US 20090143862 A1
Devices for anchoring and/or blocking spinal implants in an intervertebral disc space are disclosed. In one aspect of the invention the device includes a rigid blocking member having one end unconnected and free to block a spinal implant, and another end attached to a securing member to secure the blocking member to the spine. Methods for using the inventive anchoring/blocking implants are also provided.
1. A device for maintaining separation between naturally adjacent vertebrae in a human while cushioning the intervertebral space, the device comprising:
a first L-shaped blocking member having an anchoring arm and a blocking arm, the L-shaped blocking member being sized and adapted to be coupled to a human vertebra;
a securing member for coupling the anchoring arm to a human vertebra; and
an intervertebral disc implant sized and adapted to be positioned between two, naturally adjacent vertebrae in a human;
wherein the blocking arm of the L-shaped blocking member is sized and adapted to block the intervertebral disc implant from being expelled from an intervertebral disc space while remaining free and unconnected to the intervertebral disc implant.
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10. A device for maintaining separation between naturally adjacent human vertebrae, the device comprising an L-shaped blocking member having an anchoring arm and a blocking arm; and
a spinal implant sized and adapted to be positioned between two, naturally adjacent human vertebrae in a disc nucleus space;
wherein the anchoring arm is sized and adapted to be anchored to a human vertebra; and
wherein the blocking arm is sized and adapted to extend into an opening in a disc annulus without extending into the disc nucleus space, and is thereby to be positioned to block the spinal implant in the disc nucleus space while remaining unconnected to the spinal implant.
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15. A device for maintaining separation between naturally adjacent human vertebrae, the device comprising a pair of L-shaped blocking members, wherein each blocking member has an anchoring arm and a blocking arm; and
a spinal implant sized and adapted to be positioned between naturally adjacent human vertebrae in a disc nucleus space;
wherein each of the anchoring arms is sized and adapted to be anchored to a respective one of the naturally adjacent human vertebra; and
wherein each of the blocking arms is sized and adapted to extend into an opening in a disc annulus without extending into the disc nucleus space, and are thereby to be positioned to block the spinal implant in the disc nucleus space while remaining unconnected to the spinal implant.
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This application is a continuation application of pending U.S. patent application Ser. No. 11/173,451, filed Jul. 1, 2005, which is a divisional of U.S. Pat. No. 6,974,479, filed Apr. 21, 2003, which is based on Provisional Application 60/432,368, filed Dec. 10, 2002.
The present invention relates generally to spinal implants, and more particularly to devices for blocking and/or retaining implants in an intervertebral disc space.
The intervertebral disc functions to stabilize the spine and to distribute forces between vertebral bodies. A normal disc includes a gelatinous nucleus pulposus, an annulus fibrosis and two vertebral end plates. The nucleus pulposus is surrounded and confined by the annulus fibrosis.
Intervertebral discs may be displaced or damaged due to trauma or disease. Disruption of the annulus fibrosis allows the nucleus pulposus to protrude into the spinal canal, a condition commonly referred to as a herniated or ruptured disc. The extruded nucleus pulposus may press on the spinal nerve, which may result in nerve damage, pain, numbness, muscle weakness and paralysis. Intervertebral discs may also deteriorate due to the normal aging process. As a disc dehydrates and hardens, the disc space height will be reduced, leading to instability of the spine, decreased mobility and pain.
One way to relieve the symptoms of these conditions is by surgical removal of a portion or all of the intervertebral disc. The removal of the damaged or unhealthy disc may allow the disc space to collapse, which could lead to instability of the spine, abnormal joint mechanics, nerve damage, as well as severe pain. Therefore, after removal of the disc, adjacent vertebrae are typically fused to preserve the disc space.
Several devices exist to fill an intervertebral space following removal of all or part of the intervertebral disc in order to prevent disc space collapse and to promote fusion of adjacent vertebrae surrounding the disc space. Even though a certain degree of success with these devices has been achieved, full motion is typically never regained after such intervertebral fusions.
Attempts to overcome these problems have led to the development of disc replacements. Many of these devices are complicated, bulky and made of a combination of metallic and elastomeric components and thus never fully return the full range of motion desired. More recently, efforts have been directed to replacing the nucleus pulposus of the disc with a similar gelatinous material, such as a hydrogel. However, once positioned in the disc space, many hydrogel implants may migrate in the disc space and/or may be expelled from the disc space through an annular defect. Closure of the annular defect, or other opening, using surgical sutures or staples following implantation is typically difficult and, in some cases, ineffective.
A need therefore exists for a nucleus pulposus or other spinal implant that resists migration from the disc space, as well as for devices and methods that block or retain the implants so that the implants are more resistant to migration and/or expulsion through an opening in the annulus fibrosis. The present invention addresses these needs.
Devices and methods for blocking and/or retaining a prosthetic spinal implant member in an intervertebral disc space are provided. In a first aspect of the invention the device comprises a first blocking member having an anchoring end and a blocking end. The anchoring end is anchored to a vertebra, and the blocking end is free and unconnected to a prosthetic spinal implant, and is positioned to block a prosthetic spinal implant from being expelled from an intervertebral disc space.
In a second embodiment the device further includes a second blocking member having an anchoring end and a blocking end. The anchoring end of the second blocking member is anchored to a vertebra, and the blocking end of the second blocking member is free and unconnected to a prosthetic spinal implant, and is positioned to block a prosthetic spinal implant from being expelled from an intervertebral disc space.
Methods for anchoring a spinal implant are also provided. In one aspect of the invention the method comprises: (a) implanting a prosthetic spinal implant member in an intervertebral disc space; (b) providing a first blocking member having an anchoring end and a blocking end, wherein said blocking end is free and unconnected to a prosthetic spinal implant; (c) positioning the blocking end of said first blocking member in a position effective to block said prosthetic spinal implant from being expelled from the intervertebral disc space; and (d) securing the anchoring end of said first blocking member to a vertebra in a manner in which the blocking end of said first blocking member is maintained in a position effective to block said prosthetic spinal implant from being expelled from the intervertebral disc space.
In another embodiment the method additionally includes the steps of: (e) providing a second blocking member having an anchoring end and a blocking end, wherein said blocking end is free and unconnected to a prosthetic spinal implant; and (f) positioning the blocking end of said second blocking member in a position effective to block said prosthetic spinal implant from being expelled from the intervertebral disc space; and (g) securing the anchoring end of said second blocking member to a vertebra in a manner in which the blocking end of said second blocking member is maintained in a position effective to block said prosthetic spinal implant from being expelled from the intervertebral disc space.
In a third embodiment the method comprises: (a) implanting a prosthetic spinal implant in an intervertebral disc space; (b) providing a flexible blocking member having a first anchoring end, a second anchoring end, and a blocking portion, wherein said flexible blocking member is unconnected to said prosthetic spinal implant; and (c) securing said first anchoring end to a vertebra; and (d) securing said second anchoring end to a vertebra; wherein said securing steps are accomplished in a manner effective to position said blocking portion in a position effective to block said prosthetic spinal implant from being expelled from the intervertebral disc space.
One object of the present invention is to provide devices for anchoring spinal implants so they will be resistant to excessive migration in, and/or expulsion from, the intervertebral disc space. Further objects and advantages of the present invention will be apparent from the following description.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to certain preferred embodiments 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. All embodiments of the present invention, including those explicitly disclosed, those inherently disclosed, and those that would normally occur to persons skilled in the art, are desired to be protected.
The present invention relates to prosthetic spinal implants that are blocked and/or anchored to prevent excessive migration in and/or expulsion from the disc space. Methods of using such implants are also disclosed. The spinal implants described herein include those that may be useful as nucleus pulposus replacements, partial or complete disc replacements, and those that may be useful in other disc reconstruction or augmentation procedures.
Referring now to the drawings,
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Anchoring member 11 may be “L” shaped as shown in
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The anchoring member of the device may also, in other forms of the invention, include a flexible implant-blocking material. For example,
Implant member 104 extends into, and substantially fills, both the vacated nucleus space and opening 108 in annulus 107. In the embodiment shown in
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Blocking and/or retaining members such as those shown in
When an “L-shaped” anchoring/blocking member is used, the anchoring/blocking member is preferably mounted to contact the vertebral end plate, as shown in
It is also to be appreciated that in “flush fit” embodiments using an “L-shaped” anchoring member, the end connected to the implant need not be covered completely by the implant. Accordingly, the embodiment shown in
In the “double anchor” embodiments of
As to methods of using the disclosed anchored implants, the procedure typically begins with a discectomy to remove the degenerated natural disc. An opening is provided in the annulus, and the degenerated disc material is removed. A prosthetic nucleus in delivered into the disc space, and the anchoring and/or blocking member(s) are installed and attached.
As to the materials that may be used to make the various components of the preferred embodiments, anchoring/blocking members may be formed from rigid, semi-rigid, or flexible biocompatible materials including metals, polymers, ceramics, composites, natural or synthetic bone materials, etc. For example, carbon fiber reinforced composites such as carbon fiber/epoxy composites or carbon fiber/polyaryletherketone composites may be used, as may a wide variety of metallic materials, such as, for example, stainless steel, titanium, titanium alloys, cobalt chrome alloys, tantalum, shape memory alloys, etc.
Examples of appropriate polymeric materials include, but are not limited to, synthetic polymers such as polyurethanes, silicones, polyolefins, polyvinylalcohols, polyesters, polyacrylonitriles, polyetherketones, polycarbonates, polymethacrylates, polyamides, etc. In other embodiments natural polymers, such as cellulose, may be used.
Specific preferred polymers include polytetrafluoroethylene, polymethylmethacrylate, polymethyletherketone, polyacrylamide, polyparaphenylene terephthalamide, polyethylene, polystyrene, polypropylene, and combinations of these materials. In some embodiments the polymeric materials are braided in the form of a cord, cable, or may have some other appropriate configuration, and combinations thereof.
Examples of ceramic materials that may be used for the various components of the present invention include alumina, zirconia, alumina-zirconia composites, pyrolytic carbon, and polycrystalline diamond compact materials.
A wide variety of spinal implants for serving differing functions may be anchored or blocked with the anchoring/blocking devices described herein, including implants sized and configured for nucleus pulposus replacements, implants sized and configured for partial or full disc replacements, or other implants designed for other disc reconstruction or augmentation purposes, such as a fusion cage. Elastic, or otherwise resilient, implants are most preferred. For example, implants may be formed from hydrophilic materials, such as hydrogels, or may be formed from biocompatible elastomeric materials known in the art, including silicone, polyurethane, polyolefins such as polyisobutylene and polyisoprene, copolymers of silicone and polyurethane, neoprene, nitrile, vulcanized rubber and combinations thereof. In a preferred embodiment, the vulcanized rubber is produced by a vulcanization process utilizing a copolymer produced, for example, as in U.S. Pat. No. 5,245,098 to Summers et al., from 1-hexene and 5-methyl-1,4-hexadiene. Preferred hydrophilic materials are hydrogels. Suitable hydrogels include natural hydrogels, and those formed from polyvinyl alcohol, acrylamides such as polyacrylic acid and poly (acrylonitrile-acrylic acid), polyurethanes, polyethylene glycol, poly(N-vinyl-2-pyrrolidone), acrylates such as poly(2-hydroxy ethyl methacrylate) and copolymers of acrylates with N-vinyl pyrolidone, N-vinyl lactams, acrylamide, polyurethanes and polyacrylonitrile or may be formed from other similar materials that form a hydrogel. The hydrogel materials may further be cross-linked to provide further strength to the implant. Examples of different types of polyurethanes include thermoplastic or thermoset polyurethanes, aliphatic or aromatic polyurethanes, polyetherurethane, polycarbonate-urethane and silicone polyether-urethane. Other suitable hydrophilic polymers include naturally-occurring materials such as glucomannan gel, hyaluronic acid, polysaccharides, such as cross-linked carboxyl-containing polysaccharides, and combinations thereof. The nature of the materials employed to form the elastic body should be selected so the formed implants have sufficient load bearing capacity. In preferred embodiments, a compressive strength of at least about 0.1 MPa is desired, although compressive strengths in the range of about 1 MPa to about 20 MPa are more preferred.
It is to be appreciated that natural materials may be used to make the prosthetic implants disclosed in the present invention. For example, natural collagen material such as allogenic or xenogenic disc nucleus material may be used. Alternatively, collagen-based material derived from natural, collagen-rich tissue, such as intervertebral disc, fascia, ligament, tendon, demineralized bone matrix, etc., may be used. The material may be autogenic, allogenic, or xenogenic, or it may be of human-recombinant origin. In alternative embodiments the collagen-based material may be a synthetic, collagen-based material. Examples of preferred collagen-rich tissues include disc annulus, fascia lata, planar fascia, anterior or posterior cruciate ligaments, patella tendon, hamstring tendons, quadriceps tendons, Achilles tendons, skins, and other connective tissues.
In some embodiments the implant material is an inelastic, semi-rigid material. Such materials stretch very little, if at all, but allow some compression. The compression typically occurs when air in the implant is pushed out, such as when a small roll of fabric is compressed.
The implants can be shaped as desired. For example, the nucleus pulposus implants may take the form of a cylinder, a rectangle, or other polygonal shape or may be substantially oval.
The securing and/or blocking members may be made of any appropriate biocompatible material, such metals, ceramics, polymers and combinations thereof. Non-resorbable metallic materials include biocompatible stainless steel, titanium, titanium alloys, titanium-vanadium-aluminum alloy, cobalt alloys such as cobalt-chromium alloy, cobalt-chromium-molybdenum alloy, and cobalt-nickel-chromium-molybdenum alloy, tantalum, niobium, hafnium, tungsten, shape memory materials as described above, especially those exhibiting superelastic behavior and including metals, and alloys thereof. Resorbable materials include polylactide, polyglycolide, tyrosine-derived polycarbonate, polyanhydride, polyorthoester, polyphosphazene, bioactive glass, calcium phosphate, such as hydroxyapatite, and combinations thereof.
The anchoring devices may also be anchored with other soft tissue anchors known in the art, including suture anchors commonly used in arthroscopy or sports medicine surgeries, for example. In the case of a soft tissue or suture anchor, the end of the elongated body of the anchoring device is attached to the end of the anchor, which is embedded and anchored in an adjacent vertebral body.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.