Patent Abstract:
A surgical method of repair and reconstruction of the spinal disc wall (annulus) after surgical invasion or pathologic rupture, incorporating suture closure, or stent insertion and fixation, designed to reduce the failure rate of conventional surgical procedures on the spinal discs.  
     The design of the spinal disc annulus stent allows ingrowth of normal cells of healing in an enhanced fashion strengthening the normal reparative process.

Full Description:
CROSS-REFERENCE TO A RELATED APPLICATION  
       [0001]    This application is a continuation of U.S. Ser. No. 09/947,078, filed Sep. 5, 2001 which is a continuation of U.S. Ser. No. 09/484,706, filed Jan. 18, 2000 which claims the benefit of U.S. Provisional Application No. 60/160,710, filed Oct. 20, 1999. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention generally relates to a surgical method of intervertebral disc wall reconstruction with a related annulus stent augmenting the repair. The effects of said reconstruction are restoration of disc wall integrity and reduction of the failure rate (3-21%) of a common surgical procedure (disc fragment removal or discectomy). This surgical procedure is performed about 390,000 times annually in the United States.  
         BACKGROUND OF THE INVENTION  
         [0003]    The spinal column is formed from a number of vertebrae, which in their normal state are separated from each other by cartilaginous intervertebral discs. The intervertebral disc acts in the spine as a crucial stabilizer, and as a mechanism for force distribution between the vertebral bodies. Without the disc,  
           [0004]    The normal intervertebral disc has an outer ligamentous ring called the annulus surrounding the nucleus pulposus. The annulus binds the adjacent vertebrae together and is constituted of collagen fibers that are attached to the vertebrae and cross each other so that half of the individual fibers will tighten as the vertebrae are rotated in either direction, thus resisting twisting or torsional motion. The nucleus pulposus is constituted of loose tissue, having about 85% water content, which moves about during bending from front to back and from side to side.  
           [0005]    As people age, the annulus tends to thicken, desicate, and become more rigid. The nucleus pulposus, in turn, becomes more viscous and less fluid and sometimes even dehydrates and contracts. The annulus also becomes susceptible to fracturing or fissuring. These fractures tend to occur all around the circumference of the annulus and can extend from both the outside of the annulus inwards, and the interior outward. Occasionally, a fissure from the outside of the annulus meets a fissure from the inside and results in a complete rent or tear through the annulus fibrosis. In situations like these, the nucleus pulposus may extrude out through the annulus wall. The extruded material, in turn, can impinge on the spinal cord or on the spinal nerve rootlet as it exits through the intervertebral disc foramen, resulting in a condition termed ruptured disc or herniated disc  
           [0006]    In the event of annulus rupture, the inner-nucleus component migrates along the path of least resistance forcing the fissure to open further, allowing migration of the nucleus pulposus through the wall of the disc, with resultant nerve compression and leakage of chemicals of inflammation into the space around the adjacent nerve roots supplying the extremities, bladder, bowel and genitalia. The usual effect of nerve compression and inflammation is intolerable back or neck pain, radiating into the extremities, with accompanying numbness, weakness, and in late stages, paralysis and muscle atrophy, and/or bladder and bowel incontinence. Additionally, injury, disease or other degenerative disorders may cause one or more of the intervertebral discs to shrink, collapse, deteriorate or become displaced, herniated, or otherwise damaged.  
           [0007]    The surgical standard of care for treatment of herniated, displaced or ruptured intervertebral discs is fragment removal and nerve decompression without a requirement to reconstruct the annular wall. While results are currently acceptable, they are not optimal. Various authors report 3.1-21% recurrent disc herniation, representing a failure of the primary procedure and requiring re-operation for the same condition. An estimated 10% recurrence rate results in 39,000 re-operations in the United States each year.  
           [0008]    An additional method of relieving the symptoms is thermal annuloplasty, involving the heating of sub-annular zones in the non-herniated painful disc, seeking pain relief, but making no claim of reconstruction of the ruptured, discontinuous annulus wall.  
           [0009]    There is currently no known method of annulus reconstruction, either primarily or augmented with an annulus stent.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    The present invention provides methods and related materials for reconstruction of the disk wall in cases of displaced, herniated, ruptured, or otherwise damaged intervertebral discs.  
           [0011]    In a preferred form, one or more mild biodegradable surgical sutures are placed at about equal distances along the sides of a pathologic aperture in the ruptured disc wall (annulus) or along the sides of a surgical incision in the weakened, thinned disc annulus.  
           [0012]    Sutures are then tied in such fashion as to draw together the sides of the aperture, effecting reapproximation or closure of the opening, to enhance natural healing and subsequent reconstruction by natural tissue (fibroblasts) crossing the now surgically narrowed gap in the disc annulus.  
           [0013]    A 25-30% reduction in the rate of recurrence of disc nucleus herniation through this aperture, has been achieved using this method.  
           [0014]    In another embodiment, the method can be augmented by placement of a patch of human muscle fascia (the membrane covering the muscle) or any other autograft or allograft acting as a bridge in and across the aperture, providing a platform for traverse of fibroblasts or other normal cells of repair existing in and around the various layers of the disc annulus, prior to closure of the aperture.  
           [0015]    A 30-50% reduction in the rate of recurrence of disc herniation has been achieved using the aforementioned fascial augmentation with this embodiment.  
           [0016]    Having demonstrated that human muscle fascia is adaptable for annular reconstruction, other biocompatible membranes can be employed as a bridge, stent, patch or barrier to subsequent migration of the disc nucleus through the aperture. Such biocompatible materials may be, for example, a medical grade biocompatible fabric, biodegradable polymeric sheets, or form fitting or non-form fitting fillers for the cavity created by removal of a portion of the disc nucleus in the course of the disc fragment removal or discectomy. The prosthetic material can be placed in and around the intervertebral space, created by removal of the degenerated disc fragments. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 shows a perspective view of the annulus stent.  
         [0018]    [0018]FIG. 2 shows a front view of the annulus stent.  
         [0019]    [0019]FIG. 3 shows a side view of the annulus stent.  
         [0020]    FIGS.  4 A- 4 C show a front view of various alternative embodiments of the annulus stent.  
         [0021]    FIGS.  5 A- 5 B shows the alternative embodiment of a pyramid shaped annulus stent.  
         [0022]    FIGS.  6 A- 6 B shows the alternative embodiment of a coned shaped annulus stent.  
         [0023]    [0023]FIG. 7 shows the primary closure of the opening in the disc annulus, without an intervertebral or subannular stent.  
         [0024]    FIGS.  8 A- 8 B shows the primary closure with a stent in generic form.  
         [0025]    [0025]FIG. 9 shows a method of suturing the annulus stent into the disc annulus, utilizing sub-annular fixation points.  
         [0026]    FIGS.  10 A- 10 B show the annulus stent with flexible bladder being expanded into the disc annulus.  
         [0027]    FIGS.  11 A- 11 D show the annulus stent being inserted into the disc annulus.  
         [0028]    FIGS.  12 A- 12 B show the annulus stent with the flexible bladder being expanded by injection. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    The present invention provides methods and related materials for reconstruction of the disk wall in cases of displaced, herniated, ruptured, or otherwise damaged intervertebral discs.  
         [0030]    In one embodiment of the present invention, as shown in FIG. 7, a damaged annulus  42  is repaired by use of surgical sutures  40 . One or more surgical sutures  40  are placed at about equal distances along the sides of a pathologic aperture  44  in the ruptured annulus  42 . Reapproximation or closure of the aperture  44  is accomplished by tying the sutures  40  in such a fashion that the sides of the aperture  44  are drawn together. The reapproximation or closure of the aperture  44  enhances the natural healing and subsequent reconstruction by the natural tissue crossing the now surgically narrowed gap in the annulus  42 . Preferably, the surgical sutures  40  are biodegradable, but permanent non-biodegradable may be utilized.  
         [0031]    Additionally, to repair a weakened or thinned disc annulus  42 , a surgical incision is made along the weakened or thinned region of the annulus  42  and one or more surgical sutures  40  are placed at about equal distances along the sides of the incision. Reapproximation or closure of the incision is accomplished by tying the sutures  40  in such a fashion that the sides of the incision are drawn together. The reapproximation or closure of the incision enhances the natural healing and subsequent reconstruction by the natural tissue crossing the now surgically narrowed gap in the annulus  42 . Preferably, the surgical sutures  40  are biodegradable, but permanent non-biodegradable materials may be utilized.  
         [0032]    In an alternative embodiment, the method can be augmented by the placement of a patch of human muscle fascia or any other autograft, allograft or xenograft in and across the aperture  44 . The patch acts as a bridge in and across the aperture, providing a platform for traverse of fibroblasts or other normal cells of repair existing in and around the various layers of the disc annulus, prior to closure of the aperture.  
         [0033]    In a further embodiment, as shown in FIG. 8, a biocompatible membrane can be employed as an annulus stent  10 , being placed in and across the aperture  44 . The annulus stent  10  acts as a bridge in and across the aperture  44 , providing a platform for a traverse of fibroblasts or other normal cells of repair existing in and around the various layers of the disc annulus, prior to closure of the aperture  44 .  
         [0034]    In a preferred embodiment, as shown in FIGS.  1 - 3 , the annulus stent  10  comprises a centralized vertical extension  12 , with an upper section  14  and a lower section  16 . The centralized vertical extension  12  can be trapezoid in shape through the width and may be from about 8 mm-12 mm in length.  
         [0035]    Additionally, the upper section  14  of the centralized vertical extension  12  may be any number of different shapes, as shown in FIGS. 4A and 4B, with the sides of the upper section  14  being curved or with the upper section  14  being circular in shape. Furthermore, the annulus stent  10  may contain a recess between the upper section  14  and the lower section  16 , enabling the annulus stent  10  to form a compatible fit with the edges of the aperture  44 .  
         [0036]    The upper section  14  of the centralized vertical extension  12  can comprise a slot  18 , where the slot  18  forms an orifice through the upper section  14 . The slot  18  is positioned within the upper section such that  14  it traverses the upper section&#39;s  14  longitudinal axis. The slot  18  is of such a size and shape that sutures, tension bands, staples or any other type of fixation device known in the art may be passed through, to affix the annulus stent  10  to the disc annulus  44 .  
         [0037]    In an alternative embodiment, the upper section  14  of the centralized vertical extension  12  may be perforated. The perforated upper section  14  contains a plurality of holes which traverse the upper section&#39;s  14  longitudinal axis. The perforations are of such a size and shape that sutures, tension bands, staples or any other type of fixation device known in the art may be passed through, to affix the annulus stent  10  to the disc annulus  44 .  
         [0038]    The lower section  16  can comprise a pair of lateral extensions, a left lateral extension  20  and a right lateral extension  22 . The lateral extensions  20  and  22  comprise an inside edge  24 , an outside edge  26 , an upper surface  28 , and a lower surface  30 . The lateral extensions  20  and  22  can have an essentially constant thickness throughout. The inside edge  24  is attached to the lower section  16  and is about the same length as the lower section  16 . The outside edge  26  can be about 8 mm-16 mm in length. The inside edge  24  and the lower section  16  meet to form a horizontal plane, essentially perpendicular to the centralized vertical extension  12 . The upper surface  28  of the lateral extensions  20  and  22  can form an angle of about 0°-60° below the horizontal plane. The width of the annulus stent  10  may be from about 3 mm-5 mm.  
         [0039]    Additionally, the upper surface  28  of the lateral extensions  20  and  22  may be barbed for fixation to the inside surface of the disc annulus  40  and to resist expulsion through the aperture  44 .  
         [0040]    In an alternative embodiment, as shown in FIG. 4B, the lateral extensions  20  and  22  have a greater thickness at the inside edge  24  than at the outside edge  26 .  
         [0041]    In a preferred embodiment, the annulus stent  10  is a solid unit, formed from one or more of the flexible resilient biocompatible or bioresorbable materials well know in the art.  
         [0042]    For example, the annulus stent may be made from:  
         [0043]    a porous matrix or mesh of biocompatible and bioresorbable fibers acting as a scaffold to regenerate disc tissue and replace annulus fibrosus as disclosed in, for example, U.S. Pat. Nos. 5,108,438 (Stone) and 5,258,043 (Stone);  
         [0044]    a strong network of inert fibers intermingled with a bioresorbable (or biosabsorable) material which attracts tissue ingrowth as disclosed in, for example, U.S. Pat. No. 4,904,260 (Ray et al.);  
         [0045]    a biodegradable substrate as disclosed in, for example, U.S. Pat. No. 5,964,807 (Gan at al.); or  
         [0046]    a expandable polytetrafluoroethylene (ePTFE), as used for conventional vascular grafts, such as those sold by W. L. Gore and Associates, Inc. under the trademarks GORE-TEX and PRECLUDE, or by Impra, Inc. under the trademark IMPRA.  
         [0047]    Furthermore, the annulus stent  10 , may contain hygroscopic material for a controlled limited expansion of the annulus stent  10  to fill the evacuated disc space cavity.  
         [0048]    Additionally, the annulus stent  10  may comprise materials to facilitate regeneration of disc tissue, such as bioactive silica-based materials which assist in regeneration of disc tissue as disclosed in U.S. Pat. No. 5,849,331 (Ducheyne, et al.), or other tissue growth factors well known in the art.  
         [0049]    In further embodiments, as shown in FIGS.  5 - 6 , the left and right lateral extensions  20  and  22  join to form a solid pyramid or cone. Additionally, the left and right lateral extensions  20  and  22  may form a solid trapezoid, wedge, or bullet shape. The solid formation may be a solid biocompatible or bioresorbable flexible material, allowing the lateral extensions  20  and  22  to be compressed for insertion into aperture  44 , then to expand conforming to the shape of the annulus&#39;  42  inner wall.  
         [0050]    Alternatively, a compressible core may be attached to the lower surface  30  of the lateral extensions  20  and  22 , forming a pyramid, cone, trapezoid, wedge, or bullet shape. The compressible core may be made from one of the biocompatible or bioresorbable resilient foams well known in the art. The compressible core allows the lateral extensions  20  and  22  to be compressed for insertion into aperture  44 , then to expand conforming to the shape of the annulus&#39;  42  inner wall and to the cavity created by pathologic extrusion or surgical removal of the disc fragment.  
         [0051]    In a preferred method of use, as shown in FIGS.  10 A- 10 D, the lateral extensions  20  and  22  are compressed together for insertion into the aperture  44  of the disc annulus  40 . The annulus stent  10  is then inserted into the aperture  44 , where the lateral extensions  20  and  22  expand, with the upper surface  28  contouring to the inside surface of the disc annulus  40 . The upper section  14  is positioned within the aperture  44  so that the annulus stent  10  may be secured to the disc annulus  40 , using means well known in the art.  
         [0052]    In an alternative method, where the length of the aperture  44  is less than the length of the outside edge  26  of the annulus stent  10 , the annulus stent  10  must be inserted laterally into the aperture  44 . The lateral extensions  20  and  22  are compressed, and the annulus stent  10  is laterally inserted into the aperture  44 . The annulus stent  10  is then rotated inside the disc annulus  40 , such that the upper section  14  is pulled back through the aperture  44 . The lateral extensions  20  and  22  are then allowed to expand, with the upper surface  28  contouring to the inside surface of the disc annulus  40 . The upper section  14  is positioned within the aperture  44  such that the annulus stent  10  may be secured to the disc annulus, using means well known in the art.  
         [0053]    In an alternative method of securing the annulus stent  10  in the aperture  44 , as shown in FIG. 9, a first surgical screw  50  and second surgical screw  52 , with eye holes  53  located at the top of the screws  50  and  52 , are opposingly inserted into the adjacent vertebrae  54  and  56  below the annulus stent  10 . After insertion of the annulus stent  10  into the aperture  44 , a suture is passed down though the disc annulus  40 , adjacent to the aperture  44 , through the eye hole  53  on the first screw  50  then back up through the disc annulus  40  and through the orifice  18  on the annulus stent  10 . This is repeated for the second screw  52 , after which the suture is secured. One or more surgical sutures  40  are placed at about equal distances along the sides of the aperture  44  in the disc annulus  42 . Reapproximation or closure of the aperture  44  is accomplished by tying the sutures  40  in such a fashion that the sides of the aperture  44  are drawn together. The reapproximation or closure of the aperture  44  enhances the natural healing and subsequent reconstruction by the natural tissue crossing the now surgically narrowed gap in the annulus  42 . Preferably, the surgical sutures  40  are biodegradable but permanent nonbiodegradable forms may be utilized. This method should decrease the strain on the disc annulus  40  adjacent to the aperture  44 , precluding the tearing of the sutures through the disc annulus  40 .  
         [0054]    It is anticipated that fibroblasts will engage the fibers of the polymer or fabric of the intervertebral disc stent, forming a strong wall duplicating the currently existing condition of healing seen in the normal reparative process.  
         [0055]    In an additional embodiment, as shown in FIGS.  1 A-B, a flexible bladder  60  is attached to the lower surface  30  of the annulus stent  10 . The flexible bladder  60  comprises an internal cavity  62  surrounded by a membrane  64 , where the membrane  64  is made from a thin flexible biocompatible material. The flexible bladder  60  is attached to the lower surface  28  of the annulus stent  10  in an unexpanded condition. The flexible bladder  60  is expanded by injecting a biocompatible fluid or expansive foam, as known in the art, into the internal cavity  62 . The exact size of the flexible bladder  60  can be varied for different individuals. The typical size of an adult nucleus is 2 cm in the semi-minor axis, 4 cm in the semi-major axis and 1.2 cm in thickness.  
         [0056]    In an alternative embodiment, the membrane  64  is made of a semi-permeable biocompatible material.  
         [0057]    In a preferred embodiment, a hydrogel is injected into the internal cavity of the flexible bladder  28 . A hydrogel is a substance formed when an organic polymer (natural or synthetic) is cross-linked via covalent, ionic, or hydrogen bonds to create a three-dimensional open-lattice structure which entraps water molecules to form a gel. The hydrogel may be used in either the hydrated or dehydrated form.  
         [0058]    In a method of use, where the annulus stent  10  has been inserted into the aperture, as has been previously described and shown in FIGS.  12 A- b , an injection instrument, as known in the art, such as a syringe, is used to inject the biocompatible fluid or expansive foam into the internal cavity  62  of the flexible bladder  60 . The biocompatible fluid or expansive foam is injected through the annulus stent  10  into the internal cavity of the flexible bladder  28 . Sufficient material is injected into the internal cavity  62  to expand the flexible bladder  60  to fill the void in the intervertebral disc cavity. The use of the flexible bladder  60  is particularly useful when it is required to remove all or part of the intervertebral disc nucleus.  
         [0059]    The surgical repair of an intervertebral disc may require the removal of the entire disc nucleus, being replaced with an implant, or the removal of a portion of the disc nucleus thereby leaving a void in the intervertebral disc cavity. The flexible bladder  60  allows for the removal of only the damaged section of the disc nucleus, with the expanded flexible bladder  60  filling the resultant void in the intervertebral disc cavity. A major advantage of the annulus stent  10  with the flexible bladder  60  is that the incision area in the annulus can be reduced in size as there is no need for the insertion of an implant into the intervertebral disc cavity.  
         [0060]    In an alternative method of use, a dehydrated hydrogel is injected into the internal cavity  28  of the flexible bladder  60 . Fluid, from the disc nucleus, passes through the semi-permeable membrane  64  hydrating the dehydrated hydrogel. As the hydrogel absorbs the fluid the flexible bladder expands  60 , filling the void in the intervertebral disc cavity.  
         [0061]    All patents referred to or cited herein are incorporated by reference in their entirety to the extent they are not inconsistent with the explicit teachings of this specification, including; U.S. Pat. No. 5,108,438 (Stone), U.S. Pat. No. 5,258,043 (Stone), U.S. Pat. No. 4,904,260 (Ray et al.), U.S. Pat. No. 5,964,807 (Gan et al.), U.S. Pat. No. 5,849,331 (Ducheyne et al.), U.S. Pat. No. 5,122,154 (Rhodes), U.S. Pat. No. 5,204,106 (Schepers at al.), U.S. Pat. No. 5,888,220 (Felt et al.) and U.S. Pat. No. 5,376,120 (Sarver et al.).  
         [0062]    It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and preview of this application and the scope of the appended claims.

Technology Classification (CPC): 8