;

first and second relatively axially reciprocally moveable screw halves having first and second pluralities of axially spaced, helically extending, partial screw thread sections, respectively;

each of said first and second pluralities of axially spaced, helically extending partial screw thread sections including first and second axially spaced thread portions cooperating to form a helical screw thread;

means for relatively axially shifting said first and second screw halves to first positions in which

at least said first thread portion of said first plurality of partial screw thread sections is helically aligned with said first portion of said second plurality of partial screw thread sections to follow in the same helical path as said screw is rotated in said one direction, and

said first and second pluralities of partial screw thread sections in said first positions are each threadedly coupled to only one of said first and second vertebrae,

and for relatively axially shifting said first and second screw halves to second positions in which said first portion of said first plurality of partial screw thread sections is in helical registry with said second axially spaced portion of said second plurality of partial screw thread sections to shift said first vertebrae into alignment with said second vertebrae; and

alignment means detachably threadedly received by said first and second screw halves in said second positions to maintain said first plurality of partial screw sections and said second portion of said second plurality of partial screw thread sections in helical registry and insure that said first and second pluralities of thread sections follow in the same helical path as said screw is rotated in said second direction and unthreaded from said adjacent vertebrae.

36. The apparatus set forth in claim 35 including locking nut means detachably threadedly received by said first and second halves in abutting relation with said alignment means for detachably locking said alignment means to said first and second halves.

37. The apparatus set forth in claim 36 wherein said alignment means comprises an alignment collar which is detachably threadedly received by said first and second pluralities of partial screw thread sections when said screw halves are in either of said first positions or said second positions;

said alignment means comprises an alignment nut which is axially threadedly received in an alignment position by said first and second screw halves in either of said first or second positions but moveable to a non-aligning remote position removed from said screw halves;

said means for relatively axially shifting said first and second screw halves comprising first and second elongate bodies each having one end mounting said first and second screw halves, respectively, for movement therewith;

said one end including a nut receiving portion for receiving and stowing said nut in said non-aligning remote position.

38. Apparatus for aligning adjacent misaligned vertebrae comprising:

an elongate main tool body having a longitudinal bore therethrough and opposite ends;

an elongate rod, having opposite ends, slidably received in said bore;

a vertebrae repositioning screw, rotatable about a longitudinal axis in first and second opposite directions, having an external helical screw thread for threadedly coupling to and decoupling from said adjacent vertebrae as said screw is rotated in said first and second directions, respectively;

said screw comprising first and second complementally formed abutting screw halves having complementally formed half threads which can be helically aligned with each other in any selected one of a plurality of relatively axially spaced positions in which said half threads are helically aligned to form said screw thread;

one of said screw halves being mounted on an end of said elongate rod and the other of said screw halves being mounted to an end of said elongate tool body;

means for axially displacing said elongate rod relative to said main tool body to axially relatively move said screw halves between coextensive positions and axially displaced positions; and

locking means detachably threadedly received by said first and second screw halves in either of said coextensive positions or said axially displaced position for selectively axially locking said screw halves together in either of said coextensive positions or said axially displaced positions to preclude relative axial movement of said screw halves as said screw is being threadedly coupled to and decoupled from said vertebrae and for unlocking said screw halves as said one screw half is being axially moved between said coextensive and said axially displaced position.

39. The apparatus set forth in claim 38 wherein said locking means comprises a sleeve mounted on said elongate rod and said main tool body for longitudinal movement between a locking position detachably threadedly coupled to said screw halves when said screw is being coupled to and decoupled from said vertebrae and a non-threaded, axially removed position when said rod and said main tool body are being axially displaced.

40. The apparatus set forth in claim 38 wherein said locking means comprises a hollow threaded locking collar mounted on said elongate rod and said tool body for movement between an axially displaced, non-locking position when said screw is being coupled to said vertebrae and a locking position detachably threadedly received by said screw halves and disposed in abutting relation with said sleeve.

41. A vertebrae aligning tool for aligning first and second adjacent misaligned vertebrae comprising:

an axially partible vertebrae shifting tool head, having an external helical screw thread thereon, mounted for rotation in first and second opposite directions about a longitudinal axis to threadedly couple to and decouple from, respectively, confronting portions of said adjacent misaligned vertebrae;

said partible tool head including first and second axially slidably coupled tool head sections having first and second complementally formed partial screw threads, respectively, of the same pitch, which can be disposed in helical registry with each other, in any selected one of a plurality of different, axially spaced positions to form said screw thread;

said first and second tool head sections in at least one rotary position being threadedly coupled to only one of said first and second misaligned vertebrae;

means for axially displacing said tool head sections relative to each other, when said first and second tool head sections are in said one rotary position and threadedly coupled to only one of said first and second misaligned vertebrae, between any selected one of said plurality of axially spaced positions to relatively shift said first and second adjacent misaligned vertebrae into substantial alignment with each other; and

axial locking means detachably threadedly received by said first and second tool head sections for detachably axially locking said first and second screw halves together in said selected one of said axially spaced positions to selectively preclude relative axial movement of said first and second tool head sections when said tool is being threadedly coupled to and decoupled from said vertebrae but being threadedly moveable to a non-locking axially displaced position when said tool head sections are relatively axially moving between said plurality of axially spaced positions.

42. The vertebrae aligning tool set forth in claim 41 wherein said locking means comprises an internally threaded collar which can be concurrently detachably threaded onto said first and second screw partial screw threads of said first and second tool head sections when said first and second partial screw threads are in helical registry with each other to axially move thereon between said stowed non-locking position and a locking position threadedly received by said first and second partial threads.

43. The vertebrae aligning tool set forth in claim 41 wherein said locking means comprises an alignment nut which is threadedly received by said first and second partial screw threads when said first and second partial screw threads are helically aligned.

44. The vertebrae aligning tool set forth in claim 43 wherein said locking means includes a lock nut which is threadedly received by said first and second partial screw threads when said first and second partial screw threads are helically aligned for detachably axially locking said alignment nut to said first and second partial screw threads.

45. In an apparatus for repositioning adjacent misaligned vertebrae which have confronting portions with at least one tapped thread adapted to threadedly receive a complementally threaded fusion cage, said apparatus including a longitudinal, partible vertebrae shifting screw which can be rotated in one direction about an elongate axis to threadedly couple to said tapped thread of said adjacent misaligned vertebrae and in an opposite direction of rotation to threadedly decouple from said vertebrae;

said vertebrae shifting screw including first and second elongate screw thread sections which are longitudinally moveable relative to each other and include first and second pluralities of screw thread sections, respectively, which when said screw is in at least one rotary position, are each in threaded engagement with only one of said misaligned vertebrae when said screw is threadedly coupled to said vertebrae;

means for relatively longitudinally translating said first and second screw sections, when said screw is in said one rotary position, between

first positions in which a first portion of said first plurality of screw thread sections is in registry with a first portion of said second plurality of screw thread sections and

second positions in which said first portion of said first plurality of screw thread sections is in registry with a second portion of said second plurality of screw thread sections to relatively shift said misaligned vertebrae into alignment;

the improvement comprising;

alignment means for detachably threadedly engaging said screw thread sections in said second positions and maintaining said first and second pluralities of screw thread sections in registry as said screw is oppositely rotated in said opposite direction of rotation.

46. The apparatus set forth in claim 45 wherein said alignment means includes an alignment nut which is detachably threadedly coupled to said first portions of said first and second pluralities of screw thread sections when said first and second screw sections are in said first position and said screw is being rotated about said axis in said one direction and detachably coupled to said first and second portions of said first and second pluralities of screw thread sections, respectively, when said first and second screw sections are in said second positions and said screw is being decoupled from said vertebrae.

47. The apparatus set forth in claim 46 wherein said alignment means includes a locking nut which is threadedly coupled to said first and second pluralities of screw sections, in each of said first and second positions, in abutting relation with said alignment nut to detachably lock said alignment nut to said screw.

48. An alignment tool for repositioning misaligned adjacent vertebrae comprising:

an axially partible vertebrae displacing head rotatable in first and second directions about a longitudinal axis for threadedly coupling to and decoupling from, respectively, said adjacent vertebrae,

said head including first and second axially slidably coupled head sections provided with first and second screw thread sections, respectively, which are helically aligned with each other in first axial positions to form a helical screw thread as said head is rotated in one direction about said axis;

means for relatively axially slidably shifting said first and second head sections from said first axial positions to second, axially displaced positions in which portions of said first and second screw thread sections are helically aligned and said misaligned vertebrae are moved into alignment with each other; and

means threadedly receiving parts of said portions of said first and second screw thread sections when said first and second head sections are in said second, axially displaced positions for maintaining said first and second screw thread sections helically aligned as said head is oppositely rotated in said second direction to threadedly decouple from said vertebrae.

49. The tool set forth in claim 48 wherein said means threadedly receiving said parts of said portions of said first and second screw thread sections comprises an alignment collar threadedly received by said parts of said first and second portions when said first and second head sections are in either of said first or second positions, and but removed to a remote non-threaded position as said head sections are being relatively shifted.

50. The tool set forth in claim 49 wherein said means threadedly receiving said parts of said portions of said first and second screw thread sections comprises a locking collar disposed in abutting relation with said alignment collar and threadedly received on said parts of said first and second screw thread sections when said first and second head sections are in either of said first positions or said second positions but not when said first and second head sections are being axially shifted.

51. A method of aligning first and second vertebrae which are misaligned with an alignment tool comprising a partible screw having a longitudinal axis and including first and second screw halves provided with first and second pluralities of axially spaced helically extending partial screw thread sections, respectively, that can be helically aligned with each other in any selected one of a plurality of different axially shifted positions to form a helical screw thread on said screw, said method comprising:

axially relatively shifting said first and second screw halves to first positions in which at least a first portion of said first plurality of partial screw thread sections are helically aligned with a first portion of said second plurality of partial screw thread sections;

threadedly coupling said partible screw, with said first and second screw halves in said first positions, to said adjacent vertebrae such that said first screw half is threadedly coupled to only said first vertebrae and said second screw half is threadedly coupled to only said second vertebrae;

axially relatively shifting said screw halves relative to each other to second positions in which said first portion of said first plurality of partial screw thread sections is helically aligned with a second axially spaced portion of said second plurality of screw thread sections to move said first vertebrae into alignment with said second vertebrae;

axially locking said first and second screw halves together in said second positions to preclude relative axial shifting of said first portion of said first plurality of screw thread sections and said second axially spaced portion of said second plurality of screw thread sections; and

unthreading said partible screw from said first and second vertebrae with said first and second screw halves locked together.

52. The method set forth in claim 51 wherein said axially locking step is accomplished by threading a first collar onto said first and second screw halves in said second positions.

53. The method set forth in claim 52 wherein said axially locking step is accomplished by threadedly coupling a locking collar on said first and second screw halves in said second positions into axial abutting engagement with said first collar to preclude relative axial shifting of said first collar and said first and second screw halves.

54. The method set forth in claim 53 further including the additional locking step of axially locking said first and second screw halves together prior to said step of threadedly coupling to preclude relative axial shifting of said first and second screw halves as said partible screw is being threadedly coupled to said first and second vertebrae.

55. The method set forth in claim 54 further including the step of axially unlocking said first and second screw halves prior to said step of axially relatively shifting said first and second screw halves to said second positions.

56. The method set forth in claim 54 wherein said additional locking step of axially locking is accomplished by sequentially threading said first collar and said locking collar onto said first and second screw halves into abutting engagement with each other.

57. The method set forth in claim 55 further wherein said step of unlocking said first and second screw halves prior to said step of axially shifting is accomplished by threadedly uncoupling said first collar and said locking collar from said first and second screw halves.

58. The method set forth in claim 51 further including the additional step of locking said first and second screw halves together in said first positions prior to said step of threadedly coupling.

59. The method set forth in claim 58 wherein said additional step of locking is accomplished by threadedly coupling a first collar onto said first and second screw halves in said first positions.

60. The method set forth in claim 59 wherein said additional locking step is accomplished by threadedly coupling a locking collar on said first and second screw halves in said first positions into abutting engagement with said first collar to preclude relative axial shifting of said first collar and said first and second screw halves when said screw thread is being threadedly coupled to said first and second teeth.

61. A method of aligning misaligned adjacent vertebrae comprising the steps of:

threadedly coupling an axially partible vertebrae displacing head, having first and second abutting screw halves provided with half screw threads which are helically aligned to form a helical screw thread, along an axis to said adjacent vertebrae;

axially relatively shifting said first and second abutting screw halves in opposite directions to axially displaced positions to relatively shift said misaligned vertebrae into alignment with each other; and

axially detachably locking said abutting screw halves together in said axially displaced positions with said half threads in helical alignment to preclude relative axial movement therebetween and axially unthreading said head from said vertebrae with said abutting screw halves axially locked together.

62. The method set forth in claim 61 wherein said step of locking is accomplished by threading an alignment collar on said vertebrae displacing head when said first and second screw halves are in said axially displaced positions and threading a locking collar on said vertebrae displacing head into abutting engagement with said alignment collar.

63. The method set forth in claim 61 wherein said step of threading is accomplished by threading an alignment collar onto said vertebrae displacing head and threading a locking collar onto said vertebrae displacing head into abutting engagement with said alignment collar when said first and second screw halves are in said axially displaced positions to preclude relative axial shifting of said screw halves relative to each other and relative to said alignment collar.

64. A method of aligning misaligned adjacent vertebrae having spaced apart confronting portions comprising:

drilling and tapping a first part of said confronting portions of said adjacent vertebrae to provide a first threaded receptacle having a helical thread formed about an elongate axis;

threadedly coupling an axially partible tool screw, having first and second abutting screw halves coupled together in generally coextensive positions in which first and second half screw threads provided on said first and second screw halves are helically aligned to provide a helical screw thread, about said axis into said threaded receptacle such that said first and second screw halves are only threadedly coupled to one of said adjacent misaligned vertebrae;

axially relatively shifting said first and second screw halves to move said misaligned vertebrae into alignment and -over said screw halves to axially spaced positions in which portions of said first and second screw threads are in helical alignment with each other;

drilling and tapping a second part of said confronting portions of said adjacent vertebrae to provide a second threaded receptacle having a second helical thread formed about a second laterally spaced apart elongate axis;

threading a hollow cage about said second axis into said second receptacle;

holding portions of said first and second half screw threads in helical alignment with each other and unthreading said partible tool screw from said first receptacle; and

threading a second fusion cage into said first receptacle.

65. A method of aligning misaligned adjacent vertebrae with an alignment tool comprising a partible screw having

axially inner and outer ends;

and

a longitudinal axis and including

first and second screw halves having first and second longitudinally slidably coupled screw halves provided with first and second pluralities of partial screw thread sections which can be aligned with each other in a plurality of different axially spaced positions to form a helical thread on said screw, said method comprising;

axially relatively shifting said first and second screw halves to first positions in which at least a first portion of said first plurality of partial screw thread sections are helically aligned with a first portion of said second plurality of partial screw thread sections;

threading said partible screw between said adjacent misaligned vertebrae to a position in which said axially outer ends of each of said first and second pluralities of partial screw thread sections is disposed between said vertebrae but threadedly coupled to only one of said vertebrae, and axially inner ends of said thread and first and second pluralities of thread sections are exposed;

axially relatively shifting said screw halves relative to each other to second positions in which said first portion of said first plurality of partial screw thread sections is helically aligned with a second axially spaced portion of said second plurality of screw thread sections to move said first vertebrae into alignment with said second vertebrae; and

threading at least one nut on said axially inner exposed ends of the first and second pluralities of partial screw thread sections when said screw halves are in said second positions to insure that said first and second pluralities of thread sections will follow in the same helical path as said screw is unthreaded from said adjacent vertebrae.

66. A method of aligning misaligned adjacent vertebrae comprising the steps of:

threadedly coupling one-half of a threaded alignment head, having a helical screw thread thereon, with one vertebrae and threadedly coupling another half of said threaded alignment head by rotating said alignment head about an axis between said adjacent vertebrae;

axially shifting said one-half relative to said another half to move said one vertebrae into alignment with said adjacent vertebrae;

locking said one-half and said another half together with at least a portion of the helical screw thread on said one-half in helical alignment with a portion of the helical screw thread on said another half to preclude relative axial shifting of said one-half and said another half from said vertebrae and said another vertebrae while said one-half and said another half are locked together.

67. Apparatus for repositioning misaligned vertebrae comprising:

a vertebrae alignment head having first and second half portions forming first and second screw thread sections which cooperate to form a helical screw on said head;

said head being rotatable about a longitudinal axis in a first direction between said vertebrae to a position in which said first and second screw thread sections each threadedly engage only one of said vertebrae;

said head being oppositely rotatable about said axis in an opposite direction to an unthreaded position removed from said vertebrae;

means for axially relatively shifting said first and second halves in opposite directions to relatively move said vertebrae into alignment with each other; and

means for axially detachably holding said first and second halves together with at least a portion of said first screw thread section in helical alignment with a portion of said second screw thread section to preclude relative axial shifting of said first and second screw thread sections when said head is rotated in said opposite direction.

68. Apparatus for relocating misaligned vertebrae which have confronting portions with at least one tapped thread, adapted to threadedly receive a complementally threaded fusion cage, said apparatus comprising:

a partible alignment screw having a rotational axis and first and second partial screw thread sections provided with first and second pluralities of partial screw threads, respectively, cooperating to define a helical screw thread complementally formed to and adapted to be threadedly received by, said tapped thread when said screw is rotated in one direction of rotation about said axis and decoupled from said tapped thread when said screw is oppositely rotated in a second direction;

said first and second partial screw thread sections being adapted to be threadedly coupled to only one of said vertebrae when said screw is received by said tapped thread;

said first and second partial screw thread sections being relatively axially reciprocally moveable between first position in which a first position of said first screw thread section is in helical alignment with a first portion of said second screw thread section and second axially displaced positions in which said first portion of said first screw thread section is in helical alignment with a second portion of said second screw thread section to relatively shift and reposition said vertebrae; and

locking means threadedly receiving said first and second partial screw threads when said first and second screw thread sections are in said second positions for locking said first and second screw thread sections in said second positions as said screw is being oppositely rotated in said second direction to prevent axial shifting of said first and second screw threads and damage to said tapped thread.

69. The apparatus set forth in claim 68 wherein said locking means comprises an alignment nut and a locking nut threadedly receiving said first and second partial screw thread sections and disposed in abutting engagement with each other.

70. A method of repositioning misaligned and spaced apart adjacent first and second vertebrae comprising the steps of

tapping a first thread into confronting portions of said misaligned vertebrae;

turning a partible screw having first and second circumferentially spaced apart screw thread portions defining a screw thread complementally formed to said first thread, about its longitudinal axis in a first direction into said thread to threadedly couple said circumferentially spaced first and second screw thread sections of said screw to only said first and second vertebrae, respectively;

axially shifting said circumferentially spaced first and second thread sections relative to each other to axially displaced positions to relatively move said first and second vertebrae into substantial alignment;

threading at least one collar onto said circumferentially spaced first and second thread sections to maintain the relative positions of said first and second thread sections in said axially displaced positions; and

unturning said partible screw in an opposite direction of rotation from said thread while said one collar is received by circumferentially spaced first and second thread sections.

71. The method set forth in claim 70 wherein said step of axially shifting includes the step of helically aligning said first and second screw threads sections in said axially displaced positions prior to said threading step and further including the step of threading a second locking collar onto said first and second screw thread sections in said axially displaced positions into abutting engagement with said one collar to said first and second screw thread sections.

72. The method set forth in claim 70 including the step of threading said one collar onto said first and second screw thread sections prior to said turning, step to detachably restrict relative axial movement of said first and second screw thread sections during said turning step;

and unthreading said one collar from said first and second screw thread sections prior to said axially shifting step.

73. The method set forth in claim 71 further including the step of threading said second collar onto said first and second screw thread sections into abutting engagement with said one collar to lock said one collar to said first and second screw thread sections, and unthreading said second collar from said first and second screw thread sections prior to said step of axially shifting.