Abstract:
The present disclosure concerns implants to at least partially replace the nucleus of a spinal disc. In one embodiment, a prosthetic structure is provided which includes a bag operable to contain at least one internal implant within the bag. In another embodiment, a sinusoidal-shaped structure made of a flexible material is provided with various unique configurations to act as the internal implant and once released from a stretched or compressed configuration resumes nearly its original shape. In one embodiment, for delivery, a sinusoidal-shaped structure may be in a reduced amplitude state. In another embodiment, a sinusoidal-shaped structure is alternately woven from one end to the other with a second sinusoidal-shaped structure.

Description:
BACKGROUND  
       [0001]     Embodiments of the present invention relate generally to disc replacement therapy. More particularly, embodiments of the present invention relate to devices, materials and methods that can be used in disc replacement therapy procedures.  
         [0002]     Generally, a healthy mammalian spine includes a series of vertebrae with discs located in an intervertebral space between each of the adjacent vertebrae. The discs of the spine function to allow motion and to distribute vertical axial loads on the spine. Discs generally are formed of an annulus fibrosis, which creates a disc perimeter, and a gel-like nucleus material, which is positioned within the annulus fibrosis. The healthy nucleus acts essentially as an incompressible fluid within a container, the annulus. The nucleus is compressed by the vertical forces on the spine and deforms horizontally to distribute the vertical load into the disc annulus.  
         [0003]     Certain spinal disorders can cause damage to the disc. For example, one type of spinal disorder is a “herniated disc,” which occurs when a portion of the disc nucleus presses out a hole or herniated region in the surrounding annulus. When this happens, the extruded nucleus material can press on nerves in the spinal region, causing back or spinal pain.  
         [0004]     Pain can vary in herniated disc patients from very little to debilitating, and movement can, at times, intensify the pain. Numbness and muscle weakness also may occur. If the pressure on the nerve root is great, the legs can be paralyzed. Further, if the cauda equina (the bundle of nerves extending from the bottom of the cord) is affected, control of bladder and bowels also can be lost. If these serious symptoms develop, medical attention is required immediately.  
         [0005]     Some patients with herniated discs recover without corrective measures. Many others, however, require surgery. In severe cases, surgery may require removal of all of a disc and perhaps part of a vertebra. For example, treatments for herniated or ruptured discs can include spinal fusion and/or disc nucleus replacement. Spinal fusion includes removal of the disc nucleus and in some cases the annulus. The adjacent vertebrae then is fixed in position to the open space often times by some structure placed between the two vertebrae. A bone growth supplement then can be placed within this space to stimulate the adjacent bone and/or vertebrae to grow into this space causing them to merge or fuse together. The disadvantage to this procedure, however, is the loss of the shock absorbing feature and mobility of a healthy disc.  
         [0006]     Another possible treatment for herniated or ruptured discs is disc nucleus replacement. In this treatment, the disc nucleus is fully or partially removed and replacement material or structures are placed within the annulus. The replacement material or structures provide at least some load bearing function of the former nucleus and allows spinal motion at the effected disc level.  
         [0007]     While some nucleus replacement materials and methods currently are known, further improvements are needed. Thus, needs exist for nuclear disc replacement materials and structures that can be introduced through minimally invasive procedures and also remain within the nuclear space without a future risk of extrusion.  
       SUMMARY  
       [0008]     In one embodiment, the present invention relates to a prosthetic structure for replacement of at least a portion of the intervertebral disc nucleus. Use of this structure allows the annulus fibrosis to remain substantially intact. The device includes a bag structure made from a flexible material having a cavity therein. The bag structure includes an opening that is in communication with the cavity, and which is adapted to allow an interior implant structure to be placed into the cavity. Further, the bag structure is adapted to remain within an intervertebral disc space without extrusion from the space when combined with the interior implant material.  
         [0009]     In some embodiments, the flexible material of the bag structure can comprise a woven or non-woven polymeric fiber, a woven or non-woven metallic material, or a combination thereof. In some embodiments, the flexible material of the bag structure can include a semi-permeable flexible material. In some embodiments, the flexible material of the bag structure can include a material having an elastic or viscoelastic property.  
         [0010]     In one embodiment, the present invention comprises a prosthetic implant structure including a device formed of multiple periodic portions of flexible material, wherein the periodic portions of flexible material intersect a longitudinal axis at two points. In some embodiments, the device can be made of a woven or non-woven polymeric fiber, a woven or non-woven metallic material, or a combination thereof.  
         [0011]     Further, in another particular embodiment, the present invention can comprise the prosthetic bag structure discussed above configured to receive an interior implant structure formed of multiple periodic portions of material each intersecting a longitudinal axis at two points. Thus, in accordance with this particular embodiment, the interior implant device is flexible such that when stretched in a longitudinal direction, the device flattens sufficiently so that it can fit through an opening of the prosthetic bag structure. Further, the interior implant device can be sufficiently elastic and possess shape memory, such that when released from a stretched position, the device returns substantially to its original shape. Thus, when the interior implant structure is placed within the prosthetic bag structure, it resumes an unstretched position, which prevents it from exiting the opening of the prosthetic bag structure.  
         [0012]     In yet another embodiment of the present invention, an interior implant structure may include two or more sinusoidal-shaped devices, in which at least a second sinusoidal-shaped device is attached to or interlaced or interwoven with a first sinusoidal-shaped device. In this particular embodiment, each of the sinusoidal-shaped devices is located in a different plane from one another.  
         [0013]     In yet another embodiment, the present invention relates to a method for implanting a prosthetic structure into an intervertebral space. In one embodiment, the method includes removing at least a portion of a disc nucleus to create a cavity within the disc annulus. Next, a bag structure having an opening for receiving an interior implant structure is inserted into the cavity. Once inserted, the bag structure is expanded in the cavity. Then, an interior implant structure is inserted into the opening in the bag structure. In one embodiment, the interior implant structure is formed of multiple periodic portions of flexible material. In other embodiments, other implant structures can be used. After the implant structure is placed in the bag structure, the opening in the bag structure is sealed so that the interior implant structure cannot be extruded from the intervertebral space.  
         [0014]     A more complete understanding of the present invention may be derived by referring to the detailed description of preferred embodiments and claims when considered in connection with the figures.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     In the Figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.  
         [0016]      FIG. 1   a  is a three dimensional view of an intervertebral disc nucleus prosthetic bag structure in accordance with one embodiment of the present invention;  
         [0017]      FIG. 1   b  is a cross-sectional view of the intervertebral disc nucleus prosthetic bag structure of  FIG. 1   a;    
         [0018]      FIG. 2  is a cross-sectional view of a spinal column showing a herniated disc;  
         [0019]      FIG. 3   a  is a three dimensional view of an implant structure in accordance with one embodiment of the present invention;  
         [0020]      FIG. 3   b  is a three dimensional view of the implant structure shown in  FIG. 3   a , in a stretched configuration; and  
         [0021]      FIG. 4  is a cross-sectional view of one embodiment of an intervertebral disc nucleus prosthetic bag structure having an implant structure positioned therein in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0022]     Embodiments of the present invention relate generally to devices, materials and methods for replacing at least a portion of a intervertebral disc nucleus. More particularly, embodiments of the present invention relate to disc nucleus prosthesis structures, including prosthesis bag structures, implant structures, and a combination of prosthesis bag structures and implant structures. While various prosthetic structures discussed herein are presented with reference to replacement of part or all of a human disc, embodiments of the present invention have application beyond human disc replacement. For example, the prosthetic structures discussed herein could be used in or with discs for any suitable vertebrate animal that might need or justify a disc replacement.  
         [0023]     Referring now to  FIG. 1 , one embodiment of the present invention comprises an intervertebral disc nucleus prosthetic bag structure  100  that may be used for replacing all or part of a diseased, damaged or otherwise non-functional intervertebral disc nucleus. In the illustrated embodiment, bag structure  100  includes an outer body  110 , an interior cavity  120 , and opening  130  for receiving, for example, an interior implant structure or material.  
         [0024]     In accordance with one embodiment of the invention, bag structure  100 , and in particular, outer body  110  is formed of a flexible material. In some other embodiments, the bag structure  100 , and in particular, outer body  110  is formed of a semi-permeable flexible, resilient, elastic or viscoelastic material. The later materials can have a time dependent deformation quality that dissipates some mechanical energy; thus, there is a viscoelastic quality to the material in some of these examples. Therefore, the bag structure can be compressed, so that it can be implanted in an annulus fibrosis cavity using a delivery device, such as a catheter or the like. Once inserted into the intervertebral space, the bag structure can be released from the delivery device, so that it returns to its relaxed unstretched state. Implantation of the bag structure will be discussed in more detail below.  
         [0025]     In one embodiment, outer body  110  of bag structure  100  is formed of an immunologically inert material that is compatible with the environment found within a mammalian body, and in particular, within an intervertebral disc. As one skilled in the art will appreciate, the immunologically inert material does not induce any significant response by the immune system when the structure is implanted into a subject. Bag structure  100  can be formed of one or more materials, including in some embodiments, one or more composite materials. In addition, the outer body  110  of bag structure  100  can be formed from one or more layers of material.  
         [0026]     In some embodiments, bag structure  100  can be formed of one or more different materials, which exhibit semi-permeable, flexible, resilient and/or elastic properties. That is, the material of bag structure  100  is such that it is capable of being easily stretched, expanded or compressed, and then resuming its former shape or close to its former shape. For example, in one embodiment, a bag structure  100  can be formed from a woven or non-woven polymeric fiber material, such as, an aramid material (e.g., Kevlar™, Nomex™, Twaron™, etc.), a polyester fiber material, an ultra high molecular weight polyethylene fiber material, a nylon fiber material, a cellulose fiber material, a polyurethane fiber material, or a polyacrylonitrile based fiber material. In some embodiments the polymeric fiber material can be woven or configured into a 2-dimensional or 3-dimensional fabric configuration.  
         [0027]     In another embodiment of the present invention, bag structure  100  can be made and/or formed from a metallic material, such as nitinol, stainless steel (eg. heat-treated PH 17-7 stainless steel fabric) or the like. In still other embodiments, bag structure  100  can be made and/or formed from metallic fibers woven into a fabric-type material. In some embodiments, the fabric-type material can be a 2-dimensional or 3-dimensional fabric configuration.  
         [0028]     In further embodiments, bag structure  100  can be made of a combination of materials. For example, one combination might be a combination of a polymeric fiber and a metallic material; e.g., an aramid material (e.g., Kevlar or the like) and a metallic material (e.g., nitinol, stainless steel).  
         [0029]     In another embodiment of the present invention, bag structure  100  can be made of a semi-permeable, flexible, composite material, such as a composite comprised of an elastomeric or hydrogel matrix material and a polymeric fiber, a metal fiber or wire, or a ceramic fiber. Examples of suitable matrix materials that can be used to form bag structure  100  include, but are not limited to, a natural or synthetic polymer matrix material, an elastomer, a flexible polyolefin polymer, an elastomeric matrix material, or a hydrogel material.  
         [0030]     Discussed above are various examples of classes of materials that can be used to form bag structure  100 . Other specific materials that can be used to make bag structure  100  include, but are not limited to, polyaramid fibers, such as Kevlar 49, Kevlar 149—or the like, ultra high molecular weight, highly oriented, highly crystalline polyethylene (e.g., Dyneema or Spectra 900 or Spectra 1000), polyester fibers, such as Dacron, silk fiber, elastin fiber, elastomeric materials for (polyurethane or other thermoplastic elastomer), fused PTFE (Polytetrafluoroethylene), expanded PTFE of generally high tenacity fibers or other high strength woven or non-woven fibers or fabrics. It is also contemplated that any embodiment of the present invention may be accompanied by vertebroolasty to increase the strength of any weakened vertebrae including but not limited to disease, aging or injury.  
         [0031]     In some embodiments, an interior implant material and/or structure is placed into bag structure  100  so that the combination of the bag structure and interior implant material create a resilient disc nucleus prosthesis. In some embodiments, the interior implant material or structure conforms to at least a portion of the interior cavity of the bag structure, thus creating the resilient prosthetic structure. In accordance with some embodiments of the invention, the interior implant material or device can be, for example, a hydrogel implant, a spiral implant, a biological implant, the implant structure discussed below, or any other suitable disc nucleus implant material or device. In one embodiment, the interior implant material and/or device can be, for example, the spiral implant devices disclosed in U.S. Pat. No. 5,919,235, which is incorporated herein by reference in its entirety. Further, in other embodiments, the sinusoidal-shaped structural device discussed below can be implanted or positioned within bag structure  100 . The implantation of this device in a bag structure will be discussed in more detail below.  
         [0032]     Referring now to  FIG. 2 , a cross-sectional view of a spinal column  200  having a herniated disc or damaged disc is shown. In the illustrated embodiment, the cross-section shows a vertebrae  210 , a spinal cord  220  with nerve roots  225 , and a disc  230 , having an annulus  240  and a disc nucleus  250 . As is illustrated by location  260  in  FIG. 2 , a herniated disc occurs when disc nucleus  250  protrudes an opening or weakness in annulus  240 , putting pressure on spinal cord  220  and/or nerve roots  225 . When this occurs, one remedy is to remove the protruding disc nucleus and replace it with a prosthetic nucleus structure and/or material. As one skilled in the art will appreciate, a disc nucleus replacement procedure includes, first removing at least a portion of the disc nucleus. In addition, as one skilled in the art will appreciate, a disc replacement procedure includes estimating the size and conformation required to replace the damaged disc area. In one embodiment of the present invention, the entire disc can be removed and replaced if warranted. In some embodiments, partial and/or total disc replacement can require anchoring of the intervertebral prosthetic structure such as encouraging tissue ingrowth into a structure (e.g. 2- or 3-dimensional weave structure). These procedures are known in the art, and thus, will not be discussed in detail herein.  
         [0033]     After at least a portion of the disc nucleus is removed, the prosthetic structure and/or material can be placed within the annulus where the nucleus material was removed. In accordance with one embodiment of the present invention, once the nucleus material is removed, a delivery device (e.g., a cannula or other catheter device) can be used to introduce bag structure  100  into the annulus cavity. In one embodiment, bag structure  100  can be stretched and/or compressed and then attached to the delivery device so that it can be delivered through an opening in the disc annulus into the disc nucleus region. For example, in one embodiment, bag structure  100  is compressed into a cannula or onto a catheter, and then delivered into the nucleus region using a balloon catheter delivery technique, or the like. After the bag structure  100  is delivered into the nucleus region, it is released. In some embodiments, upon release, bag structure  100  will expand to substantially its uncompressed original shape.  
         [0034]     In other embodiments, a balloon device (e.g., balloon catheter device) can be used to deploy bag structure  100  within the disc nucleus region. As one skilled in the art will appreciate, during a balloon catheter delivery procedure, a balloon catheter is used to place bag structure  100  within the disc nucleus, and then a balloon is inflated within the bag structure  100 , causing the compressed bag structure to expand to its original or close to original shape. Once the bag structure is expanded, the balloon is deflated and then removed.  
         [0035]     After bag structure  100  has been positioned within the disc nucleus region, an interior implant structure and/or material can be placed within the interior  120  of bag structure  100  for additional nucleus support. The interior implant structure and/or material can be introduced or positioned within interior  120  of bag structure  100  through opening  130  (see  FIGS. 1   a  and  1   b ). Different delivery devices and/or methods may be used to insert the interior implant into the bag structure, and the delivery devices and/or methods used may differ depending on the type of implant material or structure used. After the interior implant material and/or structure is placed within bag structure  100 , opening  130  of bag structure  100  then can be sealed or closed, thus holding the interior implant material and/or structure within the bag structure. As one skilled in the art will appreciate, any sealing or closing process and/or device can be used to seal the bag structure, such as suturing, clamping, tying, using a single directional opening valve or the like.  
         [0036]     One aspect of the present invention relates to an interior implant structure, which can act as a disc nucleus replacement prosthesis, or at least as an interior portion of a disc nucleus prosthesis structure; one embodiment of which is illustrated in  FIG. 3 . In the illustrated embodiment, interior implant structure  300  comprises one or more sinusoidal-shaped structures  305 . In accordance with this particular embodiment of the invention, each sinusoidal-shaped structure  305  comprises a plurality of periodic portions  310 , which are formed of a flexible, resilient, elastic material. As illustrated in  FIG. 3 , each periodic portion  310  intersecting a longitudinal axis  320  of the interior implant structure  300  at two points,  330   a  and  330   b . In one embodiment, the sinusoidal-shaped structures  305  is flexible, such that when stretched in a longitudinal direction (i.e., along axis  320 ), the structure sufficiently flattens or otherwise reduces the amplitude of each of the periodic portions  310 , so that it can be placed within a disc nucleus region or holding structure within the disc nucleus region (e.g., bag structure  100 , discussed above).  FIG. 3   b  illustrates one embodiment of interior implant structure  300  (i.e., sinusoidal-shaped structures  305 ) in a stretched configuration.  
         [0037]     Further, sinusoidal-shaped implant structure  300  are formed of a flexible, resilient material, so that when released from a stretched position (typically, within the disc nucleus region, or in an implant holding structure), the device returns substantially to its original sinusoidal shape. In one embodiment of the present invention, the original sinusoidal shape of the device includes a configuration where the amplitude of at least one of the periodic portions of the sinusoidal shape when in an unstretched position is large enough to prevent the device from exiting the opening in the bag structure.  FIG. 4  illustrates sinusoidal-shaped implant structure  300  positioned within bag structure  100 , which is discussed in detail above.  
         [0038]     As illustrated in  FIG. 3 , one embodiment of the invention can comprise multiple sinusoidal-shaped structures  305  positioned together, or otherwise interwoven with each other. The embodiment illustrated in  FIG. 3  shows two sinusoidal-shaped structures  305  interwoven or otherwise joined and positioned in planes that are positioned at or near 90 degrees from one another. In other embodiments, two sinusoidal-shaped structures  305  can be positioned in different planes that are not necessarily perpendicular to one another. In still other embodiments, more than two sinusoidal-shaped structures  305  can be used.  
         [0039]     In accordance with yet other embodiments of the invention, sinusoidal-shaped structures  305  can include holes  340  through the material at or near the center of the structures (i.e., at or near longitudinal axis  320 ). As discussed in more detail below, the holes can be used to accommodate an implantation or delivery device such as a cannula, catheter, etc.  
         [0040]     As with bag structure  100  discussed above, some embodiments of interior implant structure  300  can be formed of an immunologically inert material that is compatible with the environment found within a mammalian body, and in particular, within an intervertebral disc. As one skilled in the art will appreciate, the immunologically inert material does not induce any significant response by the immune system when the structure is implanted into a subject. Further, as with bag structure  100 , interior implant structure  300  can be formed of one or more materials, including in some embodiments, one or more composite materials. In addition, interior implant structure  300 , and in particular, sinusoidal-shaped structures  305  can be formed from one or more layers of material.  
         [0041]     In some embodiments, as with bag structure  100 , sinusoidal-shaped structures  305  can be formed of one or more different materials, which exhibit flexible, resilient and/or elastic or viscoelastic properties. That is, the material of structures  305  is such that it is capable of being easily stretched, expanded or compresses, and then resuming its former shape or close to its former shape. For example, in one embodiment, structures  305  can be formed from a woven or non-woven polymeric fiber material, such as, an aramid material (e.g., Kevlar™, Nomex™, Twaron™, etc.), a polyester fiber material, an ultra high molecular weight polyethylene fiber material, a nylon fiber material, a cellulose fiber material, a polyurethane fiber material, or a polyacrylonitrile based fiber material. In some embodiments the polymeric fiber material can be woven or configured into a 2-dimensional or 3-dimensional fabric configuration.  
         [0042]     Further, in other embodiments, sinusoidal-shaped structures  305  can be made and/or formed from a metallic material, such as nitinol, stainless steel or the like. In still other embodiments, structures  305  can be made and/or formed from metallic fibers woven into a fabric-type material. In some embodiments, the fabric-type material can be a 3-dimensional fabric configuration.  
         [0043]     In further embodiments, sinusoidal-shape structures  305  can be made of a combination of materials. For example, one combination might be a combination of a polymeric fiber and a metallic material; e.g., an aramid material (e.g., Kevlar or the like) and a metallic material (e.g., nitinol, stainless steel).  
         [0044]     In another embodiment of the present invention, sinusoidal-shaped structures  305  can be made of a flexible composite material, such as a composite comprising an elastomeric or hydrogel matrix material and a polymeric fiber, metal fiber or wire, or a ceramic fiber. Examples of suitable matrix materials that can be used to form structures  305  include, but are not limited to, a natural or synthetic polymer matrix material, an elastomer, a flexible polyolefin polymer, an elastomeric matrix material, or a hydrogel material.  
         [0045]     Discussed above are various examples of classes of materials that can be used to form sinusoidal-shaped structures  305 . Other specific materials that can be used to make structures  305  include, but are not limited to, polyaramid fibers, Kevlar 49, Kevlar 149 or the like, polyester fiber (e.g. Dacron), ultra high molecular weight, highly oriented, highly crystalline polyethylene (e.g., Dyneema), silk, elastin, elastomeric (polyurethane or other thermoplastic elastomer), fused PTFE (Polytetrafluoroethylene), expanded PTFE of generally high tenacity fibers or high strength non-woven fabric polyethylene, polyaryl, and PEEK (polyetheretherkeytone).  
         [0046]     As discussed above, interior implant structures can be placed or positioned within a bag or containment structure, such as bag structure  100  discussed above. In some embodiments, interior implant structure  300  can be placed within bag structure  100  to form a resilient disc nucleus prosthetic structure (see  FIG. 4 ). In one embodiment, one or more sinusoidal-shaped structures  305  can be placed within bag structure  100  to form the disc nucleus prosthesis. In other embodiments, one or more sinusoidal-shaped implant structures  305  can be placed in bag structure  100 , along with one or more other implant materials such as hydrogel implant, a spiral implant, a therapeutic implant, a biologic implant, or a an in-situ curable material.  
         [0047]     In one embodiment, interior implant structure  300  (i.e., sinusoidal-shaped structures  305 ) can be inserted into a bag structure (e.g., bag structure  100 ) located in the intervertebral cavity using an external delivery device, such as a cannula, a catheter, or other suitable delivery device. In accordance with one embodiment, a delivery device can be inserted through holes  340  in sinusoidal-shaped structures  305 , and then the structures can be stretched along the delivery device to reduce the height or amplitude of the sinusoidal-shaped devices, as discussed above. Once the height of the structure is sufficiently reduced, it can be positioned or placed within the internal cavity  120  of bag structure  100 , for example, through opening  130  in bag structure  100 . Once inside the bag structure, interior implant structure  300  (i.e., sinusoidal structures  305 ) is released from the delivery device, which will allow structures  305  to expand back to or near its original shape, thus filling the bag structure and at least a portion of the disc nucleus regions.  
         [0048]     In some embodiments, a coating agent can be applied to a bag structure (e.g., bag structure  100 ) and/or an interior implant structure (e.g., interior implant structure  300 ). In one embodiment, the coating agent may include one or more of hydrogel, a curable biomaterial that changes states once introduced to the intervertebral disc region (e.g., by chemical or heat promotion), elastomers (e.g., thermoset and thermoplastic), polyolefins, therapeutic agents (e.g., anti-bacterial or anti-fungal agents or biological agents). Biological agents can include, for example, tissue extracts, cells (e.g., bone derived cells), growth factors (e.g., platelet derived growth factor (PDGF)), proteins (e.g. the hormone calcitonin) or genes (e.g., nerve growth or bone growth promoting genes).  
         [0049]     The foregoing discussion of the invention has been presented for purposes of illustration and description. It is not intended to limit the invention to the form or forms disclosed herein. Although the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights, which include alternative embodiments, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.