Patent Application
20060247777
During the past thirty years, technical advances in the design of large joint reconstructive devices has revolutionized the treatment of degenerative joint disease, moving the standard of care from arthrodesis to arthroplasty. Progress in the treatment of vertebral disc disease, however, has come at a slower pace. Currently, the standard treatment for disc disease remains discectomy followed by vertebral fusion. While this approach may alleviate a patient's present symptoms, accelerated degeneration of adjacent discs is a frequent consequence of the increased motion and forces induced by fusion. Thus, reconstructing the degenerated intervertebral disc with a functional disc prosthesis to provide motion and to reduce deterioration of the adjacent discs may be a more desirable treatment option for many patients.
In one embodiment of the present disclosure, a vertebral implant for interposition between two vertebral endplates comprises a first endplate component having a first exterior surface for engaging a first vertebral endplate and having a first interior surface. The implant further comprises a second endplate component having a second exterior surface for engaging a second vertebral endplate and having a second interior surface. The implant also comprises a plurality of movable bearing members attached to the second interior surface and movably engaged with the first interior surface.
In another embodiment of the present invention, a vertebral implant for interposition between two vertebral endplates comprises a first endplate component having a first exterior surface for engaging a first vertebral endplate and having a first interior surface. The implant further comprises a second endplate component having a second exterior surface for engaging a second vertebral endplate and having a second interior surface. The implant also comprises a central body disposed between the first and second interior surfaces and a plurality of movable bearing members disposed between the central body and the first and second interior surfaces.
In another embodiment of the present disclosure, a system for preserving motion in a vertebral joint comprises a first means for attaching to a first vertebral endplate, a second means for attaching to a second vertebral endplate, and a plurality of third means disposed between the first and second means for providing rolling contact between the first means and the second means.
In another embodiment of the present disclosure, a vertebral implant for interposition between two vertebral endplates comprises a first endplate component having a first exterior surface for engaging a first vertebral endplate and having a first interior surface. The implant also comprises a second endplate component having a second exterior surface for engaging a second vertebral endplate and having a second interior surface. The second interior surface has a convex or concave portion. The implant also comprises a plurality of movable bearing members interposed between the second interior surface and the first interior surface.
In another embodiment of the present disclosure, a method for repairing an intervertebral joint comprises accessing an intervertebral disc space, removing at least a portion of a natural intervertebral disc from the intervertebral disc space, and inserting an intervertebral implant into the intervertebral disc space. The intervertebral implant comprises a first endplate component having a first exterior surface for engaging a first vertebral endplate and having a first interior surface and a second endplate component having a second exterior surface for engaging a second vertebral endplate and having a second interior surface. The second interior surface has a convex or concave portion. The implant further includes a plurality of movable bearing members interposed between the second interior surface and the first interior surface.
The present invention relates generally to vertebral reconstructive devices, and more particularly, to a functional intervertebral disc prosthesis or implant. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments, or examples, illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
Referring first to
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The endplate components 22, 24 and the bearing members 38 may be formed of any suitable biocompatible material including metals such as cobalt-chromium alloys, titanium alloys, nickel titanium alloys, and/or stainless steel alloys. Ceramic materials such as aluminum oxide or alumnia, zirconium oxide or zirconia, compact of particulate diamond, and/or pyrolytic carbon may be suitable. Certain polymer materials may also be used, including any member of the polyaryletherketone (PAEK) family such as polyetheretherketone (PEEK), carbon-reinforced PEEK, or polyetherketoneketone (PEKK); polysulfone; polyetherimide; polyimide; ultra-high molecular weight polyethylene (UHMWPE); and/or cross-linked UHMWPE.
The exterior surfaces 26, 32 may include features or coatings (not shown) which enhance the fixation of the implanted prosthesis. For example, the surfaces may be roughened such as by chemical etching, bead-blasting, sanding, grinding, serrating, and/or diamond-cutting. All or portions of the exterior surfaces 26, 32 may receive a coating of a metallic substance which may be applied by sintering or by a spray coating such as a plasma spray. All or a portion of the exterior surfaces 26, 32 may also be coated with a biocompatible and osteoconductive material such as hydroxyapatite (HA), tricalcium phosphate (TCP), and/or calcium carbonate to promote bone in growth and fixation. Alternatively, osteoinductive coatings, such as proteins from transforming growth factor (TGF) beta superfamily, or bone-morphogenic proteins, such as BMP2 or BMP7, may be used. Other suitable features may include spikes for initial fixation; ridges or keels to prevent migration in the lateral and anterior direction, for example; serrations or diamond cut surfaces; fins; posts; and/or other surface textures.
The prosthesis 20 may be assembled by inserting the bearing members 38 into the retaining components 36. Within the retaining components, the bearing members may be permitted to freely rotate. A portion of the bearing members 38 may extend from the retaining component, and the endplate component 22 may be positioned such that the race 30 engages the bearing members 38 in rolling contact. The assembled prosthesis 20 may be implanted into the vertebral joint 10 in the void created by the removed disc 12 such that the exterior surface 26 engages an endplate of the vertebral body 14 and the exterior surface 32 engages an endplate of the vertebral body 16. The prosthesis 20 may be implanted using any of the approaches described above.
In operation, the bearing members 38 may permit rotational motion of the endplate component 22 relative to the endplate component 24, thus promoting axial rotation at the vertebral joint 10 about a longitudinal axis 39. The bearing members 38 are permitted to roll within the race 30 as the endplates 22, 24 rotate relative to each other. This rolling motion of the bearing members 38 results in single point, rolling contact between the bearing members and the race 30. This minimum contact may reduce friction and the associated generation of wear debris, particularly as compared to surface contact and sliding motion.
In an alternative embodiment, the retaining component may be a retaining race, rather than individual retaining pockets. In this embodiment, the bearing members would still be retained by the retaining race, but would be permitted to roll along the circuit of the retaining race. In another alternative embodiment, a viscous fluid may be applied to the bearing members to provide lubrication. It is understood that the prosthesis may be implanted completely assembled, partially assembled or unassembled. All or portions of the assembly may be completed by the surgeon within the disc space.
Referring now to
The central body 50 may have an inner portion 62 and outer surfaces 64, 65. The central body 50 may have a generally circular cross-section as viewed from a plane perpendicular to the longitudinal axis 39. The inner portion 62 may be flexible and formed from one or more resilient materials which may have a lower modulus than the outer surfaces. Suitable materials may include polymeric elastomers such as polyolefin rubbers; polyurethanes (including polyetherurethane, polycarbonate urethane, and polyurethane with or without surface modified endgroups); copolymers of silicone and polyurethane with or without surface modified endgroups; silicones; and hydrogels. Polyisobutylene rubber, polyisoprene rubber, neoprene rubber, nitrile rubber, and/or vulcanized rubber of 5-methyl-1,4-hexadiene may also be suitable. In an alternative embodiment, the inner portion 62 may be rigid and formed of any of the materials described below for the outer surfaces or the endplate components.
The outer surfaces 64, 65 may also be formed of the resilient and flexible materials described above, but in the alternative, they may be modified, treated, coated or lined to enhance the wear resistant and articulating properties of the core component 50. These wear resistant and articulation properties may be provided by cobalt-chromium alloys, titanium alloys, nickel titanium alloys, and/or stainless steel alloys. Ceramic materials such as aluminum oxide or alumnia, zirconium oxide or zirconia, compact of particulate diamond, and/or pyrolytic carbon may be suitable. Polymer materials may also be used including any member of the PAEK family such as PEEK, carbon-reinforced PAEK, or PEKK; polysulfone; polyetherimide; polyimide; UHMWPE; and/or cross-linked UHMWPE. Polyolefin rubbers, polyurethanes, copolymers of silicone and polyurethane, and hydrogels may also provide wear resistance and articulation properties. Wear resistant characteristics may also or alternatively be provided to the outer surfaces 64, 65 by modifications such as cross-linking and metal ion implantation.
The endplate components 42, 44 and the bearing members 60 may be formed of any suitable biocompatible material including metals such as cobalt-chromium alloys, titanium alloys, nickel titanium alloys, and/or stainless steel alloys. Ceramic materials such as aluminum oxide or alumnia, zirconium oxide or zirconia, compact of particulate diamond, and/or pyrolytic carbon may be suitable. Polymer materials may also be used, including any member of the polyaryletherketone (PAEK) family such as polyetheretherketone (PEEK), carbon-reinforced PEEK, or polyetherketoneketone (PEKK); polysulfone; polyetherimide; polyimide; ultra-high molecular weight polyethylene (UHMWPE); and/or cross-linked UHMWPE.
The exterior surfaces 46, 52 may include features or coatings (not shown) which enhance the fixation of the implanted prosthesis. For example, the surfaces may be roughened such as by chemical etching, bead-blasting, sanding, grinding, serrating, and/or diamond-cutting. All or portions of the exterior surfaces 46, 52 may receive a coating of a metallic substance which may be applied by sintering or by a spray coating such as a plasma spray. All or a portion of the exterior surfaces 46, 52 may also be coated with a biocompatible and osteoconductive material such as hydroxyapatite (HA), tricalcium phosphate (TCP), and/or calcium carbonate to promote bone in growth and fixation. Alternatively, osteoinductive coatings, such as proteins from transforming growth factor (TGF) beta superfamily, or bone-morphogenic proteins, such as BMP2 or BMP7, may be used. Other suitable features may include spikes for initial fixation; ridges or keels to prevent migration in the lateral and anterior direction, for example; serrations or diamond cut surfaces; fins; posts; and/or other surface textures.
The prosthesis 40 may be assembled by inserting the bearing members 60 into the retaining components 58. Within the retaining components 58, the bearing members 60 may be permitted to freely rotate. A portion of the bearing members 60 may extend from the retaining component. The central body 50 may then be inserted between the interior surfaces 48, 54 such that the bearing members 60 engage the surfaces 48, 54 in rolling contact. The assembled prosthesis 40 may be implanted into the vertebral joint 10 in the void created by the removed disc 12 such that the exterior surface 46 engages an endplate of the vertebral body 14 and the exterior surface 52 engages an endplate of the vertebral body 16. The prosthesis 40 may be implanted using any of the approaches described above.
In operation, the central body 50 may allow a variable center of rotation to permit flexion-extension and lateral bending motions. The bearing members 60 may provide a rolling interface between the central body 50 and the interior surfaces 48, 54 which permits rotational motion, translational motion, and bending motion of the endplate component 42 relative to the endplate component 44. This, in turn, may permit axial rotation, lateral bending, and flexion-extension motion at the vertebral joint 10. The rolling motion of the bearing members 60 results in single point contact between the bearing members and interior surfaces 48, 54. This minimum contact may reduce friction and the associated generation of wear debris, particularly as compared to sliding, shear-generating motion. The flexible nature of the core component 50 may also reduce wear caused by cross-shearing or by articulation in flexion-extension and lateral bending motions.
Referring now to
The central body 80 may have an inner portion 92 and outer surfaces 94, 95. The central body 80 may have a generally circular cross-section as viewed from a plane perpendicular to a longitudinal axis 39. The inner portion 92 and the outer surfaces 94, 95 may be formed of any of the materials described above for inner portion 62 and outer surfaces 64, 65, respectively. The surfaces 94, 95 may be treated with any of various techniques to improve wear resistance such as ion-implantation, diamond or diamond-like coating, or other methods that make the surface harder than the original surface. The endplate components 72, 74 and the bearing members 90 may be formed of any suitable material including those materials described above for endplate components 42, 44. The exterior surfaces 76, 82 may include features or coatings (not shown) which enhance the fixation of the implanted prosthesis such as those described above for surfaces 46, 52.
The prosthesis 70 may be assembled by inserting the bearing members 90 into the retaining components 88. Within the retaining components 88, the bearing members 90 may be permitted to freely rotate. A portion of the bearing members 90 may extend from the retaining component. The central body 80 may then be inserted between the interior surfaces 78, 84 such that the bearing members 80 engage the surfaces 94, 95 in rolling contact. The assembled prosthesis 70 may be implanted into the vertebral joint 10 in the void created by the removed disc 12 such that the exterior surface 76 engages an endplate of the vertebral body 14 and the exterior surface 82 engages an endplate of the vertebral body 16. The prosthesis 70 may be implanted using any of the approaches described above.
In operation, the central body 80 may allow a variable center of rotation to permit flexion-extension and lateral bending motions. The bearing members 90 may provide a rolling interface between the central body 80 and the interior surfaces 78, 84 which permits rotational motion, translational motion, and bending motion of the endplate component 72 relative to the endplate component 74. This, in turn, may permit axial rotation, lateral bending, and flexion-extension motion at the vertebral joint 10. The rolling motion of the bearing members 90 results in single point contact between each of the bearing members and central body 80. This minimum contact may reduce friction and the associated generation of wear debris, particularly as compared to sliding motion. A flexible core component 80 may also reduce wear caused by cross-shearing or by articulation in flexion-extension and lateral bending motions.
Referring now to
The endplate components 102, 104 and the bearing members 118 may be formed of any suitable biocompatible material including those described above for endplate components 22, 24. The exterior surfaces 106, 112 may include features or coatings (not shown) which enhance the fixation of the implanted prosthesis such as those described above for surfaces 26, 32.
The prosthesis 20 may be assembled by inserting the bearing members 118 into the retaining components 116. Within the retaining component, the bearing members may be permitted to freely rotate. A portion of the bearing members 118 may extend from the retaining components 116, and the endplate component 102 may be positioned such that the recessed portion 110 engages the bearing members 118 in rolling contact. The assembled prosthesis 100 may be implanted into the vertebral joint 10 in the void created by the removed disc 12 such that the exterior surface 106 engages an endplate of the vertebral body 14 and the exterior surface 112 engages an endplate of the vertebral body 16. The prosthesis 100 may be implanted using any of the approaches described above.
In operation, the bearing members 118 may move within the boundaries of the recessed portion 110. The bearing members 118 may provide a rolling interface between the interior surfaces 108, 114 which permits rotational motion, translational motion, and bending motion of the endplate component 102 relative to the endplate component 104. This, in turn, may permit axial rotation, lateral bending, and flexion-extension motion at the vertebral joint 10. The rolling motion of the bearing members 118 results in single point contact between the bearing members and interior surfaces 108, 114. This minimum contact may reduce friction and the associated generation of wear debris, particularly as compared to sliding motion.
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In alternative embodiments, other arrangements of roller bearings, spherical ball bearings, races, or rolling surfaces may be arranged to promote or limit certain types of motion. In still other alternative embodiments, the motion limiting bearings arrangement may be rotatably attached to an upper endplate component or a central body.
Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Accordingly, all such modifications and alternative are intended to be included within the scope of the invention as defined in the following claims. Those skilled in the art should also realize that such modifications and equivalent constructions or methods do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. It is understood that all spatial references, such as “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” “right,” “rostral,” “caudal,” “upper,” and “lower,” are for illustrative purposes only and can be varied within the scope of the disclosure. In the claims, means-plus-function clauses are intended to cover the elements described herein as performing the recited function and not only structural equivalents, but also equivalent elements.
