US 7056345 B2
A pliable band or hoop that is flexible to normal handling, but cannot stretch circumferentially once it has reached the limits of its circumferential length. The band may have a structural portal to be used for filling, or it may simply be constructed of a fabric-like material that allows a fill tube to perforate its walls to allow for filling. In the latter case, the perforated wall tends to self-seal once the fill tube is withdrawn. The band may be flat or tubular in cross-section. However, unlike a balloon, the band does not require either a bottom or a top, as we found that a top and bottom are unnecessary when using a band or hoop to enclose material injected into a reamed out intervertebral space.
1. A device for stabilizing a spinal motion segment comprising: a substantially tubular member constructed from a generally pliable, but minimally elastic material, the substantially tubular member having a first end and a second end, the substantially tubular member defining an interior space and an opening at the first end and the second end, the substantially tubular member having a circumference sized to fit in the immediate vicinity of the outer annulus of the intervertebral disc of a mammalian spine, the substantially tubular member having a central axis, the central axis extending between the first end and the second end, the central axis constructed and arranged to be generally collinear with a cephalo-caudal axis of the mammalian spine when fitted into the immediate vicinity of the outer annulus of the intervertebral disc, the substantially tubular member having a predetermined height and a predetermined thickness.
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This application is a continuation application of U.S. application Ser. No. 10/022,048 filed Dec. 17, 2001, and issuing as U.S. Pat. No. 6,712,853, which claims priority from U.S. provisional application No. 60/256,014, filed Dec. 15, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to devices that provide a means to support and/or reinforce and/or stabilize a diseased mammalian spinal intervertebral disc.
2. Description of the Related Art
It is recognized that the spinal disc consists of three parts: first, the nucleus, a central portion that is a compression-resisting cushion; second, the annulus, a peripheral rim portion that is a tension-resisting hoop; and third, the end plate, the superior and inferior borders of the disc, consisting of the up and down borders of the vertebral body bones.
Many studies have concluded that mechanical back pain is the most common and costly musculoskeletal condition affecting middle-aged humans in modem societies. Mechanical back pain may be caused by several factors, but overwhelming evidence suggests that degeneration of the spinal intervertebral disc, such as may be caused by Degenerative Disc Disease (DDD) is the most common condition causing back pain symptoms.
The inventor, in a previously published work entitled The tissue origin of low back pain and sciatica: A report of pain response to tissue stimulation during operations on the lumbar spine using local anesthesia. (Orthop. Clin. North Amer. 1991; 22(2):181–187.), demonstrated that the diseased disc rim or annulus is the principle pain generator responsible for mechanical back pain.
Many devices have been invented for the purpose of stabilizing and/or replacing parts of the disc in an effort to ease the pain associated with disc disease. Indeed, one of the author's prior inventions, the BAK has been used in more than 80,000 humans, with generally good results (See generally: the Bagby and Kuslich Method of Lumbar Interbody Fusion, History, Techniques, and 2-year Follow-up Results of a United States Prospective, Multicenter Trial. Kuslich S. D., Ulstrom C. L., Griffith S. L., Ahem J. W., Dowdle J. D., Spine 1998; 23:1267–1279; Summary of Safety and Effectiveness Of the BAK Interbody Fusion System, Food and Drug Administration (FDA) (PMA 950002), PMA Document Mail Center (HFZ-401), Center for Disease and Radiological Health, Washington D.C., Sep. 20, 1996; and Lumbar Interbody Cage Fusion for Back Pain: an Update on The BAK (Bagby and Kuslich) System, Kuslich S. D., Spine: State of the Art Reviews 1999; 13(2):295–311). Unfortunately, the BAK and many similarly structured rigid metallic implants suffer from several less than ideal features such as: the need to create fairly large surgical exposures, the need for fairly large entrance holes through the annulus of the disc, and the presence of fairly large volumes of metal that reduce bone graft surface contact at the end plate.
Any device that would more easily, and/or more effectively, and/or more safely treat degenerative disc disease would be useful in the management of hundreds of thousands of suffering individuals.
Previous patents involving intervertebral devices designed to treat DDD fall generally into the following four classes:
The first class includes rigid, three-dimensional geometric solid devices, either impervious or porous, that function as support struts. When placed in the area of the disc between adjacent vertebral bodies, they allow and/or encourage bone to grow through and/or around the device to cause a bony fusion between two adjacent vertebral bodies. Examples of such devices have been described in the following references:
U.S. Pat. No. 6,015,436 to Schonhoffer
U.S. Pat. No. 6,010,502 to Bagby
U.S. Pat. No. 5,972,031 to Biedermann et al.
U.S. Pat. No. 5,895,427 to Kuslich
U.S. Pat. No. 5,735,899 to Schwartz et al.
U.S. Pat. No. 5,720,748 to Kuslich
U.S. Pat. No. 5,709,683 to Bagby
U.S. Pat. No. 5,700,291 to Kuslich
U.S. Pat. No. 5,669,909 to Zdeblick
U.S. Pat. No. 5,514,180 to Heggeness et al.
U.S. Pat. No. 5,591,235 to Kuslich
U.S. Pat. No. 5,489,308 to Kuslich
U.S. Pat. No. 5,489,307 to Kuslich
U.S. Pat. No. 5,405,391 to Henderson et al.
U.S. Pat. No. 5,263,953 to Bagby
U.S. Pat. No. 5,059,193 to Kuslich
U.S. Pat. No. 5,015,255 to Kuslich
U.S. Pat. No. 5,015,247 to Michelson
U.S. Pat. No. 4,946,458 to Harms et al.
U.S. Pat. No. 4,936,848 to Bagby
U.S. Pat. No. 4,834,757 to Bantigan
U.S. Pat. No. 4,820,305 both to Harms et al.
U.S. Pat. No. 4,501,269 to Bagby
U.S. Pat. No. 4,401,112 to Rezaian
The second class involves the use of semi-rigid artificial joints that allow motion in one or more planes. Examples include U.S. Pat. No. 4,759,769 to Kostuik, U.S. Pat. No. 6,039,763 to Shelokov, and commercially available examples such as the Link device or Charite Intervertebral Disc Endoprosthesis.
The third class is directed to non-rigid cushions designed to replace the nucleus of the disc. Examples of artificial discs are described in U.S. Pat. No. 4,904,260 to Ray, U.S. Pat. No. 4,772,287 to Ray and U.S. Pat. No. 5,192,326 to Boa.
Finally, the fourth class is the relatively new area of initially flexible, expandable bags or balloons that become rigid when injected with materials that can support loads. Examples include U.S. Pat. Nos. 5,571,189 and 5,549,679 to Kuslich, each of which describe expandable, porous balloons or bags, useful in stabilizing a deteriorating spinal disc. In this fourth class, a porous bag or balloon is used which is closed except for a mouth through which bone graft or other graft material is inserted. The bag is placed into a reamed out intervertebral space and is expanded by the introduction of graft material. Recent research and development in the inventor's laboratory established the fact that a thin walled band or hoop, either porous or non-porous, can be placed in the region of the annulus by means of several techniques. Such a band or bands as described in detail below effectively reinforce the annulus and thereby support spinal motion segment strain deflections resulting from stresses applied in all vector directions: rotation, flexion-extension, side bending, compression and distraction. Furthermore, the inventor's experiments show that these radially applied bands or hoops can effectively contain and retain inserted or injected materials that are placed in the central region of a reamed-out disc. The current invention teaches a technique for building and using a simple band to perform many of the functions of the prior art described above. For instance, if compared to metal cylindrical implants such as described in U.S. Pat. No. 5,015,247 to Michelson and metal-walled or plastic-walled rectangular shaped implants such as may be described in U.S. Pat. Nos. 4,878,915 and 4,743,256 both to Brantigan, the bands of this invention are softer, lighter, more pliable, and without hard sharp edges, thereby offering greater safety during passage next to delicate structures such as the great vessels or the spinal cord. Also, the completely open structure at the Polar Regions adjacent to cancellous bone of the vertebral bodies, would allow for a more intimate fit between inserted graft material and living bone. This intimacy of contact, without any intervening implant material, may reasonably lead to a faster and more complete biological ingrowth through the central portion of the implant.
It is well known that greater surface area contact between graft and living bone is conducive to higher fusion rates and conversely, lower non-union rates. Thus, the current invention provides for several unique advantages over prior art in the field of interbody fusion devices.
In addition to its uses and advantages in the form of improved interbody fusion devices, the attributes of the current invention would provide a new and potentially superior technology in two other categories of treatment for degenerative disc disease: one, soft tissue reinforcement of diseased discs, and two, disc replacement.
In regard to soft tissue reinforcement of diseased discs, several new techniques have recently become available to treat early and mid-stage disc degeneration by methods less invasive and less drastic than fusion surgery. Examples include: annular tissue modulation by heat application (See generally: Saal J. et al. North American Spine Society presentations 1999, 2000); the use of a polyester tension band placed around and between pedicle screws above and below the involved disc such as, described in U.S. Pat. No. 5,092,266 to Graf; and combined tension and distraction devices placed between pedicle screws, such as may be seen in the commercially available DyneSyS.TM device from Sulzer Orthopedics Ltd. While early results from the above technologies appear promising, the current invention would obviate some of the potential dangers and drawbacks of these systems. For example:
In the case of annular tissue modulation by heat application, the current invention does not require heat. Heat can be injurious to local spinal nerves and vessels, possibly leading to paralysis or even death by hemorrhage. The current invention immediately stabilizes the annulus, rather than having to wait until the heat-damaged tissue heals and shrinks.
In the case of a polymeric tension band placed between pedicle screws above and below the involved disc, the current invention does not require the placement of pedicle screws. The placement of pedicle screws requires a significant surgical exposure with attendant bleeding and injury to local muscular, ligamentous, vascular and nervous tissues. The current invention can be installed through much smaller, microsurgical exposures that would have less likelihood of causing collateral damage.
In the case of combined tension and distraction devices placed between pedicle screws, the current invention directly stabilizes the very tissue that is causing the discogenic pain, the annulus, rather than attempting to stabilize the annulus by an external, cantilevered system that has all of the risks and disadvantages of using polyester tension bands and pedicle screws.
The current invention is a basic departure from the prior art at a very fundamental level. The core element of the invention is the simple but broad concept of applying a tension-resisting circumferential band at or near the mid or outer circumference of the annulus. A careful review of the patent and medical literature and prior art did not provide an instance of this fundamental concept having been previously described. Once conceived, the core idea of using a circumferential tension band to reinforce an injured disc annulus led to a number of alternative embodiments, spanning the treatment options all the way from simple reinforcement, to containment of graft material for interbody fusion, to radial containment of a centrally placed compressible or incompressible nuclear replacement material. In other words, the basic concept of the current invention could provide the critical element that would allow a developer and/or a surgeon a new means to structure a new and potentially better annular support for a less invasive early to mid-stage degenerative disc disease treatment method. The invention would also provide an improved means of graft support for a less invasive interbody fusion method. Finally, the invention would provide an improved means of support for nuclear material (biological or non-biological, bioactive or inert, hydrophilic or non-hydrophilic, granular or amorphous)—for nuclear replacement or so-called artificial disc replacement.
The entire content of each and all patents, patent applications, articles and additional references, mentioned herein, are respectively incorporated herein by reference.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. .sctn. 1.56(a) exists.
The invention provides for an expandable tubular member or band which has side walls and may include a fill opening. However, the expandable band does not require either a bottom or a top as it has been found that a suitable enclosure is created by placing such a band within a reamed out intervertebral space. Pressure within the interior of the band is exerted primarily against the side walls and the adjacent vertebrae surfaces. The pressure exerted by the bone graft material at the top and bottom is exerted against the exposed bone of the adjacent vertebrae which encourages bone growth through the band interior. The bone graft material is contained within the tube by a combination of the natural bony top and bottom together with the sidewall of the band.
The current invention provides a novel means to support the diseased and/or weakened annulus of the disc. This support would offer improved resistance to stresses placed on the spine and therefore would reasonably result in decreased pain and improved function to any individual suffering from the degenerated disc disease condition.
In addition to simply reinforcing the diseased annulus of the disc, the devices based on the invention herein described could also provide a means to retain and contain materials that might be inserted or injected into the disc in an attempt to heal the annulus, to replace the natural nucleus, or to create a bony fusion between the two adjacent vertebral bodies.
In at least one embodiment of the invention, the invention provides a flexible implant that may be inserted into a cavity formed in a degenerating disc. The flexibility of the band allows it to be inserted through a relatively small opening in a disc or vertebral space. The band is then positioned so its fill opening, if any, may receive biological fill material. This material is packed into the interior flexible band, causing the band to expand and conform to the cavity formed in the disc or vertebrae. Fill material is added until enough material is present to expand the disc to the desired position. At this time, the band fill opening is closed to prevent egress of the fill material.
In at least one embodiment of the invention, the invention provides for a pliable band or hoop that is flexible to normal handling, but cannot stretch circumferentially once it has reached the limits of its circumferential length. The band may have a structural portal to be used for filling, or it may simply be constructed of a fabric-like material that allows a fill tube to perforate its walls to allow for filling. In the latter case, the perforated wall tends to self-seal once the fill tube is withdrawn. The band may be flat or tubular in cross-section. However, unlike a balloon, the band does not require either a bottom or a top, as we found that a top and bottom are unnecessary when using a band or hoop to enclose material injected into a reamed out intervertebral space.
As long as the width of the band is approximately equal to the annulus height (or stated another way, the distance from one vertebral peripheral end-plate to its neighbor) the band serves well to contain particulate material inserted into the center of the disc cavity, without the need for a complete spherical enclosure, as would be provided by a balloon. Since in the case of the reamed out interdiscal cavity, the top opening and bottom opening of the band would be covered by dense vertebral bone, it is not necessary to enclose inserted particulate graft or other material in these regions.
Pressure within the cavity, as would occur when a surgeon injects material into its central region interior to the band, is exerted radially against the band and the adjacent vertebral surfaces. As the internal cavity is filled with incompressible material, such as bone graft or bioceramic beads or granules, radial displacement beyond the circumference of the band is restricted. Therefore, any additional injected material would be directed north and south against the vertebral bodies. This action would increase the distance between the vertebral bodies, and produce a so-called disc distraction. This distraction is known to have three salutary results. First, it stabilizes the motion segment by tightening the ligamentous structures. Second, it opens the exiting holes for spinal nerves—the so-called neural foramina—and thus relieves certain types of nerve compression disorders. Third, this improved stability is necessary to allow for bony ingrowth and through-growth, to produce an interbody fusion. The pressure exerted by the bone graft material at the top and bottom is directed against the exposed bone of the adjacent vertebra. This produces an intimate contact that encourages bone growth through the interior of the cavity.
In at least one embodiment, the invention consists of any continuous band or ring that would be placed around and near the outer margin of the intervertebral disc. A suture or preferably a flattened, braided or woven strand or cord, for instance, that was placed circumferentially about a disc and tied to make a tension-resisting ring, would qualify. Modern endoscopic surgical tools, combined with sophisticated surgical navigation systems make this option more practical and safer than would have been possible a few years ago.
In yet another embodiment, the band would be pre-formed to match the anatomy of the patient. It would also be available in a variety of circumferences, plies, thicknesses, widths (in the superior-inferior dimensions), weave patterns, materials and filament diameters. The band would be flexible enough to fit through a small hole made in the annulus, such as during a routine disc hernia removal operation. After removal of the disc hernia, the surgeon would introduce an expandable reamer and thereby remove the degenerated nucleus, the cartilage end plate, and the inner annulus, leaving the outer annulus intact. Examples of such a procedure and expandable reamers are described in U.S. Pat. No. 5,445,639 to Kuslich et al. and co-pending U.S. Pat. App. Ser. No. 60/182,610 to Kuslich et al., filed Feb. 15, 2000, the entire contents of both being incorporated herein by reference.
The properly sized band would be pushed through the disc portal, whereupon, owing to its inherent springiness, or as a result of material being injected in the interior of the disc, the hoop or band would expand radially against the outer annulus. Perforating the mesh fabric of the band, by means of a pointed fill tube, would allow the surgeon to fill the cavity with significant pressure using graft material; perhaps by the use of a graft injection system such as described in a co-pending U.S. patent application Ser. No. 09/738,726 filed Dec. 15, 2000 and entitled Tool to Direct Bone Replacement Material, to Kuslich et al., and is a continuation in part application of U.S. patent application Ser. No. 09/608,079 the entire contents of both being incorporated herein by reference. The resulting compressed graft, held from further expansion by the vertebral bone above and below, and the band or hoop radially, would change phase from liquid-like to solid-like, as is known to occur when granular materials are subjected to compression loading (See: Friction in Granular Flows, by H. M. Jaeger, Chu-heng Liu, S. R. Nagel and T. A. Witten, Europhysics Lett. 11, 619 (1990); Granular Solids, Liquids, and Gases, by H. M. Jaeger, S. R. Nagel and R. P. Behringer, Rev. Mod. Phys. 68, 1259 (1996); and IUTAM Symposium on Segregation in Granular Flows (Solid Mechanics and its Applications), Vol. 81, October 2000). This phase change has been observed and scientifically characterized by our laboratory experiments and by the work described in U.S. Pat. No. 5,331,975 to Bonutti (see also Formation of Structural Grafts From Cancellous Bone Fragment, by P. M. Bonutti, M. J. Cremens, and B. J. Miller, Am. J. Ortop. Jul. 27, 1998: 499–502); each of the above references being incorporated in their entirety herein by reference. This phase change would result in a construct that is capable of both stabilizing the motion segment in the short run, and would foster the development of a solid bony fusion over the long run.
To state the process in another way: the invention provides a pliable implant that may be inserted into a cavity formed in a degenerating disc. The flexibility of the band allows it to be inserted through a relatively small opening in a disc or vertebral space. The band is then positioned so its fill opening may receive fill material. This material is packed into the region interior to the band, causing the band to expand and conform to the cavity formed in the disc or vertebrae. Fill material is added until enough material is present to expand the disc to the desired position. At this time, the band fill opening is closed, or allowed to self-seal to prevent egress of the fill material.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
The invention in various of its embodiment is summarized below. Additional details of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
The abstract provided herewith is intended to comply with 37 CFR 1.72 and is not intended be used in determining the scope of the claimed invention.
A detailed description of the invention is hereafter described with specific reference being made to the following drawings.
This invention may be characterized as an improvement of the inventor's inventions described in U.S. Pat. Nos. 5,571,189 and 5,549,679, the disclosures of which are incorporated herein by reference.
With reference to the Figures,
The band 12 is pliable and malleable before its interior space 14 (not shown in
The band 12 may be constructed in a variety of ways. The band material 16 may be etched, woven or braided material such as a weave of NITINOL fibers, or a form-molded material such as shown in
Where the material 16 of the band 12 is porous, such as in the embodiment shown in
The material 16 of the invention must be flexible enough to allow it to be collapsed and inserted into an opening smaller than the expanded band size. As may be seen in
Accordingly, the fabric band 12 may be formed from a polymeric material to which a plurality of perforations are formed or added. It need not be woven and may be molded, such as the embodiment shown in
Preferably the material 16 is light, biocompatible, flexible and easily handled, but is also very strong in terms of resisting tension, and thus unlikely to rip or tear during insertion and expansion. When the device is expanded through insertion of fill material, such as is depicted in
As may be seen in
In addition, as may be seen in
Preferably the opening 26 includes a means of preventing passage of fill material out of the interior space 14. In the embodiment shown in
As may be further seen in
In the embodiment of the invention wherein the band material 16 is woven from one or more fibers, the fibers may be composed of a variety of materials as previously discussed. In the various embodiments shown in
As seen in
The double walled construction may provide the band 12 with increased strength to provide additional mechanical support for the graft material contained in the interior 14. In addition, the double walled construction may be configured to allow the various openings 18 of the respective walls 60 and 62 to partially overlap. As a result, the fibers 58 of one wall, for example inner wall 60, may overlap the openings 18 of the other wall, for example outer wall 62, thereby effectively reducing the size of the openings 18. As a result, a band 12 having a double walled construction may not require any more fibers 58 than a single walled band such as may be seen in
The members 64 and 66 may be constructed from the same or different material as fibers 58. In addition, the members 64 and 66 may be one or more wires or fibers woven or braided together and oriented in the latitudinal orientation shown. Alternatively, one or more fibers may be equatorially oriented, or may be otherwise positioned anywhere around the circumference of the band 12.
In addition to providing the band 12 with one or more latitudinally oriented wires or members 64 and 66, the band may also include one or more longitudinally oriented members 68 such as may be seen in the embodiment shown in
As with the latitudinal members 64 and 66, the longitudinal members 68 may be constructed out of any suitable material. Such material may be different from or the same as the fibers 58. Additionally, the members 68 may be characterized as one or more fibers 58 oriented in the longitudinal direction shown.
In the various embodiments shown in
As shown in
As shown in
As is shown in
The tapered distal end 102 of the tool 100 is sized to enlarge the opening 18 to allow passage of the tool 100 into the interior 14 by pushing aside the various fibers 58 as may best be seen in
The extent of tool penetration into the band interior 14 must be sufficient to allow the side opening 106 to be fully contained within the band interior 14. The tool 100 may include more than 1 side opening 106.
As shown in
If the internal diameter of the shaft 104 may be about 1.5 mm to 5 mm and is preferably approximately 2.5 mm in diameter. The length of the side opening 106 is preferably between about 1½ to 3 times the internal diameter of the shaft 104.
The distal end 102 of the tool 100 is preferably angled to direct the flow and to break down any material that has packed back into more discrete pieces.
In the various embodiments described herein, it may be desirable to stimulate growth of bone through the band 12 or fill material 108 contained therein, by direct or indirect application of electrical current. In the various embodiments described herein, the band 12 may include portions 81 and 83, where electrical leads 91 and 93 may be readily attached, such as are shown in
The portions 81 and 83 may be part of a electrically conductive member 85 which is disposed within the walls 60 and 62 of the band 12, such as is shown in
In an alternative embodiment of the invention shown in
In some embodiments of the invention, one of which is shown in
By securing the ends 202 and 204 of the member 200 about the disc, the member 200 forms a substantially continuous band similar to that previously described. When secured about a disc the member 200 preferably has a substantially concave appearance, relative to the surrounding spinal bodies, such as is shown in
In addition to being directed to the specific combinations of features claimed below, the invention is also directed to embodiments having other combinations of the dependent features claimed below and other combinations of the features described above.
The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.
Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.