Dual anchor prosthetic nucleus apparatus

• US 20050113928A1
• Filed: 10/22/2004
• Published: 05/26/2005
• Est. Priority Date: 02/16/2000
• Status: Active Grant

• Current Assignee: Mis Ip Holdings LLC
• Original Assignee: TranS1 Incorporated (Baxano Surgical, Inc.)
• Inventors: Assell, Robert L., Cragg, Andrew H., Ainsworth, Steven D., Wessman, Bradley J., Dickhudt, Eugene A.
• Granted Patent: US 7,491,236 B2
• Time in Patent Office: Days
• US Class Current: 623/17.160
• CPC Class Codes: A61B 17/70 Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
• CPC Class Codes: A61B 17/864 hollow, e.g. with socket or cannulated
• CPC Class Codes: A61B 17/8685 comprising multiple separate parts
• 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 2002/30014 differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2002/30062 (bio)absorbable, biodegradable, bioerodable, (bio)resorbable, resorptive
• CPC Class Codes: A61F 2002/30075 swellable, e.g. when wetted
• CPC Class Codes: A61F 2002/30224 cylindrical
• CPC Class Codes: A61F 2002/30242 spherical
• CPC Class Codes: A61F 2002/30289 helically-coiled
• 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 2002/30448 using adhesives
• 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 2002/30563 : having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
• CPC Class Codes: A61F 2002/30565 : having spring elements
• 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 2002/30583 : filled with hardenable fluid, e.g. curable in-situ
• CPC Class Codes: A61F 2002/30604 : modular
• 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 2002/3097 : using laser
• 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 2002/4667 : for measuring torque
• CPC Class Codes: A61F 2210/0004 : bioabsorbable
• 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 2220/005 : using adhesives
• 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 2230/0071 : spherical
• 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 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
• CPC Class Codes: A61F 2310/0097 : Coating or prosthesis-covering structure made of pharmaceutical products, e.g. antibiotics

Abstract

A spinal mobility preservation apparatus and methods are disclosed. The spinal mobility preservation apparatus may include a proximal body, an intermediate body, a distal body, and an expandable membrane. The proximal body and the distal body secure the mobility preservation apparatus to adjacent vertebral bodies. At least one of an intermediate body and an expandable membrane secure the proximal body to the distal body and provide a degree of support to a spinal motion segment defined by the adjacent vertebral bodies. A single proximal body and an expandable membrane may also compose a spinal mobility preservation apparatus. The proximal body secured to one of a superior or an inferior vertebral body and the expandable membrane extending into the intervertebral disc space to support the spinal motion segment.

Claims

1. An implantable spinal mobility preservation apparatus, comprising:

a proximal body defining a proximal lumen and having a first retention structure configured to be secured in a caudad vertebral body;

a distal body having a second retention structure configured to be secured in a cephalad vertebral body; and

an expandable membrane having a proximal end and a distal end and defining an expansion chamber, with the proximal end of the expandable membrane secured to the proximal body and the distal end of the expandable membrane secured to the distal body.

2. An implantable spinal mobility preservation apparatus, as in claim 1, with the first retention structure comprising a first thread and the second retention structure comprising a second thread.

3. An implantable spinal mobility preservation apparatus, as in claim 1, further comprising prosthetic nucleus material positioned within the expansion chamber defined by the expandable membrane.

4. An implantable spinal mobility preservation apparatus, as in claim 1, further comprising the proximal body having internal threading within the proximal lumen.

5. An implantable spinal mobility preservation apparatus, as in claim 1, further comprising the proximal lumen in fluid communication with the expansion chamber.

6. An implantable spinal mobility preservation apparatus, as in claim 5, further comprising the distal body defining a distal lumen.

8. An implantable spinal mobility preservation apparatus, as in claim 5, further comprising the distal body defining a distal cavity to receive a driver.

9. An implantable spinal mobility preservation apparatus, as in claim 5, further comprising a plug secured within the proximal lumen.

10. An implantable spinal mobility preservation apparatus, as in claim 9, further comprising a prosthetic nucleus material secured within the expansion chamber defined by the expandable membrane.

11. An implantable spinal mobility preservation apparatus, as in claim 1, further comprising the proximal lumen configured to receive a driver.

12. An implantable spinal mobility preservation apparatus, as in claim 1, further comprising an adhesive to secure the proximal end of the expandable membrane to the proximal body and the distal end of the expandable membrane to the distal body.

13. An implantable spinal mobility preservation apparatus, as in claim 1, further comprising a first ring positioned around the proximal end of the expandable membrane and the proximal body to secure the proximal end of the expandable membrane to the proximal body and a second ring positioned around the distal end of the expandable membrane and the distal body to secure the distal end of the expandable membrane to the distal body.

14. An implantable spinal mobility preservation apparatus, as in claim 2, wherein the major thread diameter of the proximal body is greater than the major thread diameter of the distal body.

15. An implantable spinal mobility preservation apparatus, as in claim 1, further comprising the proximal lumen extending co-axially through the proximal body and the proximal lumen in fluid communication with the expansion chamber.

16. An implantable spinal mobility preservation apparatus, as in claim 1, wherein at least a portion of the expandable membrane is compliant.

17. An implantable spinal mobility preservation apparatus, as in claim 3, further comprising a first portion of the expandable membrane configured to face in the direction of an adjacent vertebral body end plate is relatively more compliant than a second portion of the expandable membrane configured to face in the direction of the annulus.

18. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane comprises an elastomeric material.

19. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane comprises a silicone.

20. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane comprises a moisture-permeable bioabsorbable material.

21. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane comprises a woven fabric of polymeric fibers.

22. An implantable spinal mobility preservation apparatus, as in claim 21, wherein the woven fabric of polymeric fibers are semi-permeable.

23. An implantable spinal mobility preservation apparatus, as in claim 21, wherein the woven fabric of polymeric fibers are microporous.

24. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane comprises a silicone.

25. An implantable spinal mobility preservation apparatus, as in claim 3, wherein the prosthetic nucleus material is a saline solution an elastomeric solid.

26. An implantable spinal mobility preservation apparatus, as in claim 3, wherein the prosthetic nucleus material is a saline solution.

27. An implantable spinal mobility preservation apparatus, as in claim 3, wherein the prosthetic nucleus material is a viscoelastic gel.

28. An implantable spinal mobility preservation apparatus, as in claim 3, wherein the prosthetic nucleus material comprises a hydrogel.

29. An implantable spinal mobility preservation apparatus, as in claim 3, wherein the prosthetic nucleus material comprises a silicone.

30. An implantable spinal mobility preservation apparatus, as in claim 3, wherein the prosthetic nucleus material comprises a polyurethane.

31. An implantable spinal mobility preservation apparatus, as in claim 29, wherein the expandable membrane comprises a silicone.

32. An implantable spinal mobility preservation apparatus, as in claim 3, wherein the compliancy of the radial surface is less than the compliancy of at least one of the superior and inferior surfaces.

33. An implantable spinal mobility preservation apparatus, as in claim 3, further comprising a collar integral to the radial surface of the expandable membrane.

34. An implantable spinal mobility preservation apparatus, as in claim 3, further comprising a collar secured to the radial surface of the expandable membrane.

35. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane comprises a polymeric tube.

36. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane comprises a compliant tube.

37. An implantable spinal mobility preservation apparatus, as in claim 10, wherein the expandable membrane is at least partially filled with a prosthetic nucleus material, and wherein the physical properties of the combination of the expandable membrane and the prosthetic nucleus material enable the expandable membrane to transfer a component of axial compression into lateral force for absorption by the annulus.

38. An implantable spinal mobility preservation apparatus, as in claim 10, wherein the proximal surface and the distal surface have a greater compliancy than the radial surface.

39. An implantable spinal mobility preservation apparatus, as in claim 10, wherein the prosthetic nucleus material is modulus matched to a natural disc material.

40. An implantable spinal mobility preservation apparatus, as in claim 39, wherein the natural disc material comprises the nucleus.

41. An implantable spinal mobility preservation apparatus, as in claim 39, wherein the natural disc material comprises the intervertebral disc.

42. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane is semi-elastic and is configured to have a predetermined maximum stretching capacity along the horizontal plane.

43. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane has a predetermined maximum stretching capacity along the horizontal plane.

44. An implantable spinal mobility preservation apparatus, as in claim 1, wherein the expandable membrane is expandable radially.

45. An implantable spinal mobility preservation apparatus as in claim 10, wherein the expandable membrane further comprises a collar that abuts the disc annulus.

46. An implantable spinal mobility preservation apparatus as in claim 45, wherein the collar comprises a thicker semi-elastic band region.

47. An implantable spinal mobility preservation apparatus as in claim 45, wherein the collar comprises a noncompliant band.

48. An implantable spinal mobility preservation apparatus as in claim 45, wherein the collar is secured around the perimeter of the expandable membrane.

49. An implantable spinal mobility preservation apparatus as in claim 45, wherein the collar is integral with the perimeter of the semi-elastic membrane.

50. An implantable spinal mobility preservation apparatus as in claim 3, wherein the prosthetic nucleus material comprises a hydrogel.

51. An implantable spinal mobility preservation apparatus as in claim 2, wherein the second threads pitch is finer than the pitch of the first threads pitch in the section to induce distraction of the first and second vertebral bodies during implantation.

52. An implantable spinal mobility preservation apparatus, as in claim 6, further comprising at least one stop-flow mechanism within the proximal body.

53. An implantable spinal mobility preservation apparatus, as in claim 1, having an aspect ratio of greater than 1.

86. An implantable spinal mobility preservation apparatus, as in claim 45, wherein the expandable membrane comprises a silicone.

7. An implantable spinal mobility preservation apparatus, as in claim 167, further comprising the distal lumen in fluid communication with the expansion chamber.

54. A method for supporting the spine, comprising:

providing an implantable spinal mobility preservation apparatus having a proximal body having a first retention structure configured to be secured in a caudad vertebral body and defining a proximal lumen, a distal body having a second retention structure configured to be secured in a cephalad vertebral body, and an expandable membrane having a proximal end and a distal end and defining an expansion chamber, with the proximal end of the expandable membrane secured to the proximal body and the distal end of the expandable membrane secured to the distal body, with the expansion chamber in fluid communication with the proximal lumen;

forming an axial bore through a caudad vertebral body, an intervertebral disc and a cephalad vertebral body;

removing at least a portion of a nucleus pulposus of the intervertebral disc through the axial bore to form a disc space; and

axially inserting the implantable spinal mobility preservation apparatus through the axial bore;

securing the distal body of the implantable mobility preservation apparatus in the cephalad vertebral body;

securing the proximal body of the implantable mobility preservation apparatus in the caudad vertebral body; and

providing a prosthetic nucleus material through the proximal lumen into the expansion chamber of the spinal mobility preservation apparatus.

55. An implantable spinal mobility preservation apparatus, comprising:

a proximal body defining a proximal lumen and having a first retention structure configured to be secured in a caudad vertebral body;

a distal body having a second retention structure configured to be secured in a cephalad vertebral body; and

an expandable membrane having a proximal end and a distal end and defining an expansion chamber, with the proximal end of the expandable membrane secured to the proximal body and the distal end of the expandable membrane secured to the distal body with the expansion chamber in fluid communication with the proximal lumen; and

a plug secured within the proximal lumen.

56. An implantable spinal mobility preservation apparatus, comprising:

an expandable membrane being substantially radially symmetrical and expandable about a longitudinal axis, the expansion membrane having a proximal end and a distal end, and the expandable membrane defining an expansion chamber;

a proximal body being substantially radially symmetrical about the longitudinal axis, the proximal body secured to the proximal end of the expandable membrane, the proximal body including first threads to rotatably position the proximal body through a central bore in a caudad vertebral body, the proximal body defining a proximal lumen in fluid communication with expansion chamber of the expandable membrane; and

a distal body being substantially radially symmetrical about the longitudinal axis, the distal body secured to the distal end of the expandable membrane and substantially coaxial with the proximal body, the distal body including second threads to rotatably position the distal body through a central bore in a cephalad vertebral body.

57. An implantable spinal mobility preservation apparatus, as in claim 56, further comprising a prosthetic nucleus material positioned within an expansion chamber defined by the expandable membrane.

58. An implantable spinal mobility preservation apparatus, as in claim 56, further comprising the proximal lumen in fluid communication with the expansion chamber.

59. An implantable spinal mobility preservation apparatus, as in claim 58, further comprising the proximal body having internal threading within the proximal lumen.

60. An implantable spinal mobility preservation apparatus, as in claim 59, further comprising the distal body defining a distal lumen.

61. An implantable spinal mobility preservation apparatus, as in claim 56, further comprising the proximal body defining a proximal cavity to receive a driver.

62. An implantable spinal mobility preservation apparatus, as in claim 59, further comprising a plug secured within the proximal lumen.

63. An implantable spinal mobility preservation apparatus, as in claim 62, further comprising prosthetic nucleus material secured within an expansion chamber defined by the expandable membrane.

64. An implantable spinal mobility preservation apparatus, as in claim 60, further comprising the distal lumen in fluid communication with the expansion chamber.

65. An implantable spinal mobility preservation apparatus, as in claim 59, further comprising a plug secured within the proximal lumen.

66. An implantable spinal mobility preservation apparatus, as in claim 65, further comprising a prosthetic nucleus material secured within the expansion chamber defined by the expandable membrane.

67. An implantable spinal mobility preservation apparatus, as in claim 65, further comprising the proximal lumen configured to receive a driver.

68. An implantable spinal mobility preservation apparatus, as in claim 56, further comprising an adhesive to secure the proximal end of the expandable membrane to the proximal body and the distal end of the expandable membrane to the distal body.

69. An implantable spinal mobility preservation apparatus, as in claim 56, further comprising a first ring positioned around the proximal end of the expandable membrane and the proximal body to secure the proximal end of the expandable membrane to the proximal body and a second ring positioned around the distal end of the expandable membrane and the distal body to secure the distal end of the expandable membrane to the distal body.

70. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the major thread diameter of the proximal body is greater than the major thread diameter of the distal body.

72. An implantable spinal mobility preservation apparatus, as in claim 56, wherein at least a portion of the expandable membrane is compliant.

73. An implantable spinal mobility preservation apparatus, as in claim 57, further comprising a first portion of the expandable membrane configured to face in the direction of an adjacent vertebral body end plate is relatively more compliant than a second portion of the expandable membrane configured to face in the direction of the annulus.

74. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane comprises an elastomeric material.

75. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane comprises a silicone.

76. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane comprises a moisture-permeable bioabsorbable material.

77. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane comprises a woven fabric of polymeric fibers.

78. An implantable spinal mobility preservation apparatus, as in claim 77, wherein the woven fabric of polymeric fibers are semi-permeable.

79. An implantable spinal mobility preservation apparatus, as in claim 77, wherein the woven fabric of polymeric fibers are microporous.

80. An implantable spinal mobility preservation apparatus, as in claim 57, wherein the prosthetic nucleus material is a saline solution an elastomeric solid.

81. An implantable spinal mobility preservation apparatus, as in claim 57, wherein the prosthetic nucleus material is a saline solution.

82. An implantable spinal mobility preservation apparatus, as in claim 57, wherein the prosthetic nucleus material is a viscoelastic gel.

83. An implantable spinal mobility preservation apparatus, as in claim 57, wherein the prosthetic nucleus material comprises a hydrogel.

84. An implantable spinal mobility preservation apparatus, as in claim 57, wherein the prosthetic nucleus material comprises a silicone.

85. An implantable spinal mobility preservation apparatus, as in claim 57, wherein the prosthetic nucleus material comprises a polyurethane.

87. An implantable spinal mobility preservation apparatus, as in claim 57, wherein the compliancy of the radial surface is less than the compliancy of at least one of the superior and inferior surfaces.

88. An implantable spinal mobility preservation apparatus, as in claim 57, further comprising a collar integral to the radial surface of the expandable membrane.

89. An implantable spinal mobility preservation apparatus, as in claim 57, further comprising a collar secured to the radial surface of the expandable membrane.

90. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane comprises a polymeric tube.

91. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane comprises a compliant tube.

92. An implantable spinal mobility preservation apparatus, as in claim 65, wherein the expandable membrane is at least partially filled with a prosthetic nucleus material, and wherein the physical properties of the combination of the expandable membrane and the prosthetic nucleus material enable the expandable membrane to transfer a component of axial compression into lateral force for absorption by the annulus.

93. An implantable spinal mobility preservation apparatus, as in claim 65, wherein the proximal surface and the distal surface have a greater compliancy than the radial surface.

94. An implantable spinal mobility preservation apparatus, as in claim 65, wherein the prosthetic nucleus material is modulus matched to a natural disc material.

95. An implantable spinal mobility preservation apparatus, as in claim 94, wherein the natural disc material comprises the nucleus.

96. An implantable spinal mobility preservation apparatus, as in claim 94, wherein the natural disc material comprises the intervertebral disc.

97. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane is semi-elastic and is configured to have a predetermined maximum stretching capacity along the horizontal plane.

98. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane has a predetermined maximum stretching capacity along the horizontal plane.

99. An implantable spinal mobility preservation apparatus, as in claim 56, wherein the expandable membrane is expandable radially.

100. An implantable spinal mobility preservation apparatus as in claim 65, wherein the expandable membrane further comprises a collar that abuts the disc annulus.

101. An implantable spinal mobility preservation apparatus as in claim 100, wherein the collar comprises a thicker semi-elastic band region.

102. An implantable spinal mobility preservation apparatus as in claim 100, wherein the collar comprises a noncompliant band.

103. An implantable spinal mobility preservation apparatus as in claim 100, wherein the collar is secured around the perimeter of the expandable membrane.

104. An implantable spinal mobility preservation apparatus as in claim 100, wherein the collar is integral with the perimeter of the semi-elastic membrane.

105. An implantable spinal mobility preservation apparatus as in claim 57, wherein the prosthetic nucleus material comprises a hydrogel.

106. An implantable spinal mobility preservation apparatus as in claim 57, wherein the second threads pitch is finer than the pitch of the first threads pitch in the section to induce distraction of the first and second vertebral bodies during implantation.

107. An implantable spinal mobility preservation apparatus, as in claim 61, further comprising at least one stop-flow mechanism within the proximal body.

108. An implantable spinal mobility preservation apparatus, as in claim 56, having an aspect ratio of greater than 1.

71. An implantable spinal mobility preservation apparatus, as in claim 220, further comprising the proximal lumen extending co-axially through the proximal body.

109. A method for supporting the spine, comprising:

providing an implantable spinal mobility preservation apparatus having an expandable membrane being substantially radially symmetrical and expandable about a longitudinal axis, the expansion membrane having a proximal end and a distal end, and the expandable membrane defining an expansion chamber, a proximal body being substantially radially symmetrical about the longitudinal axis, the proximal body secured to the proximal end of the expandable membrane, the proximal body including first threads to rotatably position the proximal body through a central bore in a caudad vertebral body, the proximal body defining a proximal lumen in fluid communication with expansion chamber of the expandable membrane, and a distal body being substantially radially symmetrical about the longitudinal axis, the distal body secured to the distal end of the expandable membrane, the distal body including second threads to rotatably position the distal body through a central bore in a cephalad vertebral body;

forming an axial bore through a caudad vertebral body, an intervertebral disc and a cephalad vertebral body;

removing at least a portion of a nucleus pulposus of the intervertebral disc through the axial bore to form a disc space; and

axially inserting the implantable spinal mobility preservation apparatus through the axial bore;

securing the distal body of the implantable mobility preservation apparatus in the cephalad vertebral body securing the proximal body of the implantable mobility preservation apparatus in the caudad vertebral body; and

providing a prosthetic nucleus material through the proximal lumen into the expansion chamber of the spinal mobility preservation apparatus.

110. An implantable spinal mobility preservation apparatus, comprising:

an expandable membrane being substantially radially symmetrical and expandable about a longitudinal axis, the expansion membrane having a proximal end and a distal end, and the expandable membrane defining an expansion chamber;

a proximal body being substantially radially symmetrical about the longitudinal axis, the proximal body secured to the proximal end of the expandable membrane, the proximal body including first threads to rotatably position the proximal body through a central bore in a caudad vertebral body, the proximal body defining a proximal lumen in fluid communication with expansion chamber of the expandable membrane

a distal body being substantially radially symmetrical about the longitudinal axis, the distal body secured to the distal end of the expandable membrane, the distal body including second threads to rotatably position the distal body through a central bore in a cephalad vertebral body; and

a plug secured within the proximal lumen.